Large animals (megafauna) have cascading effects on populations, communities, and ecosystems. The magnitude of these effects is often unknown because native megafauna are missing from most ecosystems.
Now, Kansas State University researchers have documented what practitioners have long known: that reintroducing bison—a formerly dominant megafauna and the national mammal of the United States—restores plant diversity in a tallgrass prairie…doubling it, according to their study.
These plant communities have few nonnative species and were resilient to an extreme drought. Domesticated megafauna (cattle), which have replaced native herbivores in many grasslands, produced less than half of this increase in plant species richness.
The results suggest that many grasslands in the Central Great Plains have substantially lower plant biodiversity than before widespread bison extirpation. Returning or “rewilding” native megafauna could help to restore grassland biodiversity.
The widespread extirpation of megafauna may have destabilized ecosystems and altered biodiversity globally. Most megafauna extinctions occurred before the modern record, leaving it unclear how their loss impacts current biodiversity.
We report the long-term effects of reintroducing plains bison (Bison bison) in a tallgrass prairie versus two land uses that commonly occur in many North American grasslands: 1) no grazing and 2) intensive growing-season grazing by domesticated cattle (Bos taurus).
Compared to ungrazed areas, reintroducing bison increased native plant species richness by 103% at local scales (10 m2) and 86% at the catchment scale.
Gains in richness continued for 29 y and were resilient to the most extreme drought in four decades. These gains are now among the largest recorded increases in species richness due to grazing in grasslands globally.
Grazing by domestic cattle also increased native plant species richness, but by less than half as much as bison. This study indicates that some ecosystems maintain a latent potential for increased native plant species richness following the reintroduction of native herbivores, which was unmatched by domesticated grazers.
Native-grazer gains in richness were resilient to an extreme drought, a pressure likely to become more common under future global environmental change.
Photo via Pixabay.