Rocky Mountain Fens: Little-known ecosystems vital to biodiversity, water and climate

Monitoring and protecting an important part of the local ecosystem

by Tobias Nickel, Nick Catmur, Christopher Kittle, Heather Reineking and Justin Sanchez—graduate students in the Master in Environmental Management program at Western Colorado University


In front of us, Bureau of Land Management (BLM) hydrologist Andrew Breibart slogs across what from afar might be mistaken for an alpine meadow full of sedges, willow and spruce saplings. A closer look reveals that our group of Western Colorado University (WCU) students stands on neither solid ground nor water, but something in-between. The ground moves under our feet, and with every step we sink deeper into a thick, mucky substance. Protected by rubber boots, we follow Breibart across the Butterfly Fen, located 30 miles southwest of Gunnison in the San Juan Mountains near the mountain community of Arrowhead.

“I have been visiting this special place since 2015,” says Breibart, “when I first learned about the threats and impacts to this unique ecosystem.”

After a short trudge across the fen, we unload our field equipment and get to work. With direction from our professor, Dr. Jennie DeMarco, we lay out transects, fixed paths along which we take vegetation measurements and collect soil samples.

“The goal of our research is to better understand the ability of fen ecosystems to store carbon and retain soil moisture,” explains Master in Environmental Management (MEM) student Heather Reineking.

Breibart adds, “Carbon sequestration and maintenance of soil moisture are key issues in building resilience to a changing climate.”

But what are fens and why do they matter?

Fens are ancient wetlands found in different parts of the world. In the Rocky Mountains, fens started to form after the last ice age around 12,000 years ago. What distinguishes fens from other wetlands is their strong connection to groundwater as well as a thick layer (16-plus inches) of peat. Peat is an accumulation of dead and decomposing plant matter that forms over hundreds, even thousands, of years, in permanently saturated, nearly oxygen-free soils. Peat is also what lends fens their spongy characteristic, so if you have ever experienced that wet and springy sensation under your feet while hiking across the alpine, you yourself have likely stood atop a fen.

Because peat is primarily composed of plant matter, it typically has a carbon content of over 50 percent. The slow but constant accumulation of peat makes fens globally important as carbon sinks. In fact, despite covering only 3 percent of the Earth’s surface, fens and other peatlands are second only to oceans in carbon storage. However, when a fen is dried out, the peat is exposed to air and the carbon is released in the form of CO2, making them powerful greenhouse gas emitters.

While it can take thousands of years for peat to build up in fens, degradation of these ancient ecosystems can reverse this sequestration in only a few years.

Beyond their role in the global carbon cycle, fens support biodiversity and provide an ecological refuge for rare plant species. Additionally, fens are important habitat for elk, moose, amphibians and migratory birds.

Fens provide other critical ecological functions as well, including filtering large volumes of water and maintaining base flows to streams year-round.

Breibart explains, “With climate change and prolonged droughts, fens play an increasingly vital role for maintaining flows in our headwater streams and the Colorado River Basin. Fens in the San Juan Mountains and closer to home at the Iron Fen outside of Crested Butte maintain a high water table during drought years such as the ones in 2002, 2012 and 2018.”

Considering the numerous societal and ecological benefits of fens, the BLM strives to protect and restore these little-known ecosystems on the lands that the agency has been entrusted with. Threats to fens include trailing by domestic and wild ungulates (cows and elk), logging operations, water diversions, road building and climate change.

In the face of these threats, the need to study these often-overlooked ecosystems to inform their restoration is critical. This is the reason why our group of students is measuring vegetation and collecting soil cores at the Butterfly Fen. “We are collecting baseline data so that we can compare current conditions to future conditions and learn if restoration measures are effective in maintaining or even improving the ecological function of the fen,” explains MEM student Justin Sanchez.

Meanwhile, the sounds of drills and chainsaws can be heard nearby as a youth crew from the Western Colorado Conservation Corps (WCCC) is hard at work constructing a buck and pole fence to prevent cattle from trailing through the fen.

“These lands are managed for multiple uses,” says Breibart. “We have a timber sale for spruce bark beetle, livestock grazing, hunting and snowmobiling, but we also need to take into consideration the impacts on these sensitive ecosystems.”

The BLM is seeking a win-win solution by fencing off the delicate fen area and creating an alternative water source, so that livestock can still graze the surrounding meadows.

Furthermore, in partnering with students at WCU, the BLM is using the best available science to inform fen restoration measures. MEM student Chris Kittle says, “We hope that our research will support the BLM in protecting these rare ecosystems, so that the benefits fens bring to natural and human communities do not dry up.”

Breibart is elated, saying, “After four years, the BLM Gunnison Field Office finally has the resources to protect and preserve the Butterfly Fen, and I look forward to more collaborative fen restoration projects in the future.”

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