The Princeton Guide to Ecology

Perhaps the greatest challenge to biodiversity conservation is overcoming the devastating effects of habitat loss. The single best approach to preserve biodiversity is to conserve or restore large habitat areas. Yet, in landscapes dominated by farming, grazing, and development that support increasing human populations, there are limits to the areas that can be conserved. Given limited areas for conservation, can reserves of fixed area be designed to increase their value for biodiversity conservation? Ecological theory suggests that strategies that increase habitat connectivity and reduce negative edge effects will have higher conservation benefits.

connectivity. The degree to which the landscape facilitates movement

corridor. Habitat that connects two or more reserves, usually the same type as found in a reserve but long and thin relative to reserve size

ecological trap. The attraction of animals to habitats where they perform more poorly, even when higherquality habitat is available

edge effects. Changes in population sizes, species richness, or other aspects of the ecology of individuals, populations, or communities at the interface between two habitat types

habitat fragmentation. The spatial isolation of small habitat areas that compounds the effects of habitat loss on populations and biodiversity

matrix. The habitat or land use, often urban, agricultural, or degraded habitat, surrounding native habitats in reserves

The Yellowstone-to-Yukon (Y2Y) Corridor is perhaps the grandest application of ecological theory to the design of nature reserves. When complete, the reserve network would extend 1800 miles northward from Yellowstone National Park in the northwestern United States into the Yukon Territory in Canada (figure 1). It is among the most expensive applications of ecological theory in history. Conservation organizations are actively investing tens of millions of dollars in this region to protect large and connected habitats. If successful, the corridor would conserve large predators such as grizzly bears and wolves and wide-ranging ungulates such as bison and caribou by providing safe passage between the Yellowstone and Yukon regions. Ideally, conserving these large vertebrate species would create a metaphorical umbrella and also cover smaller vertebrates as well as the invertebrates, fungi, and plants that make up the bulk of biodiversity.

Conservation efforts such as Y2Y have to answer the question: Can reserves be designed to enhance biodiversity protection by targeting key parcels of land? To answer this question, there are a number of more basic questions we must address first. The most obvious is: How do we design reserves? Stated simply, reserve designs seek to increase the effective (if not the actual) area of reserves. The answer to this first question leads to others, such as: Which design criteria are most effective? Is reserve design simply a matter of “more is better”? And questions about ecological effectiveness must be evaluated in the context of scarce conservation resources. When one must actually invest tens of millions of dollars, which strategies do we have enough confidence in to spend money on?

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