One Wildfire Solution? Letting Herbivores Run Wild

Earth looked spectacularly different 15,000 years ago. Eight-thousand-pound ground sloths nibbled on twigs and bark with the help of intimidatingly long claws. Dense herds of woolly mammoths grazed on the cold, dry grasslands of the mammoth steppe alongside shaggy-haired woolly rhinoceroses. The Pleistocene, the last geologic era before our own, was home to at least 50 species of terrestrial megaherbivores—plant eaters weighing more than 2,000 pounds. Giants roamed the planet, shaping ecosystems far and wide. Then, they vanished. 

Much has been written about the extinction of the megafauna—debates persist if overhunting or climate change were responsible, nicknamed the “overkill” or “overchill” hypotheses—but less attention has been given to the consequences of a loss of such magnitude. 

The disappearance of any species ripples across an ecosystem, up and down the food chain and into the landscape itself. Some conservationists are now seeking to counteract the ecological consequences of extinction. Many have recently looked towards the idea of rewilding: reintroducing species where they once roamed, or, in many cases, using proxies when said species are extinct. One idea, still in its infancy, is that this may be the solution we need in a hotter, more fiery world. 

The loss of ancient herbivores, along with shrinking habitat for living ones, results in a buildup of dead vegetation that adds fuel to the flames of wildfires—in Canada’s boreal forests, across the African savannah, and even on the Arctic tundra. 

While fire is a natural part of any ecosystem, modern climate change, driven primarily by the burning of fossil fuels, increases fire frequency and severity. The National Oceanic and Atmospheric Administration reports that extreme wildfire activity has more than doubled in 20 years. Rewilding proponents believe that reintroducing wild herbivores—both browsers that eat woody material and grazers that eat herbaceous plants and grasses—can help. 

Herbivores reduce the available fuel for fire; create natural fire breaks in the landscape; and support ecosystems in developing into more mature, fire-resilient stages. By grazing, browsing, and dispersing seeds, these animals prevent landscapes from being trapped in the flammable early stages of regrowth, where frequent burns reset the cycle before more fire-resilient plant communities can take hold.

Scientists have seen the effect of grazers play out in the African savannah, where white rhinos engineer landscapes enough to alter fire behavior. A 2007 paper found that the presence of white rhinoceros, modern-day megagrazers, influenced fire regimes by maintaining scattered grass communities. Where white rhinos grazed, fuel load and fuel continuity decreased; where they were removed, fires were larger, more widespread, and less patchy.

This was just one example, but many argue the idea could be scaled. What if one key to containing devastating wildfires is not to control nature, but to return to it?