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Millions Of Trees Are Dying Because Of California Drought

Millions Of Trees Are Dying Because Of California Drought

By Veronica Rocha, Los Angeles Times (TNS)

LOS ANGELES — At least 12 million trees have died in California’s national forests because of four years of extreme drought, scientists say.

An aerial survey of select areas in Southern California and the south Sierra Nevada in early April showed that millions of trees have died and were “most severely drought impacted,” said biologist Jeffrey Moore, acting regional aerial survey program manager for the U.S. Forest Service.

Officials believed the trees will continue to die as summer approaches.

“It is almost certain that millions more trees will die over the course of the upcoming summer as the drought situation continues and becomes ever more long term and as bark beetle populations continue to expand,” he said.

William Patzert, climatologist for the Jet Propulsion Laboratory, has told the Los Angeles Times that California’s dwindling snowpack and warmer temperatures pose an extreme fire danger in the state’s forests.

Warmer temperatures are rapidly drying out the state, he said. Traditionally by spring, the forest is green and lush due to a substantial rainy season. But four years of drought and warm temperatures have taken their toll.

“The national forest is stressed out,” Patzert said. “The absence of snowpack has endangered the national forest.”

Bark beetles are tiny brown insects that chew away at the pines, making them brittle. As the beetles invade forests, the trees suffer a quick death and become the perfect fuel for fire.

Stressed trees competing for limited resources also become more susceptible to the beetles, which best survive in diseased, injured and drought-stressed trees.

During the aerial survey, Moore and fellow researchers looked to detect and map the severity of tree damage in Southern California’s forests.

Using a digital aerial sketch-mapping system, researchers flew in a fixed-wing aircraft about 1,000 feet above ground level and surveyed more than 4.2 million acres of forest.

The areas monitored were the Cleveland, San Bernardino, Angeles, and Los Padres national forests. Some private lands and Pinnacles National Park in Central California were also surveyed.

About two million recently killed trees were mapped in Southern California during the survey, he said. Higher-elevation trees were not mapped because it’s too early to properly assess the damage, Moore added.

“The most heavily impacted area right now is the southern Sierras,” he said.

Pine trees, including the precedence, Ponderosa, jeffrey, coulter, and pinyon species, suffered the most death, Moore said. Pinyon, for instance, is most common in lower elevations and drier, harsher environments.

Fir and oak trees were also harmed from the drought.

But it’s not all bad news for the forests. The drought means more competition for water.

“In all but the worst areas, many trees will survive and with less competition for the limited supply of water, may well survive long term,” Moore said.

A more complete picture of the statewide tree mortality will begin in June and may not be completed until the fall, Moore said.

Photo: Cyndy Sims Parr via Flickr

Water Stress Takes Toll On California’s Large Trees, Study Says

Water Stress Takes Toll On California’s Large Trees, Study Says

By Taylor Goldenstein, Los Angeles Times (TNS)

Drought, fire-suppression techniques and changes in land use have made California forests denser with smaller trees and more susceptible to fast-moving wildfires, a study being released Tuesday has found.

Researchers at The University of California, Berkeley, UC Davis and the U.S. Geological Survey compared tree surveys conducted between 1929 and 1936 with surveys conducted between 2001 and 2010. They found that large tree density fell across California, with declines of as much as 50 percent in the Sierra Nevada highlands, the south and central Coast Ranges and Northern California. At the same time, the density of smaller trees increased dramatically.

Drier conditions caused by drought reduce water available for trees to grow while making it easier for fires to start and spread. Scientists say the changes raise crucial questions about how California manages its forest land to prevent and control wildfires as temperatures increase.

“The current drought in California highlights our need to understand the role of water balance in these systems and how it will be affected by global temperature rise,” said the study’s lead author, Patrick McIntyre. “Forests and woodlands cover a third of California, so this has important implications for our state.”

The study, published in the journal Proceedings of the National Academy of Sciences, found that declines in large tree density were greatest in areas with the greatest increase in water stress (when there is more demand for water than water available).

Large trees, which are important for storing carbon from the air and providing food and habitat, can be more vulnerable to drought and water stress, McIntyre said.

“Declines in their numbers are concerning,” he said.

Researchers found that densities of small trees increased in almost every region of California surveyed. Small tree density within the Sierra Nevada highlands more than doubled, and it increased more than 50 percent in the Sierra Nevada foothills, the North Coast region and the Transverse and Peninsular ranges.

Oak trees, which thrive in warm, dry climates, increased in density as pine density decreased, the researchers found.

California has a Mediterranean climate, McIntyre said. Almost all of its precipitation comes in the winter, and in the summer it dries out. A lack of year-round water availability limits the amount of water stored in the soil and can hinder tree growth, he said.

Higher temperatures, which cause earlier snowmelt and more water loss through evaporation and plant transpiration, compound the water scarcity problem for larger trees.

Fire and timber management practices also play a major role in forest structure changes, the researchers said. The common reaction to wildfires is to quickly suppress them. But the study raises questions about how to adjust intervention techniques to allow healthy burns without jeopardizing human safety.

Mark Schwartz, professor of environmental science and policy at UC Davis and director of the John Muir Institute of the Environment, studies the effect of climate change on wildfires.

A denser forest allows fire to travel faster, causing more devastation, he said. After a fire, smaller trees grow that are more likely to catch fire, and the cycle continues.

“These are historically fire-maintained ecosystems,” Schwartz said. “The firemen are faced with this notion of when a fire is reported and started, do they go out and bring out helicopters, trucks and people and put the fire out, or do they let it burn?”

But prescribed burns and tree thinning can be controversial, said David Ackerly, a researcher involved in the study and professor of integrative biology at UC Berkeley.

Duane Shintaku, deputy director for resource management for the California Department of Forestry and Fire Protection, said letting a fire burn is never an option. The agency’s goal is to keep fires to less than 10 acres, he said.

“We’re protecting private lands and public lands where there’s many lives at stake and homes at stake, (and) infrastructure … and you can’t tell someone ‘You know what? We’re just going to see what would happen if we wait to see if it gets big,'” Shintaku said.

Over the last 50 years, Shintaku said, logging has decreased significantly, which also contributes to the increased density of California forests.

The department has a number of techniques to manage forests, Shintaku said, including using machines and people to thin trees, harvesting usable materials for wood products and energy conversion, and igniting small prescribed burns. The strategy keeps forests healthy by eliminating diseased trees and harmful insects.

From July 1, 2012, to June 30, 2013, Cal Fire’s Vegetation Management Program staff burned 7,786 acres of trees with prescribed fires. An additional 8,777 acres of trees were mechanically removed, usually when burning was too dangerous.

Still, California has much work to do to improve forest management, Shintaku said.

“We have to start going after it because we’re playing catch-up right now,” he said.

Photo: Trey Ratcliffe via Flickr