There are 8.2 billion people on the planet, and that number is only going up. All those extra humans need somewhere to live – and increasingly, it’s wildlife that will pay for it. At least, that’s according to a new study from researchers at the University of Michigan, which has calculated the likely amount of crossover between human and animal habitats in the upcoming decades.
By 2070, the team claims, more than half of Earth’s land will be seeing an increase in human-wildlife overlap – a discovery that has important implications for how wildlife conservation, as well as human settlement planning, will develop in the future.
As human populations spread ever outwards, more and more of us are going to be coming into contact – and potentially conflict – with wildlife.
“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,” said Neil Carter, principal investigator of the study and associate professor of environment and sustainability at the University of Michigan, in a statement. “This means that all sorts of novel interactions, good and bad, between people and wildlife will emerge in the near future.”
The results come from an analysis that took the known spatial distributions of more than 22,000 species of terrestrial animals and birds, and combined them with estimates of likely future human habitats. This latter projection was based on UN data run through a set of five potential scenarios for how the next few decades will play out – whether societies choose to follow sustainable economies, or chase fossil fuels, or engage in regional rivalry, and so on.
Despite the inclusion of these models, however, it’s important to note that climate change is actually not the main driver of the changes found by the study: “this increasing overlap is the result of the expansion of human population,” Deqiang Ma, lead author of the study and a postdoctoral research fellow at the University of Michigan Institute for Global Change Biology in the School for Environment and Sustainability pointed out, “much more so than changes in species distributions caused by climate change.”
So, the overall picture is one of increasing overlap between humans and wildlife – but it’s far from equally distributed. The team found that the areas with particularly high projected overlap tended to be found in places where human populations are already densely packed, such as China or India.
That said, the futures of Africa and South America – two places with low or moderate overlap historically – are also particularly worrying. Africa, for example, is set to see an increase in overlap over ten times as much land as will see a decrease; some of those areas will see a human-wildlife overlap increase of more than 10,000 percent.
Meanwhile, the regions where wildlife species richness – that is, the variety of species in a given area – is set to reduce is, well, just about everywhere, unfortunately, with the tiny exceptions of most of Europe and some of Asia and North America.
“We found that the overlap between populations of humans and wildlife will increase across about 57 percent of the global lands, but it will decrease across only about 12 percent of the global lands,” said Ma. “We also found that agricultural and forest areas will experience substantial increases of overlap in the future.”
Why is this concerning?
Well, for wildlife, the problem is obvious. More humans in their space means more chance for conflict – conflicts that animals usually lose. Even if the two species don’t actually come into contact with each other, the mere presence of humans nearby can be enough to impact local wildlife populations – including those who live in protected areas.
For example, one area of major concern highlighted by the study is forests – “particularly in forests in Africa and South America where we’re seeing a large increase in the overlap in the future,” Carter said.
“The reason that is concerning is because those areas have very high biodiversity,” he explained, “that would experience greater pressure in the future.”
Indeed, one sobering result of the study is the effect on species richness in South America: as human-wildlife overlap increases, mammal richness is projected to decline by a third. Amphibian richness, meanwhile, is set to decline by 45 percent; reptile richness by 40 percent, and bird richness by 37 percent.
In an area already suffering an onslaught by humanity, that’s an outcome that “will likely present unprecedented conservation challenges,” the paper warns.
Humans, meanwhile, have had a very recent reminder of what can happen when we start invading the territories of wild animals: “COVID19 was the result of human contact with wild animals,” Carter pointed out, “and there is concern that new diseases will emerge from greater encounters between people and certain wildlife species.”
And it’s not only increased interaction that may make disease-hopping more likely. For about 25 years now, a hypothesis originally known as the “dilution effect” has been steadily gaining traction among disease ecologists: it’s the idea that reducing the potential for novel zoonotic diseases to spread into humans depends crucially on preserving biodiversity.
“As humans alter the landscape through habitat loss, forest fragments act as islands, and the wildlife hosts and disease-causing microbes that live within them undergo rapid diversification,” explained Sarah Zohdy, an assistant professor in Auburn University’s School of Forestry and Wildlife Sciences and the College of Veterinary Medicine, in 2019 (Zohdy was not involved in the new study).
“Across a fragmented landscape we would then see an increase in diversity of disease-causing microbes,” she said, “increasing the probability that any one of these microbes may spill over into human populations, leading to outbreaks.”
What should be done about it?
With news like this, it can be difficult to see the light at the end of the tunnel. But it is there – so long as we actually go for it.
“There are cases of human-wildlife interactions that are both good and bad, but we anticipate that they’re going to become more pronounced,” Carter said.
It’s true that biodiversity is often impacted by humans encroaching on wild habitats, and that increased overlap may make deadly pandemics more likely – but none of that is a foregone conclusion. For example, Carter pointed out, “you also have species that provide important benefits to people, like reducing the abundances of pests.”
One tactic that may prove beneficial, therefore, is to rethink how humans see nature – and those species that currently live in these areas – entirely. Take species such as hyenas, or vultures, for instance: they “are vilified or persecuted because they are scavengers,” Carter explained – and yet it’s precisely this behavior that makes them so beneficial.
“They provide a lot of disease reduction benefits,” he said. “On one hand, they’re viewed as a threat, but on the other hand, they’re providing free health benefits.”
Overall, however, the advice is clear and immediate: we need to rethink current conservation strategies so that they can cope with future problems.
“With more areas of the world expected to be shared both by people and wildlife, conservation planning will have to get more creative and inclusive,” Carter said. With traditional strategies such as establishing protected areas becoming either harder to implement, or simply proving ineffective, perhaps a more effective strategy may be to engage local communities in the conservation process.
But whatever the outcome, it won’t be easy – if only because we’ve such a short time to get it done. “In some places it’s going to be really hard to do everything at once,” Carter said; “to grow crops and have urban areas and protect these species and their habitats.”
“But if we can start planning now, we have a lot of tools to help us promote sustainable coexistence.”
The study is published in the journal Science Advances.
Source Link: Human-Wildlife Overlap Is Set To Increase, And Saving Biodiversity Will Be An Important Challenge
