COVID-19 suppression of human mobility releases mountain lions from a landscape of fear
Christopher C. Wilmers, Anna C. Nisi, Nathan Ranc
Abstract
Humans have outsized effects on ecosystems, in part by initiating trophic cascades that impact all levels of the food chain.1Ripple W.J. Estes J.A. Beschta R.L. Wilmers C.C. Ritchie E.G. Hebblewhite M. Berger J. Elmhagen B. Letnic M. Nelson M.P. et al.Status and ecological effects of the world’s largest carnivores.Science. 2014; 343: 1241484Crossref PubMed Scopus (2386) Google Scholar,2Hebblewhite M. White C.A. Nietvelt C.G. McKenzie J.A. Hurd T.E. Fryxell J.M. Bayley S.E. Paquet P.C. Human activity mediates a trophic cascade caused by wolves.Ecology. 2005; 86: 2135-2144Crossref Scopus (357) Google Scholar Theory suggests that disease outbreaks can reverse these impacts by modifying human behavior,3Buck J.C. Ripple W.J. Infectious agents trigger trophic cascades.Trends Ecol. Evol. 2017; 32: 681-694Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar,4Wilmers C.C. Post E. Peterson R.O. Vucetich J.A. Predator disease out-break modulates top-down, bottom-up and climatic effects on herbivore population dynamics.Ecol. Lett. 2006; 9: 383-389Crossref PubMed Scopus (127) Google Scholar but this has not yet been tested. The COVID-19 pandemic provided a natural experiment to test whether a virus could subordinate humans to an intermediate link in the trophic chain, releasing a top carnivore from a landscape of fear. Shelter-in-place orders in the Bay Area of California led to a 50% decline in human mobility, which resulted in a relaxation of mountain lion aversion to urban areas. Rapid changes in human mobility thus appear to act quickly on food web functions, suggesting an important pathway by which emerging infectious diseases will impact not only human health but ecosystems as well.