Wildlife photography is an art. It’s also a lively, and sometimes colorful, tool for conservation.

Automatic cameras hidden throughout forests and prairies lie in wait, ready to document rare animals as they traipse by. With a snap of the shutter, the cameras build up records of which animals are roaming where, and how many there may be, helping scientists to assess entire ecosystems.

While working in Sumatra’s Bukit Barisan region, WCS and the Zoological Society of London have created the Wildlife Picture Index (WPI), a collection of virtual photo albums. Each album may contain thousands of photographs of dozens of species living in a certain area. The researchers then analyze the images to statistically evaluate the diversity and distribution of that region’s wildlife.

This information will be valuable to meeting the needs of the Convention of Biological Diversity, a treaty between 188 countries to slow the rate of biodiversity loss.

“The Wildlife Picture Index will allow conservationists to accurately measure biodiversity in areas that previously have been either too expensive, or logistically prohibitive,” said John Robinson, WCS Executive Vice President for Conservation and Science. “We believe that this new methodology will be able to fill critical gaps in knowledge of wildlife diversity while providing much-needed baseline data to assess success or failure in places where we work.”

Until now, scientists have generally used camera trap information only to track individual species or to survey wildlife in a small area. The WPI, however, offers long-term data on many species that run, charge, strut, and saunter across huge landscapes in wild places throughout the world.

Working in Sumatra’s Bukit Barisan Selatan National Park, the developers of the WPI took secret snapshots of wildlife—tigers, rhinos, and Asian elephants—for 10 years. The information retrieved showed that large, commercially valuable wildlife were disappearing faster than small primates and deer, which are usually only killed for subsistence hunting, or in retaliation for raiding crops.

The 1,377-square-mile park contains the last remaining tracts of protected lowland forest on the Indonesian island. Still, illegal logging, poaching, and agricultural development threaten the park’s wildlife as they do on the rest of Sumatra. After running the statistical analysis on some 5,450 images of 25 mammals (and one ground bird), the WPI suggested a net decline of 36 percent of the park’s biodiversity. The photographs also revealed that the loss of wildlife was outpacing the rate of deforestation.

"The Wildlife Picture Index is an effective tool in monitoring trends in wildlife diversity that previously could only be roughly estimated,” said WCS’s Tim O’Brien. “We expect that the Wildlife Picture Index can be implemented and maintained at a relatively low cost per species monitored and provide important insights into the fate of rainforest and savannah biodiversity."