University of Michigan Predicts Increased Human-Wildlife Overlap on Half of Earth's Land By 2070

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By 2070, more than half of Earth's land will see an increase in human-wildlife interactions, according to a new study from the University of Michigan. As human populations grow and expand into previously undeveloped areas, the overlap between people and animals will intensify, potentially leading to greater conflict and significant changes in ecosystems.

Published in the journal Science Advances, the study was led by Deqiang Ma of U-M’s Institute for Global Change Biology and School for Environment and Sustainability, in collaboration with researchers from the Cleveland Clinic, University of Washington, and University College London. The research predicts that this overlap will be driven primarily by human population growth, rather than climate change, raising critical questions for urban planners, conservationists, and policymakers.

Increasing Human-Wildlife Overlap: A Global Issue

The study found that 57% of global lands will experience increased overlap between humans and wildlife by 2070, with only 12% of lands projected to see a decrease. The expansion of human populations into agricultural and forested areas is expected to be a major driver of these new interactions.

“We found that the overlap between populations of humans and wildlife will increase across about 57% of the global lands,” said Deqiang Ma, lead author of the study. “Agricultural and forest areas will experience substantial increases of overlap in the future.”

This increased proximity raises the potential for both positive and negative interactions between humans and animals, creating new challenges for global conservation efforts.

Novel Interactions Between Humans and Wildlife

Neil Carter, associate professor of environment and sustainability at U-M and the principal investigator of the study, explained that new interactions between people and wildlife will emerge as human expansion continues.

“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,” Carter said. This could lead to unexpected interactions, both beneficial and harmful, that have not been seen before.

For instance, as people move into new areas, species that have traditionally stayed clear of human settlements may begin to appear. In some cases, these species could provide ecosystem services, such as insect-eating birds that help control pests in agricultural lands. However, in other instances, human-wildlife conflict could increase, resulting in crop damage, property destruction, or even disease transmission, as seen with COVID-19.

Significant Impact in High-Population Regions

The study highlights regions with high human population density, such as China and India, as areas of particularly significant concern. These areas are already experiencing high levels of human-wildlife overlap, and the trend is expected to continue. Forests in Africa and South America, which house some of the planet's most biodiverse ecosystems, are also projected to face increasing pressure as human populations encroach on these habitats.

This overlap could have dire consequences for biodiversity in these regions. The study projects significant declines in species richness—the variety of species in a given area—across forests in Africa and South America. In South America, for example, mammal richness could decline by 33%, while amphibian richness may decrease by 45%.

“These areas have very high biodiversity that would experience greater pressure in the future,” Carter said. The loss of species could disrupt entire ecosystems, leading to unpredictable outcomes for both wildlife and human populations.

The Role of Biodiversity in Human-Wildlife Interactions

While some human-wildlife interactions may result in conflict, others may provide valuable ecosystem services. For example, certain bird species help reduce crop pests in agricultural areas, while scavengers like hyenas and vultures play a crucial role in cleaning waste, which can reduce the prevalence of diseases such as rabies and anthrax.

However, as human expansion continues, the balance between beneficial and harmful interactions may shift. The study highlights the importance of preserving biodiversity to maintain these ecosystem services, which are critical for both human health and environmental sustainability.

Rethinking Conservation Strategies

With human-wildlife overlap expected to rise, traditional conservation strategies that rely on protected areas may no longer be sufficient. As human populations expand into previously untouched regions, conservationists will need to develop new, inclusive strategies to protect both wildlife and human communities.

“There’s also a significant environmental justice argument around the validity of telling communities that may have lived in a certain area for generations that they have to move,” Carter said. Future conservation planning will need to consider the needs of local communities while finding creative solutions to support wildlife.

Potential strategies include establishing habitat corridors to connect protected areas, creating temporary protected areas during critical wildlife periods, and working with local communities to build interest in conservation efforts.

Planning for a Sustainable Future

While the challenges posed by increasing human-wildlife overlap are significant, the researchers believe that careful planning and proactive conservation measures can help mitigate the negative impacts.

“If we can start planning now, we have a lot of tools to help us promote sustainable coexistence,” Carter said. Engaging local communities, protecting critical habitats, and finding ways to balance human development with the needs of wildlife will be key to ensuring a future where both people and animals can thrive.

Co-authors of the study include Briana Abrahms of the University of Washington, Jacob Allgeier and Brian Weeks of the University of Michigan, and Tim Newbold of University College London.