The Power of Pack Mules: Harnessing Partnerships With Land Stewards for Remote Ecosystem Research

Twelve thousand feet above sea level in the remote wilderness of southwestern Colorado, the once pristine Turkey Creek Lake turned pea-soup green. On a crisp July morning, our field crew of academic researchers, forest service managers, and pack mules began a five-day backcountry expedition into the Weminuche wilderness to figure out why (Fig. 1, Video S1).

Mountain lakes are climatic canaries in a coal mine (Moser et al. 2019). These naturally oligotrophic systems are highly sensitive to changes in climate and watershed processes. Small watersheds and thin soils around these lakes cause very low nutrient concentrations. As a result, even miniscule environmental shifts can manifest in observable biotic change (Fig. 2). The greening observed in Weminuche lakes is not an isolated phenomenon, but rather part of an unexpected trend of once-crystal clear systems turning green each summer (Vadeboncoeur et al. 2021). Considering algal blooms in North American systems, one may be tempted to picture the Midwest, where farm fields and concentrated animal feeding operations dominate the landscape. However, even the most remote ecosystems are vulnerable to human influence, both directly and indirectly.

It is no surprise that barriers to access create undersampling and spatial biases in limnology: most publicly available limnological data come from just a small subset of lakes (Stanley et al. 2019). In high mountain valleys, human impacts are often less conspicuous, making it more challenging to identify the drivers of change in those lake ecosystems. Identifying changes and their causes in these environments requires researchers to be creative and resourceful with equipment, strategy, and new partnerships.

Fishermen, hunters, hikers, and trail crews have been passing by Turkey Creek and the Fourmile Lakes for decades. Recently, they began reporting to the Forest Service that their beloved lakes were turning green. Eventually, those reports made it to the desk of Joni Vanderbilt, a career Forest Service hydrologist, who forwarded the reports to colleagues stationed near Weminuche and sought out the expertise of Dr. Isabella Oleksy, a researcher at the University of Colorado Boulder. Subsequently, Dr. Oleksy planned a compressed field sampling campaign to investigate the mystery of the lake blooms, limited to installing buoys in the three lakes and collecting water samples with a team of seven researchers, including three undergraduates, two graduate students, and one professional research assistant. As the field season neared, Vanderbilt brought on Ros Wu, a forestry specialist at the Forest Service, who suggested enlisting her staff and several horses and mules to help clear downed logs from the trail and carry field equipment and basecamp gear. This greatly expanded the scope of the planned research, enabling the team to bring sediment coring gear to reconstruct the lakes' histories and more deeply understand their past environments.

A few months after that initial call, the research team assembled by Dr. Oleksy packed our food alongside our sampling gear in a cavernous Forest Service garage, under the shadow of a fire truck and an Arnold Schwarzenegger banner behind a weightlifting rack (Fig. 3).

Remote lakes like the ones we were traveling to are often data limited because their location impedes frequent sampling. Limitations in data constrain researchers' ability to assess longer-term changes and make informed management decisions. Thus, to access and study Turkey Creek and the neighboring lakes, we planned to combine field work with backpacking. Carrying out this kind of extensive field work in the backcountry requires piles of gear: a myriad of sensors, heavy coring equipment, tents, dozens of instant oatmeal packets, and tens of pounds of water samples. Luckily, we had the support of six hoofed and long-eared pack animals.

Joe, Rainman, Dolly, Betty, Clyde, and Max, the horses and mules on our trip, were as much a part of the team as the scientists. We put equal, if not more, care into properly packing their loads as we did our own, painstakingly weighing and balancing each saddlebag on each animal's leather saddle to within a pound. While incorporating pack animals into our backcountry research added to our daily workload—setting up their paddock, feeding them, and repacking their saddlebags—their surefootedness on rough terrain proved invaluable. They not only expanded our research capabilities by allowing us to carry more sampling equipment, but also afforded us the luxury of carrying fresh food, a welcome reprieve from typical freeze-dried backpacking fare.

Deep in the Weminuche wilderness, our basecamp was nestled in a lush clearing surrounded by the skeletons of Engelmann spruce. Surrounding the valley, uplifted Proterozoic-era rock has eroded into eerie needles: a towering, splined ridge, perhaps a mile wide, our Forest Service leader Ros Wu calls “the breadloaf.” Piles of unconsolidated rock from the cliff spill into bleak beetle-killed stands. Below us, closer to the outflow of the greening Lower Fourmile Lake, was an electric fence enclosure for our pack animals. Three hundred miles north, in the Rawah Wilderness, a previous sampling trip revealed the same downed beetle-killed trees creating demoralizing obstacle courses around every trail bend. This time, we were quick to notice how many chest-high logs were freshly band-sawed and heaved downhill by Forest Service trail crews. Our relief at the simple privilege of freely hiking a trail thanks to the crews felt like an official collaboration in its own right.

Spending days out of cell phone coverage, Dr. Oleksy finds that her observations slow, allowing her to appreciate the interconnectedness of the natural world and humanity's place in it. For lab manager Adeline, the mountains foster a sense of community as well as individuality: her most meaningful connections were forged in the forest, along with welcome self-reflection and discovery. For Julia, an undergraduate, traversing on foot through the mountains forces researchers to perceive deeper relationships with place. Every moment collecting samples in the field situates the routine of science within the broader goals of the work. It combines a sense of responsibility and stewardship with joy and awe. Bryan, another undergraduate researcher, has always been drawn to the mountains. Alpine systems are complex yet cohesive, and have shaped and enlarged his perspective of what is most important.

Researching the limitless complexity of environmental systems requires creating artificial categories. These categories can compress vast complexities into reductive values. Consequently, researchers often trade breadth of understanding for depth of analysis. However, forming a team of researchers with diverse perspectives and backgrounds can facilitate inquiry that transcends these established categories, where the team can view an ecosystem broadly and completely, and provide a synoptic understanding of its patterns and processes. Similarly, ecosystems themselves are most resilient to changes and disturbances when they host a diverse array of processes, rather than a few. Facing mounting threats to the policies and funding sources that enable critical environmental research and protection, our resilience as scientists depends on our ability to build alliances with a wide range of stakeholders.

Oleksy's team of freshwater ecologists, biogeochemists, forest ecologists, and conservationists created a formidable mosaic of knowledge about this ecosystem. Our Forest Service collaborators helped integrate the natural history of the area with 21st-century techniques, creating a holistic understanding that is often lost from modern science. Integrating the lived wisdom from practitioners and the public—not just landowners—should be a more critical part of our hypothesis building process. Future collaborations can seek to include the knowledge of anyone who spends significant time in these environments, especially local and Indigenous communities. Our fundamental research would not have been possible without keen observations from non-scientists coupled with scientists’ willingness to take research risks.

On the last evening in the field, our crew gathered at sunset. Alpenglow cast orange light into a forest clearing where we organized dozens of sample bottles from three lakes and stowed gear for our hike down early the next morning. Adeline and Katie had stashed Swiss chard and carrots in their packs over the four days to complement a stir fry feast on our final night. Around the fire, Ros and Joni spoke with encyclopedic knowledge about the changes they had seen in the landscape and climate over their Forest Service careers. Their observations have been hard-earned through decades of field work and research and exemplify the same collaborative success that made this research expedition possible. In the lush field nearby, skittish horse Joe whinnied as he finally let Julia feed him a carrot—a victory for the week. Unseen beyond a line of trees, the lake reflected the glowing needle ridges, quivering with the breeze.