Colorado is well known for its iconic forests, sparkling alpine lakes, picturesque mountainsides and diverse wildlife. But over the last two decades, Colorado’s 24.4 million acres of forests have been devastated by beetle infestation, drought and wildfires — all of which are exacerbated by climate change.
“Most projections indicate that droughts, large wildfires and heat waves all will increase in frequency and severity in Colorado by 2050. We must be prepared to change with these forests, and adapt our management efforts accordingly,” said Ryan Lockwood, program manager at Colorado Forest Service.
And Colorado’s forests are not the only ones struggling to stay afloat under the weight of a rapidly changing climate.
Latest in a series of increasingly destructive wildfires, the Thomson Fire, currently spiraling through Southern California, has engulfed more than 270,000 acres. With this in mind, foresters and researchers in Colorado are all the more focused on ensuring that the state’s forest’s remain healthy.
Colorado’s forests provide a long list of services for the community such as filtering pollutants from the air and water, providing homes for wildlife species, furnishing outdoor adventures, supplying jobs and boosting the economy.
Every year, visitors flock to Colorado and 46 percent will make their way to a state or national park, according to the Colorado Tourism Office.
“Approximately 90 percent of Coloradans participate in some form of outdoor recreation each year, largely in our mountain forests, and 100 percent utilize the air and water coming from them. Everyone benefits from healthy forests,” said Lockwood.
Carol Wessman, professor in ecology and evolutionary biology at the University of Colorado Boulder, has made Colorado forest health a priority.
Wessman is the principle investigator for Project Forest, a collaborative research endeavor that is assessing how different disturbances -- primarily drought, wildfires and beetle kill -- interact to impact Colorado’s sprawling forests.
“So when we think about forest mortality and forest recovery, there are a lot of pieces to that puzzle,” said Megan Cattau, postdoctoral researcher for Project Forest at the University of Colorado Boulder.
In order to make a more complete picture, the team uses data from field-based inventories, drones and satellites.
The data helps Wessman and her team understand the extent of the damage that has already occurred, and in light of climate change, how to plan for the future.
The team uses an airborne observation platform, called NEON, to collect high-resolution hyperspectral, red-green- blue (RGB) as well as imagery light detection and ranging (LiDAR) information.
Hyperspectral data enables Wessman’s team to determine individual impacts to specific tree species. The RGB and LiDar imagery highlight vegetation structure, which allows researchers to measure canopy health and tree counts.
The team also utilizes Landsat data, which has been recording landscape vegetation from space for over 30 years. This data supplies the project with a long term data set, which enables researcher to evaluate the changes in forest dynamics over time.
“Project forest is looking specifically at forests in the southern rockies. But the methodology that we are developing in terms of linking the data collected from the ground, from drones and from satellites can be applied at much larger scales, potentially across the whole U.S,” said Cattau.
A critical threat to Colorado’s forests, says Cattau, is the increase in global temperatures caused in part by increased emissions of carbon dioxide in the atmosphere. Warmer and drier conditions in the last two decades have contributed to the largest bark beetle outbreaks as well as the top 10 fires in the state’s recorded history.
According to the statewide meteorological records collected by the National Oceanic and Atmospheric Administration, Colorado’s climate has increased by 2 degrees Fahrenheit over the past three decades, and predictions show that the state could see an increase between 2.5 and 6.5 degrees Fahrenheit by 2050.
In healthy ecosystems, forests filter and regulate the flow of water by intercepting rainfall and absorbing it through the forest floor. But when a forest is impacted by drought, the capacity to store water is reduced, which exacerbates the already arid Colorado conditions, leaving trees and soil dangerously dry and more susceptible to beetle infestations.
The warmer winters also allow more insects to survive the cold season, and a longer summer allows some insects, like the mountain pine beetle, to complete two life cycles in a year instead of one. This was seen in the Mountain Pine beetle epidemic from 1996 to 2014, which resulted in 3.4 million acres of infested Lodgepole and Ponderosa pine forests throughout the state.
“One of the common defenses of the tree when under attack by beetles is to pitch-out, or send sap into the bore holes created by the insects. If the forest is too dry, the trees are not able to provide those defenses and they are more likely to become infested and die,” said Cattau.
Boring beetles pierce into the bark of trees, destroying the structure of the tissues that carry water up to the leaves and nutrients down to the roots. With its essential channels of supply severed, the tree will eventually die.
Since 1996, the Spruce beetle had devastated 1.7 million acres of high-elevation Spruce forest, according to the 2016 Report on the Health of Colorado’s Forests.
Spruce beetle was Colorado’s most damaging insect for the fifth successive year, impacting 350,000 acres of high-elevation Engelmann Spruce forest. And the Western Spruce budworm was the state’s most widespread insect defoliator, impacting 226,000 acres of forest in central and southern Colorado.
Due to the high volume of dead trees from beetles and drought, much of the Colorado’s forests have become unhealthy and densely populated with essentially fire kindling, or what the CSF calls a potential 3.4 million acre campfire.
In 2008, there were an estimated 642 million dead standing trees in Colorado. By 2015, this number had increased to 834 million dead standing trees – an almost 30 percent increase over seven years, according the Colorado Forest Service.
The 2016 Beaver Creek Fire northwest of Walden is a prime example of the increased danger that beetle infestations can have, as the amount and arrangement of dead trees helped the fire burn nearly 40,000 acres of forest.
This was also seen in the 2013 West Fork Fire Complex that burned in the San Juan and Rio Grande National Forests in southwest Colorado. Similar to the Beaver Creek Fire, the complex terrain and large number of beetle-killed trees created an unsafe working environment for firefighters and allowed the flame to spread rapidly.
The long-duration fires have the potential to greatly increase suppression costs across Colorado, especially when structures are in close proximity to the fire. And with Colorado’s booming population increase in the last 10 years, foresters have a lot more to worry about.
Colorado’s wildland-urban interface population — the area where structures and other human developments meet or intermingle with wildland fuels — increased by more than 1 million people and 300,000 acres from 2000 to 2012.
And these figures continue to grow.
“If the remaining WUI land becomes populated without considering the risks of wildfire, and without landowners actively engaging in forest management, this will have serious implications for human safety, future firefighting costs and the ability to best manage our forests,” said Lockwood.
One of the most critical resources Colorado’s forests provide is a sustainable water supply. Unhealthy and overly dense forests set the stage for devastating wildfires, which increase the risk of flooding, erosion and degraded water quality.
Which is a big deal, as 80 percent of Colorado’s population receive their municipal water supply from forested, high-country watersheds, according to the Colorado State Water Plan.
But fire isn’t always the bad guy.
Wildfires play a critical role in maintaining a healthy forest ecosystem. In Colorado, lower-elevation forests rely on frequent, low-intensity fires to control regeneration and reduce ground level vegetation, while some high-elevation forests, such as Lodgepole pine, rely on high-intensity fires to naturally thin the forest.
But a long history of fire suppression has led to a dangerous build-up of “forest fire fuel” throughout the state. In addition, the wildfire season has lengthened due to climate change, meaning the fires start earlier, last longer, do more damage and pull more money from the taxpayer’s pocket.
Another concern, explains Lockwood, is a decreasing capacity for carbon storage in Colorado’s forests.
According to the Environmental Protection Agency, an estimated 14 to 15 percent of the nation’s carbon emissions are offset by carbon stored in U.S. forests and wood products each year.
One way to help forests regenerate after multiple disturbances is ensuring a diversity of tree species in the forest, as well as varying ages.
The Colorado Forest Service Tree Nursery in Fort Collins produces more than 500,000 seedlings each year, which are planted around the state to diversify the forests.
“So we know that our climate is changing. We know that humans are having a huge impact on the landscape. We are changing the characteristics of disturbances, we are changing fire regimes, which have far reaching impacts for people across the country,” said Cattau.
Tracking these changes will enable researchers, foresters and citizens to better understand forest processes to ensure long-term forest health.