Ann Arbor Times

As the human population grows, more than half of Earth’s land will experience an increasing overlap between humans and animals by 2070, according to a University of Michigan study. The findings, published in Science Advances, suggest that this greater human-wildlife overlap could lead to more conflict between people and animals.

“We found that the overlap between populations of humans and wildlife will increase across about 57% of the global lands, but it will decrease across only about 12% of the global lands. We also found that agricultural and forest areas will experience substantial increases of overlap in the future,” said Deqiang Ma, lead author of the study and a postdoctoral research fellow at the U-M Institute for Global Change Biology in the School for Environment and Sustainability.

The study showed that human population growth rather than climate change is driving this trend. Neil Carter, principal investigator of the study and associate professor of environment and sustainability, noted: “In many places around the world, more people will interact with wildlife in the coming decades and often those wildlife communities will comprise different kinds of animals than the ones that live there now.”

To calculate future human-wildlife overlap, researchers created an index combining estimates of where people are likely to populate land as well as spatial distributions of 22,374 species of terrestrial amphibians, birds, mammals, and reptiles. Their estimates were based on projections of economic development, global society, demographics, and previously published data forecasting species' climatic niches.

“The index we created showed that the majority of global lands will experience increases in human-wildlife overlap," Ma said. "This increasing overlap is the result of the expansion of human population much more so than changes in species distributions caused by climate change."

The researchers found high human-wildlife overlap regions include China and India. Forests in Africa and South America are also areas of concern due to their high biodiversity facing increased pressure. Median species richness is projected to decrease across most forests in these regions.

“There are cases of human-wildlife interactions that are both good and bad," Carter said. "COVID-19 was a result of human contact with wild animals... But you also have species that provide important benefits to people.” For instance, scavengers such as vultures and hyenas play a critical role by cleaning waste from urban areas.

Future conservation strategies must evolve according to researchers. Traditional protected areas may become harder to implement due to increasing human settlement. “Our study suggests that with more areas expected to be shared by people and wildlife, conservation planning will have to get more creative and inclusive,” Carter stated.

Co-authors include Briana Abrahms (University of Washington), Jacob Allgeier (U-M), Tim Newbold (University College London), and Brian Weeks (U-M).