According to the National Interagency Fire Center, as of Oct. 9th, 2020, wildfires have consumed just under 8 million acres of forest land across the western half of the United States. This is roughly 1.7 million more acres than the 10-year average.
More damning, however, is the fact that dozens of large fires are still burning, many unchecked by firefighters. If acreage losses continue at current levels, the U.S. will reach over 12 million acres decimated by year’s end. That’s the largest swath of forestland burned by wildfires in almost 70 years. Not since modern forest suppression methods have been in use have we seen such widespread destruction.
These sobering statistics illuminate the staggering results of global climate change. But the mechanism behind these massively destructive fires isn’t as apparent as one might assume. While it’s true that dry conditions brought on by persistent droughts have set the stage, and decades of fire suppression have increased the density of trees and kindling in many parts of the country, there’s one small actor that’s directly responsible for much of the destruction.
The humble bark beetle.
By themselves, these beetles, most of which are no larger than a grain of rice, aren’t a threat. But parched forests, driven by climate change, are weakened and stressed, creating fertile ground for these industrious bugs. In the process, they’re leaving millions of trees dead, creating zombie forests that burn quickly and readily.
Climate Change & The Bark Beetles
There are hundreds of bark beetle species. Other than a few standouts, most exploit trees that are already dead or dying. Under normal circumstances, this creates a symbiotic relationship. The beetles get the food and breeding ground they need, and in the process, prune dead trees, helping to refresh the forest and render it more fire-resistant.
Climate change is undermining this renewal. California and much of the American west has been suffering from frequent and prolonged droughts since the 1990s. Pine and spruce forests are desperate for water, and this chronic dehydration is short-circuiting the defense mechanisms that allow healthy trees to resist bark beetle colonization.
Bark beetles lay eggs in a tree’s phloem layer, the inner bark that delivers nutrients throughout the plant. Colonization begins when a beetle burrows through the outer bark and then releases pheromones to attract others. Healthy trees protect themselves by secreting a sticky resin into the burrow holes, encapsulating or driving out the insects.
This strategy isn’t available to dehydrated trees that can’t spare the excess water. Unchecked, the insects can eventually number in the hundreds, digging tunnels into the phloem, where they lay their eggs. These tunnels cut the tree off from its nutrient supply, eventually killing it.
Compounding the problem, warmer winters don’t produce the deep cold snaps necessary to drive down bark beetle numbers. Climate change is thus creating a perfect storm. Warmer temperatures support more beetles, and parched trees are more easily infested, further increasing the insects’ numbers.
According to Jeff Hicke of the University of Idaho, since 1997, bark beetles have killed roughly 5% of forested areas in the western United States. That’s tens of millions of acres, or hundreds of millions of trees dead, providing ample fuel for wildfires.
What Can We Do?
Climate change is now unavoidable. We’re already experiencing the effects. Reducing greenhouse gas emissions can slow the process and is still a necessary step, but other interventions are now required to deal with the ramifications of our earlier irresponsibility.
To save our forests, it’s going to take a concerted effort from government agencies and the private sector. And it’s going to require new ways of approaching the problem because previous attempts have been unsuccessful.
For a time, the prevailing theory assumed that thinning trees in areas likely to be affected by bark beetles would allow the remaining trees to more effectively use available water resources. This would improve their health and make them more resistant to the beetles’ advance.
Unfortunately, the efficacy of this strategy hasn’t been borne out in practice. Insects subsequently decimated thinned areas. The failure was likely caused by the sheer number of insects that climate change supports. Even healthier plants still can’t withstand a full-scale attack.
Instead, scientists are recommending a genetic approach to the problem.
Even in badly affected forests, you’ll find the occasional tree that’s mostly untouched. These trees appear to exhibit a natural resistance to the bugs. Studying their rings, scientists have also discovered that these specimens appear to grow faster and stronger during warmer and dryer spells. This enhanced drought resistance allows them to defend themselves against the beetles when other trees fail.
If we can determine which genes are responsible for this natural immunity, we can use that knowledge, along with widescale genetic testing, to find trees that can resist bark beetles. This knowledge would significantly enhance the efficacy of current thinning practices. It would allow us to remove trees likely to be destroyed by the insects while leaving those that can resist an attack. That strengthens the forest and helps limit insect populations.
In areas already affected, forest managers much be vigilant about finding infested trees. If they’re already dead or dying, they must be destroyed before the juvenile beetles inside can spread.
Because much of the affected acreage is on federal land, states are limited in their approaches to the problem. It’s up to us to contact our representatives and let them know that we’re aware of the problem. We need to push them to act. Unless the federal government spends significantly more money and resources, the problem will only get worse.
And that’s not sustainable. Diana Six, a leading entomologist from the University of Montana that studies the problem, has said:
“In the central northern Rockies, where I live, it has been predicted that we will lose 90 percent of the lodgepole pines, 80 percent of ponderosas, and 66 percent of spruce by 2060. And that is independent of the mountain pine beetle — that’s just due to the loss of suitable habitat that will support these species.”
The reality is that if we allow climate change and the current bark beetle epidemic to remain unchecked, we may not have to worry about forest wildfires in the future. But not because we’ve solved the problem. Instead, there simply won’t be any forests left to burn.