Thread by @ecfricke

What do the diets of ice age mammals tell us about the biodiversity crisis?

Our new research in @ScienceMagazine asks how extinction and range loss have affected land mammal food webs globally over the last 130,000 years 🧵

#ScienceResearch science.org/doi/10.1126/sc…

We show how declines in land mammals have rippled across the web of life by degrading food webs

We chart what we’ve lost, what more we’ll lose if endangered species go extinct, and what potential exists for reversing losses by restoring extant mammals to their historic ranges

Some background: Predator-prey interactions are part of the web of life that sustains the diversity and resilience of our ecosystems. Recent animal declines and food web disruption show the consequences of food webs unravelling

But animal declines aren’t only a new thing...

Cave art in France shows what species occurred there 30,000 years ago

Some species are extinct (cave lions, woolly rhinos), some now only exist elsewhere (hyena), some are still around (red deer)

But direct evidence of the past food webs that linked these species is super rare

Using data on predator-prey interactions and species traits, modeling to estimate where mammals would occur naturally today, and machine learning, we can 1) reconstruct the food web that would occur now at any location and 2) ask how extinction and range change have affected them

What we found:

While about 6% of land mammals have gone extinct over the past 130,000 years, we estimate that more than 50% of food web links have disappeared

And the mammals most likely to decline both in the past and now are key for mammal food web complexity

About half of food web degradation is caused by extinction. But the other half is caused by range contractions of existing mammals

This means that rewilding by restoring extant mammals to their historic ranges could reverse declines in food web complexity to a large extent

We also simulated how food webs would have changed if the same number—but random identity—of species went extinct. It shows that food webs have declined far more than expected by chance

Rather than resilience under extinction, mammal food webs are undergoing slow-motion collapse

So when we talk about the biodiversity crisis, we often think about extinction

But well before extinction, the decline or loss of species from any individual area means the unravelling of that ecosystem’s web of life, threatening its resilience and functioning

Thanks to our stellar research team for making this work possible

@ChiaHsieh33 @OwenMiiddleton @DanGorczynski Caroline Cappello @OSanisidro @jjrowan_paleo @JCSvenning @BeaudrotLydia