LAUSR

Food webs influence ecosystem diversity and functioning. Contemporary defaunation has reduced food web complexity, but simplification caused by past defaunation is difficult to reconstruct given the sparse paleorecord of predator-prey interactions. We identified changes to terrestrial mammal food webs globally over the past ~130,000 years using extinct and extant mammal traits, geographic ranges, observed predator-prey interactions, and deep learning models. Food webs underwent steep regional declines in complexity through loss of food web links after the arrival and expansion of human populations. We estimate that defaunation has caused a 53% decline in food web links globally. Although extinctions explain much of this effect, range losses for extant species degraded food webs to a similar extent, highlighting the potential for food web restoration via extant species recovery. Description Depauperate webs In the last 50 years, 60% of animal populations have been pushed to extinction. Although already tragic, such losses also have profound impacts on the ecological integrity of biological systems. Fricke et al. looked across mammalian communities globally over the past 130,000 years and found that more than half of the links, or connections, within these communities have been lost (see the Perspective by O’Gorman). This loss is due to extinction of species but also to a reduction in the ranges of extant species because the total numbers of individuals within a species have also declined. Such losses could have profound impact on the long-term persistence and function of ecosystems. —SNV More than half of terrestrial mammal food web links have disappeared because of extinction and range contractions.