The Woolsey fire has destroyed hundreds of homes in Malibu. Many residents are sleeping on friends’ couches or staying in hotels, unsure of whether they will be able to return home.
Though the city will rebuild, it will never be the same. The same may be true of Malibu’s abundant wild lands and famous shoreline.
The fire burned through 83 percent of the Santa Monica Mountains National Recreation Area, or about 130 square miles, an area approximately the size of Detroit. That represents a major habitat loss for the area’s best-known species, including mountain lions and bobcats. But the fire and its aftereffects could endanger the entire ecosystem from the ground up.
“A massive dieback”
The Santa Monica Mountains are covered in chaparral, or thick shrubbery, with some forested areas. Chaparral is prone to fires and typically grows back quickly, said UC Berkeley forest ecology professor John Battles.
However, Battles said the Woolsey fire has the potential to permanently change the landscape because a large part of the chaparral was already dead when the blaze started. Scientists have seen a widespread “dieback” in the Santa Monica Mountains over the past three to four years resulting from the unusually hot drought that ended in 2016. 38 percent of the chaparral died, according to NASA.
The drought also killed more than 120,000 trees, damaging creek ecosystems that relied on the shade they provided.
“Chaparral is fire-adapted and usually grows right back, but this is a weird case where (the shrubs) were already dead when they burned,” Battles said.
That may have contributed to the fire burning through such a large area, he said. But it could also have more permanent effects.
Battles cited a study co-authored by Jon Keeley, a scientist with the US Geological Survey, that shows residential development into chaparral is associated with a higher frequency in human-caused fire ignitions and the expansion of highly flammable non-native grasses. In Southern California, these factors caused chaparral to die or become sage scrub or grassland since the 1930s.
There were far more wildfires in areas previously covered in chaparral that became grassland, according to the study.
“The big question is we will see the same rapid recovery, will the (shrubs) not come back or will we see a type conversion from chaparral to grassland,” Battles said. “The chaparral habitat supports its own suite of biodiversity and if it switches to grassland, there will be different organisms.”
As Malibu residents brace for mudflows that could follow the Woolsey fire as early as late next week, scientists are concerned about the impact excess sediment could have on Santa Monica Bay.
Rain could come to the area late next week, forecasters said, but the rainy season is only just beginning. If rains are heavy enough, they will flow over rather than absorbing into recently burned areas, potentially eroding the soil into flows of mud that can quickly destroy houses and take lives. Mudslides following the Thomas fire killed at least 18 people in Montecito, a coastal town north of Malibu.
Local scientists said mudflows could upset the delicate ecosystem of Malibu Lagoon, an estuary at Malibu Point, as well as the Santa Monica Bay and the area’s watershed.
“If there’s a tremendous amount of sediment, the nutrients that come along with that could impair water quality and contribute to harmful algal blooms,” said Tom Ford, executive director of the Bay Foundation. “Organisms … could be buried or displaced by sediment moving down into streams, the lagoon or the open ocean.”
Algal blooms can kill fish and cause rashes in humans who swim in the affected area, as well as odors and scum along the shoreline.
Toxins associated with ash from the fire currently falling into the ocean, lagoon or watershed could also threaten the health of the ecosystem, Ford said.
Karina Johnston, the Bay Foundation’s science director, said the sediment might affect the habitats of some lagoon species, including the endangered tidewater goby, a small fish that makes its home in the sediment of tidal channels. Sediment that flowing into the lagoon may bury the goby’s burrows.
It could harm other aquatic species, she added, including invertebrates that birds and other animals rely on as a food source and plants that grow in the lagoon.
“It depends on what kind of rain we get this winter and whether vegetation (in the Santa Monica Mountains) can recover enough to retain that sediment,” Johnston said. “There’s so much concern over homes and people, and that’s really important, it’s it’s also important to recognize there are impacts on ecology and the environment.”
Ford said he believes the coast could rebound from the impacts of mudflows on the ecosystem. A storm washed debris and sediment into the watershed two years ago, but the lagoon has since recovered, he said.
“California has proved somewhat resilient in the past, and I hope that’s the case again,” Johnston said.