Technology

2023 wildfires: How plants and animals survive


Summer is only halfway over and wildfires in Canada have already burned roughly 12 million hectares of forest (about 30 million acres). That’s an area larger than Ohio and close to double the previous record.

These rampant fires are clearly bad for human communities. They have destroyed homes, forced thousands of people to evacuate, and engulfed cities in Canada and the US in smoke, threatening public health.

But for many plants and animals, from birds to beetles, fire is not such a potent, existential threat. Creatures in Canada and beyond have evolved along with wildfire over many millennia, acquiring clever adaptations to survive. Some species are actually worse off without it.

“Fire is a natural process,” Gavin Jones, a fire ecologist at the US Forest Service, told Vox. “It’s an important and critical piece of the health of our planet.”

In a new review paper, Jones and a handful of other researchers revealed just how much fire has shaped ecosystems and the biology of animals. Some woodpeckers, for example, have evolved to pick grubs only out of freshly burned trees. A tiny mouse-like marsupial, meanwhile, has adapted to shelter in place in a sleeplike state called torpor as flames pass overhead.

The growing challenge for both human and wildlife communities is that forest fires are becoming more extreme: They’re getting bigger and more destructive. Climate change is one driving force, but so are decades of fire suppression. For much of the last century, the US and Canada have focused on putting out fires instead of letting them burn, leading to a build-up of fuel. So when those forests do catch, they produce enormous fires.

Humans are racing to adapt, such as by carrying out prescribed burns to clear out fuel. What about animals? Will their existing adaptations save them? Or can they evolve new ones?

I put these questions to Jones in a recent interview. Our conversation has been edited for length and clarity.

Animals evolved with fire

Benji Jones

Wildfire tears through an environment, often destroying trees and other vegetation. Isn’t that bad for wildlife?

Gavin Jones

Right, it’s like: How can it be good?

The actual burning fire is, of course, dangerous. That can scorch and burn and kill individual animals. A recent paper showed that the 2020 fires in Brazil’s Pantanal killed 17 million vertebrates. So mass mortality can happen.

But fire is also the major agent of change in terrestrial landscapes. It creates a whole variety of niches for animals to occupy.

A coati is rescued after suffering from dehydration and burns during the 2020 fires that scorched Brazil’s Pantanal.
Lucas Ninno/Getty Images

Benji Jones

How so?

Gavin Jones

In an introductory ecology textbook, you’ll often see a successional chart [showing how a biological community evolves]. Right after a disturbance, you have a bare landscape. Then you have early colonizers — some weeds, some wind-dispersed species of plants. Then animals that eat those plants arrive. Later you get some shrubs and small trees, and more wildlife that specializes on those. And through time, without any disturbance, the landscape will reach a late successional state; it’ll have big old trees, and even some old tree death and decay.

A classic chart showing ecological succession. Wildfire can start this process over.
Rudzhan Nagiev/Getty Images

Fire is basically the reset. It creates a patchwork of different successional stages, of different kinds of habitats across the landscape. Fire basically produces the template for biodiversity.

Benji Jones

Fires are burning in many parts of the world right now, including Canada’s boreal forest. How have animals adapted to these fire-prone landscapes?

Gavin Jones

Some species are adapted to live with fire, whereas others are dependent on fire.

Fire-adapted wildlife are adapted to survive wildfire events. Those animals might, for example, know to run away. Another form of fire evasion — highlighted in a recent paper by Dale Nimmo — is something called doubling back. After evading the fire, an animal will run back to the place that just burned. This has been shown in a number of animals including chimpanzees, and it’s actually a common tactic in wildland firefighting. The safest place to go is a place that just burned because it’s not going to burn again. Other animals might seek refuge until the fire has passed and then move into an unburned area.

Then there’s the shelter-in-place strategy. In the paper, we talk about this with a small mouse-like animal in the genus Antechinus. It will enter a burrow as a fire passes overhead and go into torpor — basically a temporary hibernation. These are all behavioral adaptations to survive fire.

The beetle Melanophila acuminata — known commonly as the fire bug — lays its eggs in freshly burned wood.
Udo Schmidt/Wikipedia

Then there are these other kinds of adaptations that are not directly related to survival but to reproduction. One of the coolest examples is the beetle Melanophila acuminata. Its offspring appear to be much more successful in freshly burned areas, where there are more nutrients available. And so they’ll go to active fires and breed and lay their eggs right around those areas. [These beetles have “sensory pits” that help them locate forest fires by homing in on infrared radiation.]

A bird called Temminck’s courser, meanwhile, lays eggs on the ground that are perfectly camouflaged in a burned landscape. Some lizards that perch on tree trunks have also evolved darker colors so that they blend in with a post-fire landscape.

Some species even need fire to survive

Benji Jones

What about animals that are really dependent on fire and need it to survive?

Gavin Jones

One of the clearest examples is the black-backed woodpecker. They depend on the insect larvae that live within burned trees in recently burned forests. These birds move around like itinerant vagrants and find the recently burned areas and just go to town. And after five or 10 years, they’re not there anymore.

A black-backed woodpecker on a burnt tree in Alaska.
Getty Images

Another species, which I’ve spent most of my career on, is the spotted owl. They forage heavily in small patches, about 10 hectares or less, that have been burned by high-severity fires. If you get a burnt patch bigger than that, they avoid it.

Then you get other fire-dependent species, such as the pale field rat, that are dependent on unburned areas within a burned landscape. They don’t rely on burned land, per se, but on the broader mosaic of burned and unburned land.

Benji Jones

Is it true that some birds will actually set forests on fire to flush out prey?

Gavin Jones

I have not seen it with my own eyes, but yes, there are some studies on this. They are black kites, often referred to as fire hawks. They’ve been seen picking up burning sticks and moving them into unburned places to facilitate the capture of their prey. They are engineering their own ecosystem and actively influencing the fire regime.

Benji Jones

Many plants also have some unique adaptations to fire, right?

Gavin Jones

Plants have these really clear morphological adaptations because they can’t move.

Just last week I was in southern New Mexico catching owls as part of a GPS tagging study. We walked through this one forest patch of ponderosa pine, one of the best examples of fire-adapted trees. These trees have incredibly thick bark — inches thick in some cases. And it makes sense because these forests, historically, experienced fire all the time.

Blackened trunks of ponderosa pine, following a prescribed burn, near Sisters, Oregon, in 2017.
Andrew Selsky/AP

On the other end of the spectrum, you have trees like lodgepole pine that have really thin bark. They are not adapted to survive fire at all but to reproduce after a fire. Their cones are covered in a waxy resin. And after a fire, that waxy coat will melt away and the viable seeds will drop into the soil, which has been freshly enriched with nutrients from the fire. You’ll have this massive regeneration of lodgepole pine.

These are two different strategies: One has selected for survival and the other for reproduction.

Fires are getting more extreme. Can animals adapt in time?

Benji Jones

Why is it important to study how animals respond to fire now?

Gavin Jones

There are a couple of reasons, and one is that fire regimes [i.e., how fires burn across a region] are changing. What are these changing fire regimes going to mean for wildlife?

The other reason is that we haven’t had a lot of fire in the last century. That’s because we’ve been suppressing it. And so we have very little reference for what these animals are going through and how to deal with these kinds of landscape changes. In this new era of rapidly changing fire regimes, we don’t have a great roadmap for how to conserve wildlife.

Benji Jones

It’s not just climate change that affects fires. In the paper, you mentioned that the spread of an invasive plant in Australia is making fires burn more intensely, harming lizards.

A frilled lizard on a tree in Northern Territory, Australia.
Auscape/Universal Images Group via Getty Images

Gavin Jones

Historically, frilled lizards in Australia have had this great adapted fire response. As fire would creep along the understory, these lizards would scurry up into the tree canopies to survive, following some type of sensory cue. Once the fire passes they would come back down. Now, they still run up the trees when the fires come, but there is this invasive gamba grass in their habitat, which burns way more severely. And so you have this correct response by the lizards to climb up into trees but the grass causes the fire to burn all the way into the canopy, where it kills the lizards.

Benji Jones

Climate change is behind some of these changing fire patterns. It’s making wildfires larger and more intense. Will animals be able to adapt to keep up?

Gavin Jones

It’s an unanswered question. While animals can evolve or adapt in response to fire — and have for many, many millennia — that doesn’t mean they can keep up with the rapid pace of change. I’m very slightly more optimistic now after doing this review. Evolution can happen rapidly. It has happened and will continue to happen due to fire.