Life on earth is remarkably diverse. Plants, animals, and microorganisms, in response to local and regional environmental conditions have created distinct adaptations that collectively form the interconnected “web of life.” This biological diversity and its associated ecological processes represent the planet's “natural capital” that underpins human activities, providing us with the air we breathe, the water we drink, the food we eat, the materials that clothe and shelter us, countless medical remedies, and the cathartic psychological relief green spaces provide for us. This biological diversity also helps shape our “sense of place.”
There is a growing awareness that the health of the planet's biological diversity will, to a large degree, determine our own destiny. There is also a growing sense of urgency that biodiversity requires substantially more protection than has occurred to date (Millennium Ecosystem Assessment 2005). The Convention on Biological Diversity (1992), adopted by over 150 countries, provided a strategy for addressing the decline in biodiversity around the world. The 2002 World Summit on Sustainable Development identified the centrality of biodiversity and the importance of setting conservation targets. And the IUCN's Countdown 2010 program was established to help monitor progress toward stemming biodiversity loss.
In terms of urban biodiversity the Curitiba Declaration on Cities and Biodiversity (2007) affirmed the importance of biodiversity within cities, signalling the need “to integrate biodiversity concerns into urban planning and development, with a view to improving the lives of urban residents …” Yet, while enhancing biodiversity within cities is a laudable goal, it is a daunting challenge. The scale and pace of urban growth is responsible for the radical transformation of the spatial configuration and ecological processes of local and regional landscapes around the world (Alberti 2005, Dale et al. 2000, McDonnell et al. 1997, Dramstad et al. 1996, McDonnel and Pickett 1990). Natural areas are fragmented. Indigenous fauna are marginalised and extirpated. Hydrologic cycles are irrevocably altered while impervious surfaces increase. Productive soils, centuries in the making, are contaminated, compacted, and/or removed.
One key challenge in addressing urban biodiversity is overcoming the misunderstanding that biodiversity conservation is an optional field of action, despite overwhelming evidence to the contrary. Few local governments have dedicated resources to establishing planning frameworks and implementation strategies to explicitly address biodiversity. This complacency can be attributed, in part, to the complexity and abstraction as to what constitutes biodiversity. Consequently urban planners, elected officials, the development community, and the public continue to focus on land use, zoning, transportation, and infrastructure in isolation of their ecological consequences.
Fortunately in North America some local governments have begun to engage the complexities of biodiversity conservation by developing regionally integrated spatial frameworks based in large part on Landscape Ecology's patch-corridor-matrix principles (Forman 1995). Simultaneously, proactive site planning and design practices at the neighbourhood and site scale are including biodiversity conservation as an essential program objective. Collectively these initiatives begin to illustrate how urban design can conserve and enhance biodiversity across a region.