Researchers at Washington State University have found that the mating habits of salmon can alter the profile of the stream beds, affecting the evolution of an entire watershed. This is the first time we can say that salmon can influence the shape of the land.
Female salmon “fluff” the soil and gravel on the river bottom as the prepare their nests. The gravel and soil is then more easily moved by flooding, which exposes the underlying bedrock to erosion. By moving the sediment the fish are in fact changing the character of the stream bed, so in times of flood the base is more mobile.
the researchers modeled the changes over 5 million yrs and saw streams with spawning salmon lowering stream slopes and elevation over time. Land beside the stream can also get steeper and more prone to erosion.
Different salmon species can have a different effect. Chinook can move bigger pieces of material, while coho move finer particulate. Over time, this diversification can lead to different erosion rates and changes to the landscape.
This research highlights the role of living things to shape their environment. Trees prevent landslides, beavers build dams that slow water..creating wetlands that benefit many.
Conversely, in streams where salmon drop in numbers or disappear completely significant long-term changes in their profile and ecology may be seen.
The evolution of a watershed can be influenced by the evolution of a species.