By Wendy Anders

Researchers at Stanford, through intense observations, mapping and analysis, generated a method of estimating biodiversity based on tree cover. The results can be used by policymakers to help protect biodiversity and endangered species.

Stanford researchers discovered that in agricultural areas of Costa Rica, increased tree cover corresponds with increases in biodiversity. The results of this 10-year study in Coto Brus in southern Costa Rica give conservationists a more precise tool for increasing up biodiversity in a range of tropical agricultural landscapes.

To date, conservationists have focused their efforts largely on creating large nature preserves and parks, but most species live in ecological gray areas, as only 13 percent of the world’s land is located in protected areas, said the study researchers to the National Academy of Sciences.

Scientists have had to measure diversity in non-protected areas through time consuming field surveys.

In the Stanford study, “We’ve created a framework for counting something previously uncountable,” said Chase D. Mendenhall, a postdoctoral research fellow in biology at Stanford and lead researcher on the project. When the Stanford findings were compared to studies throughout Latin America, they were found to be generalizable.

Stanford’s on-the-ground plant and animal observations done during 3-6 month field sessions were plotted on detailed, fine-scale maps from Google Earth aerial photographs. This led to the creation of a quantitative measure of biodiversity across agricultural and urban landscapes.

When the researchers analyzed the results, the importance of tree cover became clear. For four of the six species groups (plants, non-flying mammals, bats and birds), there was a significant increase in the number of species with increasing tree cover visible on Google Earth maps.

At a single point, Mendenhall’s new model predicts biodiversity in the region within a 30- to 70-meter radius, and demonstrates how the number and kind of species change as trees are added to plots of land.

“All the animals agreed: trees are great,” Mendenhall said.

The analysis showed adding a single tree to pasture could boost the species number of bird species from near zero to 80, for example.