THE ROLE OF ECOLOGICAL RESTORATION IN BIODIVERSITY CONSERVATION: BASIC ISSUES AND GUIDELINES Prepared by: Kenneth Towle New World Consulting for Biodiversity Published by The Evergreen Foundation www.evergreen.ca Toronto Office: 355 Adelaide St. West, Suite 5A Toronto, Ontario M5V 1S2 Tel.: (416) 596-1495 Fax: (416) 596-1443 Vancouver Office: #106 - 163 West Hastings St. Vancouver, BC V6B 1H5 Tel.: (604) 689-0766 Fax: (604) 689-0768 To order a print copy, please contact Geoff Cape for purchase cost. TABLE OF CONTENTS ACKNOWLEDGEMENTS FORWARD INTRODUCTION PART 1 A BRIEF INTRODUCTION TO BIODIVERSITY AND CONSERVATION BIOLOGY a. What is Biodiversity? Is there a Biodiversity Crisis? Biodiversity Loss in Canada Why is Biodiversity Important? b. Biodiversity Conservation What is Conservation Biology? Population Viability Island Biogegraphy Habitat Fragmentation Edge Effects The Brown-headed Cowbird: A Brood Parasite Conservation Needs PART 2 RESTORATION AND BIODIVERSITY CONSERVATION Some Misconceptions and Dilemmas What Does Helping Biodiversity Mean? How Restoration Can Have an Impact on Biodiversity 1.1) Ecosystem Diversity a) Basic Issues b) Positive Potential of Restoration c) Negative Potential of Restoration 2.2) Species Diversity a) Basic Issues b) Positive Potential of Restoration c) Negative Potential of Restoration 3.3) Genetic Diversity a) Basic Issues b) Positive Potential of Restoration c) Negative Potential of Restoration Table 1 - Summary of positive and negative potential of restoration for biodiversity The Landscape Approach Enhancement of Fragments Expansion of Habitat Blocks The Pros and Cons of Corridors Summary PART 3 - THE URBAN CONTEXT Biodiversity in Urban Areas Urban Areas and Biodiversity Conservation Planting Habitat for Migratory Songbirds Summary and Conclusions The Role of Backyards and School Grounds PART 4 GUIDELINES General Guidelines The Rural Landscape Urban Areas ABOUT THE AUTHOR GLOSSARY REFERENCES ACKNOWLEDGEMENTS This document has benefitted from the critical input of many experts working in the areas of ecological restoration and biodiversity conservation. The advisory committee included Geoff Cape, Greg Filyk, Caroline Caza, Steve Hounsell, Steve Smith, Andy Kenney, John Ambrose, Diane Huffman, Larry Lamb, and Mary Gartshore. I thank all of these as well as Tove Christensen and Kevin McLaughlin for taking time to review the document and provide valuable comments. Thanks also to Kirk Biggar for helping undertake initial research. - Kenneth Towle Funding for this document was provided by Wildlife Habitat Canada, the Biodiversity Convention Office at Environment Canada and the Evergreen Foundation. FORWARD The concept of biodiversity reflects the most fundamental elements of life on earth and it is being seriously threatened by human action. Explosive population growth, urban sprawl, overindulgent resource use, and toxic pollutants have made life on earth increasingly precarious. As the search for solutions to the growing international environmental crisis continues, many claim that the most important issues lie in preserving what is left. By the same token a growing number of people are considering the massive potential held by the process of restoration. The obvious answer is an effective combination of both preservation and restoration. Preservation compartmentalizes nature, separates it from us and protects it by building a wall around it. This act is necessary and very effective in the short and medium terms. But long term change will only come with a fundamental shift in our relationship with nature. Restoration offers this hope. If managed effectively restoration can accelerate and set the stage for short and medium term improvements in biodiversity conservation, and begin to transform the way we interact with nature. As stated by Edward Grumbine ÒIf we begin to gain direct experience with ecosystems by working to protect biodiversity, we may find that nature becomes part of culture again.Ó We must begin to rethink the way we integrate our lives with nature. The process of restoration will help us reconnect with the natural world and establish an understanding of our place in the environment. As the 1990Õs progress, restoration projects are being adopted by a variety of land managers around the world. Barren landscapes are being reforested, wetlands and waterways are being brought back to life and existing forest fragments are being linked and expanded. The success of restoration lies in our ability to work effectively in this infinitely complicated field. This publication has been designed to introduce the concepts of biodiversity, present the principals of conservation and offer guidelines for action. The original hope for this study was to prove - beyond a doubt - that restoration work has a positive impact on biodiversity conservation. Unfortunately it is not that simple. An enormous learning curve lies ahead for all restorationists and we must do all we can to move along this curve quickly - time is of the essence. Geoff Cape Executive Director The Evergreen Foundation INTRODUCTION As the environmental restoration movement gains momentum, an increasing number of books and documents are appearing on the subject. Many of these are "how-to-style" manuals designed to direct action and provide resources. This document is designed to supplement existing manuals as an informative reference with a specific focus on restoration and biodiversity. As a report that deals with complex issues, it is primarily targeted towards those who are actively involved in restoration. A glossary has been provided so that the information presented should be comprehensible to all. While emphasizing that a landscape approach is needed to fully address biodiversity conservation concerns, this document makes special reference to urban areas in recognition that most public plantings occur in this context. An increasing number of programs and accompanying documents are advocating restoration as a means of helping biodiversity. Unfortunately, it is often assumed that attracting wildlife and helping biodiversity are one and the same. This is not necessarily true. Furthermore, many documents imply that public restoration and naturalization projects automatically benefit biodiversity and fail to recognize that under some circumstances serious negative consequences might also result from such actions. It is important to direct action away from potential problem areas towards genuinely positive solutions to specific biodiversity conservation concerns. Hopefully this will help ensure that the limited resources available for biodiversity conservation are wisely allocated. Thus the objectives of this document are: 1.To clearly define the concept of biodiversity. 2.To introduce some basic biodiversity conservation concerns and some fundamentals of conservation biology, the science that deals with biodiversity conservation. 3.To show how restoration (or naturalization) activities can have an impact on biodiversity in both positive and negative ways. 4.To provide guidelines on how to address biodiversity conservation concerns through ecologically sound restoration projects. Restoration ecology and conservation biology are both relatively new fields of discipline, and the issues that they deal with are highly complex. Therefore, much of the discussion about the potential impacts of restoration on biodiversity is speculative. As will become obvious, one can not address biodiversity goals in isolation. Whatever action is taken to deal with one issue will have some form of impact on biodiversity elsewhere. For this reason it is important to develop monitoring programs to study exactly how, and to what degree restoration projects do affect biodiversity. In the meantime, the best approach is to know about the issues and possibilities, and to make decisions accordingly. It is hoped that this document will contribute significantly to this awareness. It should be emphasized that, given our limited understanding of ecosystem dynamics, restoration is still very much a process of trial and error. While the replacement of lost or degraded habitat represents an important and even necessary approach to biodiversity conservation, most acknowledge that there is no substitute for the protection of existing significant habitat. PART 1 A BRIEF INTRODUCTION TO BIODIVERSITY AND CONSERVATION BIOLOGY Before exploring the potential impacts of restoration work on biodiversity it is important to clarify key concepts and to introduce some conservation concerns that might be addressed through restoration projects. This section is divided into two parts. In order to deal with common misconceptions, the first part introduces biodiversity as a concept and conservation issue. The second part is designed to aquaint the reader with the science and methodologies of conserving biodiversity. a. WHAT IS BIODIVERSITY? The popularity of the term biodiversity (a contraction of biological diversity) has increased dramatically in the past decade - to the degree that it is at risk of becoming a much misunderstood buzzword. Part of the confusion is undoubtedly based on the failure to recognize biodiversity as a broad concept rather than a specific phenomenon. In order to simplify what is in reality a complex issue, the term is frequently interpreted using the tangible concept of species. As a result, biodiversity is often mistakenly thought to be synonymous with species diversity, that is the number of species within a particular area, or what is referred to by biologists as Òspecies richness.Ó Thus ÒhelpingÓ biodiversity has often meant public action to provide opportunities for as many species as possible - especially through habitat restoration work. Yet, species diversity is only one component of the broader concept of biodiversity. Focusing on this alone while ignoring other issues can potentially work against biodiversity conservation goals. The numerous definitions of biodiversity currently in use do little to eliminate the confusion. According to the World Conservation Monitoring Center the term biodiversity Òis commonly used to describe the number, variety and variability of living organismsÓ (Groombridge 1992). A more concise definition is provided in the Global Biodiversity Strategy. This document states that Òbiodiversity is the totality of genes, species and ecosystems in a regionÓ (WRI, & UNEP 1992). Although they appear to be different, each of these definitions is correct, and in fact they are complementary. The former emphasizes variety and variability of life forms, a crucial component of the concept. The latter definition clarifies the three basic levels at which this variety and variability is recognized: genetic, species and ecosystem. What is needed is a comprehensive definition that encompasses both of those described above. Conservation biologists Reed Noss and Allen Cooperrider have proposed the following: ÒBiodiversity is the variety of life and its processes. It includes the variety of living organisms, the genetic differences among them, the communities and ecosystems in which they occur, and the ecological and evolutionary process that keep them functioning, yet ever changing and adaptingÓ (Noss and Cooperrider 1994). This definition demonstrates how complicated the concept of biodiversity is, and it includes the frequently ignored, but vitally important evolutionary context of biodiversity. In addition to the standard approach using the genetic, species and ecosystem levels of biodiversity, it has been suggested that landscape diversity also be taken into consideration. According to Noss and Cooperrider (1994) ÒLandscape or regional diversity is pattern diversity - the pattern of habitats and species assemblages across a land area of thousands of millions of acres - and can be considered a higher level expression of biodiversity.Ó Only by considering the landscape level in biodiversity conservation can we ensure the maintenance of large scale phenomena such as dispersal of wide ranging vertebrates, seed dispersal, pollination, natural fire regimes and other processes. For a variety of reasons, including climate and periods of major disturbance such as glaciation, biodiversity tends to increase from the poles towards the equator. For example, Ontario supports approximately 290 species of breeding birds (Cadman et al. 1987), while Columbia, which is only slightly larger in size, supports some 1,395 species (Forsyth 1990). By far the ecosystems that feature the highest degree of species richness are tropical rain forests, which contain well over 50 percent of all plants and animals on Earth (Collins 1990). Because the natural and perhaps optimum diversity of any given area is that which has evolved and adapted to local conditions, even areas with relatively low native biodiversity may be valuable if that is what is most suited to the site. As in any ecosystem, removal of species or genetic variability by unnatural means may place the integrity of the whole system at risk. Is There a Biodiversity Crisis? The short answer to this question is Òyes.Ó Harvard biologist E.O. Wilson estimates that in tropical rain forests alone the rate of loss of whole species (not merely genetic varieties or subspecies) is now a minimum of 27,000 per year, or three per hour, and the rate is increasing. This is believed to be at least 1000 times the ordinary ÒbackgroundÓ rate of extinction (Wilson 1992). There is little doubt then, that we are slipping into a great extinction that may well rival that which resulted in the demise of the dinosaurs some 65 million years ago (see Figure 1.1). Virtually all of this destruction is ultimately due to the activities of an ever-expanding human population. There are many individual factors contributing to the biodiversity crisis, including such major environmental problems as climate change, pollution and use of pesticides. Use of wildlife products and collecting of rare plants and animals can also have serious impacts. The single most important contributing factor in the biodiversity crisis is habitat loss, which effects all three of the principal levels of biodiversity. Today, along with the reduction in overall fitness resulting from population decline in some species and the complete demise of others, entire ecosystem types are being threatened or destroyed. Biodiversity Loss in Canada A country as large as Canada is certain to feature considerable landscape diversity, and indeed Canada has been variously divided into over 400 terrestrial and marine natural regions. According to World Wildlife Fund CanadaÕs Endangered Spaces campaign, only about 5% of these regions are well represented in protected areas, while some 55% have no representation whatsoever (WWF 1995). Given the small human population and the huge land mass in Canada, this amounts to a rather poor conservation record, and it is no surprise that biodiversity is threatened in many regions. Canada features some 1,800 species of vertebrates and about 3,300 plant species (Burnett et al. 1989). Of these, some 244 species are currently listed as endangered, threatened, or vulnerable (Environment Canada, Canadian Wildlife Service 1995). Unfortunately, the areas with highest species diversity also tend to be the areas with the best climate conditions for agriculture and human settlement. Thus, in Canada as in many areas, the principal threat to biodiversity has been the destruction of natural habitat. Causes of habitat loss are many, but in Canada it has been primarily agriculture, forestry, and urbanization that have had the greatest impacts (Biodiversity Science Assessment Team, 1994). Each of these will be discussed briefly below. Agriculture Since the early arrival of Europeans, settlement of North America has involved converting natural ecosystems - particularly forests, prairies and wetlands - to agriculture. In short, complex self-sustaining ecosystems supporting a great diversity of species have been transformed into high yield monocultures requiring substantial inputs of fertilizers and pesticides which themselves have an impact on biodiversity (Mineau and McLaughlin 1994). Agriculture has also resulted in the fragmentation of habitat, especially forests. This major concern of conservation biology will be discussed in Part 2. Forestry Unsustainable forestry practices can also be detrimental to biodiversity conservation goals. While some foresters have argued that clearcuts create edge habitat that increases diversity, species requiring large expanses of forest can be negatively impacted by the fragmentation of remaining forest blocks (Noss and Cooperrider 1994). The common practice of cutting forests before an old growth stage is reached results in a shortage of dead wood in the form of standing snags and fallen logs. Many species depend on these for food, shelter, or nest sites (Hunter 1990). Also, the heavy use of pesticides to control insect infestations may have a negative impact on other species. Finally, artificial replanting with a narrow range of genetic stock from other areas represents a loss of diversity that could have a negative impact on forest fitness (Middleton 1994a). Plantations of a few high yield species also represent a loss of biological diversity (Hammond 1991). Urbanization Urbanization is a process that involves converting landscapes into habitat for high densities of one species - Homo sapiens. This represents a substantial loss of biodiversity. In some regions cities and towns cover a considerable portion of threatened bioregions such as the deciduous forest zone of southern Ontario (Middleton 1994b). While remnants of significant ecosystems remain in some urban areas (where there may be strong public support for protection), natural areas in cities are often built over or replaced by manicured lawns and gardens featuring ornamental species that can be of limited value to wildlife. As human populations grow, the conversion of natural habitat and agricultural land to urban areas is increasing rapidly. Those non-human species that can survive in settled landscapes are those that are most tolerant of disturbance - in many cases exotic species that have been introduced either inadvertently or deliberately during the process of colonization. Fortunately, people have begun to show an interest in modifying urban habitat so that it might benefit other species as well. In summary, changes in the landscape resulting from agriculture, forestry and urbanization have an impact on patterns of biodiversity. Overall, ecosystem diversity and species richness tend to be reduced. Invasive exotics and human-tolerant native species thrive, while those that are sensitive to disturbance disappear. It is the latter that are of greatest concern to those involved in the conservation of biodiversity. b. BIODIVERSITY CONSERVATION What is Conservation Biology? Conservation biology is a relatively new science devoted to the conservation of biological diversity. Conservation biology is of necessity multidisciplinary (Primack 1993, Noss and Cooperrider 1994) in recognition of the need to involve many professional fields if success at so daunting a task is to be assured. These include ecology, biology, genetics, anthropology, philosophy, and economics among others. Conservation biology works in both ex situ and in situ contexts. That is, conservation of biodiversity can in part take place through gene banks and captive breeding of species in zoos, but the goal is best served through protection of natural areas, their component species, and the ecological and evolutionary processes occurring there. This requires a landscape approach, and it is here that the disciplines of conservation biology and landscape ecology come together. Landscape ecology has been defined as Òthe study of the structure, function, and change in a heterogeneous land area composed of interacting systemsÓ (Forman and Godron 1986). A review of some of the basic issues and concerns of these two disciplines in relation to the impacts of humans on biodiversity will be useful to introduce some of the issues that can be addressed through restoration work. Population Viability To help comprehend the impact of landscape manipulation by humans on biodiversity, it is important to introduce the issue of population viability. Obviously, the greater the population of a species, the lower the risk of extinction. As populations decrease the risk increases as a result of several factors. For example, low populations have a greater vulnerability to disease or environmental catastrophes. These can eliminate many individuals and isolate others. The demographic make up of small populations can also have a profound impact on long-term survival. In this case, large mammals that produce only one or two young every few years might be at risk if the population contains low numbers of females of breeding age. Reduction of a population below a certain level may also have negative impacts on species with elaborate social structures and behavioral patterns, possibly preventing breeding (Wilcove 1987). The concept of the minimum viable population (MVP) was introduced in response to the above risks to populations, and emphasizes the role of genetic variability in relation to species survival (Shaffer 1981, Gilpin and Soule 1986). All individuals of each species carry inherited genetic information that will help determine their ability to survive within a changing environment. Much of this information varies from one individual to another. In general, the greater the size of the population of any given species and the space it occupies, the greater will be the overall diversity of information. As populations are reduced, the corresponding lack of genetic diversity may ultimately compromise the ability of the species to survive under local conditions. This reduction in fitness reaches an extreme when populations are reduced to such an extent that inbreeding depression occurs (Primack 1993). From a conservation perspective, larger populations are the best means of maintaining genetic diversity and ensuring the survival of most species. But exactly how big must a population be for the species to survive in a given area and to continue to be viable indefinitely? The answer varies from one species to another, and from plants, to invertebrates, to vertebrates. However, conservation biologists predict that in order to prevent inbreeding depression and to maintain enough genetic variation for the species to survive and evolve, a MVP for vertebrates would be 500 to 1000 individuals or more (Lande 1988). Anything less could result in extinction over the course of several generations. Reduced availability of habitat leads to a decrease in population size. Degrading or eliminating natural areas can therefore have a negative impact on population viability. Habitat Fragmentation The theory of island biogeography (see text box) implies that parks and reserves are not in themselves sufficient to conserve biodiversity. If this is the case then the role of natural areas outside of parks becomes increasingly important. In Canada, large wilderness areas still exist to fill this role in some regions. Unfortunately, the areas that are most biologically diverse tend to be settled first leaving only remnant natural areas. A flight over southwestern Ontario for example, reveals that only small patches remain of the extensive forested areas that existed before European settlers arrived (Pearce 1993). While this is a particularly severe case, the situation is much the same wherever intensive agriculture and urban areas exist. Such fragments of habitat are also subject to the problems associated with island biogeography because of their isolation within the landscape. In fact, habitat fragmentation - and in particular forest fragmentation - has become a major issue in conservation biology. There are other impacts and processes resulting from fragmentation that have serious consequences for biodiversity. One of these is the dispersal capability of organisms within a fragment. Many small vertebrates are reluctant to cross open fields between forest patches because of the threat of predation by birds of prey, coyotes, foxes etc. For instance, a study in eastern Ontario indicated that white-footed mice, chipmunks and most birds preferred to move along fencerows rather than cross open fields (Wegner and Merriam 1979). For a number of reasons dispersal is necessary for the survival of most populations. Trapped in small fragments, a species may suffer from a shortage of food or shelter. Escape from external threats may also be impossible. Finally, finding a suitable breeding partner may not be feasible under such conditions, or inbreeding may occur, ultimately lowering the fitness of the population. Edge Effects Perhaps the most insidious problems related to fragmentation are those referred to as Òedge effects.Ó When an area of continuous forest is dissected by roads, railroads, utility corridors, drainage ditches etc., an unnatural edge is created where one previously did not exist. A forest that becomes completely isolated by surrounding agriculture or urbanization has such edges on all sides. From a mathematical perspective, long, narrow habitat fragments have more of an edge than do compact blocks of habitat with rounded borders. Of all possible shapes, the circle offers the lowest edge to exterior ratio since edge effects can penetrate 100m or more into forest fragments, large blocks are required to maintain core areas with habitat suitable for forest interior species (see Figure 1.2). An isolated patch of forest is subject to a whole series of environmental perturbations. Exposure to high winds is one example. Small patches are highly susceptible to disproportionately high amounts of storm damage such as fallen trees. High winds may also destroy bird nests in the understorey. In smaller fragments continuous penetration of the forest edge by wind can create a drier interior environment. This in turn may change vegetation patterns and discourage some animal species. Generally speaking, the impact zone for any known edge effects within a given habitat is all considered to be Òedge.Ó The issue of edge habitats in relation to biodiversity is somewhat of a paradox. Generally speaking, edges tend to support more species than interior habitats, in part because they combine a variety of physical and biological conditions. This in turn may result in a more elaborate vegetation structure, providing a greater diversity of habitats and promoting interspersion between these (Noss 1994). Thus, a forest edge for example, will have wildlife species of the forest itself, the adjacent landscape, and opportunistic species that are generally associated with edges because they can make use of several habitats. For this reason edge habitat has historically been encouraged in wildlife management (Leopold 1933, Smith 1980). Under natural conditions such as riparian areas in prairie landscapes, or natural openings in forests, edges are both important components of landscape diversity and help to maintain a greater species diversity at a regional scale. The problem arises with respect to how much edge habitat exists in relation to interior habitat. Under natural conditions an unbroken forest is composed primarily of interior habitat, with occasional treefalls or water bodies creating isolated edges. Many species are dependent on the relatively darker, cooler, more humid interior forest conditions. When forest dominated landscapes are converted to agriculture or urban dominated landscapes, remaining fragments may not only be too small to support populations of interior species, the ratio between interior and edge may favor species that prefer the latter. Thus, although diversity of common species remains high because of the amount of edge habitat, populations of uncommon forest interior species may be greatly reduced, resulting in a conservation concern. Another conservation concern is the increase in invasions of habitat fragments by exotic species. Seeds of alien plants may be windborn or transported by mammal and bird species as they move from exterior to interior habitats. While these invasions can temporarily increase the species diversity of a site, in time they may overwhelm the native vegetation to the point where overall species diversity becomes greatly diminished. The White-tailed Deer (Odocoileus virginianus) is not an exotic species, however it too is having a negative impact on biodiversity in many eastern forest fragments. This species thrives in edge habitats because of the abundant browsing material. Unfortunately, deer also take shelter in forest fragments, and browse on interior vegetation species. Ordinarily this would not be a problem. However, where natural predators have been eliminated by humans in settled landscapes, deer populations can become artificially elevated. Heavy browsing not only reduces vegetation diversity, it changes the structure of woodlands, removing much of the understorey that is the habitat of many bird species (Alverson et al. 1988, Miller et al. 1992). One of the most publicized conservation concerns related to habitat fragmentation and edge effects is the issue of disappearing migratory songbirds in eastern North America. Observations at bird monitoring facilities such as the Long Point Bird Observatory on Lake Erie indicate persistent declines in the populations of numerous species over the past few decades. There has been much speculation about the extent and causes of the declines (see Terborgh 1989, Askins et al. 1990 and Towle 1994 for overviews). Factors that have been implicated include pesticide use, air pollution, increased urbanization, tropical deforestation in the wintering grounds, forest fragmentation on the breeding grounds, and general loss of habitat on the migratory route. That birds specific to a variety of habitat types are affected suggests that a combination of factors may be involved in most cases. Nevertheless, fragmentation and the associated edge effects are thought to play a major role in the precipitous declines of forest interior species such as the Wood Thrush (Hylocichla mustelina) and the Ovenbird (Seiurus aurocapillus) which require large blocks of habitat for breeding. Increased rates of predation and parasitism (see text box on Brown-headed Cowbird) are two of the edge effects most associated with songbird decline (Wilcove 1985, Terborgh 1989). Agricultural land surrounding forest fragments has resulted in inflated populations of omnivorous or opportunistic species. These include mammals such as Coyote (Canis latrans), foxes, Raccoon (Procyon lotor), skunks, oppossoms, squirrels, chipmunks, and birds such as American Crow (Corvus brachyrhynchos), and Blue Jay (Cyanocitta cristata). All of these may supplement their diet with eggs or young of songbirds . The decline of neotropical migrant songbird populations is a conservation concern that can act as a flagship to draw our attention to a whole range of environmental problems. Of these, habitat fragmentation in particular has been called Òthe most serious threat to biological diversityÓ and Òthe primary cause of the present extinction crisisÓ (Wilcox and Murphy 1985). Conservation Needs This section has presented the impacts of ecosystem fragmentation on biodiversity within a landscape framework. By now it should be clear that large blocks of habitat and connecting links will be required if we wish to maintain the full complement of biodiversity within CanadaÕs natural regions, and to ensure the long-term functioning and integrity of these. If anthropogenic extinctions may be inevitable under present circumstances, and our parks and reserves may not be entirely adequate for biodiversity conservation, then what are the alternatives? Clearly, a different approach to land use planning will be required - one through which the needs of other species and the goal of ecosystem integrity will be addressed. It is now widely acknowledged by conservation biologists that, in order to maintain biodiversity at the national level, an adequate network of protected areas is necessary. These may then serve as protected core areas within the broader landscape matrix. This is essentially the goal of World Wildlife Fund CanadaÕs Endangered Spaces program. A document developed for WWF by Noss (1995) has provided an excellent overview of how to work towards the goal of preserving ecosystem diversity and integrity through reserve networks (Noss 1995), while another reviews the methodologies involved in choosing representative sites (Iacobelli et al. 1995). However, since we have already concluded that parks and reserves alone will not suffice, the real success of our biodiversity conservation efforts will be measured by our ability to conserve the integrity of ecosystems outside of reserve boundaries. On crown land with substantial natural areas, this will involve incorporating the goal of biodiversity conservation into development planning. The goal is already being pursued at the national and provincial levels in accordance with CanadaÕs National Biodiversity Strategy (Biodiversity Working Group 1995) and the international agreements signed at the Earth Summit at Rio de Janeiro in 1992. The success of this approach will no doubt be based on the availability of adequate funding and a balance between government commitment, corporate compliance, and public scrutiny. On private lands, biodiversity conservation will be a greater challenge, for it is here that the most degraded areas - those converted to agriculture and urban development - may be found. A number of landowner stewardship options are available for private individuals who are concerned about conservation. These include land trusts, conservation easements etc. (see Frombetti and Cox 1990 and Hilts and Reid 1993). However, the focus of these has mainly been restricted to the protection of significant remnant areas, most of which are disconnected. The next step must be to identify potential to expand the size of these areas, as well as (if appropriate) to create linkages between them. This is perhaps where restoration work can achieve its greatest potential for biodiversity conservation, while inherently involving the public in the process. Part 2 - RESTORATION AND BIODIVERSITY CONSERVATION "There can be no purpose more inspiriting than to begin the age of restoration, re-weaving the wondrous diversity of life that still surrounds us." - Edward O. Wilson Some Misconceptions and Dilemmas As might by surmised from the review of conservation biology in the previous section, "helping" biodiversity and attracting wildlife are not necessarily the same. Given that the distinction is seldom considered, this topic is worthy of some clarification before proceeding with a more detailed discussion about the potential effects of restoration work on biodiversity. The idea of planting trees, shrubs or wildflowers to attract wildlife is not a new one. Nevertheless these activities have expanded dramatically along with a growing environmental awareness on the part of the general public. Usually a specific wildlife goal is sought through such projects. For example, one might plant specific trees or shrubs to attract birds, or plant a Òbutterfly gardenÓ of wildflowers. There are now dozens of books on the market promoting planting for wildlife, many of which do not discriminate between using native and non-native species. Goals in attracting wildlife generally reflect personal preferences and prejudices, and the desired species usually are the more charismatic ones. It is unlikely that many would plant to deliberately attract spiders, snakes, skunks, etc. In urban areas there may be practical reasons for choosing what to attract and what to discourage. Raccoons might be undesirable because of their tendency to eat garbage, or worse, their potential as vectors for rabies. Certain wildflowers and other plants such as poison ivy might be considered noxious weeds. There are a number of potential problems with this approach that help to distinguish between attracting wildlife and ÒhelpingÓ biodiversity. Fundamentally, it is important to recognize that the attraction of some wildlife species for their aesthetic qualities may actually have negative impacts on biodiversity. For instance, blue jays are beautiful birds that many would consider welcome. Chipmunks too, are often encouraged. Yet for many it may come as a surprise to learn that these species will not hesitate to supplement their diet with the eggs and young of songbirds. The presence of those songbird species experiencing population declines could therefore be put at risk by this activity. In short, planting based on personal preferences does not automatically benefit biodiversity. There are moral dilemmas involved with the issue of planting for wildlife or biodiversity as well. While not everyone plants to encourage particular species, when a site is manipulated with this goal in mind its status as ÒnaturalÓ comes into question. Can we legitimately say we are attracting nature, or is this in fact a form of gardening? Have we attracted ÒwildÓ life or ÒwilledÓ life? Some serious biological implications of planting habitat need to be considered as well. Attracting desired species of wildlife is a form of management, and it may be argued that managed nature is quite different from wild nature. Given that genetic diversity and natural selection - the evolutionary process - occurs in nature under wild (unmanaged) conditions, such manipulation may ultimately work against biodiversity. This should be a concern even for professional restorationists. In essence there is a potential contradiction in the idea of managing nature for biodiversity (Towle, 1996). How Restoration Can Have an Impact on Biodiversity From the moment a shovel lifts the soil, restoration work has an impact on biodiversity. The planting of vegetation can represent a profound change in the biodiversity of the site, both actual and potential. As should be obvious from the discussion above, this impact can be beneficial, benign or even detrimental. What follows is a detailed review of such impacts on all three levels of biodiversity, while recognizing that considerable overlap exists between these levels. The objective is twofold: 1) to provide a deeper understanding of challenges facing conservation biologists, and 2) to ensure that restoration efforts do indeed have a positive effect on biodiversity. It should be noted that "true" restoration of degraded landscapes would automatically benefit biodiversity. Nevertheless, in this section the term is used in recognition that it is often loosely applied to a variety of rehabilitation approaches. 1) Ecosystem Diversity 1.Basic Issues Although in extreme situations conservation efforts are needed to address the species and genetic levels of biodiversity, a focus on the ecosystem level tends to be the most effective approach. This is because the continued existence of the various system types helps to ensure the presence of component species, and if the areas are large enough, adequate genetic diversity within these. While genetic and species concerns can and should be important for restoration, most often it is ecosystems that are to be enhanced or restored. An understanding of the basic ecology of the system in question is therefore essential in order to make sound decisions about restoration objectives and methodologies. According to Odum (1983) "Any unit (a biosystem) that includes all the organisms that function together (the biotic community) in a given area interacting with the physical environment so that a flow of energy leads to clearly defined biotic structures and cycling of materials between living and nonliving parts is an ecological system or ecosystem." The term "Ecosystem" is often used rather loosely to describe everything from isolated natural features such as ponds or meadows, to entire bioregions or even the biosphere itself. The boundaries of ecosystems are difficult to define because they are always connected to other landscape features, and many species move freely between ecosystem types. Ecosystems are a reflection of prevailing and local climatic conditions and soil types. The plant species characteristic of any given system tend to be those which are best adapted to the local conditions, and which have had the dispersal capacity to colonize. Each bioregion features a characteristic major vegetation type that is composed of a mosaic of different habitats. In forests for example, lowlands and uplands or south-facing versus north-facing slopes all have microclimates that support different tree species. A contiguous forest may also include swamp or meadow habitats. Similarly, prairies contain patches of scrubland or trees around the perimeter and river valleys with riparian habitat. In mountainous areas vegetation zones change according to elevation and the direction of the slope. Such varying patterns of ecosystem diversity across the landscape represent a major contribution to biodiversity. Habitat loss or fragmentation reduces this diversity. In addition, specific ecosystem types such as wetlands have often been targeted for destruction due to human prejudices. These, along with the species that depend on them, may be under-represented at the regional level. Ecosystem supply analysis (a process of ensuring that we maintain sufficient supplies of these ecosystem types and their various successional stages throughout the landscape) could be a useful tool for maintaining ecosystem diversity (Hounsell 1994). 2.Positive Potential of Restoration There are two principle approaches by which the conservation of ecosystem diversity can be addressed through restoration projects. First, under ideal circumstances groups would identify and restore threatened ecosystem types at the regional level. This would involve either the re-establishment of these habitats where they once existed, or construction of them on degraded sites where they could exist. Local environmental organizations, naturalist groups, or government natural resource departments are usually well aware of what ecosystem types are threatened in their area and could help in setting priorities. What makes this approach a challenge is the fact that such systems have usually become threatened in the first place through the actions of private landowners. Forests have been cleared, wetlands have been drained and prairies have been converted to agriculture or urbanization. In short, the availability of sites may be limited. Nevertheless, the crucial role that private property owners can play in biodiversity conservation is now widely recognized (Grumbine 1992, Riley and Mohr 1994) and many significant natural areas have been protected via land trusts and other legal devices (see for example Trombetti and Cox 1990, Hilts and Reid 1993). Sympathetic land owners can also be approached about providing restoration opportunities, especially in areas where large amounts of land have been taken out of production. It may even be possible to convince some land developers to include the preservation or reconstruction of threatened ecosystems such as wetlands as part of their plans. On agricultural lands, windbreaks planted with a diversity of indigenous trees, or planted buffers around streams have the potential to improve productivity and reduce erosion. A second and less direct approach to the conservation of ecosystem diversity through restoration involves simply finding a degraded area within the community (including oneÕs own property) and deciding to improve the site. This can be useful in both rural and urban contexts. While not actually replacing a rare ecosystem type at the regional level, such efforts can conceivably contribute to local ecosystem diversity or, if undertaken carefully, the increased viability of existing natural areas. For example, planting around an existing site can buffer against negative environmental impacts, reduce or soften edge habitat, and expand the size of the overall area. 3.Negative Potential of Restoration At the ecosystem level, the potential hazards associated with restoration may be limited to two main problem areas: 1.the risk of displacing an existing significant ecosystem; and 2.the planting of an inappropriate system for the site in question. The first possibility demonstrates the importance of reviewing existing literature, speaking with persons familiar with the site, or undertaking a baseline biological inventory as part of the restoration process. Unless it is obvious that the site is severely degraded, these should precede any project that might involve disruption within or adjacent to an existing natural area. In short, no action should be considered under such conditions without advice from professional field biologists, unless the restoration is limited to removal of debris or invasive exotic vegetation species. Even unattractive or degraded sites can support threatened or significant species. Planting inappropriate vegetation at a site is perhaps more of an economical hazard than an ecological one. If the species planted are not adapted to existing site conditions their survival will be jeopardized. Given the limited resources available for biodiversity conservation, such wasted efforts must be avoided. In cases of uncertainty it is best to plant naturally occurring pioneer species that may eventually provide enough cover for other species to colonize the site at a later date. With respect to limited available funding it should be recognized that some degraded areas might better be left to regenerate on their own, and may do so quite rapidly. Such areas may already be undergoing ecological succession, or have optimum conditions such as good soils and nearby seed sources. Resources may then be allocated to sites identified as having a higher priority. Professional guidance from an ecologist or forester may help to identify such priorities. 2) Species Diversity 1.Basic Issues Because species diversity and ecosystem diversity are interdependent, some repetition is inevitable in any attempt to discuss them as separate concepts within the context of restoration. For example, the most obvious outward features of ecosystems are the species of which they are composed, in particular the dominant vegetation types. Thus to a great extent the nature of any given ecosystem is based on those species which share the capacity to deal with existing physical and climatic factors and the capability to colonize the area. The issues of succession and vegetation structure demonstrate this close association between ecosystem and species diversity, and for this reason they will be dealt with first in this section. A discussion of other biodiversity conservation issues that deal more directly with the species level will then follow. Ecosystems are dynamic by nature. As they undergo the process of succession their species composition changes. If we take forests as an example, a young, early successional forest will support very different species than will an old growth forest. Yet all are characteristic of that particular forest type (be it temperate rainforest, boreal forest, temperate mixed forest etc.). The forest ecosystem is not merely what stands before our eyes here and now. It is the full range of successional stages and the characteristic species of each of these as expressed through time and space. Each ecosystem then, has an actual and potential species diversity. The implication for restoration work is that if the job is to be done well, the process of succession must be given consideration. The species targeted should be those that are characteristic of a given seral stage. In other words, an attempt to attract as many species associated with that ecosystem as possible would be inappropriate. Rather, one should decide on the level of succession to be addressed by the restoration effort and plant vegetation accordingly. Ultimately, the wildlife species that appear on their own will likely be those most suited for the restored site. In short, the diversity of species should be determined more by local conditions than by human preferences. Determining the ideal level of succession to aim for may be difficult. Our rudimentary knowledge of ecosystem dynamics and the fact that restoration ecology is as yet a young science have so far meant that most projects are carried out on a trial and error basis. Certainly, what works for one ecosystem type may not work for another. Even for the same ecosystem type, local soil and climate conditions may require different approaches. Again, it is safer to commence with early successional plant species. These ÒpioneersÓ are adapted to the rough conditions typical of disturbed areas. If a suitable source exists nearby, late successional species may eventually seed in on their own. When a site is restored, selection pressures are applied to planted vegetation by physical and climatic conditions and natural ecological associations. Although one may plant with a specific goal in mind such as establishing a threatened ecosystem or attracting target species, in the long run the vegetation community that survives on the site - whether or not it is intentional - will determine the degree of success. This is why it is important to take issues of site suitability and succession stage into consideration for the survival of planted vegetation. These must be considered not only to ensure the most efficient use of resources, but to determine the ultimate effectiveness of a project in addressing biodiversity conservation goals. The issue of vegetation structure also demonstrates the close relationship between ecosystem and species diversity. What is referred to can include both vertical and horizontal structure of vegetation within an ecosystem. Vertical structure is most obvious in forests. Here the canopy, understorey and herbaceous ground cover tend to be distinct layers of vegetation. While this in itself is an expression of vegetation diversity, the real importance of vertical structure for biodiversity is in the provision of niches for many species. Birds are an excellent example in this respect. Studies of foraging behaviour have demonstrated resource partitioning through the use of different vegetation layers (MacArthur 1958, Morse 1989). This not only reduces competition, in the long term it may promote speciation. Birds also tend to choose specific vegetation layers for nesting. "Healing is the dominant metaphor in ecological restoration." - Stephen Mills Concern about horizontal structure within the context of restoration is based primarily on vegetation associations. In addition to determining what species are most suited to local conditions, the characteristic associations between these should also be considered. It may be more appropriate to plant stands of some tree species such as cedars, birches, aspens, sumach, etc. Observing and attempting to mimic similar sites in nearby natural areas may help in this respect. Some species may even be allelopathic, making it difficult for others to become established in close proximity to them. Basic concerns that are more or less exclusive to the species level of biodiversity include threatened species and exotic species. The former topic is well documented and too complex to deal with here, although it will be considered below with respect to how restoration may make a contribution. The presence of exotic species represents a serious challenge for restoration ecologists on both philosophical and ecological levels. According to Noss and Cooperrider (1994) exotic (or alien) species are Òspecies that occur in a given place, area, or region as a result of direct or indirect, deliberate or accidental introduction of the species by humans, and for which introduction has permitted the species to cross a natural barrier to dispersal.Ó Exotics include both animal and plant species. They can be divided into two principal categories: those which are invasive, and those which are not. Even non-invasive exotics are scorned by some restorationists, in part perhaps because their mere presence represents a fundamental challenge to the idea of restoration. To such purists, restoration means recreating an ecosystem composed entirely of indigenous species, usually one that presumably existed prior to the arrival of the supreme invasive exotic, the European colonist. Given the difficulty in their removal, others tend to accept the presence of a few exotic plants within a natural area. In some cases non-invasive exotic vegetation may even be used as part of the restoration process for their ability to treat soils, prevent erosion, attract wildlife etc. However, few would consider the deliberate planting of long-lived exotics as a legitimate part of true restoration. Invasive exotics, by contrast, can be a serious hazard to ecosystems and are receiving increased recognition as a serious threat to biodiversity at the global scale. The invasion of wetlands across much of North America by Purple Loosestrife (Lythrum salicaria) and the resulting decrease in diversity of other species is one of the best known examples (White et al. 1993), and there are many, many others. Indeed, some 28% of the vascular plant species now found in Canada are exotic (Middleton and McLaughlin 1994). Exotic animals can also pose serious problems. The European Starling (Sturnus vulgaris) is a well known example. It was introduced to North America in 1890, and quickly spread across the continent. The birdÕs aggressive nature has allowed it to successfully displace native cavity nesting species such as the Red-headed Woodpecker (Melanerpes erythrocephalus) and the Eastern Bluebird (Sialia sialis) (Ehrlich et al. 1992, Terborgh 1989). Feral cats, dogs and livestock such as pigs can also have severe impacts on ecosystems and their component species. Aquatic ecosystems face similar threats. The Great Lakes Basin now contains numerous exotic fish species, including the parasitic Sea Lamprey (Petromyzon marinus), which attacks species of commercial value, and Common Carp (Cyprinus carpio), which can be very disruptive of shoreline vegetation (Ashworth 1986). Invertebrates such as the highly invasive Zebra Mussel (Dreissena polymorhpa) can also cause severe problems (Primack 1993). While the introduction of an alien species represents an immediate increase in species richness, invasive exotics can ultimately lead to a decrease in diversity as they displace native species (Saur 1992). It is likely that invasions of alien species place considerable stress on native ecosystems as they struggle to adjust to the new conditions. In some natural areas, especially those adjacent to the highly disturbed environments where exotics flourish, this stress can be acute. Ultimately, the degree to which the presence of alien species is to be tolerated is a decision for the manager. The tendency of exotic vegetation to invade disturbed areas suggests that returning an ecosystem to health through restoration may itself eliminate much of the problem (Haney 1993, Primack 1993). For example, shade-intolerant invasives may eventually die out as indigenous vegetation matures. 2.Positive Potential of Restoration Restoration can encompass more than merely planting vegetation; it can include action to ensure the survival of existing natural areas and their component species. Removal of exotic species from such habitats, especially those that are invasive, can be as important as restoring a degraded area by planting. Indeed, this alternative should receive more attention from citizen groups interested in restoration. Local naturalist clubs or natural resource departments can be consulted to learn more about exotic species and their management in any given region. Habitat can be restored or managed for the benefit of legally designated threatened plants or animals. In some cases, reintroduction of a rare species to a restored site may also be an option. However, such projects are within the domain of experts only, and should not be attempted by the public unless they involve such expertise and are sanctioned by local authorities. Some species conservation concerns can be at least indirectly addressed by the public through the planting of trees and shrubs. One of these is the problem of declining songbirds discussed in Part 1. Because the behaviour of birds is relatively well known, the food and shelter requirements of these species can be taken into consideration even in the most rudimentary community tree planting projects. The additional effort required to improve the conservation value of sites in this manner is minimal, and the process can have great educational value (Towle 1994). These efforts may be especially valuable in urban areas. Amphibian declines can also be addressed through restoration projects. Wetland breeding areas can be identified and maintained through the management of concerned citizens (Gosselin and Johnson 1995). Where these are severely degraded they may be enhanced, or in cases where they have been completely eliminated, they can be reconstructed (Hough et al. 1995, Kusler and Kentula 1990, Payne 1992). The particular needs of species can be incorporated into the restoration process in other ways as well. For example, bird boxes can provide breeding opportunities for cavity nesting species, including those which have suffered population declines such as the Eastern Bluebird. These are especially useful in early successional habitats where the older growth that may normally provide standing dead trees (snags) is absent. Snags themselves can be imported and erected at the site, or can be created by girdling mature trees (preferably exotic species). Such standing dead wood is also important as roosting habitat, and may attract birds of prey such as hawks. Management techniques can also be used to invite previously maligned creatures to restored sites. Bat boxes, for instance, have become increasingly popular in part because bats can help control insect pests at a site. This may be especially useful around wetlands where the presence of mosquitoes could otherwise reduce public support for a restoration project. Snakes can also be encouraged to a site through the construction of winter denning sites or hibernacula. Such techniques are reviewed by Payne (1992) and Payne and Bryant (1994). Local naturalist groups can be consulted about the degree to which these could be useful for species conservation. 3.Negative Potential of Restoration It was mentioned above that when working with a site that already supports a natural community, as much information as possible should be gathered about the existing species diversity before proceeding with any potentially disruptive restoration activity. Although it may be unlikely in heavily disturbed areas, there is a possibility that activities could harm a threatened species of vegetation or to disrupt the habitat of other significant wildlife. Plantings can have negative impacts on biodiversity at the species level when we use vegetation or encourage animals that can cause problems for native species in nearby natural areas. For instance, planting invasive exotics such as Common Buckthorn or Autumn Olive (Elaeagnus umbellata) (just two among many) to provide fruit for birds could result in the expansion of these shrubs into local forests. Here these aggressive species can reduce indigenous vegetation diversity by shading and their high rate of seed production. Working under the misconception that more species diversity is better, some groups have promoted the deliberate planting of edge habitat to attract as wide a variety of wildlife as possible. From a conservation perspective this trend is disturbing. As discussed in Part 2, the presence of a high species richness at a given site is not necessarily natural or desirable. Furthermore, the landscape in any settled area already contains much more edge habitat than is likely to occur under natural conditions. Therefore, creating more edge is unlikely to contribute to biodiversity conservation goals. Indeed, it may even work against such goals. The issue of edge effects in relation to species diversity has already been discussed in detail. While it is important to distinguish between forest edge and isolated plantings of edge habitat, it remains a concern that certain species associated with edges can be undesirable. Deliberate planting of edge habitat may encourage these species, conceivably increasing the negative impacts on nearby natural areas where they occur. While recognizing that in the case of small-scale community naturalization projects it may be impossible to plant anything but edge, it may nevertheless be irresponsible to deliberately encourage people to do so under the guise of Òhelping biodiversity.Ó A final concern related to restoration and species diversity is the planting of vegetation species outside of their natural range. This can happen when people confuse what is a native species according to political borders with what is indigenous to a bioregion. Because a species is considered native to Canada does not imply that it can or should be grown anywhere in the country. Even within a bioregion, species have restricted ranges. Whether or not a species planted outside of its natural range will survive depends on the genotype of the individual, the local climate and soil conditions, the presence of predators or pathogens etc. If the plant does manage to survive and reproduce, then provided it does not displace other vegetation or wildlife, we have essentially increased local species diversity. Yet we have also altered the nature of the ecosystem. Aside from the obvious moral dilemmas associated with such an action, we should be aware that our limited understanding of the dynamics of these systems means that we may not be capable of predicting the impacts of an introduction, some of which could be negative. It is safer to limit our focus to indigenous species that are known to occur locally. Even then, there are genetic concerns that should be addressed. 3) Genetic Diversity 1.Basic Issues In the past, concerns related to genetic diversity have often been ignored by restorationists - especially those with a focus on public naturalization projects. Yet it is here where some of the greatest potential harm to biodiversity can result from restoration work. Although going into a detailed summary of genetics and conservation is well beyond the scope of this paper, it is nevertheless important to review a few key concepts that anyone interested in undertaking this kind of work should be aware of. It should also be pointed out that the processes of genetic variation in relation to evolution and extinction are complex and poorly understood. Exceptions to the norm are frequent. From a conservation perspective this is all the more reason to proceed with caution. The conservation of species diversity is dependent on the degree of genetic diversity within each species (Woodruff 1989). This variation is the result of mutation and the recombination of genes (Noss 1994). Because genes can result in competitive advantages, genetic diversity at the individual and population levels ultimately determines the ability of the species to survive and adapt to environmental conditions. This measure of fitness is fundamental to the process of natural selection, and ultimately to evolution. In theory then, higher genetic diversity offers more opportunities for survival, and vice versa (Ledig 1986, Cockburn 1991). Under natural conditions a degree of genetic diversity is retained as populations of a species interact over time and space. This is referred to as the gene flow. When viable populations become isolated for long periods, adaptations to local conditions can eventually result in speciation (Primack 1993). This process, known as adaptive radiation, contributes to an overall increase in species diversity. Yet when only small populations are involved, isolation can reduce genetic diversity and eventually species diversity as well. In such cases diminished gene flow and the increased likelihood of inbreeding may lead to a reduction in overall fitness of the population, and the eventual risk of local extinction. Thus are revealed the mechanisms behind the theory of island biogeography and the potential legacy of habitat fragmentation. The mere presence of a species within a fragment then, does not automatically imply its long term survival. Without a minimum viable population (see Part 1) and sufficient resources to support this, extinction may be inevitable unless individuals are recruited from other populations. The situation with plants may be quite different from animals. Here local adaptation may be extremely important. For example, genetic variation in individuals of a species growing in one soil type or under micro-climatic conditions may be quite different from that of another population under different circumstances (Ambrose 1990, Knapp and Rice 1994). This is of concern to the restorationist because the site to be restored may be markedly different in this respect from the site where plant seeds or stock were collected (Millar and Libby 1989). Interestingly, while a higher degree of genetic diversity is often assumed to be advantageous for long-term survival of a population, the dictum that Òmore is not necessarily betterÓ (discussed previously with respect to species diversity) may be true in this case as well. For example, there is evidence that some plants and invertebrates may actually require a certain amount of inbreeding in order to maintain viability within very specific environments (Shields 1993). In such cases outbreeding (the opposite of inbreeding) could be a problem. The idea that inbreeding could actually be desirable challenges an historical trend in evolutionary theory that was based on a bias towards highly mobile vertebrates in population viability studies. As we shall see, it has profound implications for restoration work - particularly with respect to appropriate plant stock. 2.Positive Potential of Restoration The means by which restoration may directly promote the conservation of genetic diversity may be limited. One possibility would be the enhancement or creation of habitat to support a threatened genotype, i.e. a localized population of rare plants or invertebrates. Reintroductions of the genotype to a restored area could increase population size. Projects such as the above should not be attempted by the general public without professional supervision. It may be more appropriate for citizens interested in restoration or naturalization to be aware of the potential dangers of these activities with respect to genetic diversity, and avoid negative impacts wherever possible. Perhaps the most significant role that restoration can play in the conservation of genetic diversity is to ensure that biodiversity goals ar met at the landscape level. This approach would make a major contribution (albiet indirectly) by maintaining or restoring ecosystem integrity and providing the habitat linkages needed to ensure gene flow among populations. 3.Negative Potential of Restoration Based on the above discussion, an evident concern in this context is the possible disruption of significant genotypes by the construction, maintenance or improved access associated with restoration activities. Among other things, such genotypes could include isolated populations of wildflower or grass species that differ substantially from distant populations in genetic make-up. Regard for biodiversity seldom focuses on such fine details unless a species is threatened. Nevertheless, the fact that the loss of such isolated plant populations does contribute to the gradual deterioration of genetic diversity within the species as a whole should cause restorationists to weigh the benefits of their actions carefully. A preliminary biological inventory of the site by qualified experts could eliminate this risk. The greatest concern with restoration and genetic diversity is the possible contamination of local stock through the introduction of foreign genetic material. It may surprise and confuse people to learn that under some conditions even native species should be treated as though they were aliens - especially when we are dealing with plants. Imported seeds and plant stock may be genetically adapted to very different climatic or soil conditions from the site to be restored. Suppose a plant species is already established at or nearby a site to be restored and foreign genetic stock of the same species is introduced through the restoration effort. An opportunity then exists for genetic exchange between the original and introduced populations through crossbreeding to produce hybrid strains. A number of possible outcomes can result depending on the species and local conditions: 1.The exchange of genetic material improves the fitness of both populations, or at least has no negative effect (this would be the best situation). 2.The new genetic material is so different from the local stock that the offspring of crossbred parents turn out to be infertile. Theoretically, this could eventually cause the extinction of both populations if the species is rare or localized. 3.The genetic exchange could result in outbreeding depression. As the new genes spread through the local population they undermine the evolved genetic response to specific local conditions, and thus reduce fitness (see Schonewald-Cox et al. 1983, Ledig, 1986, Cockburn 1991, Padgett and Crow 1994). It may be impossible to predict which of the above outcomes is the most likely. Widespread species or those that have wind born seeds tend to be less susceptible to such negative impacts than those that are localized, or that have limited dispersal ability. These concerns should immediately preclude the use of many mass-produced canned or other seed mixes marketed for wildflower gardens. First, the variety of species in these mixes virtually assures that some of these will not be indigenous to areas where they are being sold. Second, what is indigenous may be genetically adapted to dramatically different climate and soil conditions. In short, use of these seed mixtures can conceivably be detrimental. While the effects of most plantings may well be benign, in order to avoid the risks, an attempt should be made to ensure that material planted is both from local genetic stock and, where appropriate, from a variety of parent plants. Achieving these goals will be difficult, in part because of our limited knowledge with respect to the requirements of individual species. As well, the additional expense this would entail could reduce marketability, even to restorationists. Although it is time consuming and requires a much greater commitment, the best method is to collect seeds or cuttings from the site itself or from nearby areas, and to propagate and plant these. This indicates the importance of preserving local natural areas as potential sources of restoration material (Handel, et al. 1994). Because genetic qualities can even be variable in on site micro-environments such as north versus south facing slopes and different soil conditions, material should ideally be categorized and planted accordingly (Knapp and Rice 1994). Addressing genetic diversity dramatically complicates the work of restorationists, but it is should be done to avoid placing wild plant populations at risk. It is important to at least make an effort to obtain appropriate plant stock. "I know of no restorative of heart, body, and soul more effective against hopelessness than the restoration of the Earth" - Barry Lopez SUMMARY OF POSITIVE AND NEGATIVE POTENTIAL OF RESTORATION FOR BIODIVERSITY POSITIVE POTENTIAL NEGATIVE POTENTIAL ECOSYSTEM DIVERSITY can restore threatened ecosystem types in regional context can improve degraded areas can protect existing natural areas by expansion or provision of buffers without sufficient knowledge, can displace existing significant ecosystems planting of inappropriate vegetation or ecosystem type can lead to poor survival rates and wasted effort SPECIES DIVERSITY can remove invasive exotic species that reduce indigenous diversity can improve or provide habitat for threatened species or species experiencing population declines such as amphibians or migratory birds can meet specific food & shelter needs to attract wildlife species that are poorly represented locally can address habitat fragmentation and associated impacts can introduce exotic species to environment without prior research and inventory restoration could have negative impacts on threatened species that may exist on the site can attract wildlife species that have negative impacts on biodiversity in nearby natural areas. In most cases these would be species attracted to edge habitat plant species introduced outside of their normal range may have unforeseen impacts on local ecosystems GENETIC DIVERSITY with appropriate expertise could enhance or restore habitat to protect rare genotype of plant or small animal at landscape level creation of corridors and expansion of habitat blocks can promote gene flow and help prevent inbreeding without care, can have negative impact on rare local plant genotypes importing plant stock from distant areas can contaminate local populations of the same species. Stock that has been cultivated to suit human aesthetic demands can have similar impacts The Landscape Approach In Part 1 we learned that fragmentation is a major contributing factor to biodiversity loss and that the isolation of populations in small ÒislandsÓ of habitat may inevitably lead to the local extinction of species. It was also noted that the existing system of protected areas is probably inadequate for biodiversity protection. At the same time, conventional approaches to agriculture, forestry and urbanization have dramatically altered the landscape and are compromising ecosystem integrity. In order to ensure biodiversity conservation it will be necessary to make land use practices more sustainable. Also required will be an improved and expanded protected areas network, and where bioregions with high diversity are severely degraded, extensive restoration will be necessary. So far, the majority of public restoration or naturalization initiatives have occurred within urban areas. As will be discussed in Part 3, these efforts can make valuable contributions towards biodiversity conservation goals. However, such work should not be undertaken in isolation, nor should urban restoration be the principal focus of limited resources. Although cities and towns can be viewed as simply the most heavily altered parts of the settled landscape, and they certainly do suffer from problems associated with extreme fragmentation (in addition to other pressures), the higher priority of conservation and restoration in rural areas must be dealt with if we are to succeed. There are three principal means by which fragmentation might be addressed through restoration: 1) enhancement or improvement of fragments; 2) expansion of existing habitat blocks; and 3) creating linkages between fragments. The potential of each of these will now be discussed. Enhancement of Fragments Some existing fragments of potential significance may have been degraded by overuse, livestock grazing, dumping of waste material, the presence of litter, invasions of exotic species, etc. Such sites can be improved with relative ease through habitat management or clean-up programs. Enhancement of a site could include such things as improving reproductive capacity of characteristic vegetation species through seed planting and propagation, providing cover for threatened vertebrates, selective cutting of trees, etc. Priorities will vary both regionally and by habitat type. In all cases, supervision by local authorities is recommended. Expansion of Habitat Blocks It may be possible to reduce some negative edge effects by changing the character of the existing edge (Agee 1995). For example, ÒhardÓ edges where forest abruptly meets agriculture or other forms of development can be ÒsoftenedÓ by encouraging shrubs and secondary growth around the perimeter. This can be done by creating openings through limited cutting of trees around the edge, or by planting a native shrub periphery. A softened edge can help buffer the fragment against wind, invasive exotics and predators. Planting of such habitat or changing land use practices around the outside of fragments can also help by creating a buffer zone that reduces impact on the protected area (Noss and Cooperrider 1994). If large patches of habitat are likely to be more viable than small ones, then expansion of existing areas by allowing natural regeneration or planting appropriate vegetation around the perimeter may be beneficial. This can function like the buffers described above. Exactly what vegetation to plant depends on what already exists on the site and what level of ecological succession might be addressed. In forests, expanding sites of sufficient size can create or increase regionally rare interior habitat, thus benefitting interior-dependent species such as the Wood Thrush, the Ovenbird and others. Given that edge and associated effects may extend for up to 400 metres into a forest, patches under 30 ha are likely to be entirely edge (Morrison et al. 1992). Only patches this size or larger will be good candidates for expansion if creation of interior habitat is the goal. While the amount of energy required and the expense of restoring on this scale may be beyond the capacity of most citizen efforts, this should be seen as a priority if biodiversity conservation is the goal. The Pros and Cons of Corridors Using restoration to connect significant fragments through the development of corridors has been widely advocated and hotly debated in recent years (see for example Noss and Harris 1986, Hudson 1991, Simberloff et al. 1992). Corridors can range in size from simple hedgerows, to river valleys, to huge swaths of habitat connecting existing parks and reserves. Potential benefits of corridors for biodiversity conservation include an increase in habitat diversity at the landscape level and promotion of wildlife population viability through providing dispersal opportunities. The first of these will help insure appropriate species diversity at the regional level, while the latter is crucial to the long-term local survival of non-generalist species that require large home ranges. Additional roles of corridors include erosion control and their potential as windbreaks. Based on these advantages corridors have been widely promoted by many conservation advocates. However, the potential negative impacts of corridors on local biodiversity are serious, and they should be given consideration before proceeding with this form of restoration. These have been summarized by Simberloff and Cox (1987) and Simberloff et al. (1992). They will be briefly discussed below. One potential disadvantage of corridors is the ease with which they may allow the spread of catastrophes such as fire, disease, exotic species and predation. While it may be argued that some diseases and exotics are more likely to spread into fragments because they are isolated, the potential role of corridors in this respect should nevertheless be reviewed within the context of local conditions and concerns. Newly developed corridors might also encourage predators to gain access to new sites. Here they may have a negative impact on sensitive or rare species that had survived in part because they were isolated. A second problem with corridors is their role in increasing the amount of edge habitat within the landscape. For example, long, thin strips of forest can provide habitat for opportunistic species that make use of edges. As discussed in Part 1, these may prey upon or parasitize less common interior habitat specialists nesting close to edges. A possible solution may be to make the corridors themselves large enough to provide substantial amounts of interior habitat (Noss 1994). Although planting so large an area would be difficult, a combination of long-term restoration with natural regeneration might help to address this challenge. Another negative impact of corridors may be their ability to act as population sinks in themselves, or to encourage dispersal to areas that become population sinks. The risk involves attracting populations to deficient corridor or fragment habitat rather than allowing them to remain in fragments where they may have had a better opportunity for survival (Henein and Merriam 1990, Soule and Gilpin 1991). Finally, Simberloff (1992) has argued that development of corridors may be a poor conservation investment when so little empirical evidence is available on the degree to which they may be beneficial. Given the shortage of resources available for conservation, it may be more efficient to protect large blocks of existing habitat that are known to support viable populations, or that are significant for other reasons, rather than to invest in something that involves unnecessary risk. Despite their potential hazards, it is widely accepted that corridor development, in combination with fragment improvement and expansion, will be necessary to avoid the pitfalls of island biogeography. The exact circumstances of a given region and the site context will determine if corridors are indeed appropriate, and if so, what form they should take. Obviously, in order to ensure success, any project that involves restoration for corridor development should incorporate expertise in conservation biology and landscape ecology. Summary Given the paucity of available resources, the identification of opportunities for biodiversity conservation through restoration at the landscape level should not be undertaken haphazardly. Ideally, not merely regional, but bioregional biodiversity strategies should be developed to set priorities for habitat protection and restoration. This would involve long-term partnerships between various levels of government and the public sector, as well as the voluntary cooperation of land owners. Preferably the process would occur under the supervision of conservation biologists and ecologists and would involve the following: First, at the regional landscape level areas of quality fragments that have a high potential for biodiversity conservation and connectivity must be identified. This can be done through gap analysis studies using satellite images, maps, and aerial photographs combined with existing biological records and surveyorÕs notes of the area. The potential for macro-scale corridors that cover large areas and micro-scale that can connect smaller fragments can then be assessed. Second, landowners must be contacted to determine the level of interest they may have in contributing to the conservation effort. Appropriate legal mechanisms such as land trusts can then be pursued. Next, an impact assessment should be undertaken to determine the potential positive or negative effects of a corridor on the biodiversity of the fragments to be connected. This would involve a review of local conservation concerns as well as in-depth biological inventories of the sites by qualified naturalists or field biologists. Involvement of expertise in conservation biology is essential both in the coordination of such an effort, and in the ultimate determination of restoration potential. Once restoration opportunities in rural settings have been identified, public involvement can take many forms. Those who own farms and are sympathetic to the cause may be willing to set aside land for restoration purposes, or to allow natural regeneration to occur in unproductive areas. The potential role of agricultural land and rangelands for wildlife conservation is now receiving considerable attention (Fedorowick 1992, Noss 1994, Payne and Bryant 1994), and with more research there may be many new approaches developed as well. Local naturalist or environmental groups can have a role in coordinating restoration efforts that fit within a regional strategy. Combining the efforts of these groups with other community groups and schools could provide valuable labour and education opportunities. It may also be possible to bus students from urban areas to restoration sites for interpretation and habitat planting projects. Meeting biodiversity conservation goals through restoration at the landscape level will, of necessity, involve many separate projects by concerned individuals and groups. These efforts will be most effective if they are tied into a regional strategy such as that described above. Although the organizational and logistical complexities of the task may seem overwhelming, this is a challenge that must be met if we are to conserve biodiversity and ensure the long-term integrity of our life support systems. Although it has many detractors, the Wildlands Project - which advocates large-scale connectivity and a greatly improved reserve system - has been lauded by many conservation biologists as a shining example of the required approach (Forman et al. 1992). The journal Wild Earth provides a forum for projects across North America that are working to meet these goals. The determination of many individuals and the strong partnerships between groups on such a scale are a positive sign that change is possible. PART 3 - THE URBAN CONTEXT "Rather than analyzing nature for the sake of dominating and controlling it, restorationists are synthesing it for the sake of living symbiotically within the whole." - Carolyn Merchant Most "naturalization" projects occur in urban environments. This recent trend to plant backyard and school ground habitat to attract wildlife indicates that there is a growing awareness of a need for human/nature interaction, but is there potential within an urban environment to go a step further and address biodiversity conservation goals through ecological restoration? Historically, cities and towns have been designed as habitat for one species alone. In short, they have been fundamentally at odds with biodiversity. Natural areas remained in urban environments either because they were unsuitable for development, or because they were retained as recreational zones for humans. While people have deliberately attracted birds for decades, for the most part the presence of wildlife in cities was coincidental. Urban parks and ravines have long been considered an asset, but recently (perhaps as a result of growing environmental awareness), an increased appreciation of Nature among the populace has led to a greater demand for "wild" areas as an important component of western cities. Biodiversity in Urban Areas VanDruff (1979) suggested that most metropolitan areas can be divided into three distinct zones: 1) metropolitan centres, 2) suburbia, and 3) the rural-urban interface. Each of these provides different opportunities for wildlife and supports a distinct pattern of species diversity. In some metropolitan centres vegetation and natural habitat may be so sparse that only a small variety of species is present. Trees may be limited to exotic pollution-tolerant ornamental, or invasive exotics such as Tree of Heaven (Ailanthus altissima). Exotic, human-tolerant species such as House Sparrow (Passer domesticus), European Starling (Sturnus vulgaris) and Rock Dove (Columba livia) may be the only birds capable of breeding here. Beyond these the expression of diversity may be limited to a few scavengers such as Ring-billed Gull (Larus delawarensis) and American Crow (Corvus brachyrhynchos) that enter the city centre from surrounding areas to take advantage of abundant garbage. Mammals may be restricted to exotic pests such as the House Mouse (Mus musculus) or Norway Rat (Rattus norvegicus). Suburban areas provide a mosaic of green spaces such as manicured lawns, and trees or shrubs - mostly exotics - planted as ornamentals. Here the bird diversity is considerably higher. The American Robin (Turdus migratorius) gains easy access to worms on open lawns. Mourning Dove (Zenaida macroura), House Finch (Carpodacus mexicanus), American Goldfinch (Carduelis tristis) and Northern Cardinal (Cardinalis cardinalis) do well in part because of bird feeders, while the Blue Jay (Cyanocitta cristata), crows, grackles and others are opportunistic, and therefore equally adaptable to suburban and rural conditions. Mammals can include opportunistic native species such as Raccoon (Procyon lotor) and skunks, as well as rodents such as Meadow Vole (Microtus pennsylvanicus) and Woodchuck (Marmota monax) which enjoy open areas. Species associated with metropolitan centres and suburban environments are thriving in areas where rising human populations have resulted in the accelerated growth of urban areas. The rural-urban interface can provide a greater diversity of habitats such as farmland, floodplain, and woods. Here the many species associated with each of these live in close proximity to those found more typically in suburban areas. In summary, ecosystem and species diversity tends to increase as the density of human population and settlement decreases. Therefore, although restoration within urban centres and suburban areas is needed as part of a broad landscape continuum, and there are many such efforts underway, ultimately it may be within the rural-urban interface that the best opportunities for biodiversity conservation occur within the urban context (Adams and Dove 1989). Where large metropolitan areas have been thoroughly developed within their existing boundaries, surrounding municipalities will present the best opportunities in this respect. In addition to VanDruff's three general categories, cities frequently contain remnants of the ecosystems that existed before urbanization. These can survive in suburban areas, or even within metropolitan centres amidst high density human settlement. Such fragments can be of importance for erosion control, water retention and aesthetics (Agee 1995). They also provide refuges for wildlife and increase local biodiversity in an otherwise impoverished environment. Other than the occasional forest fragment, meadow, or utility and railway rights-of-way, river valleys or ravines are perhaps the most common example of remnant natural areas in cities. Ravines that have experienced minimal disturbance can support wildlife not normally associated with urban environments, including threatened species. Furthermore, they can form natural linkages or green corridors between urban habitat nodes such as parks, or between city centres and the rural landscape. This allows for migration and dispersal of wildlife populations, increasing the viability of connected fragments (Adams and Dove 1989, Hough 1995). Ravines may also provide crucial habitat for migratory birds that must pass through ever expanding urban areas each Autumn and Spring. Species intolerant of human disturbance, including those experiencing population declines, may be especially dependent on these areas. Improving such habitats through restoration can help ensure the survival of these species. Remnant natural areas may also include threatened ecosystem types. In such cases urban centres can play a crucial role in biodiversity conservation. High Park in Toronto provides an example of the challenges involved under such circumstances. Much of the park is a degraded but significant remnant of Black Oak (Quercus velutina) savanna. This is perhaps CanadaÕs rarest ecosystem, supporting up to 30 percent of OntarioÕs rare plant species (Hoepfner 1994). A number of factors have contributed to the degradation of the High Park site, including human recreation pressures, invasion of exotic vegetation and the deliberate planting of ornamental tree species. Most importantly, the natural disturbance regime that maintains oak savanna systems - in this case periodic fires - has been eliminated (Whitney 1994). Thus, in order to preserve remnants such as High Park, selective removal of ornamental trees and periodic controlled burns will be necessary (Suhanie 1994). Under such circumstances public education becomes a crucial component of the restoration program. Urban Areas and Biodiversity Conservation Urbanization represents a radical and more or less permanent alteration of the environment to suit human needs. Disturbance of this magnitude affects ecosystem diversity by eliminating large areas of natural habitat. Because of the limited dispersal capacity of many species found within remaining habitats, genetic diversity is also reduced. The inevitable local extinctions under these conditions result in the dramatically reduced species richness characteristic of urban natural areas. In addition to the direct loss of habitat there are other factors that have a strong influence on urban biodiversity. These include pesticide use, pollution, nutrient loading, degraded soils, and the presence of invasive exotic species and feral animals such as dogs and cats. The influence of these factors may be so extensive that only limited restoration of a given site may be practical. For example, severely degraded or contaminated soils may prevent the growth of many vegetation species, while pollutants absorbed by existing plants could be passed up the food chain to harm other wildlife. Furthermore, polluted water on the site may be uninhabitable by sensitive species of wildlife. Under ideal circumstances cleaning up such sites would be seen as fundamental to any true restoration project, and to biodiversity enhancement. However, removing contaminants is likely to be too complex and expensive a procedure for the average community restoration program to tackle. In lieu of such measures, a number of options remain. It may be more practical and expedient in the short-term to allow such sites to regenerate naturally (to the degree to which this is possible), so that they provide at least a minimal amount of habitat, while focusing restoration efforts on more promising areas. If there remains a determined local effort to do more, some energy might be devoted to site enhancement by removing invasive species or attempting to diversify the habitat types present. Finally, it may be possible to gradually improve degraded sites through creative use of ecological succession, beginning with pioneer species and combining this with limited clean up programs, use of fertilizers and so on. Obviously this would demand a serious commitment to the site and the involvement of expertise in the fields of waste management and restoration ecology. Invasive exotic plants do particularly well in disturbed areas, hence they have become firmly established in many urban green spaces. These plants can be so pervasive on a site and in the vicinity that their complete removal may be difficult. Ravines in cities provide a good example of the challenges facing restorationists under such conditions. Despite their importance as remnant natural areas and corridors, ravines are often plagued by exotic plants. Here seeds spread in riparian areas through flooding, while uplands are invaded by wind-born seeds and those dispersed by wildlife. Crack Willow (Salix fragilis), Common Buckthorn (Rhamnus cathartica), Siberian Elm (Ulmus pumila), Dog-strangling Vine (Cynanchum medium), Purple Loosestrife (Lythrum salicaria), Garlic Mustard (Alliaria officinalis), Japanese Knotweed (Polygonum cuspidatum), and other aliens now dominate many sites, reducing species diversity and homogenizing ecosystems. Discerning between invasive and non-invasive species is an appropriate first step towards management of exotic vegetation. If the commitment exists to do so, non-invasive species can be removed from small sites with relative ease. Where this becomes impractical it may be of little concern if the plants are having a minimal impact on the restored system. Removal of invasive exotics, by contrast, can involve intensive management in both the short and long terms. Indeed, with some species, managers may find themselves facing a losing battle. Unless positive results are evident, one must question the validity of investing limited resources in ordinary restoration efforts. Nevertheless, this intensive management approach may be justified as a form of restoration in itself in cases where the continued existence of rare species or ecosystems is threatened by the invasive vegetation. Approaches of enhancement, expansion and connection of habitat have been introduced as means to address biodiversity conservation at the landscape level. This strategy can also provide a framework for dealing with many urban biodiversity conservation issues. Isolated populations of threatened species can survive in metropolitan areas, or sometimes these may be threatened by expanding suburbs. Such species are likely to be those with limited capacity or need for movement such as plants, invertebrates or herpetofauna. In some cases ensuring the protection of existing habitat may be sufficient to sustain a population. This can involve designation of core reserve areas within an urban zone, as was the case with the Coachella Valley Fringe-toed Lizard (Ulma inornata) near Los Angeles (Beatly 1994). However, if a species is in a precarious position and it has been determined that extinction will be imminent without intervention, then the enhancement or expansion of habitat becomes a viable option. The needs of uncommon wildlife, including certain species of reptiles and amphibians or birds can also be considered in urban restoration projects. Placement of snags, decaying wood or use of other techniques discussed in Part 2 can enhance habitat for the benefit of these. One of the easiest ways to address a conservation concern through restoration is by creating or enhancing urban habitats to help migratory birds in passage (see text box). As in rural areas, there may be opportunities to not only enhance, but to expand and connect significant urban habitats through restoration (Agee 1995). For example, wooded areas surrounded by open areas or degraded habitat might be expanded to provide more forest interior. As with any forest fragment, rounded edges can help to reduce negative external threats. Providing buffer zones through such enhancement and expansion efforts can be particularly useful in urban situations where recreational overuse can be highly damaging to sensitive areas. Adams (1994) and Adams and Dove (1989) have emphasized the importance of designating core protected areas and developing corridors between these in urban areas. As in rural landscapes, providing linkages between such habitat nodes can contribute to population survival by allowing dispersal opportunities. A visual example of corridors and habitat enhancement opportunities is provided in figure 3.1. The potential dangers involved in corridor development were discussed in detail in Part 2. As always, these should be considered before proceeding with linkages. What is necessary in this context is to draw a distinction between connecting urban nodes with other urban nodes in metropolitan centres and suburban areas, and connecting urban nodes with rural nodes in the rural/urban interface. Because of their proximity to heavily settled landscapes and the degree of disturbance to which they are subjected, the ecology of urban natural areas may be profoundly different from their rural counterparts. For example, wildlife that is intolerant of human activities is likely to be absent, while artificially high populations of opportunistic species such as raccoons, skunks, foxes etc. is characteristic. Also typical is an abundance of roaming domestic dogs and cats as well as the preponderance of exotic plant species. The extent of degradation in these remnant natural areas suggests that with respect to potential negative consequences for biodiversity, connecting urban nodes through corridors may have fewer risks than might be the case in rural landscapes. However, caution should still be taken when considering this option, especially if there is a substantial difference in the degree of degradation at the sites. In this case biological inventories and studies of historical records are recommended. Landscape linkages through corridor development may be most problematic at the urban/rural interface. Theoretically, making such connections could increase the population viability of some urban wildlife by improving dispersal capacity and thus opportunities for genetic exchange. Simultaneously, the increased access to metropolitan areas would probably result in a higher species diversity within the urban setting. Countering these possible benefits are a number of serious negative consequences that could result from creating such linkages. The principal concern in this respect is the issue of biological invasions. We have already noted that urban natural areas frequently contain inflated populations of opportunistic species and tend to have problems with invasive exotic vegetation. Is it wise to allow these greater access to previously isolated and less disturbed sites in the rural landscape? Could this put the integrity of such sites and some sensitive species at risk? Given these risks, it would be irresponsible to freely advocate corridor development without careful consideration of the consequences. Indeed, it is possible that severing existing linkages could be an equally valuable management option under some circumstances. Certainly, impact assessments based on thorough biological inventories should be undertaken before any such linkages are contemplated, with expertise in conservation biology informing the decision-making process. A second negative impact involves movement of wildlife in the opposite direction: from rural habitat into metropolitan areas. The problem referred to is the attraction of undesirable species into settled areas. While under some circumstances this could be a threat to urban biodiversity (such as increased predation on a threatened species), it is more a social issue relating to the human tolerance of wildlife. Ecological restoration is a process of working towards long-term ecosystem integrity. Assuming this would of necessity involve replacing the full complement of species associated with the ecosystem restored, then some of these species are bound to be incompatible with human settlements. Bears, Coyote, or even Beaver (Castor canadensis) (to name but a few examples), are not likely to be welcome in the average neighbourhood. Yet watershed restoration combined with landscape linkages at the rural/urban interface could invite these into metropolitan areas. The question to be asked is: How far are we willing to go with restoration in the urban context? In urban areas then, it may be difficult to achieve true restoration. Perhaps the best opportunities for addressing the needs of biodiversity here may lie in some combination of naturalization and restoration. Enhancing existing habitat and creating new habitat on degraded sites can help to maintain or improve existing species richness in an urban area without directly contributing to a conservation concern. In limited circumstances these activities might be undertaken to benefit uncommon or threatened plant or small animal species found at specific locales in urban areas. Summary and Conclusions As suggested previously, a broad landscape approach will be required to conserve biodiversity where natural habitats have been fragmented by agriculture and urbanization. Given that enhancement or expansion of existing habitats and the development of linkages between them are priority approaches, then obviously opportunities will be greater in rural areas than in urban settings. The extent of degradation in urban natural areas and the potential negative consequences of connecting these with rural habitats further emphasizes the need to channel resources beyond urban centres. In general then, rural landscapes have much greater potential for biodiversity conservation than do urban areas. Ultimately our success or failure in the conservation of biodiversity will be dependent on our ability to concentrate our limited resources on identifying, protecting, enhancing and connecting significant natural areas within the broader landscape matrix. This is not to exclude urban areas or to imply that these are of little value for conservation. For one thing, it is largely urban residents that have an interest in the naturalization alternative. Furthermore, natural habitats in urban areas provide excellent educational opportunities, and education is fundamental to biodiversity conservation (see text box on backyards and schoolyards). As discussed above, restoration can be applied to urban areas to enhance significant habitat, to improve population viability of uncommon species, and to help birds during migration. Cities and towns are prominent features within the landscape. Their impact on surrounding natural areas - for example through the importation of resources and export of waste - is dramatic. Therefore the ÒgreeningÓ of urban areas, through promoting environmentally sound behavior and development as well as restoration, is an essential component of addressing biodiversity and ecosystem integrity. The actual and potential role of urban areas in both the destruction and protection of biodiversity must be addressed. In Part 2 the need for regional biodiversity strategies was emphasized. It is recommended that local strategies be developed by municipalities within the context of regional concerns. These should identify local conservation concerns and significant areas for biodiversity. Restoration opportunities should be based on opportunities to improve, expand, connect or create significant habitats. This would involve the following: 1.identifying local expertise and information sources; 2.biological inventories of natural areas within the metropolitan area; 3.developing maps of priority sites for restoration; 4.determining appropriate vegetation for each site; 5.coordinating municipal and public plantings to address designated priority areas. This approach should be combined with an effort to promote greener forms of development that have a low impact on biodiversity, or better, that enhance or encourage natural diversity and allow for habitat continuity at the landscape level. Ideally such development would be consistent with local and regional biodiversity strategies, and would recognize that habitat protection and restoration is not only necessary to maintain the integrity of our life-support systems, it can be a real asset to the community. PART 4 - RESTORATION FOR BIODIVERSITY: SOME BASIC GUIDELINES If an individual or an organization has taken an interest in restoration or naturalization that goes beyond backyard plantings, and biodiversity is an important concern, what steps should be taken to ensure that work is successful and the results are ecologically sound? The following basic guidelines are designed to answer this question while incorporating the concerns addressed in other parts of this document. General Guidelines No matter what type of restoration is undertaken - be it in school grounds, parks, ravines, or in rural environments - a number of basic steps should be considered before proceeding. 1.Try to involve people with expertise in biology and conservation in your project. Local naturalist groups and provincial or federal government departments may be able to provide some support, or help make connections. 2.Consider options such as removing waste or exotic species to enhance an existing site as a possible alternative to planting a new site. 3.Undertake research into historical site conditions. Can current soil and climate allow restoration of the original ecosystem, or would another type be more appropriate? 4.Choose an existing ecosystem similar to the one to be restored to act as a reference. 5.Plant only locally indigenous vegetation species. 6.Study the on-site microclimate, the soil type and condition, and the types of habitat found nearby. What type of ecosystem will be most appropriate for the site? 7.Consider ecological succession. What stage of succession do you wish to address? The best bet may be to plant pioneer species the first year, and add others in successive years. 8.Select plant species according to what is appropriate for the site more than for personal preferences, or for the sake of maximizing species diversity. It is better to plant only a few suitable species than to risk the survival of many. 9.Attempt to obtain seed from local stock that has grown under conditions similar to the planting site. Always be sure to leave enough for the plant to reproduce. Collect and propagate your own seed, or look for a nursurey that obtains stock from local sources. 10.Draw up a site plan so that you and your partners are clear about your objectives and approach. 11.Design and implement a monitoring program to determine both the survival rate of your planted material and the ultimate impacts of your work on biodiversity. Consultation with an expert can help you choose a method that suits your objectives and capacity. This involves a long-term commitment because it entails returning to the site in consecutive years. 12.Conduct a biological inventory of the site before proceeding to ensure that no significant features will be disrupted and to provide a baseline for future monitoring. The Rural Landscape This is where restoration has the greatest potential to deal with conservation concerns, particularly habitat fragmentation. 1.Identify regional conservation issues that might be addressed and groups that may already be involved in similar work, or that could be potential partners. 2.Protecting existing habitat should be the priority. From here attempt to restore buffers and corridors. 3.Identify priority areas for restoration. These can range from addressing the needs of threatened species, finding habitat blocks that can be enhanced or enlarged, or identifying areas where connecting links may be feasible. 4.Undertake research into conservation mechanisms such as land trusts or alternative agriculture methods that may have potential in your area. 5.Contact land owners that hold key sites to determine potential interest. This is a delicate business that should only be undertaken by individuals who are both knowledgeable and diplomatic. Working with respected community members and innovative farmers may help to garner respect and open doors. 6.Develop a restoration strategy at the local or regional level, depending on your capacities. Include an education and outreach component. 7.Choose demonstration sites and involve the local community, naturalist groups, conservation authorities etc. in the planning and restoration process to the greatest degree possible. Urban Areas As discussed in the main text, urban biodiversity issues can be very different from the rural context, primarily due to the degree of habitat degradation and the different species composition that results. In addition to the general guidelines above, the following are suggested: 1.Decide whether you wish to plant habitat in an isolated school ground or park context, or adjacent to an existing natural area. The former may be of limited direct value for biodiversity conservation, although such projects can be extremely valuable education tools. If the latter option is chosen, more care must be taken, and involvement of appropriate expertise is recommended. 2.There may be opportunities to clean up or remove invasive exotic species from existing natural areas. This form of restoration may be more valuable than planting new habitat, or could complement naturalization projects. 3.Identify local biodiversity conservation issues that might be addressed through restoration such as threatened or uncommon species, rare ecosystem types, fragmentation etc. Contact local naturalist groups for information and advice. 4.Make sure that whatever caused the conservation concern in the first place has been eliminated as an obstacle. There is little point in trying to encourage wildlife that cannot tolerate existing disturbances or that will likely end up as road kills. 5.Identify any opportunities to enhance or expand existing natural areas to reduce edge effects or promote forest interior habitat. Can or should significant nodes be connected by corridors? 6.Based on site conditions and local counterparts, decide what type of habitat is most appropriate for the site. 7.Identify any possible external threats to the site or the wildlife that may be attracted before proceeding. There is little point in trying to attract small animals, for example, if there is a good possibility they will end up as road kills. Are any major developments planned that will affect the integrity of the site? 8.Consider the degree to which human access should be encouraged or discouraged. Will trails compromise the siteÕs conservation capacity? Can buffers be planted to protect core areas? 9.Consider what types of wildlife are likely to be attracted to the site. Are these likely to have a negative impact on sensitive species in nearby natural areas? Are there ways to discourage undesirable species? ABOUT THE AUTHOR Ken Towle has been involved in temperate and tropical biodiversity conservation for the past ten years as both a consultant and educator. He has undertaken numerous biological inventory and habitat evaluation studies and is an active promoter of conservation biology and restoration ecology. For the past four years he has coordinated the Bring Back the Birds program for neotropical migratory bird conservation, now being undertaken by the Association for Biodiversity Conservation in Toronto. He can be reached at: New World Consulting for Biodiversity 10 Deering Crescent North York, ON M2M 2A3 Telephone/Fax: (416) 221-1534 GLOSSARY Allelopathic Plants. Plants which by chemical means change soil qualities to suit their own species while excluding competitors. Biodiversity. A contraction of biological diversity. The variety and variability of life forms as expressed through the sum total of genes ecosystems and species in a given area. Biogeography. The science that studies the distribution of organisms. Bioregion. Variously defined as a particular region based on ecological features such as dominant vegetation types or geographical features such as watersheds. Conservation Biology. The science dealing with the conservation of biodiversity. Corridor. A habitat linkage between natural areas that allows movement of wildlife across the landscape. Dispersal. The movement of organisms from one location to another, for example from their place of origin to new territory. Edge Effects. Negative impacts to habitat fragments resulting from exposure to the surrounding landscape. The habitat edge may be susceptible to wind damage, increased predation and parasitism, invasions of exotic species etc. Edge effects can penetrate up to several hundred metres into a forest fragment. Exotic Species. Usually defined as a plant or animal introduced from other continents, the definition can also include species that are not indigenous to a particular region or ecosystem type. Fragmentation. The process of isolating patches of natural habitat through conversion of the surrounding landscape to human use. Gap Analysis. In conservation, a process of designating priority areas through overlaying a series of maps depicting environmental parameters such as land use, existing protected areas, species ranges, suitable habitat, potential threats, etc. The ÒgapsÓ are significant sites that have yet to receive protection. Gene. The basic unit of heredity as transmitted through chromosomes. Genotype. The genetic structure of an organism. Horizontal Structure. The variety of vegetation associations representing a mosaic of habitat over a given area. Hybridization. Cross-breeding of individuals of different populations or races. Inbreeding. Mating of related individuals. Inbreeding Depression. Reduction of fitness or vigor as a result of inbreeding. Invasive Exotic. A prolific exotic species that can become so well established in natural habitats as to be detrimental to indigenous species. Minimum Viable Population. The minimum number of individuals required to maintain long-term fitness and vigor in a species population within a given area. Monoculture. A plantation of a single species. Outbreeding Depression. Reduction of fitness resulting from cross-breeding between individuals genetically adapted to different environments. Population Sink. A habitat insufficient in size or resources to support a viable population of a species, yet which may attract dispersing individuals. Seral Stage. A given stage in ecological succession. Speciation. The process of forming new species. Succession. The gradual replacement of one ecological community by another, presumably to the point of reaching a characteristic ÒclimaxÓ ecosystem. Vertical Structure. 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