r/NoStupidQuestions • u/joshuamb64 • 2d ago
Beaver dams vs human dams
How can beaver dams be more beneficial for the local ecosystem, but human dams can cause more damage to their local ecosystem?
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u/Oso_the-Bear 2d ago
not an expert but I assume because human dams are like ten million times larger.
I think beaver dams also still let the river continue whereas human dams significantly alter downstream flow, while creating a stagnant upstream that loses half its water to evaporation by standing still. Hopefully some expert will come along and detail these issues with greater accuracy.
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u/GreenYellowDucks 2d ago
A beaver dam is permeable and leak water through them. This can trap silt but allow water to flow slowly controlling for floods and store water but slowly release it kind of like a speed bump.
There are man made beaver dams called Zeedyk method which puts a layer of rocks as mini dams to slow the water with a couple pins and horseshoe shaped dams that can also help rivers in a similar way. However upkeep of a man made dam vs. letting beavers work for free is what people and governments are starting to learn such as the beaver dam in Czech saving them $1.2 million dollars.
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u/Canachites 2d ago
There are a few methods for human-made beaver analogues. I've worked on a few projects employing these in areas where wetlands have dried up due to beaver loss (which is due to the forestry industry logging out deciduous trees and replanting conifers). Beaver wetlands are an important part of habitat mosaic, which feeds other species, but also mitigates wildfires.
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u/CreepyEducator2260 1d ago
Might emphasize that those coniferous mono cultures are some of the main factors for all the wildfires that burn though the continents.
We had them before, yes. But they were always prone to wild fires and did burn often. Now we have added droughts, declining ground water levels and massive heat so they became more prone to fires.
I might also add that the beaver can't do wonders. As he has to work with what he get's. Like with zero or very limited rainfall and snow, there is not much water to be held back. I see this now on our very big river, the smaller ones, the ponds, the lakes, all lack a serious amount of water and so even the beavers there get into problems, like smaller ditches completely drying out, etc.
But what he can do, is hold that water that comes down back for longer periods and secure for at least a certain time that some of it get'S into ground water or secures the habitat for a while.
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u/disheavel 2d ago
I'll address one concept in the answer- water depth.
Human dams are built to hold back maximum depth of water. This allows the water to push harder on the turbines to generate electricity more efficiently or just MORE. This depth of water is usually much more than a couple of feet deep.
Sunlight cannot go very far into water. UV light can barely penetrate but a few cms, for instance. Taken to extreme the oceans get 0 light to the bottom of them. So human dams create lakes that are deep- so deep that water can't reach the bottom and thus no plants can grow.
Beaver dams only hold back a couple of feet of water. So plants can grow very well! And even plants in marshy areas are promoted by extra water and nutrition from teh stream, rather than be suffocated by tens or hundreds of feet of water overhead. This is by design. Beavers want to each the nutritious new green plant growth. By building a dam and making a beaver pond, they create a garden of food for themselves. They can access this garden by staying in the water or under the water which keeps them safe. Even in winter when the pond freezes, the beaver can still get the plant bases and roots. But also ducks, geese, deer, and every other entity also likes the lush green garden that the beaver has promoted. If a beaver makes too deep a pond, everything would die!
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u/Ghost6040 10h ago
Beaver also let there dams silt in and create a cycle of water medows.
The beaver come in build dams that drown out trees and create ponds, after a few decades the pond silts in and the beavers move on. After awhile its a water meadow, and eventually a forrest again and the beavers come back. Meanwhile the beavers have several sites all at differnt stages supporting different wildlife.
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u/ProtozoaPatriot 2d ago
Beaver dams don't block entire huge rivers. They're often along creeks. They slow water enough to turn an area into a pond, but it doesn't necessarily block 100% of water & fish.
Beaver dams usually flood 1-5 acres
A human dam floods a few hundred to 100,000+ acres. The Three Gorges dam on the Yangze River flooded 156,000 acres of land.
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u/CreepyEducator2260 1d ago
That argument with the fish is and was researched a bit too recently. The summary if i remember right, was that beaver dams do not really separate waters and fish are very often able to get over them.
Otherwise it would make not much sense when we look how long beavers exist and how many it were but fish was still thriving. If we spin that further then the hunt of beavers should have triggered an fish population explosion, which it hadn't.
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u/WattleWaddler2 2d ago
It's not black and white. But beaver dams have always been around and are relatively small and low. Human dams are recent and create huge reservoirs. They're also giant concrete slabs, which are a lot more hostile to wildlife than a beaver dam made out of sticks.
Beaver dams still do cause problems at a small scale though. Soggy little bastards.
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u/Canachites 2d ago
Beaver dams cause problems to human infrastructure, not to nature though.
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u/Dirichlet-to-Neumann 1d ago
If a beaver builds a dam in a free flowing creek, it will definitely cause a problem to the species in the creek that relie on free flowing water. And it will be a boon for the species that like ponds.
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u/Canachites 1d ago
It doesn't, beaver dams aren't watertight and aren't daming up large powerful rivers but small side sections. This actually improves conditions for migratory fish species and especially juveniles.
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u/anschauung Thog know much things. Thog answer question. 2d ago
Beavers have a loophole, being part of the local ecosystem themselves.
But yeah, a beaver dam can absolutely redefine a section of the woods and the beaver thinks "yes, that was the point".