For millennia, people have transformed landscapes, forcing wildlife to adjust to cities, farms, roads, and other human activity. But new research suggests animals are responding not only to the environments we build, but also to the simple fact that people are physically nearby. Researchers from UC Santa Barbara, the Smithsonian's National Zoo and Conservation Biology Institute, and Yale University combined GPS tracking information from 37 animal species with cellphone location data collected across the United States.
The study, published in Science, found that wildlife responses to humans differ substantially depending on the species and on how heavily a landscape has already been altered. Those differences could help scientists develop more precise strategies for wildlife management and conservation. "Humans have complicated effects on wildlife -- from our physical presence to how we reshape habitats -- but we can't understand our full impact without information on both," said co-lead author Ruth Oliver, an assistant professor in UCSB's Bren School of Environmental Science & Management.
COVID Lockdowns Created a Rare Wildlife Experiment COVID-19 lockdown policies dramatically altered where and how people moved. That unusual shift gave researchers a chance to separate the influence of human presence from the effects of permanent changes to the landscape. The team examined weekly GPS records from 4,581 individual mammals and birds across the continental U.S. during matching periods in 2019 and 2020.
Measuring animal movement was relatively straightforward, but determining exactly where people were present required a more detailed source of information than scientists normally have access to. Public data that precisely tracks human locations and movements is difficult to obtain. Because of this, studies of interactions between people and wildlife often rely on indirect measures such as urban development, agriculture or, during the COVID-19 pandemic, whether an area was subject to lockdown restrictions.
These measures provide clues about human activity, but they do not directly show how people are moving. To overcome that limitation, the researchers used anonymized cellphone geolocation data with neighborhood-level resolution. According to the team, this marks the first time such data have been used to examine how human presence affects animal movement.
"The cell phone data we used was made available to researchers during the pandemic to help reveal the impacts of COVID-19 shutdowns," said co-lead author Scott Yanco, a research ecologist at the Smithsonian's National Zoo. "Typically, private companies hold onto these, which made this a rare opportunity for us to quantify how human presence impacts wildlife, and to demonstrate that there is more to consider than just land modification to create robust conservation plans." Human Presence and Habitat Changes Work Together The researchers examined how human activity affected both the physical area used by each animal and its environmental niche, which describes how an animal uses habitats and resources. For most of the species included in the analysis, the researchers found that human impacts could not be fully understood by looking at landscape modification alone.
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