On two continents, scientists fight the bark beetle battle

Hot weather, windstorms, too much rain, not enough rain – the climate is amplifying the conditions for a devastating bark beetle infestation across Germany, the Czech Republic and other European forests, with 40 million cubic meters of wood destroyed just in Central Europe last year.

That’s according to experts at University of Würzburg, one of many international institutions that in recent years have focused on how to defend forests against the beetle and how climate change is making that task harder. They note that for the conifer-tree industry, the lowly bark beetle has the biggest global economic impact. It also represents the loss of climate-critical forest resources and certainty about how the wider ecosystem will work.

Future climate variables will likely add threats to the forest. “The expected increases in the frequency and intensity of extreme weather events will additionally weaken German timberlands,” said Jörg Müller, a University of Würzburg professor and assistant manager of the Bavarian Forest National Park. Müller and his colleagues published in October a paper exploring the “unprecedented” damage, and lamenting that there is still so little known about the beetle despite more than 200 years of research.

The industry-specific Forest Economic Advisors group puts the losses higher when counting both insect and wind damage, which they say has claimed more than 100 million cubic meters. Extremely hot and dry summers have “fanned the flames” of the outbreak, while climate-induced drought “has weakened mature trees’ natural defense mechanisms, giving beetles a wide-open field to multiply unchecked.”

“The resulting massive infestation has forced landowners to quickly harvest their attacked forests across the Bavarian region of Germany, as well as in the Czech Republic, northern Austria, Slovakia, Poland and half a dozen other European countries,” added the FEA, which is based in North America. That has wider impacts for global trade, as well as the management of stricken forests to better contain the beetles.

For example, an upcoming article in January’s Journal of Environmental Management warns that at least 80 percent of trees felled by wind need to be removed to make a significant impact on bark beetles – and climate change is reducing how effective the industry’s “sanitation logging” practices are for Central Europe. The researchers, led by Czech scientist Laura Dobor, think that focusing these practices on logging roads may create a “wall” similar to a wildfire firebreak that deters the beetles from spreading.

Canada and the United States have also seen devastating infestations and are looking at potential solutions. The U.S. state of California saw a four-year drought cycle support bark beetles that ultimately destroyed 129 million trees. The conditions led biologist Patricia Maloney and her team at University of California-Davis to collect the seeds of hardy sugar pine trees that survived the beetles in the Lake Tahoe Basin.

They spent two years growing some 10,000 seedlings from the surviving trees and they’re being used to reforest the same region.

“These survivors matter,” said Maloney, a scientist who works in the university’s Tahoe Environmental Research Center. “Essentially, these are the offspring of drought survivors. This is hopefully the genetic stock of the future.”

If the sugar pines have the genetic resilience to be more climate-tolerant, it’s another way scientists may solve the bark beetle dilemma.