Written by: Gavriela Mallory

Maine’s Forest Climate Change Initiative (FCCI) hosted a discussion of long-term research, hydrology, soil chemistry, and conservation at its winter field tour in early December. Exhales created small clouds of fog as participants circled up for introductions. The nearly 0o morning didn’t dampen the excitement for a field visit to the decades-long experiment at Bear Brook Watershed in Maine (BBWM) on Lead Mountain in Beddington. 

BBWM is a testament to the importance of science in policy-making. In the 1960s, as industry boomed across North America, scientists at Hubbard Brook in New Hampshire noticed drastic increases in the acidity of routine rain samples, like carbon dioxide, sulfur, and nitrogen oxides released by burning fossil fuels. These gasses spread widely with wind, typically moving from the west to the northeast in the eastern United States. As they combine with water particles in the air, precipitating rain, snow, and fog become dramatically more acidic than normal. 

Acid rain was one of many industry-tied ecological and public health concerns raised in the 20th century, and growing evidence of impacts led to the passage of the Clean Air Act (CAA) in 1970. The CAA was developed based on the available science, but many questions remained unanswered. As Congress looked ahead to policy revisions over the coming decades, investment in air pollution studies was prioritized. 

Experimentation to better understand ecosystem response to acid rain was among such prioritized initiatives. Ivan Fernandez, then an early career researcher at UMaine Orono, proposed, along with colleagues, a project that would become the now third-century-long study at Bear Brook. The foundation of the experimental model is two adjacent, “paired” watersheds:  East Bear Brook and West Bear Brook. 

Watersheds are geographic units characterized by surface water flow. Precipitation and snowmelt move across the landscape in patterns based on geographic features, like hills and streams. A watershed is an area of land that drains all water on its surface to one defined point. Thanks to Ivan and his team at East Bear Brook and West Bear Brook, these drainage points are home to V-notch weirs, concrete installations that allow scientists to measure and sample all outflows from each watershed. 

Participants view the V-notch weir at the base of East Bear Brook. Photo by: Roger Merchant

FCCI participants warmed up by hiking up to the outflow of East Bear Brook to explore the V-notch weir. The seasonal road up Lead Mountain climbs through a dense hardwood stand, and snow crunched underfoot. As the group gathered around the large concrete basin, Ivan shared BBWM’s origin story and some highlights from a third-century of fieldwork. 

For 26 years, helicopters dropped ammonium sulfate (a chemical composed of Nitrogen, Hydrogen, Sulfer, and Oxygen) on Bear Brook West every other month. These drops mimicked the chemical impact of acid rain on the western watershed, while the eastern watershed served as an untreated ecosystem of reference, its changes reflecting environmental shifts on a broader scale. By comparing data on tree physiology, soil chemistry, stream chemistry, and many other ecosystem factors in the treated western watershed with the untreated eastern watershed, scientists at BBWM began to tell a more comprehensive story of the impacts of acid rain. 

BBWM’s weirs sit below catwalks loaded with data collection equipment. Ivan pointed out one instrument used to measure precipitation volume on a systematic timescale. Water runs into a pan. When the pan fills fully, it dumps. This movement mechanically triggers a notch mark on a record sheet wrapped around the device. The instrument is hand-wound by field technicians, who measure the marks to record flow volume over time. Ivan chuckled as he described the analog process, noting it as a reminder of the longevity of the research. 

Catwalk above the V-notch weir. Photo by: Roger Merchant

Findings from the BBWM study informed amendments to the CAA in the 1990s as initially intended and continue to inform pollution and climate policy-making today. The impacts of this research extend beyond policy. Since its establishment, the experiment has been an educational tool, providing students with valuable and applicable field experience. Sean Smith, a professor in UMaine’s School of Earth and Climate Sciences, regularly uses data from the BBWM experiment in classes. With these data sets, students answer impactful questions such as: How does land use impact water flow across a landscape? And, how does climate impact hydrologic patterns over time? 

Participants view the restoration project on the Narraguagus River. Photo by: Maddie Eberly, Forest Stewards Guild.

After visiting both weirs and the streams that feed them, FCCI attendees closed out the field tour by descending Lead Mountain and crossing Route 9 to see a habitat restoration project on the Narraguagus River. Owned by the same entity that leases the BBWM to UMaine, this property has also received investment for decades-long returns. Here, hardwood boles and coarse woody debris were engineered into bank buffers to improve Atlantic Salmon habitat. When Maine’s timber industry depended on waterways to move logs to mills, channels like the Narraguagus were widened and homogenized to support efficiency. These buffer installments reintroduce differences in temperature and flow rate within the river, while also impeding erosion, all of which support habitat for freshwater species. As with the Clean Air Act, this project was guided by research that provides insight into what interventions and protections this ecosystem needs to thrive. 

In Maine, we are lucky to have an abundance of forested land. The BBWM demonstrates how much we have to gain from observing these landscapes carefully, often, and on the timescale of ecological change. Such investments support effective and economically efficient policy-making and management. They support the learning and practice necessary to foster future generations of scientists. They support the endurance of habitats and ecosystems that characterize the landscapes we call home. 

FCCI is a collaborative effort between Maine TREE Foundation, the Forest Stewards Guild, and UMaine’s Center for Research on Sustainable Forests (CRSF). Through quarterly webinars and field tours, the initiative fosters conversation and learning on the impacts of climate change in the Maine woods. 

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