When she looks at the Narraguagus River, Valerie Ouellet sees what others can’t: a thermal mosaic that explains why it’s one of the last places in America where wild Atlantic salmon come to spawn.

This 55-mile-long waterway in Downeast Maine is a hodgepodge of cold-water pockets hidden within the warmer river where adult salmon can find refuge from the state’s increasingly hot summers.

Atlantic salmon do their best growing and spawning in 68-degree water. Any higher and they stop eating; they lay fewer, smaller eggs. At 73 degrees, they swim erratically. If they don’t find cold water created by shade trees, spring-fed tributaries or groundwater seepage, some will die.

Ouellet is an ecologist with the Atlantic Salmon Federation and is part of a state and federal research team that has spent two years documenting the river’s temperature and flow to explore how close, how big and how cold these spots must be for salmon to survive.

Her research suggests cold water spots are shrinking or disappearing, especially during drought years. The Narraguagus now spends a lot of July and August above 73 degrees, according to U.S. Fish and Wildlife Service monitoring data. On July 17, 2023, a legendary salmon pool in the Cherryfield section topped 83 degrees.

“Wild salmon are an indicator of ecosystem health,” Ouellet said. “If they go away because the water is too warm or not clean enough, what, or should I say who, do you think is in trouble next? That’s us.”

“If we lose them,” she said, “that means we’ve failed ourselves, too.”

The salmon’s struggle— which is shared by alewife and brook trout — is part of a much larger story unfolding across Maine. Projected to heat up by as much as 10 degrees by the year 2100, the state’s landscape is changing in ways that scientists are only just starting to understand, from its deepest waters to its highest peaks.

There is already a phenological disconnect in some areas — the dwarf bilberry shrub, for example, is flowering before the bumblebee and flies are ready to pollinate it. Experts say these are powerful indicators of a biological rhythm thrown out of sync by rising temperatures.

The Portland Press Herald/Maine Sunday Telegram spoke to two dozen expertsthis summer about the ways increasing heat is affecting Maine’s environment, ranging from the short-term impacts of heat waves on bats and birds to the long-term effects of warming lakes, forests and oceans.

A FOREST IN FLUX

Maine’s evergreen cloak is beginning to show strain.

The state’s iconic spruce and fir populations are declining and heat-tolerant hickories and oaks are taking their place. Even the tree line is changing, inching up the warming mountainsides by about a foot a year, putting the squeeze on the plants and animals that had adapted to the harsh conditions at the top.

This is perhaps nowhere more visible than at Acadia National Park, where the red spruce’s prickly yellow-green needles scent the trails like orange rind when crushed by hikers’ boots. It is where the boreal and temperate forests meet. Many trees there are at the edge of their range.

With summer temperatures projected to warm by as much as 8 degrees, the amount of suitable red spruce habitat at Acadia is expected to drop by 50% by 2100, according to a 2022 U.S. Forest Service report that outlined how a warming climate would change the park.

“Acadia National Park is experiencing unprecedented change,” Laura Gibson, who runs a climate adaptation program at Friends of Acadia, said at a lecture this month about finding new ways to protect Acadia’s forests. “Thinking about the future can certainly be daunting at times.”

The red spruce provides winter cover for American marten and white-tailed deer and food for grouse, snowshoe hare and white-winged crossbill, whose twisted bill is designed to pry open spruce cones to get at its seeds.

As Acadia’s forest changes, the songbirds that make up its soundtrack could disappear. The Maine Audubon, a statewide wildlife and habitat conservation group, predicts that as many as 60 bird species will leave the park by 2150.

The husky call of the boreal chickadee will be replaced by the cardinal’s telltale pew-pew-pew or the red-bellied woodpecker’s shrill churr.

“Nature is clearly trying to tell us something, but we’re not listening,” said Sally Stockwell, the director of conservation at Maine Audubon. “We’re watching one species after another decline. … I never thought I’d see such dramatic changes right here in Maine.”

WILDLIFE FEEL THE HEAT

Moose can be quite vocal. During the fall mating season, males make deep grunts while females will use a long, nasally call to attract a mate. Calves often call out to their mothers. Both sexes will use snorts or roars when they are in danger, in distress or in a fight. 

Then there is another, manmade sound — a kind of digital death rattle — that comes when Maine moose die. It is the notification tone Lee Kantar, the only state-appointed moose biologist in the country, hears come from his phone when a tracking collar has not moved for six hours.

It almost always means a moose is dead, he said, and it’s nearly always climate change, or more specifically the winter tick, that is to blame. The longer summers have given these native bloodsuckers an extra three weeks on average to find a host.

And once one latches on, it and tens of thousands of its friends will cling to that single host from fall through spring, slowly bleeding the moose to death. Kantar and others say it has turned the animal, which once numbered more than 100,000, from a symbol of Maine into one of climate change.

“As a scientist, I try to be objective, and maintain an emotional distance, but it can be difficult,” Kantar said in an interview this month after the debut of the film “Guardian of the Giants,” which highlights his work.

“With our changing climate, and what that means for winter ticks, I end up dealing with a lot of death,” he said.

The rising heat is also taking a direct toll on endangered bats, rare turtles and various species of birds that fall from their nests or are hit by cars when roused from dormancy too early.

At the Center for Wildlife in York, director Kristen Lamb sees the consequences. The nonprofit rehabilitation facility treats about 500 sick, injured or orphaned wild animals a year. During heat waves, chimney swifts are admitted with broken wings after the spit they use to hold their homes together dissolves in the heat, causing whole nests to drop to the ground.

The center often treats bats, already stressed from deadly white nose syndrome, thatare injured after falling from exhaustion during a heat wave when the caves they use for roosting become dangerously hot, and the tiny creatures, unable to cool down, simply fall, Lamb said.

Extreme heat also confuses some animals, throwing their natural instincts out of sync. Normally dormant in summer, turtles are waking up in response to the warm ground. They begin to move across roads in search of food and water, only to be hit and injured or killed by cars. 

“Every single wild animal that comes into our clinic tells a story,” Lamb said. “Many of the stories serve as a warning for humans. Because what we do to wildlife, well, we are also doing that to ourselves. Their problems will be our problems.”

WARMING WATERS

The average surface water temperature of Maine’s 100 biggest lakes has risen by 5.5 degrees between 1980 and 2020, according to monitoring data collected by the Maine Department of Environmental Protection. That’s faster than Maine’s air and its oceans.

Those changes can result in a bumper crop of algae and invasive plants, according to researchers at Lakes Environmental Association and Lake Stewards of Maine. Algal blooms, once a rare occurrence, are becoming more frequent in shallower lakes and ponds as temperatures climb. These blooms can be toxic, posing a risk to human health and wildlife.

Consider Lake Auburn, a critical reservoir for the Lewiston-Auburn area. Historically, its deep, cold waters have been remarkably resilient. Now, longer, hotter summers have increased stratification — where oxygen levels in the deeper layers are dropping, impacting aquatic life and water quality, research from the Lake Auburn Watershed Protection Commission shows.

Rising lake temperatures also allow harmful bacteria and pathogens, such as E. coli, to survive longer, said Ben Peierls, research director for Lakes Environmental Association. This risk is compounded on hot days when more people visit lakes to cool off, which can increase the spread of these bacteria.

That exposure can sicken people, but it can also harm fish, Peierls said, causing infections, weakened immune systems and growth and reproduction problems.

At the same time, the Gulf of Maine is one of the fastest-warming bodies of water on the planet, and its transformation is sending ripples through the aquatic food chain, down to a tiny zooplankton called Calanus finmarchicus.

This minuscule crustacean is a temperature-sensitive species whose decline impacts a broad array of other marine wildlife and shows how interconnected they can be, said Kathy Mills, a senior scientist at the Gulf of Maine Research Institute.

As the zooplankton moved out of the Gulf of Maine, past the Bay of Fundy and into a new habitat in the Gulf of St. Lawrence, both the herring and the critically endangered North Atlantic right whale followed, according to a separate studies on the species.

But the habitat switch brought new dangers. According to the National Marine Fisheries Service, 12 right whales out of 450 died in the Gulf of St. Lawrence from ship strikes or fishing gear entanglement in 2017, leading to regulatory changes that reshaped lobstering on both sides of the border.

A warmer Gulf of Maine is also less suitable for herring, the fish that puffin, a beloved symbol of Maine’s coast, likes to eat and feed its chicks, said Don Lyons, the director of conservation science at the Maine-based Audubon Seabird Institute.

During marine heat waves, they’ll often fall back on Atlantic butterfish, a less heat-sensitive species, but its round body can be too large and oddly shaped for puffin chicks to swallow, Lyons said.

“We’ve found butterfish piled up outside of burrows with dead chicks inside,” he said. “It’s not that there was no food at all, but it wasn’t the right food. A few degrees warmer, a different fish supply. It can make all the difference.”

REASON TO HOPE

Maine scientists believe that people can help the environment adapt to the changing climate.

Researchers at the Appalachian Mountain Club are investigating whether alpine plants that grow atop southern New England mountains — which may have evolved with a higher heat tolerance — could be transplanted to Katahdin, the Whites and even Acadia National Park.

Maine’s puffin colonies had a successful nesting season this summer thanks to a break from the year-on-year heat waves that have dominated the Gulf of Maine over the last decade. Scientists counted 672 active puffin burrows at the Seal Island National Wildlife Refuge, about 100 more than the previous census five years earlier.

Some chicks drowned at Eastern Egg Rock and Hog Island, the two sites monitored by Audubon Seabird Institute, when storms in May and August flooded the low-lying burrows, but those that survived the storms had plenty of bite-sized fatty fish to eat, Lyons said.

This summer, Ouellet, the salmon researcher, is focused on the indirect impact of a warming climate — drought, which leads to lower water levels and reduces the ability of rivers to absorb and dissipate heat, making them more susceptible to warming, and thus more harmful to salmon and other aquatic life.

“It’s not looking good for Atlantic salmon this year,” Ouellet said.

She and the research team conducting thermal mapping of the Narraguagus are still processing their data, trying to determine the farthest a salmon will swim between cold spots, but they have already started sharing somewith conservation groups.

In certain areas, when the conditions are just right, they may be able to create new cold spots, she said. If the thermal maps identify a warm pond spilling into a tributary, that’s fixable, Ouellet said. If too many trees have been cut back, they can plant more.A drainage ditch dumping warm water into a stream can be rerouted.

“We can’t stop our rivers from warming, but we can slow down how fast it is happening,” Ouellet said. “We created this problem, so we have a responsibility to fix it when we can.”

This story was reported as part of a collaboration between the Portland Press Herald/Maine Sunday Telegram and Maine Public.