Beaver Dams reduce the Impacts of Climate Change

 

During late summer of 2021, the Bootleg fire ravaged the Upper Klamath Basin area in Oregon, destroying vegetation and damaging its wildlife. Surveys of the area following the fire season in autumn of that year showed that many rivers and tributaries ran black, polluted by ash and debris. Runoff from autumn rains transferred wildfire sediments into the river, killing off the native trout population. However, it was observed that in an area of the Dixon creek, a tributary flowing into the Sprague River, that lush green vegetation was preserved and water flowing from the creek was clear. The difference? Dixon creek was home to 8 beaver dams that effectively filtered sediment from the water upstream. 

The Sprague River runs through Klamath County in Oregon

This sighting agreed with previous observations of the effects of beaver dams on riverbank ecosystems post-wildfire in the western U.S. It was also known that beaver dams in a river system could filter sediment from eroded rocks, but this was the first-time scientists had seen this principle applied to wildfire runoff. Beaver dams accomplish this by decreasing the current of water passing through them. Sediment contained in this water is allowed to sink to the bottom of the river floor where it is less likely to block the gills of fish living in the river. Beaver dams are helpful in ecosystem recovery, but beavers themselves are not as common as they once were. 

An example of a natural sediment filter - otherwise known as a beaver dam   

Beavers used to be a common animal in the U.S with populations as large as 200 million when European settlers arrived. They were hunted to a population a fraction of the size by the 19^th century due to the popularity of the fur trade. Today, there are only around 15 million beavers nationwide. Beavers and by extension beaver dams can improve water quality where wildfires are common, especially as they’ve become more frequent due to climate change. Because of their ecological benefit, some scientists and organizations are pushing for conservation and reintroduction of beavers to the western U.S. Despite this, some landowners believe that beavers are pests, as they can be responsible for knocking down trees and flooding roads. 

To provide temporary wildfire runoff protection in anticipation of the rainy season, scientists have applied their observations to create beaver dam analogues (BDA). The U.S Fish and Wildlife Service in collaboration with a nonprofit conservation group called Trout Unlimited, have placed 41 BDAs along the Sprague River. However, BDAs do not replace the need for naturally made beaver dams, since they require maintenance to sustain. The Klamath Tribes are aware of this fact, and plan to use BDAs to restore the habitat of the Klamath Basin to attract beavers or make their reintroduction easier. They hope for a future where the basin can return to its natural state before the fur trade.