Beaver dams may buffer against temperatures that threaten sensitive species

May 17, 2017

Both natural and artificial beaver dams may alter stream temperatures which may benefit temperature-sensitive salmonid species, according to a study published May 10, 2017 in the open-access journal PLOS ONE by Nicholas Weber from Eco-Logical Research, Inc., USA, and colleagues. 

Beavers are ecosystem engineers, altering stream temperatures by building dams that increase surface water storage and connectivity with groundwater. Some studies suggest that the dams make water warmer and so are detrimental to salmonids, which are sensitive to temperature. Weber and colleagues tracked beaver dams and monitored water temperatures along 34 kilometers of the John Day River in Oregon over eight years. In addition, the team assessed the impact of artificial beaver dams on water temperature along four reaches of Bridge Creek.

The researchers found that beaver dams may alter stream temperatures to the benefit of salmonids. Studies suggest that juvenile steelhead salmonids in Bridge Creek experience extreme stress at about 25°C, and the researchers found that maximum daily temperatures in much of the study stream exceed this temperature for much of the summer. However, temperatures rarely exceeded 25°C after the proliferation of beaver dams, likely because they help moderate temperatures both by increasing water storage and encouraging exchange between surface water and groundwater exchange. This fits with the fact that both beavers and salmonids were once more abundant and widely distributed in North America, and suggests that beaver dams could help mitigate the thermal degradation that can threaten sensitive species.

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