Two years ago, Dale Williams, a volunteer docent at Torrey Pines Natural Reserve, started wondering what is killing the rare trees. Williams says about 25 percent of the reserve’s trees, which numbered about 6000, have died since 2014 — and not because of bark beetles, which is the reason given by California State Parks, which manages the reserve.
12600 N. Torrey Pines Road, La Jolla
Williams believes that high levels of aluminum, made more harmful by the acid pH of the fog, are killing off the trees. While owning up to having little technical expertise, Williams has asked the state parks to test the trees for high aluminum levels. After they declined, he started an online petition drive on Change.org. As of Monday (October 2nd), 356 people have signed it.
At the beginning of September, state parks district services manager Darren Smith sent a letter to Williams asking him to remove the petition from the site.
“From what I understand there is a significant amount of aluminum within the native soils that likely account for the aluminum concentrations found in your testing. As for acid fog, California State Parks has no jurisdiction over air quality nor do we have the ability to control it,” Smith wrote. “We greatly appreciate your concern and work in looking out for the Reserve. I do not think testing for one potential stressor will help manage the species within the Reserve,” Smith added.
“They said it was drought and beetles,” Williams said. “But about 38 Torrey pines have died and been removed at the golf course where they were being watered. So I started questioning why they were dying.”
The state-parks theory is that trees are more vulnerable to boring beetles when they aren’t getting enough water. The park has long been fighting an infestation by the colorfully named red turpentine beetle and the five-spined engraver beetle, according to a parks press release.
The beetles prefer trees that are stressed because strong trees make a defensive coating the bugs can’t penetrate. They like the area just inside, past the bark.
A mapping project in 2010 found about 5400 trees in the reserve. It’s unclear how many of them remain. In December 2014, park staff removed 100 of the trees, according to a press release. A city inventory report notes a resurgence of bark beetles since 2014.
According to Williams, the majority of tree deaths occurred along the Guy Fleming trail — he estimates that 50 died near the North Overlook on the loop trail. The second group to die off was along the road to the visitors’ center near the top of the hill, and the third area was behind the visitors’ center. But many other trees have died, including some in the Torrey Pines Annex, north of Carmel Valley Road.
“We docents aren’t technically adept at lab tests,” Williams said. “So I sent a piece of bark from a dying tree to a lab and they found high levels of aluminum in the bark.” A trip to Google alerted him to other tree die-offs that were tied to high levels of aluminum, he said. And there he learned that acidity contributes to the absorption of the aluminum.
“I tested rainfall and fog,” he said. “Rain has high levels of aluminum and fog tested as highly acid, which helps the aluminum penetrate the tree by making it easier to be absorbed….
“We’re just trying to get the park to test the trees. It’s a simple and inexpensive test but if they did their own testing, they would take the results seriously.”