How invasive grasses may have contributed to the size of the Maui fires

Overlooking the historic city of West Maui are plantation-era relics. Fields that used to grow sugarcane are now dry and covered with the invasive weed.

Officials found that several factors contributed to the deadly wildfires on Maui, including dry conditions and high winds. However, some say the non-native grass played a major role in fueling one of the deadliest wildfires in U.S. history.

For years, environmentalists have been calling for vegetation management as invasive plants spread in urban areas.

The problem has been exacerbated by the worsening wildfires, prolonged droughts and high winds caused by frequent storms, according to Christy Martin, program manager at the Alien Pest Species Coordination Group.

“We have an invasive fuel supply problem, and we have plenty of opportunities for the spark to take hold,” Martin said, adding the need for long-term solutions in invasive species management.

Diane Fitzmaurice for NPR

Volunteers help those who lost their homes in Lahaina stop to pray on a hill. The city is surrounded by invasive, highly flammable dry grasses.

About 25% of Hawaii’s land is covered with non-native grasses and shrubs, according to USDA researchers.

Non-native plants such as buffalo grass, guinea grass, and molasses grass were brought to Hawaii from Africa to feed livestock or use as ornamental plants.

As Lahaina’s sugarcane industry ended in the late 20th century, thousands of acres of unmanaged land became home to invasive species, according to Lisa Strohecker, outreach and education specialist for the Maui Invasive Species Commission.

“We have large areas full of these fire-resistant grasses, and all it takes is one spark,” she said.

Invasive weeds are already spreading

It’s been more than a month since wildfires devastated the city of Lahaina and killed at least 115 people. While the buildings are in ruins, plant experts say the invasive grass is already growing.

“They can either regenerate from roots or quickly from seed,” Strohecker said. “So the top may burn, but it will be one of the first things to come back after the fire is over.”

Molasses is common in people’s yards, Strohecker said, adding that the plant contains a lot of oils, so it burns quickly. Buffalo grass and guinea grass are commonly found in open fields and can reach at least four feet tall, she added.

Wildfire devastation is seen outside Lahaina, Hawaii, Thursday, August 10, 2023.

Wildfire devastation is seen outside Lahaina, Hawaii, Thursday, August 10, 2023.

These fire-adapted grasses are mostly found in low-level areas. However, researchers at the University of Hawaii have found that climate change is increasing the invasion of non-native grasses at high elevations.

Invasive grasses are difficult to manage because of their adaptability, said Elliot Parsons, a specialist with the Pacific Regional Invasive Species and Climate Change Management Network.

He said there are several hypotheses as to why the invasive species is so successful in its new environment, including escaping natural predators from its ancient ecosystem.

“It makes managing these weeds even more complex and difficult because some of them may have been kept in check in their home range by species that have eaten them or managed their leaf tissue,” Parsons said.

He continued: “When they get into this new environment, they don’t necessarily have those controls, so they can grow quickly and spread quickly, and they are much more difficult to deal with.”

Preventing widespread growth

Some ideas for vegetation management would be grazing livestock, mowing grass or building firebreaks to prevent the spread of fire, Parsons said.

According to Frannie Brewer of the Big Island Invasive Species Committee, each plant should be treated differently. Some invasive weeds will be impossible to eradicate because they are so widespread, she said, adding that the only option is long-term management.

One solution could be to replant the area with native or non-invasive grass, she said.

“This is probably the most labor-intensive work, so he gets the biggest price up front,” Brewer said.

Wildfire experts map fire incidents throughout Hawaii.

Courtesy of Hawaii Wildfire Management Organization.

Wildfire experts map fire incidents throughout Hawaii.

Wildfires are complex, said Elizabeth Pickett, co-executive director of the Hawaii Wildfire Management Organization.

In Hawaii, less than 1% of fires are caused by lava and lightning and about 99% are caused by humans, according to Pickett.

She pointed out that experts consider grasslands to be the engine behind forest fires because they can transmit fire.

“We also look at it as something that can be managed,” Pickett said. “So it’s invasive, but any type of grass and any type of vegetation that will dry out during our dry season is going to be flammable. It’s a matter of active management.”

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