Anthropogenic environmental changes such as fossil fuel extraction and glacial retreat are two negative impacts affecting salmon species. But not all news is bad news. With retreating glaciers comes the possibility of producing new habitat for certain salmon populations, according to recent research published in BioScience.
Connecting Climate Change with Salmon Species
A total of five species of salmon swim within the rivers of the United States: chinook, coho, sockeye, pink and chum. Glacial retreat presents a variety of unknowns for these salmon species.
Among the climate change consequences, glacial melting upstream leads to changes in magnitude, timing, and frequency of flow downstream, which impacts nutrient levels as well as sediment levels. Warming of glacier-fed rivers due to warmer atmospheric temperatures could destabilize ecosystems and cause population die-offs. Significant warming of the oceans will also lead to damaging conditions for salmon species.
On a more positive note, glacial retreat could also drive the formation of new habitat for salmon species. Salmon use evolutionary adaptive strategies to colonize new streams and therefore are able to stray from their natal streams to find more productive waters. Evidence of this colonization has already been documented in Glacier Bay National Park with coho salmon.
How much new habitat will be created?
The Earth to Oceans aquatic ecology research team, led by associate professor Jonathan Moore, looked at the impacts of glacier retreat on salmon habitat, specifically which glaciers will establish new habitat. Kara Pitman, a researcher in the lab and a Ph.D. candidate at Simon Fraser University, told GlacierHub that approximately “thirty to fifty ocean-terminating glaciers in Alaska will produce new habitat.”
Areas in the Pacific Northwest and Alaska that have large, low-elevation glaciers will retreat back to expose this new habitat. The Bering Glacier in Alaska is one glacier that is likely to produce new habitat due to its low valleys, according to the researchers.
Pitman suggests that pink and chum species that spawn near the ocean in the river mouth may benefit due to new downstream habitats, and chinook, which spend more time in the freshwater rivers, may also benefit.
All species of salmon rely on both freshwater and saltwater throughout their lives to varying degrees. Adult salmon spend a few years in the ocean following primary development, but once adult salmon reach reproductive maturity, they undergo physical changes that prepare them to return to freshwater streams. When they reach appropriate stretches of freshwater, they release eggs and sperm into the water, allowing fertilization and the continuation of the cycle of life.
It’s also important to note that salmon are limited by stream gradient; as a result, they will not be able to swim up into many of the new habitats.
Pitman says that there are no salmon present in these newly formed waters at the moment, so there are currently no negative consequences of glacial retreat on these salmon populations.
“There may be no salmon now, but there might be in several years, so there will be impacts,” shesaid.
Mining’s Impact on Salmon Populations
At the same time, human interference such as negligence and reliance on fossil fuels negatively impacts salmon ecosystems across the world, including in Alaska and the Pacific Northwest. Industrial runoff from mines leaches into nearby streams, pollutes the water and poisons the fish. Preventative measures to manage waste and clean up efforts are not yet developed and little effort seems to focus on advancing protective policies.
For example, mining in Northwest British Columbia and Southeast Alaska is a serious issue that affects Taku, Stikine, and Unuk watersheds. The Taku River contains all five species of salmon and is glacial-fed from Taku Glacier. It is likely that in the near future acid mine drainage will harm fishing and tourism industries, indigenous cultural activities, and local peoples.
Similarly, near Bristol Bay in southwestern Alaska, a new mega mine is undergoing proposal and review. The Pebble Mine would be the largest mine in North America and could wreak havoc on one of the most productive salmon ecosystems.
Immediate action is required to halt future fossil fuel excavation projects and protect wild salmon populations in Northern Pacific and Alaska.