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22 - Assessing positive and negative ecological effects of corridors
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- By Nick M. Haddad, North Carolina State University, Brian Hudgens, Institute for Wildlife, California, Ellen I. Damschen, University of Wisconsin, Douglas J. Levey, University of Florida, John L. Orrock, University of Wisconsin, Joshua J. Tewksbury, University of Washington, WA, USA, Aimee J. Weldon, Potomac Conservancy, MD, USA
- Edited by Jianguo Liu, Michigan State University, Vanessa Hull, Michigan State University, Anita T. Morzillo, Oregon State University, John A. Wiens
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- Book:
- Sources, Sinks and Sustainability
- Published online:
- 05 July 2011
- Print publication:
- 30 June 2011, pp 475-504
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- Chapter
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Summary
The most popular landscape-level strategy to conserve biodiversity is to link reserves with corridors. Despite much theoretical and empirical support for their benefits in creating or maintaining population sources, corridors may have negative effects and create sinks by altering the dynamics of competitors and natural enemies. In this chapter, we synthesize results from the largest and longest-running experiment to test the effects of corridors, the Savannah River Site Corridor Experiment, and assess their positive and negative ecological effects. In addition to reviewing previously published studies from this experiment, we present new findings about corridor effects on seed mass and number, bird-dispersed seed rain, and bird nest predation and density. Taken together, these empirical studies broadly affirm the positive effects of corridors, particularly on dispersal and diversity. Where there are negative impacts of corridors, the underlying processes are nearly always linked to edge effects, a side-effect of creating corridors. These negative edge effects have the potential to change source patches into sink patches. To further explore the balance of positive and negative corridor effects, we conducted a modeling study, and found that corridors can benefit populations despite edge effects, as long as the edge effects associated with corridors are not too large. Our synthesis serves to highlight areas for future research, particularly on the effects of corridors on population persistence and how corridor characteristics (e.g., width, length) and matrix permeability alter corridor efficacy. As long as efforts are taken to reduce the negative effects of edges, our findings generally support efforts to reconnect landscapes for biodiversity conservation.