Drought is projected to intensify in frequency and severity, bringing with it more wildfires, insect-induced tree mortality and a host of economic impacts as global temperatures rise, according to a comprehensive scientific assessment released by the U.S. Forest Service.

Simply put, the report released Monday synthesizes a growing body of research that finds that drought is not good for America’s forests.

“Looking at 300 pages as a whole, the main message is that even if we don’t know exactly how drought will manifest in the future, the consequences for forests are likely to be worse,” said Charles Luce, a research hydrologist with the Forest Service’s Rocky Mountain Research Station and co-editor of the report.

Authored by 77 scientists from the Forest Service, other federal agencies and universities across the United States, the report outlines the way forests respond physiologically to drought-stress, as well as steps land managers and foresters can take to mitigate the impacts of rising temperatures and a lack of water.

Historically, drought has been observed in forests and other ecosystems for millennia. But the report notes that as of late, “recent trends are a growing global concern.”

Specifically, higher temperatures seem to spell doom for many trees.

“Trees are sort of like cold-blooded animals; they regulate their temperatures from the outside,” Luce said. “When it warms up, they use their food faster.”

Whiskey barrels in danger

A study released in December by the Carnegie Institution for Science at Stanford University estimated as many as 58 million trees in California are suffering from severe water loss because of drought conditions (ClimateWire, Jan. 4).

Starved and water-stressed trees are more susceptible to disease and insect activity and have a higher rate of death, said Marvin Brown, a former state forester of Oregon and Missouri who was not involved in the assessment.

For example, he said Missouri’s white oak population, a hardwood species used to make whiskey and wine barrels, is experiencing high levels of mortality because multiple seasons of drought weakened the stands, leaving them open to disease.

Although the focus of the Forest Service’s report is on the 193 million acres of national forest, the purpose of the guidance is to provide technical information to any interested party. The document provides input to the National Integrated Drought Information System and National Climate Assessment, which projects major trends and tracks the effects of climate change on forests as well as other sectors.

From a forest management perspective, the report notes that “management actions can either mitigate or exacerbate the effects of drought.”

Thinning forests is one option that could be employed. So, too, is favoring or planting drought-adapted species. Both are strategies Brown said he sees used on the ground.

“The absolute best thing you can do from a management standpoint is keep the density of the forest at an appropriate level,” he said. “The more trees on the ground, the more water that is required.”

Research needs still not met

Luce said those on the front lines of forest management have a lot to think about, and planning specifically for how climate change will impact drought conditions is “probably at the early stages.”

However, he added, exposing forest managers to the connection between changes in climate and the threats to forests gives them ammunition to respond appropriately in their forests.

In addition to economic value lost in the timber sector, drought reduces water quality, harms the quality of recreation activities, decreases rangelands suitable for livestock grazing and boosts wildfire risk. Tribal values as well as goods and services produced by tribes from forest ecosystems are also at risk, according to the assessment.

Although current drought worries have been focused in the West—Western states have experienced insect outbreaks; mass tree die-offs; loss of water and carbon; bigger and more costly wildfires; and economic impacts to timber stands due to severe, multiyear drought—in the wake of a changing climate, the report notes that “all U.S. forests are vulnerable to drought.”

Despite the plethora of research, more needs to be done, said the report, which ends with a wish list of critical research needs including better predictive capabilities and models, as well as ways to measure the socio-economic impacts of drought outside of money spent by the Forest Service suppressing fires.

“Our forests and rangelands are national treasures, and because they are threatened, we are threatened,” Agriculture Secretary Tom Vilsack said in a statement. “This report confirms what we are seeing, that every region of the country is impacted by the direct and indirect effects of drought conditions and volatile weather patterns.”

Click here to read the report.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500