Valerie Ouellet sees more than just a river when she looks at the Narraguagus River in Maine. To her, it’s a complex network of cold-water pockets, vital for wild Atlantic salmon spawning. This 55-mile river has become one of the last havens for these salmon as summer temperatures rise.
Atlantic salmon thrive in waters around 68°F. When the temperature surpasses 73°F, they struggle. Higher temps make them erratic and can even lead to death. Ouellet, an ecologist with the Atlantic Salmon Federation, is part of a research team studying how these cold pockets impact salmon survival.
Recent monitoring shows that these cold spots are shrinking, especially during droughts. In July 2023, temperatures soared above 83°F in some salmon pools. “Wild salmon are indicators of ecosystem health,” says Ouellet. “If they vanish due to heat, we might face similar risks.”
The salmon’s struggles reflect a broader narrative in Maine. The state could warm by up to 10°F by 2100, impacting everything from wildlife to plant blooming cycles. For instance, certain plants are flowering too early—before pollinators like bees are active—creating a disconnect in nature’s timing. This information comes from recent expert discussions about the effects of heat on Maine’s environment.
Climate change is reshaping Maine’s forests, with iconic spruce and fir trees giving way to heat-tolerant species like hickories and oaks. At Acadia National Park, the red spruce populations could drop by half in suitable habitat by the year 2100, according to a U.S. Forest Service report.
Laura Gibson, who directs a climate adaptation program, emphasizes, “Acadia National Park is experiencing unprecedented change.” The shift in trees and habitats also threatens wildlife that depends on them, like the boreal chickadee, whose range is retreating due to rising temperatures. Maine Audubon predicts that up to 60 bird species could leave the park by 2150.
Warmer summers also bring challenges for moose populations. Lee Kantar, Maine’s only state-employed moose biologist, notes that longer summers give the winter tick a better chance to latch onto moose. The result is often deadly, with ticks draining the animals’ blood and causing significant population declines.
Extreme heat is reshaping Maine’s aquatic environments too. The average surface temperature of the state’s largest lakes has risen by 5.5°F from 1980 to 2020, leading to more frequent algal blooms that harm both wildlife and human health. For example, Lake Auburn, a key water source for the area, is facing challenges with oxygen levels and water quality as summer temperatures climb.
As marine ecosystems respond, one tiny organism—the zooplankton Calanus finmarchicus—shows how interconnected the food web is. This species is vital for larger marine life, including fish and whales. Changes in water temperatures impact its survival, which has a cascading effect on other species.
Despite these daunting challenges, researchers are finding reasons to hope. Efforts are underway to adapt Maine’s ecosystems to changing climates. For instance, the Appalachian Mountain Club is exploring whether heat-tolerant plants from southern New England could thrive in cooler, northern environments like Katahdin and Acadia.
Ouellet’s team is also working to create new cold spots in rivers. Simple changes, like planting trees along riverbanks or rerouting warm drainage water, can help slow down warming. She emphasizes a crucial point: “We can’t stop our rivers from warming, but we can slow down the process.”
As humanity grapples with these shifts, the stories from wildlife serve as critical warnings. What affects them will ultimately echo back to us.
To learn more about these shifts, visit the U.S. Fish and Wildlife Service and U.S. Forest Service.
