Colorado’s Forests in a Changing Climate

Climate

The Earth’s climate is highly dynamic. We experience its short-term volatility – over minutes to days – as weather. It also changes over much longer time scales, over years to decades. Although the global climate has experienced many such changes throughout history, in recent decades changes to the climate have been especially rapid, with increasingly observable impacts in the environment.

How is Earth’s Climate Changing?

According to NASA and the National Oceanic and Atmospheric Administration (NOAA), global average temperatures are continuing to rise, with the 10 hottest years on record all occurring since 1998. In fact, 2014, 2015, 2016 and 2017 were the four hottest years in recorded history. As a result, changes in our environment already are happening: Northern Hemisphere snow and ice cover is shrinking, wildfire seasons are longer and more severe, plant and animal habitat ranges are shifting, and some trees are flowering sooner than in the past.

Recent Trends

Based on statewide meteorological records collected and analyzed by NOAA, over the past 30 years Colorado’s climate has warmed by about 2°F. And this change is having impacts. Periodic warmer and drier conditions in the past two decades have already contributed to the largest bark beetle outbreaks in the state’s recorded history, as well as the top 10 largest fires all occurring since 2002.

Further Changes to Come

Significant further warming is expected in Colorado, by another 2.5°F to 6.5°F by 2050 based on projections from Global Climate Models (GCMs) developed by NOAA, NASA, the National Center for Atmospheric Research and other research groups. Earlier springs and hotter summers are projected throughout the state, with more frequent and severe heat waves. The hottest summers from Colorado’s past may be indicative of the average summers of the future. Temperatures experienced today only at lower elevations are projected to creep upward into the mountains. Continued warming is expected to reduce Colorado’s spring snowpack levels and cause earlier snowmelt and runoff, and potentially lower runoff overall, impacting water availability for municipalities, agricultural producers and native trees and vegetation.

Most climate projections also indicate that droughts and wildfires will increase in frequency and severity in Colorado by 2050, mainly as a consequence of continued warming.

The Role of Forests

Forests in both our wildland and urban areas play a critical role in our ability to deal with climate change, because of how they utilize and store carbon.

As a greenhouse gas, carbon dioxide in the atmosphere – whether from human emissions or natural sources – traps heat from Earth and re-radiates some of it back toward the planet’s surface. Increasing atmospheric carbon dioxide leads to warming. But trees store and absorb carbon that might otherwise end up as carbon dioxide in the atmosphere, with young and vigorously growing forests most effectively absorbing this climate-altering gas. 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.

Insect & Fire Effects

Unhealthy forest stand conditions, long-term droughts and warmer temperatures have together been to blame for Colorado’s recent bark beetle epidemics. And while stand conditions and short-term weather patterns – rather than longer-term climate patterns – largely dictate fire potential in Colorado’s forests, longer-term climate trends could influence fire behavior, intensity and occurrence in the future.

Forest Management

From a forestry standpoint, one of the best defenses against threats associated with a changing climate is to ensure diverse, resilient forest ecosystems. As forest conditions change in response to climate shifts, the CSFS can help landowners manage forest composition, stand density and the fuels available for wildfire, while improving forest resiliency to insects and disease.

Managing Forests in a Changing Climate

Planning approaches that explore multiple possible future conditions, rather than a single future outcome, are ideal to manage for current climate projections and help forest managers and landowners best prepare for an uncertain future.

Examples of ways to increase forest resiliency to climate change, retain carbon within forests and capture additional carbon dioxide through managed forestlands include:

• Ensure a mixture of older and younger trees. Larger, older trees act as reservoirs that store the most carbon while young, vigorously growing trees actively absorb the most carbon dioxide from the atmosphere.
• Help forests regenerate after wildfire or other catastrophic events, through plantings of seedling trees, to allow the new trees to recapture carbon as they grow.
• Manage for diverse tree species to provide more resilient forests in uncertain future environments, in both wildland and urban settings.
• Reduce tree densities in historically fire-prone and less-dense forest types, to help reduce the risk of intense crown fires burning in the forest canopy and killing entire stands (which later would decompose and release carbon into the atmosphere).
• Utilize wood obtained from timber harvesting efforts, either as lasting wood products or to heat homes and other structures on or near the project site (as an inexpensive and more carbon-friendly alternative to fossil fuels).
• Prepare for longer fire seasons and potentially more intense fire behavior when planning fuels-reduction and wildfire mitigation actions in or near communities.

Besides forest management, a focus on utilizing wood products instead of other materials for durable goods is a great way to offset carbon emissions, because of wood’s carbon-storing capabilities. In fact, a 2014 study by Yale University indicated that 14 to 31 percent of all global CO2 emissions could be avoided merely by using wood (treated for fire resistance) to construct larger buildings, rather than steel and concrete – which are very carbon-heavy to produce.

The management choices landowners make now – and the actions we all take to address climate change concerns – will have long-term implications for Colorado’s residents and forests. The CSFS encourages careful consideration of what we want our future forests to provide, and selecting management options that best achieve those outcomes for the benefit of future generations.