“The Bug That’s Eating the Woods.”
“Small Pests, Big Problems: The Global Spread of Bark Beetles.”
“Eighty-Nine Million Acres of Abrupt Climate Change.”
The terrifying beetle-kill headlines from the mid-2010s were as relentless and depressing as the swaths of rust-red dead lodgepole on your favorite drives or hikes in Grand County. Coloradans wondered if their beloved forests would ever recover from the onslaught of bark-boring pests, and if tourism would suffer a big bite.
A decade later, there’s good news and bad news, according to the annual aerial survey of state trees from Colorado State University’s forestry department.
The notorious spring rains and floods of 2013 slapped back one voracious, drought-opportunistic pest, the mountain pine beetle, according to CSU. And a relatively wet 2023 for much of the state bolstered many trees against the spread of that beetle, the separate spruce beetle and the spruce budworm.
But a dry 2024 set the pests marching and eating again by sapping forests of the water they need to stay healthy and fight off infestations, said Dan West, entomologist with Colorado State Forest Service. Colorado’s higher-altitude forests need several normal to wet seasons in a row to build up true resiliency, he said.
- One dry season meant Western spruce budworm affected 217,000 acres of state forests in 2024, up from 202,000 acres in 2023, according to the CSU survey. Precipitation in four of the last five years was below the 100-year average.
- Mountain pine beetle, which creates the highly visible rust patches in hillsides crammed with lodgepole, grew to 5,600 acres of impact.
- The Douglas-fir beetle impacted 21,000 acres in 2024, its largest total damage in almost 10 years, West noted.
- Western balsam bark beetle, which attacks subalpine fir and other species, is still the deadliest forest pest, as distinguished from being the most widespread by acreage. The acres affected by the balsam bark beetle held steady at 27,000, but more of those trees die. Other pests like the spruce budworm can damage trees but don’t necessarily kill them, West said.
(For context, Colorado has about 4.1 million acres of pines, such as ponderosa and lodgepole, at relatively lower elevations; and 4.5 million acres of spruce, such as blue and Englemann, at mid- to higher elevations.)
Much of the damage to Colorado forests has been accelerated by recent years of climate change, bringing higher summer temperatures and lower snowpack for trees to soak up, West said. But save some blame for earlier generations of Coloradans, he added, for older firefighting policies like “the 10 a.m.” rule.
Previous forestry managers dictated that any new wildfire must be put out by 10 a.m. the next day, West said. That prevented the natural culling by lightning-caused fires, and hurt the resilience of diverse forests by allowing dominant species to continue building up.
Now, West added, those same mountain forests are getting hit hard by climate change nearly every year.
“Trees are not just sitting ducks out there, but they are when we have these increased temperatures and reduced precipitation,” West said. “We haven’t seen temperatures below the 100-year average in the last 31 years. So of course, it’s really tough to be a tree.”
