Northeastern University plant ecologist Sarah Swope says the dense thickets of native chaparral that grew along the coastline may never grow back.
OAKLAND, Calif. — At least 27 people have died in fires still burning in the Greater Los Angeles area and more than 12,000 structures have burned to the ground. At least some of these losses will be restored with time.
But the dense thickets of native chaparral that grew abundantly along the coastline may be gone forever, Northeastern University plant ecologist Sarah Swope says.
“In a more natural fire, you would look out over the landscape and it would look like everything above ground has been burned and that there’s nothing left,” Swope says. “But the roots are still alive and plants resprout from the roots.”
The fires burning in Los Angeles are burning hotter and faster than natural fires that sweep lightly through forests and woodlands. Dubbed “firenados” for the winds of up to 100 mph that whipped flames through wildlands and neighborhoods, the Palisades, Eaton and Hurst fires have the potential to permanently change the landscape, says Swope, who will co-teach a course on fire ecology on the Oakland campus in the fall.
“In a very intense fire what you might find is that the roots underground are also on fire,” she says, “and that prevents plants from being able to resprout.”
Instead of the evergreen shrubs that thrive and cover coastlines and hillsides in Mediterranean climates like Southern California, Swope says, the burn sites in Los Angeles may be taken over by invasive grasses. Hardy and fast-growing, these grasses are already abundant in California after having been inadvertently introduced by humans centuries ago. After an event like a fire, says Swope, seeds for these grasses are likely to sprout and grow before native plants.
“You’ve wiped the slate clean,” Swope says. “And now whoever gets there first is going to be the winner, and we could see this area utterly transformed.”
Nearly 40,000 acres have burned so far in the fires, razing neighborhoods and surrounding wildlands. This is another way these fires vary from natural fires, Swope says, which are usually patchy and peter out before developing into more destructive blazes.
But conditions are much more extreme, with rising temperatures and declining rainfall creating a “changed fire regime,” she says, noting that these fires are happening during what should be the wet season. Winds that drive fire are themselves driven by the temperature differential between the hot desert and cool coastal areas.
“As the differential increases as the deserts get hotter, the winds become more intense,” Swope says. “This is an element of climate change that’s altering fire behavior.”
Invasive plants do well in burned environments, she says. They grow quickly, so they can use nutrients left in the soil and out-compete native species for water, space and sunlight.
“A Redwood is never going to become invasive no matter where you put it, because it grows so slowly and it’s so particular in its requirements,” says Swope.
In the long term, she says, some native plants could survive and re-sprout. Mammals, birds and wind could eventually bring native seeds in from other areas. But another possibility is that the area will never go back to the way it was before.
It’s a phenomenon called state change, Swope says. An area that used to be pretty much all native species reverts post-fire to largely invasive plants.
“We’re losing our regionally unique flora,” she says. From a global perspective, she added, intense fires contribute to a decline in biodiversity. “It’s entirely possible that at least some areas will be transformed from beautiful coastal chaparral into what we call exotic annual grasslands.”