How beavers are reviving wetlands

A happy beaver

A happy beaver

We are losing wetlands three times faster than forests, according to the Ramsar Convention on Wetlands. When it comes to restoring them to their natural state, there is one hero with remarkable powers: the beaver.

Wetlands store water, act as a carbon sink and are a source of food. According to the Ramsar convention on wetlands, they do more for humanity than any other terrestrial ecosystem – and yet they are disappearing at an alarming rate.

The main problems are agricultural and urban expansion, but also drought and higher temperatures due to climate change.

But if you have a river and a beaver, it may be possible to stop this process.

These hairy, sharp-toothed rodents build dams on waterways to create a pond, in which they build a “hut” where they can protect themselves from predators.

Their technique is to chew logs until they fall, and to use the trunk and branches as building material, along with stones at the base, and mud and plants to seal the dam’s upstream wall.

The dam creates flooding, slowing the flow of water and keeping it in the landscape longer.

“This transforms simple streams into thriving wetland ecosystems,” said Emily Fairfax, an ecohydrologist at California State University.

“The amount of food and water available in their wetlands makes them ideal habitats for many different species. That’s part of the reason beavers are a so-called keystone species.”

A tree chewed by a beaver

Beavers chew on the base of selected trees until they fall

Over the past 50 years, Canada and several states in the US have reintroduced beavers. Initially this was done to restore beaver numbers, after they were hunted almost to extinction for their fur and meat in the 19th century.

But the restoration of wetland ecosystems has also brought huge biodiversity benefits, including the return of many species of frogs, fish and invertebrates.

A 2018 study by Finnish researchers found that ponds created by beavers contain almost twice as many mammal species as other ponds. Weasels, otters and even moose were all more common.

“Beaver wetlands are quite unique,” said Nigel Willby, a professor of freshwater science at the University of Stirling.

“Anyone can make a pond, but beavers make amazingly good ponds for biodiversity, in part because they’re shallow, littered with dead wood, and generally messed with by beavers feeding on plants, digging canals, repairing dams, building huts etc.

“Basically, beavers excel at creating complex wetland habitats that we would never match.”

Enthusiastic beavers

  • Dams built by beavers can be up to 5 meters high, and the largest on record to date – in Alberta, Canada – is 850 meters long

  • As beavers cut down trees, the stumps often sprout new shoots instead of dying – in effect, the beavers carry out coppice

  • In the 1970s, the North American beaver and the Eurasian beaver were confirmed to be separate species

A healthy wetland ecosystem also sequesters large amounts of carbon, and by acting like a sponge and soaking up floodwaters, it could mitigate the effects of climate change, scientists say.

Wetlands store water during wet seasons and release it slowly during periods of drought.

“If you go into a period of drought, all the plants that live in a floodplain rely on stored water in the soil to stay green and healthy. If they don’t have a lot of water, they will wilt and wither and dry out,” says Dr. Fairfax .

A beaver dam at sunset in Grand Teton National Park in Wyoming, USA

A beaver dam in Wyoming, USA

She and her team studied 10 different wildfires in five U.S. states between 2000 and 2021 and found that beavers and their ecosystem engineering reliably created and conserved wetland habitats even during megafire events.

“Beaver wetlands have a lot of stored water, so plants don’t really feel drought. They stay green and lush. And when wildfire came through, they didn’t burn and we found they stayed well watered.”

But experts say beavers are only part of the solution to restoring wetlands. Other necessary measures include planting forests along the banks of lakes and rivers and restoring peatlands and salt marshes, says Prof. Willby.

And crucially, beavers are only found naturally in North America and Eurasia.

Introducing them to inappropriate places can be counterproductive. This was demonstrated in Argentina and Chile, where beavers introduced from North America in the 1940s multiplied exponentially without predators, resulting in severe forest loss.

The Global Wetlands Outlook, published in 2021 by the Ramsar Convention on Wetlands, noted the most widespread wetland degradation in Africa, Latin America and the Caribbean.

Lake Chad

Lake Chad is a shadow of its former self

The drastic shrinkage of Lake Chad, closer to the borders of Chad, Cameroon and Nigeria in West Africa, is one of the most striking examples.

It has shrunk by 90% since the 1960s, mainly due to a surge in water demand from a rapidly growing population, unplanned irrigation and now climate change-induced drought.

“Conflicts, mainly between farmers and pastoralists, over the limited remaining water of the lake were already there and now the lake is drying up and fighting for water has gotten worse,” said Adenike Oladosu, a wetlands conservation activist in Nigeria. .

Rio Negro

The Rio Negro is the largest wetland protected under the 1971 Ramsar Convention on Wetlands

Barron Joseph Orr, chief scientist at the United Nations Convention to Combat Desertification, says wetlands are often resilient ecosystems, but prolonged drought is now a growing threat.

“Climate change projections show increased drought in arid areas that could compromise wetland resilience and reduce important habitat services,” he says.

Drought can also damage wetlands in other areas, but the beaver can help protect them. There have already been more than 100 successful reintroduction projects in North America and Northern Europe.

According to Prof. Willby, the population in Europe is said to have tripled in the past 20 years and beavers are now back in most European countries. Sweden, Germany and Austria led the way, according to the Natural History Museum, but the United Kingdom followed suit in the early 2000s.

“The early motivation for bringing beavers back to the UK was mainly about playing a role in restoring a declining species to its native range,” says Prof Willby.

“But the value it could have as a keystone species for other biodiversity and in natural flood management has gained much traction, and these are the arguments usually put forward for the local release of displaced animals or fenced trials that are taking place in many places. to support. .”

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