Biodiversity concepts and urban ecosystems
Introduction
In the last decade, biodiversity concerns have been in the forefront of conservation efforts worldwide (Environment Canada, 1994, UNEP, 1995). Biodiversity has been defined in various ways (McNeely et al., 1990, Salwasser, 1990) but the term has generally been used in a very comprehensive manner meaning the variability of life (composition, structure and function). Biodiversity can be represented as an interlocked hierarchy of elements on several levels of biological organization (Noss, 1992). Since the term ‘biodiversity’ transcends all levels of life from genes to communities and all spatial and temporal scales (Noss, 1990, Savard, 1994), it has generated a lot of confusion and misunderstanding (West, 1993, Lautenschlager, 1997). However, when understood and used properly biodiversity concepts can provide a useful framework for conservation efforts (Savard, 1994).
Urban ecosystems have usually been examined in terms of their impact on biodiversity (Middleton, 1994, Wackernagel and Rees, 1996). However, while the impact of a city on adjacent ecosystems can be significant (Douglas, 1983), much can be learned by applying biodiversity concepts to the urban ecosystem itself. Enhancement of biodiversity in urban ecosystems can be quite important as some evidences suggest that personal exposure to natural things in everyday life is a major determinant of sensitivity to environmental issues (Sebba, 1991; Rohde and Kendle, 1994). As the proportion of urban residents increases every year worldwide, the nature of urban ecosystems would become increasingly important in shaping people’s views about natural ecosystems. Also, from an ecological perspective, urban ecosystems are highly dynamic (Gilbert, 1989, Adams, 1994) and can provide useful insights into the management of biodiversity in other ecosystems. They are characterized by a high level of heterogeneity often organized along gradients extending from the surrounding landscape to the town centre (McDonnell and Pickett, 1990, McDonnell et al., 1993).
Biodiversity concerns related to urban ecosystems can be divided into three major groups: (1) those related to the impact of the city itself on adjacent ecosystems; (2) those dealing with how to maximize biodiversity within the urban ecosystem and (3) those related to the management of undesirable species within the ecosystem. While species diversity and abundance are often related to the quality of urban life (Adams, 1994, Middleton, 1994) the overabundance of some species can be at times undesirable (Cooper, 1987, Clergeau et al., 1996).
This paper deals with concerns related to the urban ecosystem itself using birds as a target group. Birds are quite sensitive to changes in habitat structure and composition and are therefore excellent indicators of changes and stresses in the urban ecosystem (Savard and Falls, 1982, Clergeau et al., 1998). We start by reviewing some important concepts related to biodiversity preservation. We then review the importance of local and landscape attributes in influencing the abundance, diversity and distribution of birds in urban ecosystems and finally, we identify approaches and activities than can enhance urban bird diversity.
Section snippets
Hierarchy of scales
Life is structured in a hierarchical fashion starting with cells forming individuals, which regroup into populations, which in turn form species, who end up as communities. Biodiversity concerns can occur at any level of organization. Levels of biological organization often correspond to specific spatial and temporal scales and must be addressed at their appropriate scale. Some concerns may focus on managing a population of geese in an urban park, others on increasing the number of bird species
Importance of local and landscape attributes for bird abundance and biodiversity
Three species have adapted particularly well to urban ecosystems and have colonized them worldwide: the House Sparrow, the European Starling and the Rock Dove. These species dominate the urban avifauna of most cities and are usually quite dominant in the most urbanized part of a city (Table 2). Although often neglected by ornithologists, these species constitute the core of urban avifauna and their role is quite crucial, especially in the more densely populated areas. Species richness tends to
Approaches to enhance urban biodiversity
There is no single best starting point when dealing with biodiversity. Local actions as well as regional actions are equally important on their respective scale. In urban areas home-owners can take various actions on the scale of their lot. It is important to realize that it is the concerted efforts at various scales that produce the best results. It is essential that home-owners realise that their own local action can contribute to a larger collective effort that would culminate in the
Management of people–wildlife conflicts
Urban ecosystems are highly dynamic and in constant evolution. Like in natural ecosystems, wildlife communities fluctuate and evolve. New species invade urban areas (Morneau et al., 1999) and some species explode in abundance creating conflicts with people (Cooper, 1987). These conflicts need to be properly addressed and they pose quite a challenge as they are often caused by inadequate human behavior. Furthermore, since the dynamics of urban ecosystems are still poorly documented, management
Conclusions
Principles used for managing or enhancing biodiversity can be applied to urban ecosystems. Because of the highly dynamic nature of urban ecosystems a small effort in management can have a great effect on bird abundance and diversity. As we have shown, actions are required on several spatial scales simultaneously and local as well as landscape features are important to consider. Although we limited our paper to birds and emphasized species richness, which is only a small component of
Acknowledgements
We would like to thank G. Falardeau for his assistance. This work was supported by the Canadian Wildlife Service and the ‘Centre national de recherche scientifique, Université de Rennes I’.
Jean-Pierre L. Savard is a Research Scientist for the Canadian Wildlife Service (CWS) in Québec. He holds a bachelor’s degree from Université Laval, Québec, an M.Sc. from the University of Toronto, Ontario, and a Ph.D. from the University of British Columbia. He spent 14 years with the CWS in British Columbia, where he studied the distribution and ecology of molting and wintering seaducks (scoters, goldeneyes, Harlequin Duck), the breeding ecology of Barrow’s Goldeneye and the Eared Grebe,
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Jean-Pierre L. Savard is a Research Scientist for the Canadian Wildlife Service (CWS) in Québec. He holds a bachelor’s degree from Université Laval, Québec, an M.Sc. from the University of Toronto, Ontario, and a Ph.D. from the University of British Columbia. He spent 14 years with the CWS in British Columbia, where he studied the distribution and ecology of molting and wintering seaducks (scoters, goldeneyes, Harlequin Duck), the breeding ecology of Barrow’s Goldeneye and the Eared Grebe, old-growth forest birds, and seabirds (Marbled Murrelet). His current research interests in Québec include urban wildlife ecology, impact of forest practices on birds, bird survey techniques, seaduck ecology (breeding, staging, moulting and wintering) and biodiversity concepts. He has adjunct status at several Québec universities where he co-supervises graduate students.
Philippe Clergeau is a wildlife biologist at ‘Institut National de Recherche Agronomique’ in France. He had received his Ph.D. and his ‘Habilitation a Diriger des recherches’ from Rennes University. He teaches wildlife management and biodiversity control in agronomic schools and universities, and he collaborates with a ‘Centre National de la Recherche Scientifique’ team (UMR EcoBio) on landscape ecology. His research activities focus on the pest bird biology and management, and on biological relations between rural and urban areas. He is project leader for several Publications on relations between humans and animals in towns.
Gwenaelle Mennechez has just received her Ph.D. from Rennes University. She has studied behavior and fitness of European starlings in different landscapes (gradient of urbanisation). She has participated in research projects on biodiversity and avifauna in urban areas.