Beavers play role in protecting trout from worst of changing climate

By John Zablocki

Heraclitus of Ephesus, an ancient Greek philosopher, is quoted to have said “No man steps in the same river twice.” One supposes this Greek sage was a fly-fisherman. Anybody that’s fished our nation’s wild trout streams long enough can undoubtedly attest firsthand to the truth of his statement: our rivers are constantly changing.

Learning to adapt to those changes is what makes us good fishermen …  and good conservationists.

Some changes occur gradually, like the shifts in stream flows and temperature from climate change we’ve observed over the past few decades. But what happens when our favorite trout stream is completely transformed before our eyes?

beaver, climate change, trout unlimited

Love them or hate them, beavers play a role in protecting trout from the worst of a changing climate.

Just ask anybody who has fished in a stream before and after beavers were present.

The large-scale changes beavers cause have earned them the title of “ecosystem engineers.” It is a fitting name. The arrival of beavers into a stream can lead to a truly re-engineered stream system.  Is this a good thing? It depends on who you ask.

Critics cite the problems beavers cause for people and wildlife in certain cases, such as blocking fish passage in a stream, washing out roads or flooding agricultural areas adjacent to streams. And in places where they are non-native (e.g., South America) ecologists have noted the catastrophic effects of beavers unchecked by natural predators, restructuring an entire ecosystem by opening up new habitats for invasive species and decimating forests.

Proponents of beavers argue that the little dam-builders help hold water on landscapes during times of drought, help regulate flooding, provide critical wetland habitat for fish and wildlife, filter water, trap sediment and help maintain healthy forests. All of this is good for fish, and beavers provide these services for free .

Last autumn, I spoke with two ranchers with whom TU  works on Lahontan cutthroat trout restoration projects.  Asked about beavers, one rancher told me “I hate them with a passion.” The other rancher mused, “One thing is for sure, if it hadn’t been for those beavers, which 20 years ago we would have been shooting, we wouldn’t have had water for our cattle on our ranch this year.”

beaver, Lahontan, climate change, Trout Unlimited

A Lahontan cutthroat trout stream in Oregon inhabited by beavers after a wilfire blew through.

beaver, Lahontan, wildfire, climate change, Trout Unlimited

Stretches of the same stream where beavers weren't present burned right up to the water's edge, likely killing trout.

Shortly after these conversations, I led a field crew to survey the effects of a massive wildfire along the Oregon-Nevada border in one of the last remaining strongholds for Lahontan cutthroat trout. With climate change and invasive grass species increasing the frequency and intensity of wildfires, I wondered how the fish were ever going to survive. Looking at the burned landscape, it felt like standing on Mars, where there is no life at all, nor even the possibility of it. I was sure the fish were goners. But everywhere there were beaver ponds, the fish survived, along with frogs, dragonflies and native plants.

Love them or hate them, I wonder if beavers are maybe one of our best allies in protecting some of our nation’s most threatened populations of native cutthroat trout from the effects of climate change.  It’s definitely something to chew on…

John Zablocki works on Lahontan cutthroat trout restoration projects for Trout Unlimited.

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