The effects of conservation easements on bird biodiversity in the Shenandoah and Piedmont regions of Virginia

Conservation easements—voluntary legal agreements in which a landowner forfeits some development rights in exchange for tax incentives—have become a central part of efforts to limit development in the US. Given the importance of biodiversity conservation on private lands and the rapid growth in conservation easements, they are often celebrated as a win-win scenario. However, there are also increasing questions about the ecological benefits of conservation easements. The kinds of studies necessary to better understand this issue are challenging for several reasons, and there is a special need for more field studies. We draw on a unique cooperative study of bird biodiversity on private lands conducted by Virginia Working Landscapes, a program of the Smithsonian Institution. We compared bird species abundance on private farmland protected by a conservation easement to private farmland not protected by a conservation easement. We estimated a probability of 0.90 that there was a weak positive effect of conservation easements on bird species abundance at the full community level but found no effect on a smaller subset of grassland-obligate birds. However, this relationship varied highly across bird species, with some individual species showing positive or negative associations with easements. We argue that (a) these results support recent calls to promote or mandate specific conservation practices on eased properties; (b) the limitations of publicly available data present significant challenges to assessing the ecological impacts of conservation easements; and (c) given these limitations, researchers should exercise caution when making generalized claims about the effects of conservation easements on biodiversity.