The annual snowpack in the Rocky Mountains and Sierra Nevada Mountains has been dropping over the past several decades. With the three-year drought that California has endured (thankfully lessened with heavy rains in recent weeks), California agriculture has taken a big hit, as I described in a blog several weeks ago.
Mountain snowpack has played a huge role in storing water that feeds our western rivers—upon which so many Americans are dependent for drinking water and food production, and upon which ecosystems depend. Snow builds up over the span of five or six months, and then the water in that snow is slowly released over the spring and summer months as the snow melts.
Not only has total precipitation dropped in the past 20-30 years, but warming temperatures have meant that more of the precipitation falls as rain rather than snow. Rainfall runs off the land much more quickly than melting snow, so there is more opportunity for infiltration and the recharging of aquifers. The increased intensity of rainfall events over the past 50 years is another huge concern.
These trends are predicted to continue, according to leading climate scientists. Areas that have grown dramatically in population over the past hundred years will become increasingly vulnerable not only to drought but also to flooding.
Ecosystem services provided by beavers
Conventional practice in places like California, Arizona, and Eastern Washington that are experiencing less reliable precipitation, is to build massive public works projects to impound water behind huge dams. These reservoirs, in a sense, do what snowpack does, and they provide more control. But such projects cost billions of dollars and wreak havoc on ecosystems.
There’s a better way.
Land managers are increasingly turning to the ecosystem services of our largest native rodent, the beaver (Castor canadensis). There used to be as many as 400 million beavers in North America, according to widely quoted estimates. Before the American West was settled and before we modified our land cattle and grain production, beavers were the dominant influence on the landscape.
Nearly every stream in the west is believed to have harbored beavers—typically dozens per mile. Beaver dams impounded water, created slow-moving, sinewy channels that supported tremendous biological diversity. Verdant valleys, rich with grazing ungulates and alive with singing birds, defined the landscape even in places that we think of today as dry and largely barren—like Nevada, southern Arizona, eastern Washington and Oregon, and lower-elevation regions of Colorado, Utah, and New Mexico.
The fur trade nearly wiped out beavers—almost totally eliminating them from the United States and leaving just 100,000 or so in hard-to-reach parts of Canada. In some cases, the motivation to kill beavers extended even beyond the production of beaver pelts (which were mostly used in making fine felt for hats). In the 1820s, according to a 2012 article in The Atlantic, Britain’s Hudson Bay Company sought to kill off every beaver in the Columbia River Valley, thinking that if there were no beavers then the area wouldn’t be threatened by U.S. westward expansion. Within 20 years, beavers were largely removed from the ecosystem across an area of the Northwest as large as France.
As early as 1901, efforts began to reintroduce beavers in some areas, such as the Adirondacks of Upstate New York, and widespread reintroduction efforts were underway in many states by the late 1930s. Animals were live-trapped in parts of Canada where pockets of the mammals remained and reintroduced in the U.S. and Canada where they had been extirpated.
The species is continuing to make a strong recovery, with the North American population today estimated to be between 10 and 15 million. As the impacts of climate change are beginning to be felt, the importance of re-establishing beavers is becoming widely recognized.
An answer to the loss of snowpack
The excellent 2014 PBS Nature documentary Leave it to Beavers describes how beavers modify the landscape to retain moisture. It turns out that beavers don’t only create ponds by damming creeks, the excavate ponds deeper, allowing them to hold more water. Biologist Glynnis Hood, Ph.D., who has been studying beavers near Edmonton, Alberta, described how important a role beavers play in Alberta by holding water.
“In 2002 we had the worst drought on record,” she reported. “The only places where we had water in natural areas was where we had beaver, and farmers were actually seeking out neighbors who had beavers on their landscape to water their cattle. So with beavers back on the land, even during the worst drought on record, they were mitigating the effects of drought and keeping water on the landscape.”
That idea was echoed in the PBS documentary by hydrologist Suzanne Foudy, Ph.D., of the U.S. Forest Service in describing the impact new beaver arrivals have been having on Susie Creek in north-central Nevada, near Elko. “If the snowpack’s coming off earlier and ranchers want water,” she said, “then we’ve got to figure out a way to keep it on the landscape, because it’s no longer going to be stored as snow in the mountains.” She continued: “What beavers do in all these itty-bitty streams is they create these small savings accounts, these pockets where it’s stored—no longer as snow, but as surface and groundwater.”
The bottom line is that the reintroduction of beavers in more arid parts of the American West may help to alleviate some of the impacts of climate change—more quickly, at far lower cost, and with far lower environmental impact—than can be done through our own engineering. In fact, instead of a metric of environmental impact we can refer to environmental improvement through ecological restoration.
Concern about methane emissions
One potential downside of more beaver ponds impounding water across the country is the emissions of methane, a potent greenhouse gas. Methane forms when organic matter decomposes without adequate oxygen—as often occurs in ponds that are rich in vegetation.
Concerns about methane emissions are very real and should be taken seriously, but my own take on this is that the methane emissions from beaver ponds are natural emissions, just as were the methane emissions from millions of bison that roamed the West until the mid-1800s. Those are the emissions that we should have.
In the case of beaver ponds, the biological activity that those wetlands allow may well compensate for much of the global warming potential of the methane. Yes, we should study it and fully understand it, but I’m confident that we’ll find the environmental benefits of beavers exceeding the environmental downsides.
Letting nature lend a hand
As someone trained in environmental biology who has devoted his career to protecting the environment—largely by focusing on the built environment—I am always pleased to find examples of nature providing the solutions we need. The role that beavers can play in adapting our environments to climate change is a wonderful example of this.
Knowing more about how important beavers are to us in an age of climate change will help me enjoy these delightful mammals all the more on my canoeing adventures.