By Jenessa Duncombe, News Writing and Production Fellow
When a wildfire tears through a landscape, there can be little left behind.
A new study, though, suggests that beavers may be protecting life around streams, thanks to their signature dams. Satellite images from five major wildfires in the United States revealed that corridors around beaver habitat stayed green even after a wildfire.
Millions of beavers live in forests across North America, and they make their homes in a particular way: By stacking piles of branches and rocks in a river’s path, they slow its flow and create a pool of calm water to call home. They even dig little channels radiating out from their pools to create “little water highways,” said Emily Fairfax, an assistant professor at California State University Channel Islands who led the study.
Fairfax wondered whether beaver dams would insulate riparian vegetation, as well as the fish and amphibians that live there, from wildfire damage. Wildfires course through landscapes naturally, but blazes will become more frequent as climate change dries out forests.
Fairfax sifted through records of past fires in the U.S. Geological Survey’s database and chose five recent fires that occurred in beaver habitat. She then analyzed the “greenness” of vegetation before, during, and after the fires. She used measurements from NASA’s Landsat satellites, which use red and near-infrared light to detect the lushness of vegetation.
Fairfax found that vegetation along sections of a river without dams burned straight to the river’s edge. But for sections with a resident beaver, “essentially, the plants don’t know a fire is happening.” The channels dug by beavers acted like irrigation channels, said Fairfax, keeping vegetation too wet to burn, even during drought. In all, stretches of river without beavers lost 51% of their vegetation greenness, compared with a 19% reduction for sections with beavers.
Joseph Wagenbrenner, a research hydrologist at the U.S. Forest Service who was not involved with the research, said that protecting the vegetation around rivers can help prevent problems downstream. Contaminants and sediment can clog rivers right after a fire, degrading water quality and threatening life. He said the work could be important for scientists’ efforts to reduce wildfire’s negative impacts.
Fairfax presented the research at AGU’s Fall Meeting 2019 in San Francisco, Calif. She created this stop-animation story of one little beaver’s influence during a burn.