California is famous for trees that can grow to heights of 87 metres, some of which are around 2,700 years old. But now 58 million trees could from the four-year drought. California relies on its forests for water provisioning and carbon storage. Hopes now lie in El Niño, reports John Dyer in Boston.
California fears for its world-famous trees, some of which can grow up to 58 metres and live for 2,700 years. But now many of them are in danger from the state’s four-year-old drought. Unless it comes to an end soon, as many as 58 million trees could die, according to scientists from the University of Stanford.
Long-term changes to the ecosystem
In a study published in the Proceedings of the National Academy of Sciences in late December, the scientists found that the severe drought was drying out trees from the Pacific Coast to the mountainous high deserts bordering Arizona and Nevada.
“California relies on its forests for water provisioning and carbon storage, as well as timber products, tourism, and recreation, so they are tremendously important ecologically, economically, and culturally,” said Greg Asner, an ecologist at Stanford’s Carnegie Institution for Science, in a statement.
“The drought put the forests in tremendous peril, a situation that may cause long-term changes in ecosystems that could impact animal habitats and biodiversity.”
Scope of damage shocking
Using an airplane called the Carnegie Airborne Observatory, Asner and his team flew over California and used a laser to sense water levels contained in leaves in the forest canopy.
They discovered that around 888 million trees over 10.6 million hectares were seriously threatened, with around 6.5 per cent of those trees had lost a third of their water and were on the verge of withering to death.
The scientists were shocked when they saw the scope of the damage from the dry weather, however.
“There was a lot of silence in the lab in the back of the plane because it was just so bad to see,” said Asner. “So much of the forest underwent a loss of canopy water. Within that there are lots of pockets of deeply stressed landscapes — not just individual trees, but entire landscapes of trees.”
Conservation measures to remain
Scant rainfall and high temperatures since 2011 have created a crisis in California, a state that would be the eighth-largest economy in the world if it were its own country.
While recent snowfall has been returning to pre-drought levels, most reservoirs in the state are now only half-full, too little to change water conservation measures that have angered Californians who are used to using as much water as they please.
“Last year was so abysmally bad that even coming up to the average we have now looks good,” said Doug Carlson, spokesman for California’s Department of Water Resources.
Hopes lie in El Niño
One of the few hopes for the forest is El Niño, a pattern of warmth in the Pacific Ocean that results in more precipitation on the West Coast of the US, said Anser.
“There’s this huge pool of trees that’s teetering on death,” he said. “The only way to know what will happen in the end is to measure again and see if they bounced back. And with El Niño, who knows?”
But even with more El Niño rainfall, much of California’s forests are likely to change forever because of the drought. Pests that eat trees are likely thriving as the trees weaken, said Anser.
“During drought, when trees are stressed, they’re more susceptible to infestation,” he said. “The interaction between the bark beetle, the tree and climate — we’re just figuring it out now.”
Dying trees that are currently absorbing greenhouse gases won’t continue to do so, too, potentially releasing massive amounts of carbon into the air in the long term, said Anser.
Aquifers under pressure
In the short term, the absence of many of those trees means that much of the rain water that the trees currently capture might flow into the ocean, thus putting more pressure on aquifers that are crucial to growth in the booming cities of Los Angeles and San Francisco.
While the current situation is grim, state officials said that the researchers’ data has actually helped them grasp the scope of the drought crisis for the environment.
“It will be important to bring their cutting-edge data and expertise to bear as the state seeks to address the effects of this epidemic of dying trees and aid in the recovery of our forests,” said California Environmental Protection Agency Deputy Secretary Ashley Conrad-Saydah.