Southern California is facing a serious tree catastrophe

LA trees
CC BY 2.0 Wikimedia Commons

Stricken sycamores, waning willows, ailing oaks – thanks to years of drought and invasive pests, tens of millions of trees are at imminent risk of a massive die-off.

While visions of sunny Southern California may conjure up thoughts of its iconic palm trees, anyone who has admired the region’s lush canopy knows there is so much more. Home to 71 million trees, the urban forest there is an exquisite thing – giant graceful sycamores, exuberant live oaks, swaying willows, myrtle, avocado, liquidamber … the list goes on and on.

But the outlook for this dense verdant treescape isn’t looking so good.

As Louis Sahagun writes in the Los Angeles Times:

The trees that shade, cool and feed people from Ventura County to the Mexican border are dying so fast that within a few years it’s possible the region will look, feel, sound and smell much less pleasant than it does now.

“We’re witnessing a transition to a post-oasis landscape in Southern California,” says Greg McPherson, U.S. Forest Service researcher who has been studying what many are calling an unprecedented die-off of the region’s precious trees.

The native sycamores may be the hardest hit so far, compliments of the polyphagous shot hole borer beetle, which McPherson says could kill 27 million of the trees in Los Angeles, Orange, Riverside and San Bernardino counties. That’s 38 percent of the region’s trees. This particular tiny menace is from the group of beetles known as ambrosia beetles and hails from South East Asia; pregnant females drill into the trees and lay eggs, along with a pathogenic fungus to feed the new babes, all of which can prove lethal to the host trees.

“Here’s the sad news about sycamores,” says plant pathologist Akif Eskalen from the University of California, Riverside. “If we cannot control the shot hole borer, it will kill all the sycamores in California. And when they’re done with sycamores, they’ll move to other trees.”

And that’s just one insect. There are plenty of others – the Kuroshio shot hole borer killed more than 100,000 willow trees in Tijuana River Valley Regional Park last year – as well as other threats altogether.

“Many of the trees we grow evolved in temperate climates and can’t tolerate the stress of drought, water restrictions, higher salinity levels in recycled water, wind and new pests that arrive almost daily via global trade and tourism, local transportation systems, nurseries and the movement of infected firewood,” McPherson says.

“Catastrophic loss of our canopy,” McPherson adds, “would have consequences for human health and well-being, property values, air-conditioning savings, carbon storage, the removal of pollutants from the air we breathe, and wildlife habitat.”

As the loss of trees is cascading across Southern California, it has been likened to watching a slow-motion train wreck. “It’s heartbreaking,” says plant pathologist Jerrold Turney, “to see trees dying in such dramatic numbers in famously lush cities like Pasadena, Alhambra and Arcadia: sycamores, all the maples, olives, liquidambers, flower plums, myrtles, oleanders and oaks.”

The problem is complicated and tragic and completely disarming, and you can learn much more about what’s at stake in the Times article – it’s a great (and greatly depressing) read.

In the meantime, McPherson hopes that his report on the topic gets some attention from the government, which appears to be asleep. From here we need to start “monitoring the unprecedented damage the urban forests are suffering, and taking steps to remove dead trees and plant new, probably different ones,” McPherson says, “a new, diverse palette of well-adapted species that may not be currently available in nurseries.”

The loss of So Cal’s trees would be devastating on so many levels, hopefully the siren has been sounded before it’s too late. And at the very least, that contingency plans are in the works.

Tags: California | Drought | Invasive species | Trees

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