Bear and Lion Attacks May Become More Common — A New Paper Reveals Why
The research offers a new way to look at human-wildlife conflict under climate change.
High up in the Himalayan mountains of Nepal, a big-horned blue sheep known as a bharal munches on a patch of grass. Not far off in the distance, a snow leopard lies, waiting to pounce on its prey.
Or at least, that’s what would happen under normal conditions. But due to climate change, vegetation is becoming scarce up in the high mountain region, forcing blue sheep to venture into human-inhabited lower elevations and search for their next meal among human crops — with snow leopards hot on their heels. This shift in the blue sheep’s migration leads to both economic losses for farmers dependent on their crops and snow leopard attacks on human livestock, prompting humans to kill the already-threatened animal in retaliation.
This encounter is just one of the many case studies showing how climate change is driving human-wildlife conflict, according to a paper published Monday in the journal Nature Climate Change. The paper analyzes thirty years of scientific literature to create a framework for how climate change drives interactions between humans and wild animals.
“Our study shows that the connection between climate change and human-wildlife conflict is nearly ubiquitous around the globe, and provides strong evidence that climate change is exacerbating these conflicts,” Briana Abrahms, an assistant professor at the University of Washington’s department of biology, tells Inverse. Abrahms served as the lead author on the Nature study.
How Climate Spurs Human-Wildlife Conflict
“Climate-driven human–wildlife conflicts are becoming more visible,” write the researchers.
Climate change conversations tend to focus on the impacts of global warming on humans, but nearly every animal on the planet is impacted, too. The research examines how these dual impacts on humans and wildlife increase conflict between the two groups through specific pathways.
Changing the Distribution of Wildlife
Climate change alters the habitat range of wildlife across a variety of landscapes, bringing them into contact with humans. The researchers found this pattern occurred in 69 percent of the case studies they examined, making it one of the most important pathways.
If climate change threatens animals’ resources — like food, shelter, or mating opportunities — in their current habitat range, they may move into new human-inhabited areas out of necessity. Elephants in both Tanzania and elephants in Kenya have been affected by drought, which brings them into human villages in search of food and water.
“Climate change may open new opportunities for species in previously unsuitable areas,” write the researchers.
Flooding, fire ice melt, and increased snowfall are common climate drivers that affect animal-ranging habitats. Ungulates — hoofed animals like cattle, deer, or horses — in the northern hemisphere are more likely to travel along roads or railroad tracks during years of extreme snowfall, increasing the likelihood of collisions with vehicles. Similarly, forest fires following an El Niño-induced drought drove tigers and elephants out of their normal habitat, killing at least one human.
Affecting Animals’ Seasonal or Daily Activities
Climate-driven changes in wildlife activity appeared in 12 percent of the scientific studies that researchers analyzed. These include activities like migration or hibernation. In North America and Asia, global warming makes black bears’ “active seasons” longer — and their hibernation shorter — making it more likely that they’ll wander into human areas in search of food.
But this climate pattern can also affect aquatic animals. One case study the researchers analyzed found that a heat wave led blue whales to alter their migration habits. The whales spent more time than unusual in areas where ships pass through, increasing the risk of collision.
Transforming Animal Behavior
Climate change altered behavior and led to conflict in nearly half of the scientific case studies. One common behavioral change included animals attacking livestock after their normal food resources were depleted. As drought reduces vegetation — which lions hide in to ambush their natural prey — in Botswana, the desperate animals become more likely to hunt domesticated animals. It’s not just mammals — one case study found brown snakes became more aggressive toward humans as drought reduced their vegetation cover, making them more vulnerable.
Similarly, as sea ice melts in the Arctic due to global warming, polar bears aren’t able to hunt in their usual spots. The starving polar bears descend upon human settlements looking for food, and humans kill them in return. These encounters tripled between 1970 and 2005 in Churchill, Manitoba — the world’s “polar bear capital.”
Shifting Demographic Patterns
In 10 percent of the scientific studies, climate change affected the population of wild animals, increasing human-wildlife encounters.
Some animals, like the barnacle geese in Islay Island, Scotland, have benefited from global warming, which creates more favorable breeding conditions. More geese trample grass, causing economic harm to sheep farmers that depend on the untrampled landscape. Likewise, in Chile, milder winters have boosted the survival and population of guanaco — a wild animal closely related to the llama — leading them into greater competition with livestock herders over limited vegetation for feeding.
Climate change can also have more nuanced impacts on the population demographics of wild animals. It’s a known fact that juvenile — younger — male animals tend to be prone to more conflict. As drought made prey more vulnerable in a South African reserve, juvenile male lions tended to fare better. As the number of young males increase, they are more likely to interact aggressively with humans.
Changing Human Patterns
“The effects of climate change on where people live, work, and recreate can impact the degree to which humans and wildlife interact,” explain the study authors.
In roughly 14 percent of case studies, humans altered their use of the landscape as a result of climate change, potentially in ways that lead to conflict. In South Sudan, livestock herders moved their animals onto riverbanks to access water during dry periods, leading to more crocodile attacks on their herds — an increasing problem as desertification spreads across the world due to rising global temperatures.
Another way climate change alters human patterns is through the timing of their activities. The researchers highlight a case study from the West Coast of the U.S., where a marine heatwave and a resulting algal bloom led to a delayed fishing season. The delayed fishing season coincided with whale migrations, leading to “record numbers of whale entanglement in fishing gear.” More recently, we’ve seen a record number of whales dying off the coast of New Jersey due to ship collisions — and reports suggest climate change-driven migration may be partly to blame.
On the other side of the globe, reduced sea ice has opened up shipping routes and fossil fuel extraction opportunities in the Arctic. Oil and gas exploration in this region is expected to expand by 70 to 80 days by 2080, increasing the exposure of wildlife to ship collisions.
Some humans try to anticipate climate change and adjust their behavior, but that altered behavior can counterintuitively lead to more conflict with wild animals. In India, farmers brought their livestock into their homes during drought— anticipating greater attacks from hungry wild animals — but the lions came into their homes instead and attacked humans they wouldn’t otherwise.
As global warming increases these negative interactions between herders and subsistence farmers and animals, humans are more likely to engage in retaliatory killings — such as the spate of elephant killing that occurred during a 2009 drought in Tanzania, as starvings elephants grazed on human crops.
It’s not just workers’ livelihoods that are at risk, but recreational activities can put tourists in harm’s way too. Higher temperatures lead to more beach visits, leading to bites from white sharks and alligators.
How Can We Reduce Human-Wildlife Conflict?
“It is important to understand the root cause of human-wildlife conflict so that we can work on treating the source and not just the symptoms,” Abrahams says.
If we start recognizing climate as a key driver of conflict across the globe, scientists believe we can begin to proactively come up with solutions — and hopefully reduce these negative encounters going forward.
Some solutions even came up in the case studies the researchers analyzed. Global warming threatens the natural water supply in Central America, so researchers proposed setting out artificial water troughs for tapirs — large herbivores — to help the animals deal with droughts and make it less likely to they’ll compete with livestock for water.
Over on the West Coast of the U.S., humpback whales have switched their diets from krill to anchovies — which live closer to shore — since the latter fare better in warmer waters due to global warming. This change in behavior, along with the crab fishery delaying its opening due to a heatwave, led to a historic number of whales getting tangled in fishing gear in 2015.
To prevent this tragedy from happening again, the state of California developed the Whale Entanglement Risk Assessment and Mitigation Program (RAMP) to proactively assess seasonal risks to whales based on climate change, fisheries, and other factors.
Retaliatory killings of wildlife are also a big problem resulting from climate change-driven conflict. Such killings account for more than half of snow leopard deaths every year, threatening an already near-endangered mammal.
Simple approaches, like educating locals about the climate change impacts on wildlife and compensating them for lost livestock, can reduce retaliatory killings of wild animals and reduce negative encounters overall.
“We hope that this research will help policymakers develop more proactive and climate-ready policies for mitigating human-wildlife conflict,” Abrahms says.