“The density of trees is very low here, so much so that some people liken the vegetation to savanna,” says Fay. “But the fact is that human populations over the past thousand years have probably heavily impacted the forest here.”

Large openings punctuate what forests there are, which means Fay expects to find large gatherings of mammals. The polygon holds perhaps 10,000 elephants, 20,000 gorillas, and 3,000 buffalo—the largest groups in the Republic of the Congo.

To the south, where the forests have been gone for perhaps hundreds of years, there are a few hundred elephants and what could be the last population of Bateke lions—probably fewer than ten.