How climate change brings wildlife to the yard

As climate change increases the frequency of droughts, UCLA researchers found one overlooked side effect: people report more conflicts with wildlife.

For every inch that annual rainfall decreases, UCLA scientists found a 2%-3% increase in reported clashes with a variety of carnivores during drought years, according to a paper published Nov. 12 in the journal Science Advances. Whether knocking over trash cans, chewing on yard furniture, digging up vegetable gardens, or even hopping into swimming pools, clashes or conflicts with wildlife included a range of property damage or other negative encounters

The scientists reached their findings by poring through seven years of data from the Wildlife Incident Reporting database, run by the California Department of Fish and Wildlife. The results are likely broadly applicable outside of California, said lead author Kendall Calhoun, a UCLA postdoctoral researcher and conservation ecologist also affiliated with UC Davis.

"Climate change will increase human-wildlife interactions, and as droughts and wildfires become more extreme, we have to plan ways to coexist with wildlife," said Calhoun, a member of UCLA's Tingley Lab on ecology and conservation and of UC Davis' Smith Lab. "Animals coming into human spaces are generally framed as wildlife trying to take resources from humans, but it's often because we've taken the resources away from the wild areas."

Wildlife interactions don't increase with all animals during droughts, but four animals stood out in the data. Across all ranges of precipitation, for every 1-inch decrease in annual rainfall, the researchers found that reported conflicts increased:

• 2.1% for mountain lions
• 2.2% for coyotes
• 2.6% for black bears
• 3% for bobcats

Actual attacks on people are exceedingly rare and not included in the database, Calhoun explained. In the study, the researchers analyzed reports to the California Department of Fish and Wildlife highlighting property damage and "nuisances," rather than reports categorized as lower-level "concerns" or "sightings." But what counts as a conflict can vary from person to person, said Calhoun.

"One person might have sympathy for wildlife grazing from their tomato garden, while another person might call it property damage," Calhoun said. "It's unclear whether the number of reports increases only because there are subjectively more conflicts, or also because people perceive wildlife more negatively when their own resources are more stressed. Regardless, it's clear that climate change will mean more conflict between humans and animals if we don't create more climate-resilient landscapes for wildlife."

Previous studies have shown the benefits of creating safe zones and other refuges for wildlife. Calhoun anticipates that the resources in those areas could dissuade animals from venturing into more human-dominated spaces.

"Now that we know how droughts make wildlife interactions worse, why couldn't we make them better?" he said. "Mitigating how much water we take out of natural landscapes could mitigate conflict."

There are few comprehensive databases collecting community-reported wildlife incidents, making the CDFW database used for the study a rare and valuable resource, Calhoun noted, without which his research would not succeed. It's an important example of community-driven science, Calhoun said.

Calhoun's research expertise focuses on mega-fires and how climate-change-driven fire trends influence animal habitats. Animals can often flee the fire itself, but to find food, water and shelter, they have to move into areas protected from the flames - and that often means into human-inhabited areas, Calhoun said.

"I look at ways to improve human-wildlife interactions, and climate change is going to make that path more difficult," Calhoun said. "But if we can make it worse, then we can make it better. People just need to be invested in their local environment to make conservation work."