San Diego's Forests Face Possible Extinction
The forests of San Diego County that have shaded 500 generations of local people and provided pine needle bedding, oak woodland and spiritual renewal could disappear. Overly intense fires in quick succession, along with drought, borer insects and climate extremes are laying waste to trees and creating a hostile environment for regrowth.
Beloved local places — the Laguna mountains, Cuyamaca Rancho State Park, Palomar Mountain — could convert to chaparral or even to grasses. Some scientists mention even the Torrey pines as possibly at risk.
“The people of San Diego County are going to lose all their forests in the next fire cycle,” said Richard Minnich, a fire ecologist at UC Riverside, meaning one more overheated fire in a given place.
California has lost 66 million trees since 2010, the U.S. Forest Service said in June. Many of these succumbed in just the months since Gov. Jerry Brown issued a tree mortality emergency declaration last October. Cal Fire, the California Department of Forestry and Fire Protection, estimates 52,000 trees have died from all causes in San Diego County from 2010 to 2015, 10 times as many last year as the year before.
The U.S. Forest Service used to put out all the forest fires it could reach. This created too dense a forest, because the periodic fires that used to pass through the woods would burn out smaller trees, keeping the forest more widely spaced. Minnich cited that former practice as the main cause of the current conditions.
Entire landscapes where generations of San Diegans developed their relationship with nature have already burned and converted. They are no longer forested.
“I can tell you the Laguna mountains look very different from when I was a kid. We are already in my opinion seeing the effect of climate change and climate extremes. I’m actually quite shocked at the change in vegetation in the Lagunas over my lifetime,” said Walt Oechel, a San Diego State University professor of biology and director of the university’s global change research group. “We are seeing the change in communities, right before our eyes and it is very strong and very palpable.”
A back country enthusiast, San Diego State biogeographer and physical geographer John O’Leary has noticed the changes at Palomar Mountain, among other places.
“You drive up there and look around, it is remarkably apparent there is a great deal of mortality,” he said. “Some of the conifer species and even oaks are not able to endure, withstand the drought that is taking place there.”
Trees in large areas between Ramona and the Santa Ysabel Reservation have died. A Tree Mortality Viewer produced by a joint state federal task force tallies tracts of former woodland: “744 acres of coast live oak, 80-85 percent dead from boring insects; 1,286 acres of coast live oak, 75-80 percent dead from drought.”
Minnich estimates 70 percent of the fir forest on Palomar Mountain was wiped out in the drought of 2002-2003, and that Cuyamaca has lost 94 percent of its trees to fire, and Volcan Mountain 50 percent.
Mountain peaks in San Diego County reach only to about 6,500 feet, giving limited cooler habitat to trees and wildlife compared to the San Gabriel peaks flanking Los Angeles. They are in the 9,000-foot range and San Gorgonio Mountain in the San Bernardino mountains, the highest in Southern California, is nearly 11,500 feet.
Many trees here, and the animals that live among them, are in effect living in refuges. These are a particular concern for Oechel.
“I can imagine the Torrey pines are going to have a rough time in the future,” he said, referring to San Diego’s iconic solo pines, sometimes flat across their tops, that populate the ocean bluffs in La Jolla.
Other oases, like Peñasquitos Canyon Preserve, can’t be taken for granted either. The multi-mile, partly shaded canyon offers so much variation: sage plant communities that telegraph the message, “you are in Southern California,” with their scent, chaparral plants on the north facing slopes and sycamores alongside the gently flowing creek.
“But again with overly frequent fire, the likelihood of changing the vegetation to something that is very, very largely non-native is a very real prospect, and I think even a likely prospect. Sad to say,” O’Leary said.
Places that are right within the urban area, such as Peñasquitos, are easier for firefighters to reach than the back country. So a fire might not have as much chance to burn. But they are still subject to increasing heat and drought extremes, which can push plants and animals past their limits.
Up in the mountains, not every brown pine bough you see means a tree is dying, said Nicole Molinari, the province ecologist for Southern California federal forests. But if you see brown at the top of a pine tree, say a prayer.
“Within a year or so, that tree will be gone,” she said.
Browning at the top means beetles are overcoming the tree. Molinari asks two things of the public, both related to fire. The first is to be more careful with it. People are the cause of nearly all the fires here.
In 2003, a hunter, lost and dehydrated, set two signal fires, hoping to be found. Over the coming days, the Cedar fire caused incalculable human loss as it swept in four directions, burning from Miramar Marine Corps Air Station to Sunrise Highway. It killed 15 people and destroyed more than 2,200 homes.
When that fire hit Cuyamaca Rancho State Park and the Cleveland National Forest, it ran into stands that had become very dense with trees under the old fire suppression practice. Before fire suppression, wildfire used to burn through the region on average every 35 years, according to Oechel, every 50 according to Minnich, and it was sparked by lightning.
“We removed a process that has been there ever since there has been oxygen in the air,” Minnich said. “What an arrogance.”
Stands of trees just across the border in Mexico have fared far better, without the policy of extinguishing fire, he said.
But forest managers were also doing what the public wished, protecting the property of people who moved into the woods. The buildup of unburned plant material contributed to the blistering temperatures of the Cedar fire. It roasted the trees out of a hospitable environment. In some places now, only chaparral will grow. In other places, only grass.
“Despite reforestation efforts, we didn’t have lot of success,” Molinari said. “We don’t see conifers coming back in those places.”
That is why Molinari’s second request is to allow the Forest Service to thin out the forests and burn them in a controlled way, at lower temperature. The government has worked for years to persuade the public about such beneficial fire and thinning. But Molinari said people still complain when the Forest Service reduces the number of trees per acre or plans a burn.
She also hypothesizes that too-close trees may be robbing water from each other. If they can be thinned to a spacing more akin to pre-Spanish times, they might each have access to a little more scarce water. That might allow them to plump up slightly and pitch out beetles, rather than fall victim to them. She is testing this hypothesis in plots of trees in the Cleveland and Los Padres national forests. Much is at stake.
“There is a true risk of losing these forests,“ Molinari said. “I have a 2-year-old and a 4-year-old. I want these forests to be here when they grow up and have children. And so thinking about ways to make these ecosystems resilient to climate change and changes in fire regime is, in my mind, the most important thing we can do to save them.”
There is a phenomenon known as shifting baselines that worries many environmental scientists. It’s the idea that generations only knows the natural places they themselves experienced as children. Oechel worries that people who are young now will never have known a world without climate change.
“I think it is very important to expose our kids to the vegetation that exists now,” Oechel said. “It is sad that they may not be there and they may not be able to bring their kids there. But I think it is extremely important for them to see the systems as they are now and to see as many of the natural systems as they can.”