By 2070, the overlap between humans and wildlife is expected to increase across more than half the planet.

By 2070, more than half of the planet’s land surface will experience increasing overlap between humans and wildlife due to population growth, according to a study published on Wednesday by the University of Michigan (UM) in the United States.

Having two groups occupy the same space could lead to more conflicts between them, and the researchers were trying to understand where overlaps were most likely to occur and which animals were most likely to interact with people in specific areas. This is important information for urban planners and conservationists.

“We found that the overlap between human and wildlife populations would increase on about 57% of global land area and decrease by only about 12%,” with most of the disease occurring in agricultural and forested areas, said Deqiang Ma, the study’s lead author and a U-M postdoctoral researcher cited in the school’s statement.

The study also found that the overlap would be caused by human population growth, which expands habitat, rather than climate change, which forces animals to shift their habitats.

To calculate future overlap, the researchers created an index that combined estimates of where humans might populate the Earth and the spatial distribution of 22,374 species of land amphibians, birds, mammals and reptiles.

The first took into account economic, social and demographic forecasts, while the second took into account previously published data predicting where species would live, given the impacts of climate change on their “habitats.”

And they found that the areas predicted to have high human-wildlife overlap in 2070 are concentrated in regions where population densities are already high, including China and India.

Beyond these places, the situation is also worrying for forests, particularly in Africa and South America, where there is expected to be “significant increases in overlap in the future” and “very high biodiversity” that will be under great pressure, explained Neil Carter, the study’s principal investigator and an associate professor at UM.

According to scientists, average species richness (the diversity of species in a given area) “is expected to decline in most forests of Africa and South America.”

“In South America, mammal richness is expected to decline by 33%, amphibian richness by 45%, reptile richness by 40% and bird richness by 37%.” In Africa, mammal diversity is expected to decline by 21% and bird richness by 26%.

Carter noted that preserving biodiversity in overlapping areas has real benefits.

Regarding the subsequent increase in interactions between humans and wildlife, the study raises concerns about the emergence of new diseases, as has happened with Covid-19, while noting that there are also species whose proximity benefits people, for example by reducing the abundance of pests.

Increasing the areas where humans and animals coexist will require the development of conservation strategies that have been based primarily on the creation of protected areas where human access is restricted, which is “becoming increasingly difficult to implement.”

“Our research shows that as more of the world’s areas are expected to be shared by people and wildlife, conservation planning will need to be more creative and inclusive,” he said.

It is recommended that local communities be involved to generate interest in improving the conservation process, which could “include the creation of habitat corridors to link existing protected areas with potential new areas, or the creation of temporary protected areas during periods of critical wildlife status, such as reintroduction, and other innovations.”

“We’re very concerned about areas where populations of endangered species like tigers may be present,” given how people “interact with these species,” Carter said.

“In some places it will be very difficult to do everything at the same time: have agriculture, urban areas and protect these species and their habitat. But if we can start planning now, we will have many tools to help us promote sustainable coexistence.”

Co-authors of the study, published in the journal Science Advances, are Jacob Allgeier and Brian Weeks of UM, Briana Abrams of the University of Washington and Tim Newbold of University College London.