A large-scale study of human mobility and wildlife movement across the United States suggests that the day-to-day presence of humans – not just how they alter the landscape – is a major ecological force that shapes how animals move through and use their environments, researchers report. Human activity is accelerating global biodiversity loss by transforming climates and rapidly reshaping natural landscapes. Yet beyond these physical alterations of the environment, there is a growing recognition that the direct presence of humans themselves may greatly influence how animals behave, including how they perceive risk, move through their habitats, compete for resources, and interact with other species. Despite this, large-scale comparative research has rarely examined human presence as a distinct and dynamic pressure on wildlife, largely due to the fact that detailed data on where and when people move are difficult to obtain. Most existing studies have focused on local settings or broad proxies of human presence, such as pandemic-related lockdowns, and have concentrated largely on mammals. As a result, relatively little is known about how interacting forms of human activity and presence combine to affect wildlife.
To address this gap, Ruth Oliver and colleagues combined data on numbers of mobile devices and vehicles in each U.S. census block as a measure of human presence, along with detailed measures of human landscape modification, with animal tracking data from more than 4,500 birds and mammals representing 37 species. By centering their study on the years 2019 and 2020 and leveraging the unique, temporary decline of human movement in modified landscapes during the COVID-19 pandemic, Oliver et al. were able to disentangle the direct effects of human activity from the broader impacts of landscape change and evaluate how each factor influenced the amount of space animals used. According to the findings, direct human presence influenced the movement patterns or use of the environment of 65% of species examined. Many mammals reduced the amount of territory they used in response to greater human activity, particularly in less-developed habitats where animals may perceive humans as a threat. On the other hand, some species, like gray wolves, expanded their ranges, likely to better avoid people. Adaptable species such as white-tailed deer appeared more comfortable incorporating human-modified environments into their usable habitats. Birds likewise showed highly variable responses, with some species becoming more spatially constrained and others altering their habitat use depending on the surrounding degree of development. In a related Perspective, Lydia Beaudrot discusses the study and its findings in greater detail.
