Hawaii didn't used to get pummeled by highly destructive wildfires. What has changed? A big part of the answer lies in the interaction between climate change and invasive species.
Begin with a couple paragraphs buried in a NY Times article:
The area burned annually by wildfires in Hawaii has quadrupled in recent decades. Declining rainfall and rising temperatures have left the islands more susceptible to blazes, climatologists say.A University of Hawaii website points to one that has been particularly destructive:
Invasive grasses that are highly flammable have crowded out native vegetation in some areas, and climate change has exacerbated dry and hot conditions in the state, allowing wildfires to spread more quickly.
Guinea grass (Megathyrsus maximus), a nonnative invasive grass in Hawaii, forms dense stands that outcompete native plants and has very high fine fuel loads that greatly increase fire potential, spread, and severity.
Wikipedia describes guinea grass as a tough customer, growing ten feet tall. Though it can thrive in full sun, it can also tolerate shade, allowing it to invade native woodlands and thereby increase their vulnerability to fire during droughts. Native to Africa, the grass was introduced not only to Hawaii but also to south Texas.
How did guinea grass get to Hawaii (also spelled Hawai'i)? Wired provides an answer:
When Europeans arrived in the late 18th century and established plantations for growing sugarcane and pineapple, they also brought invasive grasses. Now the economics have changed, and those fields lie fallow. But the grasses have spread like a plague. “Those fire-prone invasive species fill in any gaps anywhere else—roadsides, in between communities, in between people’s homes, all over the place,” says Pickett. “At this point, 26 percent of our state is covered in these fire-prone grasses.”An article in ABC News explains how the more intense and frequent fires affect the soil and human health:
This stuff is highly sensitive to short-term fluctuations in rainfall. The grass will grow like crazy when the rains come, then quickly desiccate when the landscape dries. “When we get these events like we’re seeing these past few days—when the relative humidity really drops low—all those fine fuels become very explosive,” says fire ecologist Clay Trauernicht of the University of Hawaiʻi at Mānoa.
Elizabeth Pickett, co-executive director of the Hawaii Wildfire Management Organization, a nonprofit working with communities to prevent and mitigate fires, lamented the changes wrought by fire.A Philosophical Footnote
Invasive and fire-prone grass species have moved in over time and during a fire they can burn into native forests, which means the forests are replaced by more grass, Pickett said. The soil burns and sloughs off, leading to massive post-fire erosion that smothers coral, impacts fisheries and reduces the quality of the ocean water, she said.
The state is windy and the dust blows for years, harming human health, she added.
“When you lose your soil, it’s really hard to restore and replant. And then the only thing that can really handle living there in many cases are more of those invasive species,” Pickett said. “It’s systemic. Air, land and water are all impacted.”