Beavers and their dams: what effects do they have?

Hi everyone,

Today we're talking about beavers and their effects on the surrounding ecosystems and environments. 'Beaver' referres to two species in the genus Castor. They are found in North America, Europe and Asia and are the largest rodents in those places and the second largest rodents in the world. Beavers grow up to 80 cm long with a flat, paddle-shaped tail up to 45 cm. They have a small head, large incisor teeth and fur lined lips to avoid inhaling water while cutting and transporting branches underwater. They weigh 16-30kg and are nocturnal.

Beavers live in streams, rivers, marshes, ponds and lakes where they construct dams. These have earned them the title 'ecosystem engineers' but we'll talk about that later. The dams are constructed with branches, sticks and rocks. They create a calm pool with a higher water level on one side. Beavers make their homes (lodges) in these calm pools. Beaver dams are both have both positive and negative effects on the environment.

Probably the biggest problem with beaver dams is the flooding. The water that is held back by the dam has to go somewhere and it normally floods the surrounding landscape. This is where the name 'ecosystem engineers' comes from because they change the entire landscape by redirecting/expanding the rivers and streams and therefore drastically change the flora and fauna. This can cause severe damages to surrounding ecosystems and human infrastructure.

Beaver dams also interfere with migration of fish species such as salmon, as they block the rivers that these fish are trying to travel up/down. Also, methane producing microbes thrive in the sediment that forms around beaver dams. This is a big problem in regards to climate change. The water also has a severe lack of oxygen, causing many underwater plants die.

However, beaver dams have a lot of benefits. The flooding of the surrounding area creates wetlands which promote biodiversity. The beavers thin out trees while making their dams which prevents the domination by a single plant species and reduces the risk of forest fires. Different species of plants, animals and microorganisms thrive in the pools behind the dams. These pools also store carbon as the submerged wood decomposes a lot slower due to the lack of oxygen. The carbon stays locked in the wood for a long time leading to beaver meadows to be a large carbon store. The problem is that when the beavers leave the area or get killed, the dams eventually break and the wood is exposed to oxygen.

The dams reduce erosion, which is a big problem that waterways and coasts are facing at the moment. The dams also mean that sudden flooding is reduced. When floods of water come down a river, they can cause massive destruction but the beaver dams and surrounding wetland can catch the floods and lead to just a small slower increase of water further downstream.

We hope you found this post interesting. And who knows you may have beavers in your local area! In the UK, they have been reintroduced as a very cheap form of flood protection and water management.

Your Green World Blog Team💚

Sources:

https://www.britannica.com/animal/beaver

https://www.forestwildlife.org/how-do-beaver-dams-affect-the-environment/

https://www.science.org/content/article/what-role-do-beavers-play-climate-change

https://www.stir.ac.uk/news/2018/10/beavers-impact-on-biodiversity-revealed/

https://iopscience.iop.org/article/10.1088/1755-1315/201/1/012015/pdf

Images:

1: This image, owned by Michael Levine-Clark (on flickr.com) is liscensed under CC BY-NC-ND 2.0.
2: Beaver Dam in Winter, owned by Gerry Dincher (on flickr.com), is licensed under CC BY-SA 2.0.

3: This image, owned by Fred Moore (on flickr.com) is liscensed under CC BY-NC 2.0.

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