How invasive plants sparked the Maui fires
When Hawaii’s last sugarcane plantation closed on Maui in 2016, it marked the end of an era when sugar dominated the archipelago’s economy. But the latest harvest at the 36,000-acre farm underscored another pivotal shift: the continued spread of highly flammable non-native weeds on idle land where cash crops once flourished.
Varieties such as guinea grass, molasses grass, and buffalo grass—which originated in Africa and were introduced to Hawaii as livestock fodder—now occupy nearly a quarter of Hawaii’s land area. These grasses grow quickly when it rains and are drought-resistant when land is dry, fueling wildfires across Hawaii, including a blaze that killed at least 93 people on Maui last week.
“These weeds are very aggressive, grow very quickly and are very flammable,” said Melissa Chimera, whose grandmother lived on the Hawaiian Commercial and Sugar Company farm on Maui after immigrating from the Philippines. “This is a recipe for much larger and more destructive fires,” added Ms. Chimera, who now coordinates the Pacific Fire Exchange, a Hawaii-based project that shares fire science between Pacific island governments.
Investigators are still searching for clues about what ignited the Maui Fire, which has become the deadliest US wildfire in more than a century. But as the planet warms, it has become clear that even tropical places like Hawaii, known for its rainforests and verdant hills, are increasingly vulnerable to wildfires.
The islands have long had barren expanses of lava fields and drier grasslands, with rainfall varying from one side of the island to the other. But in recent years, the state has also seen a long-term decline in average annual precipitation, less dense cloud cover, and drought caused by rising temperatures. Taking advantage of data showing a sharp rise this century in destructive fire activity in Hawaii, wildfire risk mitigation specialists had already been issuing warnings for years about Maui’s growing vulnerability.
In 2020, for example, a hazard mitigation plan prepared for Maui County said that the West Maui area — where Lahaina, the city destroyed by fire last week, is located — had the highest annual probability of wildfire of all the communities in the region. boycott.
The document listed the West Maui area as having a “very likely,” or more than 90 percent, probability of wildfires each year on average. Six other Maui communities ranked lower, ranging from 10 percent to less than 90 percent.
After West Maui in 2018 was hit by an earlier round of fires that destroyed 21 homes, Clay Trauernicht, one of Hawaii’s leading wildfire experts, warned in a subsequent letter to Maui News that the island was facing a potentially dangerous threat. Do something about it. “Fuels — all that grass — are the only thing we can directly change to reduce fire risk,” he wrote.
Fast forward to 2023, and Mr. Traurnicht, a specialist in wildland fire science and management at the University of Hawaii at Manoa, said the deadly Maui fire clearly showed how non-native grasses — many of them on former ranch lands — had been largely left behind. that cannot be managed by large corporate landowners – can cause what might otherwise be a controllable fire to balloon in size.
In Lahaina, much of which was destroyed in a fire last week, invasive weeds cover the slopes above the city, growing to the edges of residential areas.
“We have entered the post-agricultural era,” Mr. Traurnicht said to publish Last week on X, formerly known as Twitter.
Concerns about the dangers from such weeds have been growing since farms began to decline in the 1990s, marking the end of the agricultural model that attracted migrant workers from around the world and shaped Hawaii for nearly 200 years. As tourism overtakes plantations in importance, the shift from sugarcane and pineapple plantations to tropical grasslands has allowed tropical grasslands to grow without care, reinforcing what firefighting specialists call the “grass fire” cycle.
Heavy rains that fall on the Hawaiian Islands can cause non-native grasses to grow in some cases as much as six inches per day. Then comes the dry season and the grasses burn. Furthermore, after fires sweep through certain areas, non-native grasses grow and spread rapidly, displacing native plants that are less adapted to wildfire, making the cycle even more destructive.
Non-native trees such as mesquite, wattles, and, at higher elevations, pines that were planted in the 1900s to stop erosion and provide timber, pose additional wildfire risks.
“We have a problem with a lot of conifers on Maui,” said Lisa Strohecker, an education specialist with the Maui Invasive Species Committee, an organization that seeks to contain high-threat invasive species.
When a number of conifers caught fire in a fire on Maui in 2018, it caused their cones to burst, causing the fire to intensify, Ms. Strohecker said. Then, air currents carried the seeds to new locations, creating seedlings — and new fire risks — in other parts of Maui.
Tropical fire specialists stress that there are ways authorities can curb this destructive cycle. They include building firebreaks, introducing more fire-resistant plants, and allowing livestock to keep grasses at a manageable level.
For many years, Mr. Traurnicht and other experts have been calling for such moves to mitigate the risk of wildfires in Hawaii. And in 2021, the County of Maui’s Wildfire Prevention Report noted that “weeds act as an incendiary agent and quickly invade road shoulders” while calling for “reduction of exotic plant life.”
The need for more aggressive wildfire mitigation efforts has been a topic of discussion for years in Hawaii; Throughout the islands, reducing the spread of invasive plants can be expensive and logistically complex. Hawaii also competes for federal wildfire grants with more than a dozen other Western states where large fires generally get more attention; Some officials have urged the state government to provide more of its own funding to combat the invasive weed.
Hawaii faces other challenges, such as its highly diverse terrain. Firefighters have to work across areas including tropical forests, semi-arid lands and cold highlands on the slopes of volcanoes, and are sometimes forced to resort to expensive chartered helicopters to fight fires.
There are also human factors in place where activities such as campfires, fireworks and sparks from cars are already responsible for most fire starts. Hawaii’s severe housing shortage, reflected in a large homeless population that often cooks outside, increases the risk of further ignitions, researchers say.
A hazard mitigation plan prepared by Jamie Kaplan Consulting, a Massachusetts-based firm specializing in natural hazard mitigation, for Maui County in 2020 also warned that steadily rising temperatures are impacting Hawaii’s vulnerability. He went on to say: “Forest fires may become more frequent in the future as drought conditions become more frequent and more severe with climate change.”
Maui County saw 80 wildfires between 1999 and 2019 — an average of about four per year, according to the report, the largest in 2009 that burned more than 8,358 acres on the island of Molokai.
As for West Maui, the report painted a picture of a population group particularly vulnerable to wildfire damage.
West Maui has the highest rate of non-native English speakers in the county — nearly 6 percent, she said.
“This may limit residents’ ability to receive, understand and take appropriate action during hazardous events,” the plan states.
The area has the second-highest rate of car-less households in the county, nearly 7 percent, which could make it difficult for people to escape the fire, she said.