Kenya’s national parks serve as oases in an increasingly human-crowded world, but they are not a conservation panacea. As in much of East Africa, a striking two thirds of the country's wildlife resides outside of national parks—and these animals are not welcome visitors for many landowners, who see them as competition for livestock. But in a rare win-win situation for humans and nature, researchers have now shown that livestock and wildlife can benefit from each other's presence. A study published last October in Nature Sustainability found that wildlife can boost bottom lines by providing opportunities for tourism, and livestock improve the quality of grass for all grazing species.

Recent history explains this symbiosis. Animals and savanna grasses evolved together for millennia—but Kenya's wildlife population dropped by about 70 percent between 1977 and 2016, according to a 2016 PLOS ONE study. With fewer animals around to encourage new growth by removing old and dead grass stems, it seems livestock have stepped in to fill that ecological role.

“Think of livestock as the ghosts of wildlife past,” says Felicia Keesing, a community ecologist at Bard College and lead author of the new study. “Without the assist from livestock, wildlife could keep going into a downward spiral.”

Keesing and her colleagues focused on Laikipia, a heavily ranched region home to 10 percent of Kenya's wildlife but no national parks. The researchers looked into common landowner concerns about disease transmission and competition by surveying ticks, grass quality and animal numbers at 23 properties covering 40 percent of Laikipia. Some properties had only livestock or wildlife; others were integrated. To the team members' surprise, they found only benefits in combining moderate numbers of cattle and wildlife. At mixed properties, livestock treated for ticks reduced the overall number of those pathogen-carrying parasites by 75 percent—and grass quality was higher than in livestock- or wildlife-only areas, which tended to be overgrazed or undergrazed, respectively.

“To me, one of the most amazing things about this work is that wildlife conservation and ranching can benefit each other over big spatial scales,” says Jacob Goheen, an animal ecologist at the University of Wyoming, who was not involved in the study.

Keesing notes, though, that drought, poverty and politics can easily overpower such solutions. In 2017 Laikipia suffered a series of violent raids by cattle herders from other parts of drought-stricken Kenya. “People and wildlife in this region have figured out ways to coexist that can work,” Keesing says. “But the ecological, economic and social potential of this kind of management can be stressed by circumstances largely beyond their control.”