Results of ACES’ Initiatives

Forests are in a state of constant flux. Yet, often these changes occur so gradually that they are hardly noticeable to casual observers. For instance, an area once dominated by aspen forests may gradually transition to spruce and fir trees, or a hillside previously covered by pinyon pine and juniper may transform into a landscape of Gambel oak and sagebrush following a wildfire.

Historically, changes in forests have resulted from natural processes. However, human activities are increasingly becoming the primary drivers of forest change. Factors such as wildfires, climate change, and heightened recreational usage are all impacting forest ecosystems. ACES is actively monitoring changes in Colorado forests through programs including the Colorado Forest Health Index and focused studies on spruce beetle research.

Colorado Forest Health Index

Since 2016, ACES has produced an annual Forest Health Index (FHI) for the Roaring Fork Valley (www.foresthealthindex.org). In 2019, we expanded the FHI to encompass all 38 forested watersheds in Colorado, defining “forested watershed” as any watershed with more than 30 percent forest cover. The FHI informs users about the changing drivers of forest health over time, focusing on 12 indicators: temperature, precipitation, streamflow, snowpack, fire risk, ozone, soil moisture, extreme temperatures, frost-free days, resource use, and insect and disease activity.

While year-to-year variability is expected, consistent shifts in any of these domains can lead to a deterioration in forest health. For instance, over the last 50 years, temperatures have consistently risen due to human-caused climate change. These changes manifest in forests as tree decline, increased wildfires, and bark beetle outbreaks.

ACES is committed to maintaining and enhancing the Colorado Forest Health Index. This year, we integrated the site into the ACES website (under “Resources”) instead of maintaining it as a separate entity. The appearance of the FHI has changed as a result, but the functionality and information remain the same. Over the coming year, we plan to introduce new metrics, including measures of drought, phenology, and forest productivity.

Spruce Beetle

ACES continues its collaboration with the Independence Pass Foundation (IPF) to monitor potential increases in spruce beetle activity within the Roaring Fork Watershed (for more information about spruce beetles, see “Insect and Disease Update” in this report). Research conducted in partnership with IPF and Colorado State University revealed that the upper Roaring Fork Watershed experienced frequent, low-severity outbreaks in the 1800s, with heightened spruce beetle activity detected every 20 to 30 years. However, this pattern ceased in the early 1900s, and we have found no evidence of an outbreak in the past 125 years. This lull in beetle activity has allowed more trees to mature, which could potentially fuel a high-severity spruce beetle outbreak in the future. The ongoing spruce beetle activity to our south and east further increases this risk. ACES and IPF have been carrying out annual ground surveys of local forests to monitor current spruce beetle activity. The data from these surveys complement aerial survey information and aim to identify significant outbreaks early. This knowledge enables the community to make informed management decisions based on up-to-date information.

ACES recently completed an ambitious project to enhance the infrastructure that forms Hallam Lake and to restore the wetland habitat surrounding the lake. Miners constructed Hallam Lake in the 1890s by building a large berm to dam the area’s natural springs. Before it was transformed into a nature preserve in 1968, the site served various purposes, including recreation, ice harvesting, livestock grazing, and functioning as a fish hatchery. After more than a century, the berm sustaining Hallam Lake was starting to deteriorate. The Hallam Lake restoration project, begun in fall 2021, utilized muck, sand, and rocks from the bottom of Hallam Lake to reinforce, and in some cases entirely replace, the 1890s berm. Throughout this process we introduced emergent wetlands around the lake, enhanced the lake’s depth diversity, and improved the length and quality of spawning channels. These measures will enhance the habitat in and around Hallam Lake for the foreseeable future.

The project culminated with the planting of the new wetlands, a restoration that created an additional .75 acres of emergent wetlands around Hallam Lake. In spring 2022, as the snow melted, these wetlands were barren muck. To combat the spread of invasive species and enhance animal and plant diversity, ACES opted for an aggressive revegetation of the new wetlands. This initiative began in early May 2022 when over 70 volunteers planted hundreds of willow saplings. The effort continued into the first week of June, when a professional crew planted more than 10,000 grass, rush, and sedge starts sourced from a native plant nursery. Since then, ACES staff has vigilantly maintained the area, monitoring and removing invasive species. We have been delighted by positive feedback from many long-time members and visitors.

Restoration work aims to enhance or repair native ecosystems, often by reversing or mitigating damage caused by humans. A common restoration practice in Western forests is reintroducing fire into landscapes after a century of suppression, as we did with Hunter Creek. Prescribed fires improve forests’ health, wildlife habitats, and reduce future fire risk. Restoration projects have a greater impact when conducted on a landscape scale—thus, a key objective is to create connectivity between restored areas, which benefits both wildlife and fire mitigation. Wildlife relies on connectivity between similar habitats, enabling species to move across the landscape—a necessity as many native species migrate with changing seasons or in response to varying elevational and slope conditions. From a fire mitigation standpoint, creating connected areas of recently burned forests offers firefighters strategic points on the landscape to potentially contain wildfires, which is why we are planning the Red Mountain prescribed fire in 2025.

Hunter Creek Prescribed Fire

A successful prescribed burn in the Hunter Creek Valley was conducted on May 13, 2022 by the U.S. Forest Service with the support of ACES, the Aspen Fire Protection District, the City of Aspen, and Pitkin County. This endeavor, the second burn in the area, utilized a helicopter and drip torches for ignition, resulting in a fire that covered approximately nine hundred acres. This effort built on the 2016 Hunter Creek prescribed burn, which also treated roughly nine hundred acres.

This second burn achieved two primary objectives. First, it targeted areas that did not burn during the 2016 operation, particularly at higher elevations that were snow-covered at that time. Second, it burned some areas at a higher intensity than in 2016, which is particularly beneficial for aspen forests. High mortality in mature trees is necessary to stimulate the new growth desired after a prescribed fire. The combined effects of both fires have been highly encouraging. Following above-average precipitation in the summer of 2022, just after the prescribed burn, native vegetation began to establish across the burn area. During our 2023 visits to the site, ACES observed new aspen saplings that had already grown over 10 feet tall, native songbirds, and signs of deer, elk, and bear within the burn area.

2025 Red Mountain Prescribed Fire

A long-term goal for restoration and wildfire mitigation in the Aspen area is to link the restoration efforts in the Hunter Creek Valley with previous prescribed burns in the Wood Creek Valley. This involves introducing fire on the front side of Red Mountain. In addition to connecting existing restoration projects, a prescribed fire has the potential to rejuvenate several aspen stands on Red Mountain that are in decline.

The U.S. Forest Service, Aspen Fire Protection District, and ACES are preparing the areas in anticipation of conducting a prescribed fire in 2025. Preparing for a prescribed fire involves substantial work. Fire managers must finalize burn plans and collaborate with the Colorado Department of Health and the Environment to secure the necessary smoke permits. Biologists and archaeologists are tasked with surveying the planned burn area to ensure the fire will not adversely affect threatened or endangered species or historic sites. Efforts must be made to remove as many invasive plants as possible to reduce the chance of their proliferation post-fire. Additionally, mechanical work, such as vegetation removal using chippers or chainsaws, is necessary in select areas to ensure firefighter safety and that the fire remains within planned boundaries. If all the preparatory work is completed as scheduled and weather conditions are favorable, the fire will occur as planned.

Every native conifer species in the Roaring Fork Watershed has evolved to coexist with a native bark beetle. But over the past eight years, our watershed has been experiencing a significant outbreak of the Douglas-fir beetle (Dendroctonus pseudotsugae). Douglas-fir beetles are native to Colorado and play an important role in our forest ecosystems. However, recent droughts and above-average temperatures, effects of anthropogenic climate change, have facilitated the beetles’ spread and increased tree infestations beyond what our ecosystems can sustainably support. For more information on the outbreak, refer to the Insect and Disease Update.

The options for managing bark beetle outbreaks are quite limited. On a large scale (thousands of acres), there are no effective treatments. On a medium scale (hundreds of acres), we have a few options, the most effective being pheromone treatments. Bark beetles communicate through the release of pheromones, including an anti-aggregation pheromone that signals other beetles to move on when a tree is fully occupied—similar to a “no vacancy” sign at a hotel. If an area is saturated with anti-aggregation pheromones, beetles will fly from tree to tree, eventually running out of the energy needed to make a successful attack. Pheromone treatments use the synthetic chemical MCH (Methylcyclohexanone) to mimic the beetle’s natural anti-aggregation pheromones. These treatments, while effective, are labor-intensive, requiring foresters to apply pheromone packets by hand to trees in the targeted area.

Although protecting the entire forest from bark beetles is impossible, we can manage outbreaks in select high-value areas. ACES is working to protect specific areas of Douglas fir on Aspen Mountain in collaboration with the City of Aspen, Pitkin County, Aspen Fire Protection District, Aspen Skiing Company, Colorado State Forest Service, and the U.S. Forest Service.

Protecting selected areas offers benefits ranging from environmental to economic. Douglas fir trees are among the most drought-tolerant conifers in the upper valley, which makes them crucial for maintaining a healthy seed source for forest longevity under changing climate conditions. The trees on Aspen Mountain are also important for recreation and tourism. They make up a significant part of Aspen’s viewshed and ski terrain. Additionally, high numbers of standing dead trees could complicate firefighting efforts in the event of a wildfire.

The pheromone treatments on Aspen Mountain began in 2022 and continued in 2023; this is a process that will need to continue for several years to assess its effectiveness. Additionally, nine traps have been set up to monitor beetle populations. Data from the past two years of monitoring show that beetle numbers have been holding steady. We plan to continue pheromone treatments until the beetle populations have significantly decreased.

Humans have aggressively suppressed fires in the Roaring Fork Watershed for decades. These efforts were successful in limiting local wildfires, but over time they have had a negative impact on overall forest health. Fire is a natural and necessary process in most ecosystems across the West, including the Roaring Fork Watershed. From afar, burn zones might appear as scars or blights on the landscape, but a closer look reveals a more complex and vibrant story.

To help people see this firsthand, ACES organizes free community hikes in local areas affected by recent wildfires or prescribed burns. In 2023, hikes were conducted in areas treated by the 2022 Hunter Creek prescribed fire and those impacted by the 2018 Lake Christine fire. Participants were amazed to see new life flourishing among the towering burnt trees as they observed sights such as thousands of aspen saplings, marveled at fields of fuchsia fireweed, or heard woodpeckers feasting on insects within the charred trees. These hikes were organized in collaboration with the Aspen Fire Protection District and the U.S. Forest Service.

The story differs in areas where fire burned intensely, leaving soil covered in ash and showing little new growth. But although we can’t see it, recovery is underway there as well. Bacteria and fungi in the soil are busy replenishing nutrients that were made inaccessible by the fire. The recovery process may be slower in these areas, but severe fires are a natural occurrence. ACES will continue to lead hikes into these burn areas to educate the community about the effects of fire on our forests.

In addition to the wildfire hikes, ACES leads weekly Know Your Trees hikes at Hallam Lake to educate residents and visitors about local tree species.

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