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Dead tree crisis: How mortality impacts environment

Escalating fire threats are a primary concern. Changes in Sierra Nevada ecosystems are among long-term effects.


U.S. Forest Service / Courtesy photos Drought-stressed, beetle-infested trees are riddled throughout the Stanislaus National Forest.

More than 60 million dead trees in the Sierra Nevada mean mountain forests are changing. Air and water quality, forest composition and wildlife habitat are all susceptible, but there is no consensus on how bad it might get.

Federal forest custodians, researchers, advocates, environmentalists and people who work in the timber industry are all watching closely for not only what the dead trees mean today but also what it could mean over generations.

Megafires burning dead fuel could release pollutants into the atmosphere. Erosion could impact mountain watersheds.

Pine-dominant forests could transition to hardwoods and healthy populations of animals could suddenly find themselves competing for limited food supplies or moving to higher elevations to find a more hospitable home.

“Looking at the big picture, this truly spectacular four-year drought and all the associated bark beetle mortality have combined to squeeze dramatic habitat change into a few years,” said John Buckley, of the Central Sierra Environmental Resource Center in Twain Harte.

Add the magnitude of the 2013 Rim Fire, the 2015 Butte Fire, and other local fires in the last few years, and consider what will happen to wildlife species if there is another devastating fire this year or next, drought and bark beetle impacts have already devastated wildlife and watersheds in Tuolumne and Calaveras counties, Buckley said.

Forest Service

Kerry Greene, with Forest Service Region 5 in Vallejo, said trees die and the bark beetles are part of the ecosystem.

“But it is out of whack because so many trees are dying at once due to drought. It’s an unprecedented number of dead trees and it’s a bark beetle population explosion,” Greene said.

The Forest Service announced last week that there are now a record 66 million dead trees in the Sierra Nevada based on aerial surveys conducted by the Forest Service in May.

Scientists identified 26 million more dead trees across more than 1,100 square miles in Tuolumne, Mariposa, Madera, Fresno, Tulare and Kern counties since October 2015.

“This is going to last three to five to seven years,” Greene said. “When it’s all said and done the forest will look different. They might not go back to same makeup in terms of species. It’s likely they’ll never be the same again.”

Less water may be permanent, Greene said.

“There might not be the same amount of water as there was when these forests became established,” Greene said.

On a small scale, losing 75 pines out of 100 pines across five acres doesn’t make a big difference for the overwhelming majority of wildlife species, Buckley said.

But if there are 500,000 acres of pine forest across the lower and lower-middle elevations of the Sierra Nevada that become mostly oak with a few scattered pines due to bark beetles, then all the nuthatches in those 500,000 acres must crowd into already-occupied forest habitat where other nuthatches are living and feeding, Buckley said.

“If red-breasted nuthatches reside primarily in cavities and find highly suitable habitat in conifer forests with tasty seeds in conifer cones, they may lose some patches or blocks of pine forest as the majority of pines die from bark beetles,” Buckley said.

Stanislaus National Forest

Buckley and his staff at the nonprofit CSERC have spent the past 25 years observing changes in the Stanislaus and other parts of Tuolumne and Calaveras counties. The organization bills itself as a principal defender of 2 million acres of forests, rivers, lakes, wetlands, roadless areas, old growth groves and oak woodlands in the North Yosemite region, including the Stanislaus National Forest.

He talked Tuesday about what will happen as pine trees die and other species grow in their place.

“Over on Mount Provo and Mount Lewis, south of Twain Harte, and other places, most of the mature pines are dying on those low elevation mountains, on south-facing and west-facing slopes, the slopes that are hottest and driest,” Buckley said. “During drought years they have the least amount of water and they are easiest for the bark beetles to get high in numbers.”

What will happen is that unless there are enough small young trees to come up and take their place, they will shift to become oak forest, dominated by oaks, Buckley said.

“Right now they might be 60 percent pine, 40 percent oak,” Buckley said. “But if the pines die, part of the forest can be 10 percent pine or less and 90 percent oaks or more.”

Tree mortality is devastating in the Stanislaus National Forest but it’s worse to the south, in the Sierra National Forest.

“Instead of pines dying in lower elevations, they have pervasive mortality at lower and middle elevations, and at some higher elevations,” Buckley said. “They truly are losing 80 percent of their ponderosa pine and sugar pine. It’s the same for the Sequoia National Forest. They have just been hammered.”

Previous tree mortality

Trees have died off before in the Sierra Nevada, Buckley said. There was a significant bark beetle event in the 1930s.

Forty years ago there were two winters in a row with severe drought conditions, 1976-77 and 1977-78. In the late 1980s, with three years of drought out of four, there was a massive die-off from bark beetles that killed ponderosa, sugar pine and a limited number of firs, Buckley said.

Trees died in the Stanislaus National Forest and at Calaveras Big Trees State Park, Buckley said. But these previous die-offs took place in a cycle that allowed more natural recovery.

“Five years after an event enough trees survive that it doesn’t show up as a big impact,” Buckley said. “This time it is an ecosystem-shifting event. The ecosystem is changing, from conifers to hardwoods. On top of that there’s been an exceptional die-off of larger ponderosa and sugar pines in the lower and middle elevations.”

Sierra Club

Bruce Hamilton is a deputy executive director for the Sierra Club, founded by conservationist John Muir in 1892. It’s billed as the nation’s largest grassroots environmental organization with more than 2 million members and supporters.

Hamilton believes the Sierra Nevada will continue to produce conifers in areas now impacted by tree mortality.

“Hardwoods are basically confined to creek bottoms,” Hamilton said. “Alders, willows and cottonwoods, the hardwoods are in riparian waterway types of habitat. So when trees do come back they are likely to be conifers. In some places you might initially have small shrubs, like ceanothus — buck brush — but eventually conifers will come back in.”

Hamilton says the current die-off is unnatural because there is a climate change component, which is human caused.

“There are natural cycles of drought and insect infestation and major fires and those are historic and they will continue,” Hamilton said. “But this is compounded by climate change. If you look at the average annual temperatures that have been occurring over the past decade, they’re hotter than they have been historically. If you look at the snowpack it is also at record lows for recent history. The combination of the two lead to a different kind of situation than we regard as normal in the Sierra Nevada.”

The Sierra Club opposes cutting down all dead trees, Hamilton said. He says there is an over-reaction by the Forest Service that seeks to get lots of money and cut down all the dead trees, supposedly to try to protect private property and people’s lives.

“Since we have limited dollars to respond, with such a wide area of dead trees the most important thing to do is to really clean up the fire hazard right next to urban areas and residences,” Hamilton said. “If you look at what they’re trying to do with emergency legislation they want to go into the backcountry and do broad scale logging over wide areas of the national forests. We don’t have enough money to take out all those trees.”

Air quality

Andrzej Bytnerowicz, a senior scientist and research ecologist with the Forest Service Pacific Southwest Research Station in Riverside, has been focusing recently on how pervasive tree mortality could impact air quality.

“I think in the future it can affect air quality significantly,” Bytnerowicz said Tuesday. “If the trees are dead they are not taking up CO2 from the atmosphere. All healthy trees photosynthesize. Evergreens do photosynthesis just like deciduous, big-leaf trees.”

Healthy trees take up carbon dioxide and ozone but dead trees do not. Bytnerowicz said that in the more densely populated western Sierra Nevada, there’s potential that tree mortality will result in less uptake of toxic pollutants by healthy trees.

Air quality is always a concern when large fires occur, including the 2013 Rim Fire and the 2015 Butte Fire. Tree mortality will be a root cause of air quality concerns if more megafires break out, Bytnerowicz said.

“If fire happens, the dead trees will burn and we will have release of various gases during the fire,” Bytnerowicz said. “Toxic gases like nitrogen oxides and sulphur oxides and various organic compounds including benzene.”

Fine particulate matter is another problem during large forest fires.

“These are really tiny particles which get into our lungs and blood stream and they affect our respiratory system, breathing, asthma things like that, and they have various negative cardiovascular effects,” Bytnerowicz said.

That’s what firefighters deal with when they fight fires, and that’s what residents can face when they are downwind from fire smoke, Bytnerowicz said.

Sierra Resource Management

Mike Albrecht runs Sierra Resource Management in Jamestown, one of the surviving timber businesses in the Mother Lode.

“There’s definitely two effects, short-term and long-term,” he said.

Short-term is the impact on lives and property, Albrecht said.

“We need to get our subdivisions cleared of all these dead trees,” Albrecht said. “We need to keep our roads open and provide access for both emergency response to fire and other needs and for recreation.

“Long-term there are impacts on watersheds, wildlife habitat, forest products we’re not going to be able to get out, from Mariposa south,” Albrecht said. “It’s in the process of doing that from Tuolumne County north up to Calaveras, El Dorado and Placer County, moving north in the Sierra Nevada. These effects will be felt beyond our lifetimes and change the forests for generations.”

The positive thing is Sierra Nevada forests are made up of a multitude of tree species, Albrecht said.

“Pine species will be reduced but other species such as fir and cedar and other evergreen species, and hardwoods like oaks will increase,” Albrecht said. “The forest isn’t going to be reduced or quit producing oxygen and stop being healthy watersheds. Those functions will continue. Our forests are resilient.”

Sierra Pacific Industries

Mark Pawlicki is the Redding-based director of corporate affairs and sustainability for Sierra Pacific Industries, which owns 1.6 million acres of timberlands in California, most of it in the Sierra Nevada from Yosemite to the Oregon border.

“We don’t dispute the numbers. We think it will probably get worse with the drought and insect activity,” he said.

SPI timber managers are trying to harvest as many dead trees as possible, Pawlicki said. The logging giant also buys timber from other sources, including the Forest Service and other private landowners.

“But it’s hard to keep ahead of the dying trees particularly on the national forest lands,” Pawlicki said. “There clearly will be long-term effects, especially in areas where dead timber is not harvested. It’ll deteriorate. It’s hard for a new forest to get re-established on its own. If the timber is not harvested, replanting and reforestation takes longer to occur. That affects wildlife habitat and water quality and other natural resources.”

There are no easy or simple solutions, Pawlicki said. If dead trees are on federal land, agencies have to follow the National Environmental Policy Act and other laws that can delay harvest and recovery of the land, similar to timber harvest delays in the aftermath of the 2013 Rim Fire.

“We’d like to see Congress take action to expedite the salvage of dead timber, more than what is allowed under current law, and to provide funding for the Forest Service to undertake projects dealing with the dead trees,” Pawlicki said. “Once you solve the short-term problem, you are taking a good step toward the long term solution, harvesting timber and stabilizing soil and replanting.”

"Looking at the big picture, this truly spectacular four-year drought and all the associated bark beetle mortality have combined to squeeze dramatic habitat change into a few years.”

— John Buckley, director of the Central Sierra Environmental Resource Center in Twain Harte