There are salmon in Alaska’s trees. No, they’re not magically climbing the limbs or hanging from the branches like leaves. Fish nutrients do, however, course through the trees, as they do through much of the state’s wildlife.
At the heart of the relationship between salmon and trees are bears. Some of Alaska’s most iconic coastal landscapes — like the Tongass National Forest, the Kenai Peninsula and Kodiak Archipelago — are ecosystems that have been shaped in part by the relationship between bears, salmon and forests.
Bears play an important role in transferring the nutrients found in salmon to riparian zones. When bears catch salmon, many will take their catch to the shoreline or deeper into the forest to eat, especially when more bears congregate in the same area. When salmon are abundant, bears may only eat 25% of their catch, focusing on the most nutrient rich parts. The rest of the salmon carcass is left behind to meet several fates.
Over 80 species regularly consume salmon, with many scavenging the carcasses left by bears. As ravens, pine marten, mink and eagles feed on these remains, the carcasses are further scattered, sometimes hundreds of meters away from the stream. What isn’t consumed decomposes and deposits nitrogen and phosphorous, among other nutrients, into the soil.
The surrounding trees and plants can absorb these nutrients through their roots and use them to fuel their growth. Healthy riparian zones provide shade that keep water cool for salmon and vegetation roots stabilize stream banks and prevent erosion.
Salmon: A Recipe for Healthy Bears and Forests
A single salmon can rival some commercial fertilizers when it comes to nitrogen and phosphorous. Both are important for plant growth.
Nitrogen, for example, is a “limiting factor” meaning trees and plants can only grow at the rate the nitrogen content in the soil allows. Decomposing salmon can provide up to 24% of the nitrogen in riparian soil and the plants use every bit they can. Some research suggests as much as 70% of the nitrogen in streamside foliage comes from salmon.
Alaskan bear populations that consume more salmon typically have larger litters, are larger than their inland counterparts and occur at higher population densities. Salmon are not, however, the sole food source for coastal bears in Alaska.
Berries also make up a significant portion of bear diets, making bears important seed dispersers for a variety of berry producing shrubs in Southeast Alaska, especially of devil's club and blueberry seeds. A single bear scat deposit contains as many as 150,000 seeds. While it may sound a little gross to us, these seed-filled scats also provide a source of food for small mammals like northwestern deer mice and northern red-backed voles.
You Can Help This Circle Continue to Flow
Healthy forests and salmon populations sustain Indigenous traditions and practices, allow for commercial fishing and tourism opportunities, and provide unique outdoor recreation opportunities for locals and visitors alike. Salmon, bears and their habitats, however, face a variety of environmental threats, largely driven by a changing and ever more unpredictable climate. Outside of environmental factors, conflict with humans is a significant long-term threat facing bears and Alaska’s forests.
To help Alaskans learn how to better coexist with bears, Defenders of Wildlife and Alaska Department of Fish and Game hold multiple workshops throughout the spring and summer on the Kenai Peninsula and in southeast Alaska. The workshops cover bear awareness and safety measures, including how to properly use bear spray and information on electric fencing. We also explore the critical role bears play in the environment and why coexisting with them is important.
Defenders is also working to protect Alaska’s forests, like the Tongass National Forest, using the best available science to advocate for wildlife and habitat, including siting, design and management of old growth reserves and ensuring connectivity between them.
For the benefits and relationships between salmon, bears and forests to continue to support one another and us, we must reduce the threats and create a safer world for people, wildlife and their habitat to thrive. Subscribe to our email list to learn more about this wildlife, its habitat and how you can help them!
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