Hungry Animals Can Change How Badly a Landscape Burns

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The study also considered other critters, specifically insects, that are raising the risk of fires thanks to their eating habits. When invasive species like bark beetles attack vegetation, the plants produce defensive compounds—like the organic polymer lignin—to make themselves less tasty. But the side effect is that they may also make themselves more flammable. If a pest kills a tree outright, it becomes tinder. But now the extra-flammable tree debris also falls to the ground along with it, creating a bed of yet more burnable material. Still more problematic, a previous study from a separate group of researchers in Minnesota found that when lace bugs attack bur oak, the increased lignin content cuts decomposition rates of leaves by a quarter, meaning that tinder stays on the ground just asking to burn.

That doesn’t mean that all bugs are bad for forests. In fact, insects play a critical role in breaking down the leaf litter to make forests less flammable. The fewer insects, the more that leaf litter is going to pile up. And the prognosis doesn’t look good here: One review published last year, by researchers in Australia and China, estimated that 40 percent of insect species are in decline, and a third are endangered.

Making matters worse, invasive predators are wiping out native species that play their own part in redistributing vegetation—small mammals, for instance, that pull vegetation underground for use in their nests. In Australia, this is a particular problem, as foxes and feral cats hunt native species like the malleefowl. This bird rakes soil and leaves into mounds, where it then deposits its eggs. “So they’re not doing all those things like turning over leaf litter and burying it,” says Foster, which means there is more dry material left on the surface to burn.

When it comes to fire risk, the most problematic actor of all is humans. As a city-building, farming species, we have long set small burns to lower the risk of future big ones and to encourage the growth of new vegetation. We’ve also used it on grasslands to herd prey for easier slaughter. But as our species transitioned away from the hunter-gatherer lifestyle, we started seeing fire as a threat, not a tool.

“Humans have been setting fires in grasslands for thousands of years, and then it kind of went out of style,” says University of California Davis ecologist Truman Young, who wasn’t involved in this new work. “There’s a sense that you don’t burn your resource, right? If grass is what cattle eat, you burn it, you lose it.” The long-term reality, though, is that fire is a natural phenomenon. Smaller, periodic fires mean fewer out-of-control blazes, and the vegetation that does bounce back is more nutritious for grazers, because it’s growing in the nutrient-rich ashes of the previous flora. It’s a sort of hard reboot for the landscape.

In California, where we’ve been obsessively putting out fires for decades, this is now a full-blown crisis, as mountains of dead brush have piled up, turning whole landscapes to tinder. Traditionally, these landscapes would burn regularly and more mildly. Now, supercharged blazes are pretty much leveling ecosystems. Climate change is a major factor, too. Simply put, a warmer, drier world is built to burn catastrophically; we’re now living in what fire historian Steve Pyne is calling the Pyrocene, or the age of flames. Nowhere was this more dramatic than in Australia over the past few months. Those bushfires weren’t just unprecedented—models didn’t even predict they could happen for another 80 years.

In this new age of flames, there’s a lot we can do to support the native fauna that have naturally worked to attenuate wildfires for ages and to make sure that invasive species don’t eat them. “By getting these animals back out into landscapes, we’re potentially reducing the fire risk in some of those systems,” says Foster. Plus, we’d be saving species, which is nice.

Goats may be adorable and all, but they won’t be getting us out of this mess.


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