Rivers of Change: The Impact of Climate Shifts on Salmon Habitats in Southeast Alaska

Water is the thread that weaves Lingít Aaní or Southeast Alaska together. It falls from the sky as relentless rain, clings to mountains as snow and collects in ice fields and glaciers. It trickles through peat-rich muskegs and carves deep fjords that open into the sea.

The region’s residents are no strangers to water’s many forms. Stroll down Juneau’s South Franklin Street, and you’ll see outfits of Xtratuf boots, rain jackets and soaked hair. Waiting for the rain to stop isn’t an option; you dress for the rain and embark on your adventures anyway.

Layering becomes an art form, and rain gear is never kept far from reach, even on sunny days. Locals explore soggy trails. Muddy boots and wet dogs are part of the experience. Fishing, hunting and foraging are deeply tied to the variety of watersheds. Deer, berries and mushrooms are found along streams and wetlands, while large tidal swings facilitate beach foraging and harvesting. People rely on halibut, rockfish, salmon, clams and other foods harvested from the water in Lingít Aaní. Whole seasons are shaped around preserving water-based abundance through smoking and freezing. There’s pride in being able to get things done regardless of the weather. Water is an integral part of cultural identity.

The Tongass rainforest thrives under the weight of all that water, with Sitka spruce and western hemlock rooted in rain-soaked soil. Glaciers store centuries of snowfall, releasing meltwater that feeds rivers even in the driest months. Snow blankets mountaintops, storing seasonal moisture that sustains life during the spring and summer. Where rivers meet the sea, estuaries abound with richness, providing crucial nurseries for juvenile salmon, herring and shellfish.

Salmon have a palpable heartbeat in this landscape. As they migrate upstream to spawn and die, they give back to their surroundings by delivering the building blocks of life: nitrogen, phosphorus, carbon and other essential compounds and minerals. Trees absorb these nutrients through their roots, incorporating them into their bark, wood and needles. Studies show that trees along rivers with salmon grow at faster rates than those near streams without salmon. When bears, wolves and eagles dra salmon carcasses deep into the forest, their decaying flesh, with its pungent and distinctive smell, serves as a natural fertilizer. Everywhere, salmon are part of the forest.

Year-to-year instability and loss of habitat diversity: The twin challenges facing salmon in Southeast

For generations, Indigenous peoples of Alaska have understood that a good snow year often means a good year for salmon, a time when rivers run full, water stays cool, and spawning conditions are ideal. Today, scientists are beginning to reaffirm these deep-rooted connections, showing how snowmelt feeds salmon rivers in spring and glacier runoff sustains them through the summer. This understanding is a reminder of the profound and enduring interdependence between snow, ice, salmon and all life in Lingít Aaní.

However, communities and scientists have started to see this relationship change. As the climate changes and alters the timing and scale of global environmental systems, Southeast Alaska is expected to become both warmer and wetter, with overall less precipitation falling as snow. This change is reflected in the glacial changes. In the last two decades, Alaska has accounted for 25% of the global glacier mass loss and 38% of accelerated global glacier thinning.

With less snow and ice in the winter and more rainfall predicted in Southeast Alaska, water temperatures in streams and rivers become less predictable year to year. Nine years ago, when scientist Ryan Bellmore arrived in Juneau to work at the Forest Service Pacific Northwest Research Station, researchers were focusing on the biogeochemistry of glacial, snow-fed and rain-fed streams. Nutrient concentrations, water temperature and flow regimes were particularly important.

One evening, while Bellmore and Jason Fellman, a collaborating scientist, were walking along at the confluence of snow fed Montana Creek and Mendenhall Glacier’s McGinnis Creek, they noticed a contrast; one stream was turbid, cloudy and opaque, full of suspended matter, while the other was stained with tannins: natural compounds found in plants, especially leaves, bark and roots that stain rivers a rich, earthy color without making it dirty. Bellmore wondered how the source of a stream affects its ability to support salmon, and how that might change as the climate warms. This curiosity led to new research on how those differences affect salmon.

After several years of collaborative research between the Pacific Northwest Research Station, the Alaska Coastal Rainforest Center, and the Alaska Climate Adaptation Science Center, Bellmore and Fellman better understand how climate impacts salmon in two separate but related ways.

One is short-term, year-to-year variability. This includes the increasing number of extreme flow or water temperature events, such as low flows, droughts, or high water temperatures. Communities are also observing how these changes are impacting salmon across the region.

Annika Ord – now an Alaska CASC Climate Adaptation Catalyst – conducted research at the University of British Columbia, which learned from fishermen, Indigenous Knowledge holders and local scientists about how glacier retreat is impacting downstream salmon systems in Southeast Alaska.

In one of her interviews, a fisherman from Hoonah recounted what it was like when two snow-fed systems near his hometown dried up.

“In recent years, we’ve had streams that produce salmon that had no water in them, and they literally died at the mouth of streams waiting for water,” Ord said.

Judy Daxootsù Ramos, a Tlingit Knowledge Holder and anthropologist from the town of Yakutat on the glaciated outer coast of Lingít Aaní, expressed similar concerns.

“Lots of the salmon rivers are getting too warm for the salmon, and I think they have to migrate further north, which is really hard on our subsistence-based economy and our commercial fishing,” she said. “In many streams, we’ve seen the king salmon just drop down to zero. You can’t even harvest king salmon anymore. And sometimes the rivers get really hot, it’s kind of alarming how hot the rivers are sometimes. So that’s a concern. If we don’t have salmon runs returning anymore, it’s going to really impact the economy.”

With less snow and ice overall, water temperatures become less predictable from one year to the next. Stream flow regimes, the pattern of discharge including quantity, duration and seasonal variation, become chaotic and dependent on rainfall and air temperature. A different fisherman from Hoonah describes how glacial runoff plays a role in the T’aakú Héeni (Taku River) watershed south of Juneau.

“The Taku system has obviously been influenced by glacier water. The pink run has been pretty good in that system, and it’s been able to persist through the warming temperatures. So, I think those glacial systems really do well when other systems are affected by a lack of snow because they have a big resource to draw upon, almost like a fat resource that they slowly burn down, and then in big snow years, they get it back. If you lose that bumper, that cushion, then the stream could be in peril for sure.”

The expedited retreat and eventual loss of glaciers will have far-reaching effects on salmon, people, and industry. Eric Jordan, a Sitka-based salmon troller, spoke about his fears on the matter.

“Glacier retreat totally concerns me because snowmelt and glacier melt are a big part of what keeps these streams going all year round, and if they’re gone, then you’re dependent on the rainfall, which can be really cyclic. One of the things about the glaciers is that they just stabilize everything. Because if it’s really warm and dry, then they’re melting and that’s adding runoff to the system.”

Short-term shifts in snowmelt are already straining salmon survival. The second deeper and more troubling transformation for salmon is occurring over a longer timescale: the retreat of glaciers and permanent ice fields is altering the foundational structure of salmon habitats. This process, described by Bellmore as a loss of habitat heterogeneity, may have even more profound implications for the resilience of salmon populations. Initially, it was thought that glacial rivers did not provide high-quality fish habitat because they have high turbidity, cold water and unstable channels. An observation made by Eran Hood, a local environmental scientist, suggests that salmon use glacial systems more than previously thought.

“We’ve gone out and put out all kinds of fish traps, minnow traps, in Herbert River, and there are fish living in there all the time,” Hood said. “So, I think the glacier rivers are more productive in that way then they’ve been given credit for just from looking at what the environmental conditions look like.” (Ord, 2024)

Towards predictive models: Understanding how stream diversity shapes the future of salmon

Recent studies by Bellmore and Fellman have revealed something surprising: when glacial, snow-fed and rain-fed streams are all part of the same watershed network, the diversity gives salmon a major advantage. This is known as the “portfolio effect,” a term borrowed from the world of finance that follows the principle: diversity offers security.

Each of these streams carries water with its unique timing and chemistry. Glacial streams are cold and cloudy, snow-fed ones flow strongly in early summer, and rain-fed streams swell with autumn storms. These differences create a seasonal rhythm across the landscape, offering waves of food and habitat that shift over time.

Using food web modeling and field sampling, Bellmore and Fellman’s findings suggest that by moving between these types of streams, juvenile coho salmon and other fish species can take advantage of staggered pulses in food availability. Instead of being limited to one stream’s food source, they feed in tune with the changing season across the watershed. This resulted in a projected 20% increase in their growth rates.

However, the benefit of varied streams only exists when that patchwork of glacial and non-glacial streams remains intact. As glaciers disappear and more streams begin to look and behave the same, warmer and simpler with only rain driving them, the rich variety that once supported these feeding strategies starts to fade.

In response to these troubling shifts, Bellmore and Fellman, along with a broader team of collaborators, secured new funding through the Alaska Climate Adaptation Science Center to deepen their work on climate-salmon interactions. Their current project aims to develop predictive tools that model how salmon populations might respond under different climate futures.

But this is not research for research’s sake; it’s designed with communities in mind. The idea is to build models in Juneau because it has a mix of accessible watersheds and decades of existing data. Eventually, the models will be used across Southeast Alaska and beyond. Communities will be able to plug in their stream data, temperature, flow and chemistry, and explore how salmon survival might change under different climate scenarios. By studying these ecosystems, researchers can collaborate and create tools that help people understand and prepare for potential changes.