Animals can alter fires in unexpected ways

Animals eating plants might appear to be an obvious way to suppress fires, with the likes of goats, deer and cows already used to reduce wildfire fuel.

Now, Australian research reveals that other animals like birds, termites and even elephants can also double as ecosystem engineers, naturally reducing or enhancing the chances, spread or severity of wildfires.

“Some of the animals we don’t necessarily think of are the insects that, by feeding on leaves, stimulate the production of defensive chemicals in the plants, changing the flammability of their leaves,” says first author Claire Foster from the Australian National University.

“Other kinds of insects likely play a strong role in removing dead leaves from the forest floor and, in some cases, can even provide shelter for other animals from fire.”

Termites in savanna ecosystems, for example, create massive structures with a variety of animals choosing to live in them.

“These ‘nutrient islands’ attract large herbivores that preferentially graze around the termite mounds, making them less likely to burn and creating a safety zone during moderate-severity bushfires,” says Foster.

Some animals can manage fire spread by changing the arrangement of plants or dead plant materials within their habitat.

Similar to how you might rake your yard, malleefowl birds (Leipoa ocellate) gather dead leaves into piles to incubate their eggs, helping to clear the ground of leaf litter. Larger animals, like elephants, can trample down plants to form wide corridors between foliage.

“Gaps in fuel can be really important for fire spread; animal tracks can act like mini roads, creating breaks that can cause extinguishment of the fire front,” says Foster.

However, when it comes to this method of fuel reduction, it’s important to consider which species of plants the animals are eating, and what’s left behind.

“A lot of things that make a plant good to eat are the things that make it hard to burn,” says Foster.

“When you take out all the nutritious, palatable plants, those left over tend to be drier and more flammable.”

This means when grazers aren’t used properly, they can promote the growth of the less tasty, more fire-prone plants.

“It’s very clear that when used strategically, and in the right ecosystems, mammals like goats and cattle can have strong fire-suppressive effects,” says Foster, “but I’ve also seen many examples where they actually do the opposite and increase the risk of severe fires.”

The research is published in the journal Trends in Ecology & Evolution.