Jet Propulsion Laboratory Says California's Drought Is Killing Oaks

Published : Monday, April 2, 2018 | 5:05 AM

JPLHumans weren’t the only ones who suffered — and continue to suffer – thanks to California’s recent drought.

Take those glorious live oaks in places near Topanga State Park where mountainous open space separates Calabasas and Pacific Palisades.

This is an area once covered by a natural arbor of these trees, but now there are more trunks and branches covering the ground than healthy specimens.

“This would’ve been pretty deep shade in the past,” said Witter, a fire ecologist with the National Park Service, according to media reports.

While experts say that if the drought itself isn’t killing area oak trees, the lack of water has put a definite strain on them, as well as other problems like insects and fungi.

It’s true that Gov. Jerry Brown lifted the drought emergency last year, but thousands of trees across the Santa Monica Mountains, which stretch from Hollywood to Point Mugu, have been unable to return to their glory days due to lack of water.

Rosi Dagit, a senior conservation biologist with the Resource Conservation District of the Santa Monica Mountains, said in media reports about 9,000 oaks in the area have died because of the drought.

Dagit, along with her co-workers teamed with NASA’s Jet Propulsion Laboratory to study trees in the Santa Monicas.

The report was released in December and contained some harsh discoveries. For instance, between 2013 and 2016, about 30 percent of the 110,000 acres of live woods in the local mountains have died.

“When you put it all together, it looks pretty bad in the Santa Monica Mountains, and the rain last year really did not make much of a difference,” Dagit said.

John Tiszler, a plant ecologist with the National Park Service stationed at the Santa Monica Mountains National Recreation Area, said even though Southern California is getting precipitation, “it will take years of consistently good rain for trees to rebuild their resources enough that they can heal and protect themselves.

“No doubt the rains have helped, but they haven’t solved that stress the trees are feeling from the previous four years of drought,” he said.

Other plants and animals are dying, too, he said.

Dagit said oaks are the main species in the area and wildlife in the Santa Monica Mountains is dependent on the trees.

“There are literally thousands of species of insects, birds, reptiles, mammals and even fish, where if we lose oak trees all these other species disappear,” she said. “These species are tied, at least for certain parts of their life cycle, to the oaks.”

Though some of the forests appear green after recent rains, proof of the plant die-off is clear.

Witter said trees shed leaves and branches when stressed from little to no water. True, since a little rain, has returned, some oaks are regrowing what they lost. However, others aren’t, and the remains of oaks, which Witter said can be some of the more resilient species of tree, could have lasting damage.

Even trees that have survived for decades are dying off. And if the drought isn’t killing them, the lack of water has weakened them.

The damage isn’t limited to oak trees. Dagit said riparian trees, which border rivers and creeks, are also affected. Additionally, more than 100,000 sycamores, alders and willows died between 2013 and 2017.

“When you lose that canopy, it has all these adverse impacts on the sub-canopy, the water and the stream environments beneath those trees,” Tiszler said. “The impacts resulting from that can be profound.”

This trend may continue Dagit added because based on the age of the trees in the Santa Monica Mountains, the past few years have been the first time these trees were exposed to rainfall this low and an increased number of days at 95 degrees or more.

Witter said climate change could make conditions like this more common, further damaging the trees’ chances of returning to normal.

Instead of covering the Santa Monicas, trees may end up growing only in the most temperate and wettest parts of the mountains. Animals and other plants would follow the trees to find pockets where life can thrive, Witter said.

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