By Christine E. Hatch, Professor of Geosciences, UMass Amherst. Originally published at The Conversation
It’s no accident that both the Massachusetts Institute of Technology and the California Institute of Technology claim the beaver (Castor canadensis) as their mascots. Renowned engineers, beavers seem able to dam any stream, building structures with logs and mud that can flood large areas.
As climate change causes extreme storms in some areas and intense drought in others, scientists are finding that beavers’ small-scale natural interventions are valuable. In dry areas, beaver ponds restore moisture to the soil; in wet zones, their dams and ponds can help to slow floodwaters. These ecological services are so useful that land managers are translocating beavers in the U.S. and the United Kingdom to help restore ecosystems and make them more resilient to climate change.
Scientists estimate that hundreds of millions of beavers once dammed waterways across the Northern Hemisphere. They were hunted nearly to extinction for their fur in the 18th and 19th centuries in Europe and North America but are making comebacks today in many areas. As a geoscientist specializing in water resources, I think it’s important to understand how helpful beavers can be in the right places and to find ways for humans to coexist with them in developed areas.
Scientists are studying ways to use beavers to mitigate wildfire and drought risks in the western U.S.
How Beavers Alter Landscapes
Beavers dam streams to create ponds, where they can construct their dome-shaped lodges in the water, keeping predators at a distance. When they create a pond, many other effects follow.
Newly flooded trees die but remain standing as bare “snags” where birds nest. The diverted streams create complicated interwoven channels of slow-moving water, tangled with logs and plants that provide hiding places for fish. The messy complexity behind a beaver dam creates many different kinds of habitats for creatures such as fish, birds, frogs and insects.
Human dams often block fish passage upstream and downstream, even when the dams include fish ladders. But studies have shown that fish have no trouble migrating upstream past beaver dams. One reason may be that the fish can rest in slow pools and cool pond complexes after navigating the tallest parts of the dams.
The slow-moving water behind beaver dams is very effective at trapping sediment, which drops to the bottom of the pond. Studies measuring total organic carbon in active and abandoned beaver meadows suggest that before the 1800s, active and abandoned beaver ponds across North America stored large amounts of carbon in sediment trapped behind them. This finding is relevant today as scientists look for ways to increase carbon storage in forests and other natural ecosystems.
Beavers may persist in one location for decades if they aren’t threatened by bears, cougars or humans, but they will move on if food runs out near their pond. When abandoned beaver dams fail, the ponds drain and gradually become grassy meadows as plants from the surrounding land seed them.
Dried meadows can serve as floodplains for nearby rivers, allowing waters to spill out and provide forage and spawning areas for fish during high flows. Floodplain meadows are valuable habitat for ground-nesting birds and other species that depend on the river.
The Value of Slowing the Flow
As human settlements expand, people often wish to make use of every acre. That typically means that they want either land that is solid and dry enough to farm or waterways they can navigate by boat. To create those conditions, humans remove floating logs from streams and install drains to draw water off of fields and roads as quickly and efficiently as possible.
But covering more and more land surface with barriers that don’t absorb water, such as pavement and rooftops, means that water flows into rivers and streams more quickly. Rainfall from an average storm can produce an intense river flow that erodes the banks and beds of waterways. And as climate change fuels more intense storms in many places, it will amplify this destructive impact.
Some developers limit this kind of damaging flow by using nature-based engineering principles, such as “ponding” water to intercept it and slow it down; spreading flows out more widely to reduce the water’s speed; and designing swales, or sunken spots, that allow water to sink into the ground. Beaver wetlands do all of these things, only better. Research in the United Kingdom has documented that beaver activity can reduce the flow of floodwaters from farmlands by up to 30%.
Just look at the engineering ?@rcampbellpalmer‘s camera traps & @joshharriswild‘s time-lapse skills have produced this amazing footage of beavers maintaining their dam ?
When a dam is damaged or washed away, beavers usually get to work on the repairs within 48 hours ?️ pic.twitter.com/rxi7FMpmIc
— Beaver Trust (@BeaverTrust) September 30, 2021
Beaver meadows and wetlands also help cool the ground around and beneath them. Wet soil in these zones contains a lot of organic matter from buried and decayed plants, which holds onto moisture longer than soil formed only from rocks and minerals. In my wetland research, I have found that after a storm, water entering the ground passes through pure mineral sand in hours to days but can remain in soils that are 80%-90% organic matter for as long as a month.
Cool, wet soil also serves as a buffer against wildfires. Recent studies in the western U.S. have found that vegetation in beaver-dammed river corridors is more fire-resistant than in areas without beavers because it is well watered and lush, so it doesn’t burn as easily. As a result, areas near beaver dams provide temporary refuge for wildlife when surrounding areas burn.
Making Room for Beavers
The ecological services that beavers provide are most valuable in zones where nobody minds if the landscape changes. But in the densely developed eastern U.S., where I work, it’s hard to find open areas where beaver ponds can spread out without flooding ditches or roads. Beavers also topple expensive landscaped trees and will feed on some cultivated crops, such as corn and soybeans.
Beavers are frequently blamed for flooding in developed areas, even though the real problem often is road design, not beaver dams. In such cases, removing the beavers doesn’t solve the problem.
Culvert guards, fences and other exclusion devices can keep beavers a safe distance from infrastructure and maintain pond heights at a level that won’t flood adjoining areas. Road crossings over streams that are designed to let fish and other aquatic animals through instead of blocking them are beaver-friendly and will be resilient to climate change and extreme precipitation events. If these structures are large enough to let debris pass through, then beavers will build dams upstream instead, which can help catch floodwaters.
A growing body of research shows that setting aside pockets of land for beavers is good for wetland ecosystems, biodiversity and rivers. I believe we can learn from beavers’ water management skills, coexist with them in our landscapes and incorporate their natural engineering in response to weather and precipitation patterns disrupted by climate change.
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I think that I see a difference between how humans use land these days and how beavers typically use it. With us humans, we like a monoculture, especially for commercial reasons. That is why you see farmers cutting down the trees on the edge of their crops or try to wipe out any species that are in competition for those farmlands, even bees. And even in the cities you see this desire when people have their yards in the form of a lawn, even though it must be continuously mowed. But people love their lawns.
But you read about what the beaver does with its terraforming and it is all ‘gradients.’ They dam streams to form ponds and the trees that die are left in place and form nests for birds. Sediment drops out behind the damn instead of just being carried downstream, the tangled with logs and plants form homes for fish, birds, frogs and insects to hide from predators. The wetlands created help limit floods and bank erosion. So there are a whole variety of ‘environments’ created that become niches for other species and change the land around it. The only thing that I have heard about that does something similar is those old, traditional country hedges but they are man made.
Speaking of traditional country hedges, RevKev, I discovered this film, made in 1942 by The Ministry of Information for The Ministry of Agriculture, on laying a hedge. I have become obsessed with hedgerows and have obtained a sharp axe and am working on getting a billhook and slasher. Oh, and a pipe!
I watch the film when I am feeling stressed and overwhelmed by modern technology.
Thanks for that. I first learned about hedges from a book that a commenter recommended called “Wilding: The Return Of Nature To A British Farm” by Isabella Tree. Talked about what happened when a farm they bought they returned to old practices. It mentioned how ‘hedges were grubbed up – 75,000 miles of them between 1939 and the 1990s – as little fields were merged to form prairies and small, complex farms were combined into big monocultural estates’-
https://literaryreview.co.uk/let-it-grow
In this part of the world, our beavers are bilingual. Link:
https://watershedmg.org/river-run-network/beavers
“…hundreds of millions of beavers once dammed waterways across the Northern Hemisphere. They were hunted nearly to extinction for their fur in the 18th and 19th centuries in Europe and North America…”
Capitalism, it is often claimed, develops the productive forces. Consider, if you will, the colossal destruction of productive forces represented by that one “incidental” fact alone. And remember that it is entirely typical of the effects of “progress” on the living world.
Would you believe that it was a change of fashion which saved those beavers? They were hunted relentlessly for their hides which went into making those top hats people often associate with the early 19th century. Then one day, the younger generation refused to buy them because that was what their parents and grandparents wore and so beavers were not shoved off into extinction-
https://en.wikipedia.org/wiki/Beaver_hat
https://www.nps.gov/parkhistory/online_books/smithsonian/terminus-reservoir/sec6.htm
No reason why beavers couldn’t be reintroduced here, but where is the will to do so?
In my experience there are lots of what you might call ‘urban beaver’ in the Sacramento Valley. Over the years I’ve lived here there’s been some lovely dammed habitat along the stretches of Putah Creek through UCD’s property, but by and large local beaver seem to eschew dam-building in favor of underwater bank excavation. They’re almost cryptids.
Before anyone brings it up, I promise you I’m not confusing some other rodent for the big guys. That would be like confusing our little riparian blacktail deer for moose.
(Reading over what I’ve typed, ‘urban beaver’ looks like it might be an unintended double-entendre. I meant to convey the heavily modified nature of rural landscapes here in the Central Valley.)
All of the rivers so laden with beavers that Smith mentioned are all well to the south of Sacramento, and it is my understanding that your neck of the woods had them reintroduced. It’d be nice to have them back home here too.
It would have been interesting to see the Sierra as it was once upon a time.
They translocated some of the 2 herds of Sierra Nevada Bighorn Sheep from the east side over to the west side past the Kern River in order to repopulate the Sierra as it once was and they are somewhere on the outskirts of the Chagoopa Plateau around the Big Arroyo.
Historically they would have been throughout the entire range of the High Sierra, and I read an account of the 2 herds each of approx 75 Sierra Nevada Bighorn Sheep that called Farewell Gap & Timber Gap home on opposite sides of Mineral King Valley, that were there in the 1870’s, which i’m thinking got eaten by hungry miners with a good aim into non-existence. The last account I can find in MK was in the 1920’s.
https://wildlife.ca.gov/Conservation/Mammals/Bighorn-Sheep/Sierra-Nevada/SEKI/Arroyo
I love this kind of story. Between the growth of small pollinator gardens and regenerative farming, ideas like letting beaver do beaver things, which end up benefiting local wildlife AND humans, there’s a steady growth of thinking that rejects much of our bigger-is-better and technology will pave the way forward world. There definitely seems to be a trend towards a more reasonable, naturalistic way of living, with it possibly leading to conflicts of some type (probably legislative with regulations but also with some monkey-wrenching thrown in) with big ag and it’s mono-crop, tech-driven mindset.
There definitely seems to be a trend towards a more reasonable, naturalistic way of living, with it possibly leading to conflicts of some type (probably legislative with regulations but also with some monkey-wrenching thrown in) with big ag and it’s mono-crop, tech-driven mindset.
While I’m all for optimism, this is wishful thinking. Landowners own the gov and beavers work is considered “stealing”. Most of our industry is located in floodplains. The BBB had zero for wetlands for the reason that big ag, monocroppers, and tech don’t/didn’t want it.
Humans also built low dams like this for thousands of years here in California to create fish habitat and for wetland food production. Humans can clearly do this kind of work as well but it’s generally illegal to repair our watersheds. It remarkable how the human watershed work has been eliminated from conversations even as the salmon go extinct.
The ancients did too. The Inca in Peru; the Laotians in Southeast Asia both (and many others in quasi-desert or monsoon climates) terraced the hillsides. We need to start to understand how we can avoid demolishing good sense solutions for the sake of short-term convenience. One of the most pernicious things pushing our monoculture mindset is mass production. Done, of course, for mass consumption cheap enough to achieve mass profits. To reinvest, of course, in more mass convenience (some call that efficiency or productivity) projects.
I wonder if humans have the capacity to see what kinds of “repair” will lead to homeostatic conditions. Even the ones trying to get “close to the earth” don’t have a long tail of the kinds of interactions that led to beavers doing what they do. Even the author of this piece loges for the “humans know best” in a small way:
“ I think it’s important to understand how helpful beavers can be in the right places and to find ways for humans to coexist with them in developed areas…” Fortuitously, beaver behaviors benefitted people who were often less rapacious in their “use and dominion” of the world. Given our penchant for “we-know-best-ism,” and domination behaviors even in the world of “living gently on the land:” https://midlandexpress.com.au/latest-news/2018/07/24/living-gently-on-the-land/ Check the “vision” thing for what looks like a green-washed housing development.
Who’s going to decide where the right places, and the right set of homeostatic behaviors, are?
I think many of our human “mistakes” are driven by market demands to maximize short term extraction. Greenwashing is a problem. We can learn from the systems used by people and animals before us. I think humans in California built on the wetland plant systems that evolved with mammoth and other mega fauna for thousands of years. We can study these patterns and build on them. There are also plenty of damaged places that we can improve without much risk of more damage. With the right incentives people can do many good things.
When I was a MN DNR Area Hydrologost for the MSP 7 county metro area, I would receive 20-30 beaver nuisance calls a year. About 2/3 of the complaints were within the developed metro, not the exurb fringes. Private citizens would get referred to the wildlife staff to get a trapper to remove them, a local government would work directly with the wildlife staff for removal. MN rules are explicit as to dam removal and steam restoration, which surprisingly most people followed.
Beavers are incredibly adaptable when given a chance.
People are incredibly eager to dynamite beaver dams (not allowed in MN).
Don’t get me started on muskrats. Triple the calls and impossible to get rid of. I even had one example of muskrats destroying a water control structure (aka dam) on a creek, in addition to the scores of complaints each year.
MN readers- lots of beavers in the Minnehaha golf course in Minneapolis (they generally don’t remove them). The trail on the south side of that lake is a good place to see the beavers’ work, and sometimes an actual beaver.
We have a small pond on the property, perhaps a bit less than one acre in size. One day while walking along its bank I spotted what was very obviously the work of a beaver that had chewed a distinctive circle around a Virginia pine of around 4-5 inches in diameter. About two thirds of the trunk was gone and the pine was still standing.
The beaver must have been some kind of scout that moved on for some reason, as we never saw any more evidence of beavers. Was it because there were no succulent plants nearby, or do they not like the taste and texture of pine pitch?
The creek that feeds the pond is of very low volume, and it must have taken several years to fill up the depression that the previous owner, a farmer, had created by scraping up a levy. Before selling out, he managed to submerge an entire pickup truck in the stream bed that leads away from the pond. Nothing like a big backhoe for disposing of a problem!
Don’t forget, alligators do the same thing despite the ridiculous notion they are cold blooded idiots…they are environment architects…had a few properties with gators as my boat deck and backyard buddies…as misunderstood as sharks…
My daughter’s house backs up to about 30 acres of mostly wetlands. The beavers have built a dam on the stream that flows through it and created a very nice pond for her ducks.
The first time they did, she tried to take it down (it was still pretty small) but the limbs, etc. were so well interlaced that it was an exercise in futility.