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Invasive plants may be causing an increase in wildfires

After the deadliest fire in the U.S. in over a century ravaged Maui, experts say invasive plants may be a cause of the increase in wildfires.
Invasive plants may be causing an increase in wildfires
Posted at 7:29 PM, Aug 17, 2023

The deadliest fire in modern U.S. history had a fury that seemed too overpowering for the island of Maui. Now, some experts are trying to amplify the same message they've been hammering home for years.

"What we've been trying to communicate this whole time is that this is not outside of our control. The climatic or weather conditions, that is, there's not a lot we can do about that, but we can take measures long ahead of the fires when they occur that can reduce risk and prevent these the extent of the fires, the intensity of the fires, and just limit the impacts that we've been seeing," said Clay Trauernicht, a fire scientist at the University of Hawaii.

Fire scientists like Trauernicht have long pointed to invasive plant species as a potentially lethal threat.

He wrote an op-ed five years ago highlighting the dangers of the grass-fire cycle, when rains cause grass to grow, the rains stop, the grass dries out and then it burns. The problem isn't just in Hawaii, but across the U.S.

Take the great basin in the Rocky Mountain West, where fire scientists say the invasion of cheatgrass has increased fire frequency. In the case of cheatgrass, fire stimulates its seed germination. In other words, it grows more after fires, becoming even more invasive.

"Any kind of introduced vegetation is going to present a problem like that, particularly if it spreads quickly and grows quickly, then you have that much more fuel for the fire. And some of that's very significant," said Michele Steinberg, the wildfire division director at the National Fire Protection Association.

Again, this isn't a new conversation. This study co-authored by Trauernicht eight years ago predicted increases in wildfire because of a growing population, rising temperatures and expanding invasive grass cover. Authors say grasslands and shrublands composed 24% of Hawaii's land cover at the time.

Between 2005 and 2011 in Hawaii, 54% of the area burned was from fires that took place in dry grasslands dominated by non-native grasses. 

SEE MORE: New evidence points to power-lines as cause of catastrophic Maui fires

Part of the catalyst is unmanaged and abandoned agricultural lands, like former sugarcane plantations. Scientists call this land the driver for fire-prone non-native grasslands statewide.

"In the past several decades, as agriculture kind of declined — this is across the state — these spaces fill in with tons, literally tons of fuel. And these grassy fuels are highly sensitive to quick, quick drying out, and ... really easy to ignite," said Trauernicht. 

In Hawaii, non-native plants like guinea grass have taken over much of that abandoned agricultural land. It can grow as much as 6 inches a day in a wet season. And then it dries out.

"In hotter conditions, drier conditions, more variable rainfall, it's only going to exacerbate the problem," said Trauernicht.

Some fire experts say native plants can be just as harmful — consider palmetto trees in Florida.

"It carries fire, meaning when it starts burning it lofts with the wind, and then the fronds go everywhere. Palm trees do the same thing. And they're a nightmare from a fire perspective. But that is their reproductive system, is fire. So we don't want to say all natives are good, all all invasive are bad, but invasive, just by its very nature ... It's invasive in the sense that it's crowding out other species that need the space, the light, the water," said Steinberg. 

While we may not be able to get a handle on extreme weather events, fire scientists say we can start to do something about fuels — both native and invasive — now.

"The good news in the sense of the fuel problem is that that's within our control ... there are actions that we can take that would reduce that vulnerability, that would make conditions safer," said Trauernicht.

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