How beavers are reviving wetlands

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 a hero with remarkable powers: the beaver.

Wetlands store water, act as carbon sinks, and are a source of food. The Ramsar Convention on Wetlands says they do more for humanity than all other terrestrial ecosystems, and yet they are disappearing at an alarming rate.

The main problems are agricultural and urban expansion, as well as droughts and high temperatures caused by climate change.

But if you have a river and a beaver, you might stop this process.

These sharp-toothed, furry rodents dam waterways to create a pond, within which they build a “shelter” where they can protect themselves from predators.

Their technique is to chew the tree trunks until they fall off and use the trunk and branches as building materials, along with stones at the base and mud and plants to seal the upstream wall of the dam.

The dam causes flooding, slows the flow of water and keeps it on the landscape longer.

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

“The amount of food and water available in their wetlands makes them ideal habitat for many different species. That’s part of why beavers are what’s known as a keystone species.”

A tree chewed by a beaver

Beavers chew the base of selected trees until they fall off

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

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

A study by Finnish researchers in 2018 found that beaver-engineered ponds contained almost twice as many mammal species as other ponds. Weasels, otters, and even moose were more frequent.

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

“Anyone can make a pond, but beaver ponds are incredibly good for biodiversity, partly because they’re shallow, full of dead wood, and generally beavers play them when they feed on plants, dig canals, repair dams. , they build shelters, etc.

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

eager beavers

  • Beaver dams can be up to 5 m high, with the largest so far recorded, in Alberta, Canada, being 850 m long.

  • As beavers cut down trees, tree stumps often sprout new shoots instead of dying; in fact, beavers carry out the regrowth.

  • The North American beaver and the Eurasian beaver were confirmed to be separate species in the 1970s.

A healthy wetland ecosystem also sequesters large amounts of carbon, and by acting like a sponge and soaking up flood waters, it can soften the impacts of climate change, scientists say.

Wetlands store water during wet seasons and slowly release it during dry spells.

“When you go into a dry spell, all the plants that live in a floodplain depend on water stored in the soil to stay green and healthy. If they don’t have a lot of water to access, they will start to wither and dry up,” 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 US states between 2000 and 2021 and found in each of them beavers, and their ecosystem engineering reliably created and preserved wetland habitats, even during megafire events.

“Beaver wetlands have a lot of stored water, so the plants in them don’t really feel drought, they stay green and lush. And when a wildfire hit, 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 the planting of forests along the banks of lakes and rivers, and the restoration of peat bogs and marshes, says Professor Willby.

And more importantly, 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 in the absence of predators, causing severe forest loss.

The Global Wetland Outlook published in 2021 by the Ramsar Convention on Wetlands found the most widespread wetland deterioration in Africa and Latin America and the Caribbean.

lake chad

Lake Chad is a shadow of its former self

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

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

“Conflicts, mainly between farmers and herders, over the limited remaining water in the lake already existed and now the drought is drying it up even more and the fight for water has worsened,” says Adenike Oladosu, a wetland conservation activist in Nigeria.

Black river

The Río Negro is the largest wetland protected by the 1971 Ramsar Convention on Wetlands

Barron Joseph Orr, senior scientist for the United Nations Convention to Combat Desertification, says wetlands are often resilient ecosystems, but prolonged droughts now pose a growing threat.

“Climate change projections show increased dryland severity in drylands that could compromise wetland resilience and reduce important habitat services,” he says.

In other areas too, drought can damage wetlands, but beaver can help protect them. There have already been over 100 successful reintroduction projects in North America and Northern Europe.

In Europe, the population is believed to have tripled in the last 20 years, according to Professor Willby, and beavers have now re-established in most European countries. Sweden, Germany and Austria led the way, according to the Natural History Museum, but the UK followed in the early 2000s.

“The initial motivation for bringing beavers back to the UK was mainly to play a role in restoring a declining species to its native range,” says Professor Willby.

“But the value it might have as a keystone species for other biodiversity and in natural flood management was gaining much more traction, and these are the arguments that are now generally put forward in support of local releases of translocated animals or fenced-in trials that They are held in many places. .”

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