Loss of land mammals has decimated food webs for 130,000 years

New research shows what land mammal loss has done to food webs over the past 130,000 years.

“While about 6% of land mammals went extinct in that time, we estimate that more than 50% of mammals’ food web links have disappeared,” said ecologist Evan Fricke, the study’s lead author in Science. “And the mammals most likely to decline, both past and present, are key to the complexity of the mammalian food web.”

A food web contains all the connections between predators and their prey in a geographical area. Complex food webs are important for regulating populations so that more species can coexist, supporting biodiversity and stability of ecosystems. But the decline of animals can erode this complexity and undermine the resilience of ecosystems.

While the decline in mammals is a well-documented feature of the biodiversity crisis — with many mammals now extinct or remaining in a small part of their historical geographic range — it hasn’t been clear to what extent those are losing the world’s food webs. have affected.

Above, all mammalian species that today would inhabit Southern California (top), New South Wales, Australia, (center), and central Colombia (bottom), if not for human-related range reductions and extinctions from the late Pleistocene to the present. (Credit: Oscar Sanisidro/U. Alcala)

To understand what was lost through food webs connecting land mammals, Fricke led a team of scientists in using machine learning to determine “who ate who” from 130,000 years ago to today. Fricke conducted the research during a faculty fellowship at Rice University and is currently a research scientist at the Massachusetts Institute of Technology.

Using data from contemporary observations of predator-prey interactions, Fricke and colleagues trained their machine learning algorithm to recognize how species’ traits influenced the likelihood that one species would prey on another. Once trained, the model was able to predict predator-prey interactions between pairs of species not directly observed.

“This approach can tell us who is eating who today with 90% accuracy,” said Rice ecologist Lydia Beaudrot, senior author of the study. “That’s better than previous approaches have been able to do, and it allowed us to model predator-prey interactions for extinct species.”

The research provides an unprecedented global picture of the food web that linked Ice Age mammals, Fricke says, as well as what food webs would look like today if saber-toothed cats, giant ground sloths, marsupial lions and woolly rhinoceroses still roamed alongside survivors. mammals.

“While fossils can tell us where and when certain species lived, this modeling gives us a richer picture of how those species interacted,” Beaudrot says.

By mapping changes in food webs over time, the analysis shows that food webs worldwide are collapsing due to animal decline.

“The modeling showed that the food webs of land mammals are much more affected than would be expected if random species went extinct,” says Fricke. “Instead of resilience under extinction pressure, these results show a slow-motion food web collapse caused by selective loss of species with central food web roles.”

The study also shows that all is not lost. While extinction caused about half of the reported food web decline, the rest resulted from contractions in the geographic range of extant species.

“Restoring those species to their historic ranges offers great potential to reverse this decline,” Fricke says.

He says efforts to restore native predator or prey species, such as the reintroduction of lynx in Colorado, European bison in Romania and fishermen in Washington state, are important for restoring the complexity of the food web.

“When an animal disappears from an ecosystem, its loss reverberates across the web of connections connecting all species in that ecosystem,” Fricke says. “Our work provides new tools to measure what has been lost, what else we have to lose if endangered species become extinct, and the ecological complexity we can restore through species recovery.”

The study’s co-authors are from the University of Sussex, the University of Washington, the University of Alcalá, the University of Albany and the University of Aarhus.

The research was supported by Rice University, the Villum Foundation and the Independent Research Fund Denmark.

Source: Rice University