GeoLog

EGU General Assembly

Could beavers be responsible for long-debated deposits?

Could beavers be responsible for long-debated deposits?

Following her presentation at the European Geosciences Union General Assembly in Vienna, I caught up with geomorphologist and environmental detective Annegret Larsen from the University of Lausanne, Switzerland, about beavers, baffling sediments and a case she’s been solving for the past seven years.

Back in 2012 the German geomorphology community was seriously debating the source of buried black soils, a stark black layer of sediment found in floodplain deposits all over Europe. Such dark sediments are usually associated with organic, carbon-rich materials, like peat. But unlike the other dark deposits, these soils are low in organic carbon, leading to a wide spectrum of ideas about their origin.

“They’re almost everywhere, and many people have had big fights about them and where they come from. Fire might have played a role, or human impact, or a rising water table associated with changes in climate,” explains Larsen.

The soils themselves are quite variable. Some deposits are quite muddy, while some trap fragments of long-dead plants. “They look a little like the relic of a swamp, containing grassy vegetation, sticks, leaves and little nuts, and they’re mainly black,” said Larsen. At the University of Lausanne, Switzerland and the University of Manchester, UK, she and her colleagues have been studying the composition and chemistry of black soils in an effort to understand how they formed.

Recently, Larsen has uncovered a possible connection between the black soil deposits and European beaver habitats. She presented her findings at the annual EGU meeting earlier this month.

The accused: a European beaver. Credit: Per Harald Olson via Wikimedia Commons

The idea began to take shape while Larsen was driving within the Spessart region of Switzerland. During her travels, she had found the soil situated in environments where beaver populations had been dwelling for some 25 years.

“There are huge swamps, what we call beaver meadows. And the vegetation communities are just like the ones found in those deposits,” said Larsen.

This discovery led her to develop a field experiment with the aim to determine whether beavers could be responsible for these puzzling black deposits.

“It’s like a big mystery for me. To find out if the black floodplain soil really come from when there was a widespread beaver population, before humans eradicated the beaver, I need to understand what the beaver does nowadays, and that’s how I started the project.”

Larsen thinks the beaver-created landscapes change with age, and she has been keeping a close watch on four sites across Switzerland and Germany, where beaver communities have been established for up to 25 years.

The long-toothed mammals have striking impacts on the landscape, which differ depending on where they build their dam. Upstream architecture results in beaver cascades, a series of closely packed ponds, each separated by a beaver dam. Down river, efforts go into one ‘megadam’ that stretches across a slow, meandering section of the stream and cause it to spill out into a large swampy floodplain.

The cascades, Larsen describes, are pretty dynamic. “Sediment gets trapped behind each dam, then they get strained, breach and break, causing sediment to flush downstream. It’s collected by the next dam and that then overtops and then that breaks” and the process starts all over again.

One of Larsen’s field sites: the Distelbach beaver reach. Credit: Annegret Larsen

Beaver meadows begin as large expanses of water, ponds teeming with semi-aquatic vegetation. Over time, fine sediment gathers in the ponds. As the sediment builds up, the area becomes a swamp – a patchwork of shrubs, trees, running water and tough, grassy plants. “You definitely get an explosion in diversity, but it’s a complete change, the area becomes a wetland,” adds Larsen.

And the wetland contains plants that resemble those found in the buried floodplain soils.

“For me, it’s fascinating to think about how all our streams would have looked with a beaver in there: before humans impacted those streams, before humans eradicated the beaver, and before [humans] settled there. There must have been beavers everywhere. Every stream would have been a beaver stream. And a beaver stream looks totally different [to what we see today].”

With the deposits all over Europe, it isn’t hard to imagine that, in years past, beavers shaped the streams, swamps and landscapes of the continent. It’s feasible that these regions might have been swampy landscapes at one point in history.

So, are the beavers behind the black soils? “I think we’re on a good path to contribute to this discussion. It’s at least as reasonable as fire and climate,” she replies.

Larsen makes a strong case, but the jury, it seems, is still out.

By Sara Mynott, EGU Press Assistant

GeoTalk: “Grown-ups are not focusing on the plastic problem, not as much as I want them to”

GeoTalk: “Grown-ups are not focusing on the plastic problem, not as much as I want them to”

Lucie Parsons, a ten-year old girl from the small village of Walkington, in England, is on a personal mission to save the environment from plastic pollution. After seeing on the BBC Blue Planet II documentary how litter in the ocean is damaging ecosystems, she decided to take action. Now she gives talks and is co-researcher in her mother’s PhD on climate change and the youth voice. Lucie has come to the European Geosciences Union General Assembly in Vienna with her mother, Katie Parsons, to tell scientists that children want to be involved in addressing environmental issues.

Unless the flow of plastics and industrial pollution into the world’s oceans is reduced, marine life will be poisoned by them for many centuries to come.

David Attenborough, The Blue Planet II: Episode 4, BBC One

 

How did you learn about the impact of plastic pollution in the oceans and marine life?

L: Through Blue Planet. I saw an episode about a whale and her calf, and how the contamination poisoned the whale’s milk. When I saw that I got really, really upset so I wrote a poster about it. Then I asked my mummy and daddy to photocopy it so that I might be able to put it around the village. I read and watched documentaries to learn more, and I found out that it is a big problem. I wanted to do something about it.

So you started giving talks… 

L: Katy Duke, the head of the [aquarium] Deep in Hull, got in touch with daddy because she saw my poster.

K: I tweeted Lucie’s poster to show what she had done after she was so moved by the documentary. The CEO of the Deep saw that and contacted us to ask if Lucie would like to give the opening talk at the European Union of Aquarium Curators Conference, which the Deep were due to host.

What do you tell people in your talks?

L: I have done two conferences and talks, also at schools. I have also been interviewed for the radio and profiled by the Earth Day Network. In my talks I basically tell people how bad the problem is, what it is doing to the animals and what they can do to help.

Here at the EGU General Assembly people were really touched by your presentation. Do you think your talks make people take action? 

K: Gilles Doignon, from the European Commission for Environment, was really moved about what Lucie had said at the Deep. He promised her that he would get the aquariums to sign up to a plastic pledge.

L: And he managed to do it.

K: He said that, thanks to Lucie, thousands of turtles will be saved. This is where she got her inspiration from to carry on. If she can talk and say the things she has done, even if just one or two people do something about it, that creates a knock-on effect.

Why do you think children should be involved in the fight against climate change?

L: Children are the next generation; when they get older they will take over the work grown-ups have done. So they should start now. Children can do the same things as grown-ups, there is not really a difference with helping, you need to get as many people to help as you can get.

K: Getting schools and individual children involved in science will make it real and manageable, part of life. Otherwise much science ends up in dusty journals. We need people to live it and understand it.

Are grown-ups doing enough?

L: I think they should be doing a tiny bit more. They are not really focusing on the problem, not as much as I want them to.

You have talked to politicians before, why do you think it is important to talk to scientists also?

K: When Lucie was affected by Blue Planet she luckily had me and her dad to help her. But other children will have their passion stopped unless they have an adult who supports them. Some schools don’t do environmental education, it is not within many curriculums, and some parents might not carry on informing their children.

There is amazing science going on and some scientists who communicate get through to the children. There is a youth rising at the moment. Children are interested, they want to know and they want to be involved. But, how? Scientists have to continue feeding the information to the children and involve them in citizen science so they will carry on with that passion.

What can people do to help?

L: Inform other people, go on litter picks and map the areas where they found the litter to help prevent more litter. With my friends and my family, we have cleaned three areas so far in my village and we are mapping them to feed in the data about where we found the litter. Also, stop using single-use plastics.

Is there any other documentary, book or podcast you would recommend to people who want to learn about plastic pollution in the oceans?

L: Drowning in Plastic. We have watched about three quarters of that.

K: You are enjoying that, aren’t you?

L: Yes… Well, I wouldn’t say we are enjoying it.

Interview by Maria Rubal Thomsen, EGU Press Assistant