Biology Professor Mark Ritchie is part of an international study of the effects of human activity on Africa’s Serengeti-Mara ecosystem—the largest, most protected on Earth. Drawing on more than 40 years of data, he has observed a 400-percent increase in the human population in some boundary areas and up to a 75-percent drop in larger wildlife species populations, particularly on the Kenyan side. “Keeping people out of an area to protect biodiversity is not enough. We need to address human activities and conservation outside the reserves, as well,” says Ritchie, co-author of an article on the subject in the journal Science (American Association for the Advancement of Science, 2019).