Penn State University: Agroforests in the tropics provide key conservation landscapes for amphibians

Although tropical forest ecosystems around the world have been modified and fragmented by agroforests planted to produce commodities such as coffee, rubber and areca palm, amphibian communities can survive in those transformed landscapes — if the agroforests are managed to support biodiversity.

That’s the conclusion of a new study led by Penn State wildlife ecologists who surveyed frog populations in the Western Ghats, a mountain range that covers an area of 62,000 square miles parallel to the southwestern coast of India. Although the rainforest there has been extensively interrupted by human-modified land uses and infrastructure, the region is one of the eight “hottest” biodiversity hotspots in the world.

The Western Ghats, which shelters amphibians not found anywhere else in the world, was an ideal place to conduct the research, according to research team member David Miller, associate professor of wildlife population ecology. The region has more than 250 amphibian species, some of which are threatened and many only very recently discovered.

“What happens ecologically in the Western Ghats has international significance,” said Miller, whose research group in the College of Agricultural Sciences has studied the health of frog and salamander populations around the world. “Maintaining a level of rainforest biodiversity sufficient to sustain amphibian populations is important. The production landscapes of agroforests can offer secondary habitats that can support and sustain local biodiversity.”

The research started a decade ago when researchers at the Centre for Wildlife Studies — India, led by Krithi Karanth, Shashank Dalvi and Vishnupriya Sankararaman, now a doctoral student in the Ecosystem Science and Management program at Penn State, searched for amphibians on 106 agroforest tracts across an 11,000-square-mile area. Using a combination of visual and auditory encounter surveys, they detected the presence of 26 unique frog species that occurred in the agroforests over two years.

“Frogs, like birds, make different chirps, peeps and croaks,” she said. “So, species can be identified by sound as well as sight. We had birders among our group, and they helped us get very good at detecting various types of frogs by their calls.”