Rethinking natural Habitats - a Nature publication


Protecting wildlife while feeding a global population predicted to reach 9 billion by 2050 will require a holistic approach to conservation that considers human-altered landscapes such as farmland, according to an article in Nature co-authored by Gretchen Daily and led by her PhD student Chase Mendenhall at Stanford University.

Wildlife and supporting natural habitats may become an increasingly scarce commodity. Current projections forecast that half Earth’s plants and animals will become extinct over the next century because of human activities, particularly agriculture. However, altering agricultural landscapes could play a vital role in nurturing wildlife populations, while also feeding a growing human population. Gretchen Daily capturing and releasing bats in the forest and farmland of southern Costa Rica.

The Nature article shows that a long-accepted theory for estimating extinction rates, predicting ecological risks and making conservation policy recommendations is overly pessimistic. An alternative framework offers more effective ways of accounting for human-altered landscapes and assessing ecological risks, according to the authors.

Nature is not an island
The study examined the well-established biological ‘equilibrium theory of island biogeography’, whereby landscapes fractured by human development are considered virtually incapable of supporting wildlife, thus driving establishment of nature reserves as the only solution.

To test the "island” theory against a more holistic theory of agricultural or countryside biogeography, populations of bats acutely sensitive to deforestation were studied within a mosaic of forest fragments and farmland in Costa Rica and on lake islands in Panama.

The ”countryside theory” performed well whereas the "island” theory failed to accurately forecast bat responses to forest losses in the Costa Rican countryside. It predicted e.g. that Costa Rican coffee plantations would provide inadequate habitat to sustain a single bat species. In reality, they typically supported 18 bat species, compared with 23-28 in tropical forest fragments and nature reserves, indicating that human-altered landscapes can foster more biological diversity than previously anticipated.

Conservation and food production need to co-exist
The study points to the need for new approaches that integrate conservation and food production, making agricultural land more hospitable to wildlife by reducing chemical inputs, preserving fragments of forest and other natural habitats and rewarding farmers for the resulting benefi ts. ”A theory of countryside biogeography is pivotal to conservation strategy in agricultural ecosystems, which occupy roughly half of the global land surface and are likely to increase in the future”, the researchers conclude.

Citation: Mendenhall, C.D., D.S. Karp, C.F.J. Meyer, E.A. Hadly, and G.C. Daily. 2014. Predicting biodiversity change and averting collapse in agricultural landscapes. Nature 509: 213-217.