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Alaska Seward Peninsula Arctic tundra, the above image shows infrared aerial photos in 1980, the blue arrow shows the flow of water; below is a satellite image in 2022, the white arrow shows some of the more obvious dams (image source: Tape.et al, 2019) from a biodiversity point of view, the Arctic tundra is not as lonely as the desert, but it is not nearly as lively as the tropical rain forest. The thick permafrost beneath it makes it difficult for tall plants to take root, making it a world of moss, lichens, some herbs and dwarf shrubs. Some animals also visit from time to time, such as Arctic rabbits and moose. For them, the food on the tundra is not delicious, but it is enough. Rain and melting snow bring running water to the tundra, and with luck, you can still see salmon in the water. When it is warmer, some southern migratory birds come here to rest, although the cold in the Arctic can not keep their winter, but at least leave their summer memories.

Write an article | Ma Dongyuan

Revision | 2 / 7

The Arctic tundra is like a quiet town, deserted but not lonely. At this time, I do not know who actually built a "water conservancy project" on the tundra.

The two images below, an infrared aerial photograph of 1980 and a satellite image of 2019, show the same arctic tundra stream on Seward Peninsula Peninsula, Alaska. Seen from the sky, the stream in 1980 was just a thin line, and by 2019, the thin line had swelled out of several ponds.

The emergence of these reservoirs is not because of mountain torrents and wildfires, nor because of earthquake subsidence, but because "people" built a large number of dams on the stream, stopped the running water, and the water spread around and gradually accumulated into reservoirs.

Dams in the Arctic tundra (photo adapted from Tape et al, 2018) although such projects seem to be human in any way, this is not the case, and the construction of water conservancy projects in these places is not allowed by local law. Of course, these laws can only govern people, not beavers, a group of famous "construction freaks" in nature who are good at building dams. These dams are their masterpieces, and they have obviously extended their "infrastructure business" to the Arctic tundra.

Beaver: unexpectedly, I built all the dams. (photo: pixabay)

Hydraulic engineers there are two kinds of beavers in the world, this time the North American beaver (Castor canadensis) is "decorated" in the Arctic, mainly living in North America, and another kind of beaver is called Eurasian beaver (Castor fiber), which is also distributed in China. Beavers' webbed rear claws and oar-like tails make them good swimmers in the water, but once on land, they become immobile small hairballs, which can easily be used as a buffet by natural enemies such as wolves and coyotes. So, to try to stay in water that gives them more sense of security, beavers engraved the skills of "hydraulic engineers" in their genes.

Beavers' webbed feet and oar-like tails make them better swimmers, but they can't move easily on land (photo: Steve-CC BY-SA 2.0). The dam stems from the beaver's pursuit of a "villa in the middle of the lake". The beaver's nest is usually located in a "cabin" built of branches and soil on the water. The entrance to the cabin is underwater, and there is a small opening above it for air circulation in the nest. Beavers enter and leave the nest through underwater entrances, making their movements more hidden from predators.

Schematic diagram of the beaver's nest (drawing: Ma Dongyuan, original photo source: Bridesmill, CC BY-SA 3.0; pixabay) however, there are only such "cabins", they are not satisfied at all, and the surrounding environment must be comfortable enough! The current around the nest should not be too fast, it would be better to be still water, otherwise the "cabin" is unstable; the water level must be high enough to ensure that the entrance can be repaired underwater; the surrounding water must also be wide enough so that they have more room for movement. and when looking for food, they can take less land and swim in time when in danger; the water temperature must be appropriate and not too cold.

So the beavers began to build the dam. First of all, they use mud, branches and small stones to stop the flow of water, then constantly reinforce and repair them with tree trunks, and finally build dams one after another. Under the action of the dam, the riparian zone is enlarged, the water level is raised, the amount of water is large, and the flow is slow, which makes it more able to conserve heat and become warmer. After the dam is built, they will come back from time to time for inspection, maintenance and reinforcement to ensure the normal operation of the dam. Not only that, beavers build a lot of small "canals" around them to expand waterways for themselves, sometimes to facilitate the transport of wood for dam construction, and sometimes to get closer to food. In short, wherever the beaver goes, all kinds of "water conservancy projects" are almost essential.

A dam built by a beaver (photo: pixabay)

When the dam was built, the Arctic was built. "the scale and speed at which beavers transform the Arctic landscape from the sky is like burning a fire in the Arctic," Ken Tape, an ecologist at the University of Alaska at University of Alaska Fairbanks, said in an interview.

Once upon a time, beavers were not considered animals living in the Arctic, nor did the Arctic tundra seem to be a suitable habitat for beavers: most of the places were frozen, and "hydraulic engineers" could not use their dam technology. and can't find a place to build their own "cabin." The pitifully thin vegetation on the tundra also makes it impossible for them to find "building materials" to build the dam, and there is pitifully little food.

But today, under the trend of global warming, the Arctic is also facing the problem of climate change. The average temperature in the Arctic has risen by 1.8 ℃ since the end of the 19th century. The temperature continues to rise, the freezing time of running water shortens, the growing period of plants increases, and more shrubs (and even trees) grow. The environment is gradually changing, and the beaver is one of those guests who did not want to come before.

On the Arctic tundra, a dam built by beavers around their nests has transformed the nearby environment into a "beaver pond". (photo source: Tape. Et al, 2018) based on 70-year (1949-2019) remote sensing data from the Arctic tundra of Alaska, USA, and interviews with local residents, Tepp and colleagues found that beaver ponds first came here to build dams and form "beaver pond" (beaver ponds) around 1980, and since then the number of dams has continued to increase, with the number of beaver ponds in most areas doubling in just over a decade from 2003 to 2017. By 2019 they had discovered 11377 "beaver ponds".

Density map of 11377 "beaver ponds" in the Arctic tundra of Alaska, USA (Tape et al. 2022) "there are not many animals like beavers that leave traces on the earth that can even be seen from space. Of course, another animal with such ability is called man." Tepp said.

Beavers'"water conservancy projects" undoubtedly make them key species (keystone species) that significantly affect ecosystems and species composition in the forests south of the Arctic tundra. The beaver's dam changes the velocity, water level, temperature and other properties of the water, thus changing the composition of invertebrates and microorganisms in the water, thus changing the nutritional composition of the water. For fish, the dam may hinder the swimming and migration of fish on the one hand, and provide a suitable spawning and breeding environment for many fish on the other. Factors such as riparian widening provide growth conditions for many riparian plants, followed by animals that feed on these plants or birds that inhabit them. Some studies have shown that beavers also play a key role in soil and water conservation and drought defense of their wetland ecosystems. Once, American scientists even succeeded in using the Beaver Dam to save a rainbow trout (Oncorhynchus mykiss) by introducing beavers into rivers.

The ecological role of beavers should not be underestimated. American scientists have successfully used the Beaver Dam to improve the population, survival and reproduction rate of rainbow trout (Photo: Oregon State University-CC BY-SA 2.0). The arrival of beavers to the North Pole may be good for the biodiversity of the Arctic itself. But not necessarily for the global climate.

There is no definitive conclusion about what the beaver's arrival means for the Arctic ecosystem, but Tepp and his colleagues have made positive predictions. The frozen water environment and low temperatures have stopped many creatures from looking at the Arctic tundra. The emergence of "beaver ponds" has increased the area and depth of surface water, making it more capable of retaining heat and less likely to freeze, which is likely to attract many new aquatic species to migrate here. Although there are several species of salmon in the Arctic tundra, they used to be more of a passer-by, and beavers' changes to the water environment here have made it possible for these salmon to lay eggs and breed here. Minerals stored in the permafrost may also be exposed with the beaver's "water conservancy project", promoting the growth of the surrounding shrubs, which in turn attract more other creatures. The appearance of the beaver may be like building some bazaars in the quiet town of the Arctic tundra, gradually attracting the scattered residents around to come and party, and gradually become a lively place.

The impact of beavers may be positive for the biodiversity of the Arctic tundra, but one possible negative impact deserves our attention. The price of vitality brought by the Beaver Pond is the melting permafrost. It is estimated that the carbon content in the permafrost is about twice that in the atmosphere, and the sudden thawing of the permafrost will release carbon dioxide and methane, which will continue to exacerbate climate change. The area covered by the "beaver pond" will cause the permafrost beneath it to thaw, and if beavers continue to build dams on a large scale in the Arctic tundra, they may really be "burning the Arctic". Continue to release greenhouse gases from the permafrost.

Changes in the water environment of the Arctic tundra by beavers, the red arrow indicates the beaver's dam, and the yellow arrow is a possible site for melting permafrost (photo source: Jones et al, 2020) Beavers come to the North Pole because of climate warming, and they may continue to contribute to global warming. Tepp and colleagues also predict that the number of beavers in the Arctic tundra will increase in the future, and their range of activities will become more and more northward. More research and management of Arctic tundra beavers will also be important in the future.

But for better or worse, one thing may be certain that the future of the Arctic tundra in Alaska is undergoing upheaval because of the arrival of beavers.

Possible effects of beavers on Arctic tundra (photo source: Tape et al, 2018) references:

Https://www.nature.com/articles/s41598-022-09330-6

Https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14332

Https://iopscience.iop.org/article/10.1088/1748-9326/ab80f1?utm_source=mp-fotoscapes#erlab80f1f8

Https://web.archive.org/web/20200123132507/https://www.aphis.usda.gov/wildlife_damage/beaver_damage/downloads/Baker%20and%20Hill%20Beaver%20Chapter.pdf

Https://wires.onlinelibrary.wiley.com/doi/10.1002/wat2.1592

Https://www.nature.com/articles/srep28581

Https://www.businessinsider.com/beavers-invade-alaska-arctic-tundra-photos-satellite-images-damage-2023-1

Https://www.livescience.com/why-beavers-build-dams

Https://animaldiversity.org/accounts/Castor_canadensis/

Https://ucmp.berkeley.edu/exhibits/biomes/tundra.php

This article comes from the official account of Wechat: global Science (ID:huanqiukexue)

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