Insects kill more trees each year in the United States than wildfire. Over time, forests and bark beetles co-evolved together. Their relationship can be beneficial or destructive, depending on the balance of power. Right now the beetles are winning. Amazing that a tiny rice-grain sized insect could take down a massive tree several hundred years old. Like an alcoholic, the bark beetle has an enabler supporting its rise to epidemic levels: human-caused climate change.
If you have ever walked through a dead standing beetle-kill forest, it’s an eerie experience, similar to a ghost town or a cemetery. Missing from this dead zone are the smells and sounds of a bygone ecosystem. It feels empty.
I recently spoke with Dan West, forest entomologist with the Colorado State Forest Service, to learn more about the threat climate change poses to our forests. He is a scientist and a passionate tree lover: “Our forest resources affect every citizen every day — from turning on the tap to taking a breath of air. We take these gifts for granted. We need to be good stewards of these valuable and vulnerable resources, especially as water is becoming scarce in the West."
Water helps trees resist bark beetles. Like a human who is dehydrated, trees become vulnerable from drought-stress. They can’t form enough sap to fend off the invaders boring into their bark. Once underneath, one female can lay 50 to 200 eggs. Beetles can kill a tree in one season, before moving on to the next host. In Montana, beetles have infested millions of acres of spruce, Douglas fir, lodgepole and ponderosa pines.
In Montana the average annual temperature has increased about 2-3 degrees Fahrenheit over 70 years. Snowpack in the mountains is shrinking, wildfire seasons are longer and more severe, and plant and animal habitat ranges are endangered. Impacts hurt Montana's agricultural industry and decrease ecosystem resiliency.
Dan West explains that heat plays a part in the bark beetle’s population explosion. Icy winter low temps (-40 degrees F) used to help kill off beetles. Warmer winters effectively give the pests a free winter pass. Earlier and warmer springtime temperatures allow the beetle larvae more time to chew away, carving destructive “galleries” below the tree bark. After years of drought, we are not “out of the woods” (excuse the pun) because of one snowy year. “It takes a few years of average precipitation for trees’ defenses to rebound,” said West.
A single acre of mature forest can absorb 2.5 tons of CO2 and release 4 tons of oxygen annually. Unfortunately, the heat/drought interaction plays like a downward spiral on our forests’ carbon cycle. The hotter and drier the climate, the higher the tree mortality. The more tree die-off, the less carbon is absorbed from the atmosphere. The higher the number of dead standing trees, the hotter and longer wildfires burn, releasing more damaging greenhouse gasses into the atmosphere, and so on.
It’s foolish to passively watch the warming climate destroy what we hold dear: forests, wildlife habitat, air and water quality, and productive croplands. Individual action to reduce our own carbon footprint is great, but it’s not enough to stop climate change. We need systemic change through national legislation that prices carbon pollution and incentivizes clean technologies.
According to the 2018 Yale Climate Opinion Poll, 74% of Montanans support policy to regulate CO2 as a pollutant. If you want healthy forests and a livable climate, please ask Congress to put a price on carbon pollution and protect our future.