How atmospheric rivers impact wildlife habitat, aquatic ecosystems

Parts of B.C.'s coast continues to see heavy rain as Environment and Climate Change Canada warns of a prolonged atmospheric river this week.

The B.C. River Forecast Centre is warning residents to use caution because of the risks of flooding, landslides and avalanches, while an evacuation order has been issued for those living in part of Martin Valley near Bella Bella. 

But what about the furry, feathered and scaled residents living throughout the province? 

Here’s how atmospheric river weather events can impact B.C. wildlife.

Jonathan Boyd, a hydrologist with the B.C. River Forecast Centre, said it’s very unusual for the province to be hit by atmospheric rivers at this time of year.

"It does happen, but it’s not very frequent," Boyd said.

An atmospheric river is a large stream of water vapour that travels through the sky, affecting a specific point on the ground for an extended period of time, which Boyd said, usually lasts between 24 and 72 hours. 

Typically, he said, atmospheric rivers start impacting the North Coast and Haida Gwaii between late July and September, and start moving south in the fall and winter seasons.

"In the Lower Mainland and Vancouver Island, the peak time period for atmospheric rivers is usually, like, late October through mid-January," Boyd said.

CBC News previously reported that the warmer the air is, the more water vapour atmospheric rivers can carry and grow. In turn, it can release more rain or snow when it makes landfall.

The immediate impact on aquatic life is often through flooding caused by the rain, said Raincoast Conservation Foundation biologist Kristen Walters.

"Rising water levels can cause sediment to be mobilized from the landscape, from mountains, from slopes," Walters said, adding it can harm salmon when water flows through their gills, for example.

"Often the fast water flow can scour the riverbed, which can actually just remove incubating eggs from the gravel, which can be challenging for salmon populations that might be at risk," she said.  

Pointing to the 2021 historic floods in the Fraser Valley, Walters said the organization studied fish habitat and found a number of contaminants, including cocaine, painkillers, fertilizer and pesticides which she said came from overwhelmed water treatment plants and agricultural areas.