In recent years, governments have begun to connect parks and other large natural areas by conserving wildlife corridors – swaths of semi-natural land intended to allow the free flow of animals between natural areas. The hope is that the connected areas will sustain large, genetically diverse populations and ecological processes, such as pollination and seed dispersal. But there is little science to guide how wildlife corridors are put into practice and to minimize their costs, including costs of restricting human uses of the land. How many and what types of fences, roads, pastures, gardens, and buildings can be permitted in the corridor? How wide do corridors need to be? Do some wildlife species use corridors more readily than others? Most of what we think we know about corridors comes from small experiments on 3-acre patches of habitat connected by 100-ft-wide corridors with no human activities nearby, and using animal presence or movement to measure corridor effectiveness. This study will involve corridors and patches 100 times larger, and in landscapes with various human activities nearby. Furthermore, this project will use genetics instead of animal presence or movement as a better way to measure how well corridors work. By these innovations and by measuring responses of multiple species, this study will help scientists understand corridor effectiveness. It will also help society implement corridors that are effective while minimizing all sorts of costs.

This study will use large corridors and habitat patches that have been stable for 50-200 years, so that genetic patterns reflect the influence of landscape pattern. Each landscape contains a corridor connecting two natural patches and two types of reference conditions, namely two patches lacking a connection that are about the same size and interpatch distance as the connected patches, and an intact natural area containing two sampling locales with similar size and spacing. The study will use 20 independent landscapes to quantify how corridor traits affect gene flow, and will use non-flying mammals as focal species because they are strongly affected by fragmentation. The research team hypothesizes (1) a strong non-linear decline in success (gene flow) with corridor length, reflecting the skewed distribution of dispersal distances within species; (2) success will drop steeply as corridor width falls below a threshold, with the threshold determined by species traits; and (3) species that are bigger, are habitat specialists, or have greater dispersal abilities (relative to brain size or reproductive rate) will benefit more from corridors. Testing these hypotheses will allow generalization to a wide range of mammal species not included in this project. We will use highly flexible Random Forest models to answer the overarching question: What landscape traits (e.g., corridor width, degree of human disturbance) and species traits (mobility, affinity to particular land cover types) are associated with effective corridors?

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Douglas Levey
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University of North Texas
United States
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