Stanford, California - A new study shows the effects of deforestation and climate change are amplified into a one-two punch that pushes particularly vulnerable rainforest species towards extinction, while dry-climate species persist. The findings could help guide decisions about where land can be converted to agriculture while minimizing species losses.

“The current and future climate of a region must be considered when evaluating the impact of habitat conversion,” said lead author Luke Frishkoff, a Stanford biology doctoral student at the time of the research. “By paying attention to current and future regional climate, agricultural landscapes may be modified in practical ways to minimize harm to, and maybe even benefit, wildlife.”

The paper, published in Ecology Letters, warns of the possible beginning of the Homogocene – a new era in which global biodiversity rapidly becomes more homogenous.

Protecting wildlife while feeding a world population predicted to reach 9 billion by 2050 is a defining challenge of our era. At least three-quarters of the world’s land surface is directly affected by humans and the rest is vulnerable to human-caused impacts such as climate change. Current projections forecast that about half of Earth’s plants and animals will go extinct over the next century because of human activities, mostly due to our agricultural methods.

“We focused on the wildlife-rich tropics, because change is expected to be especially dramatic there – with temperature increases of up to 4 degrees Celsius and precipitation declines by as much as 20 percent over the next century,” said co-author Gretchen Daily, the Bing Professor in Environmental Science and a senior fellow at the Stanford Woods Institute for the Environment.

She noted, “People depend on forests and the many animals living in them in a wide array of ways, for pollination of crops like coffee to provision of ample, healthy water supplies.”

The team studied more than 300 bird species across Costa Rica over 12 years, compiling one of the most extensive data sets on biodiversity in the tropics. They found that when rainforests were cleared for agriculture, bird species that require wetter climates tended to die out, while dry-climate birds took their place. This is likely because agricultural areas more closely resemble the scrubland and savannah habitats of many dry-climate birds. Whatever the reason, it seems clear that dry-climate species will be more resilient to future changes in both climate and land use.

“When people cut down trees, there are cascades that impact tropical forest species and de-forested environments,” said co-author Elizabeth Hadly, the Paul S. and Billie Achilles Professor in Environmental Biology and a Stanford Woods Institute senior fellow. “Not only do these cleared landscapes lead to a decrease in humidity, but their air temperatures increase locally too.”

Recognizing the relationship between species land-use and climate requirements lays the groundwork for accommodating human food production while minimizing species extinctions.

For example, future studies may show that drying regions are those best converted to agriculture, because they will support fewer native species already. But alternatively, conserving native habitats might be particularly necessary in drying regions because increasing natural habitat will buffer the effects of climate change.

In previous related studies, the researchers highlighted the need to make agricultural lands more hospitable to wildlife, to vary farming practices to preserve wildlife diversity and to assign monetary value to rainforests’ pest-control benefits for agriculture.

Other co-authors of “Climate Change and Habitat Conversion Favor the Same Species” include Daniel Karp of the University of British Columbia, Vancouver; Jon Flanders of the University of Bristol; Jim Zook of Unión de Ornitólogos de Costa Rica; and Leithen M’Gonigle of Florida State University.