Instant Genius - How the successful return of beavers to UK rivers is a positive argument for rewilding

Episode Date: October 19, 2023

Around a decade ago, beavers were spotted in the rivers of southwest England for the first time in 400 years. But exactly what impact have they made on the waterways they live in during this time? In this episode we speak to Prof Richard Brazier, a researcher based at the University of Exeter and co-director of the Centre for Resilience in Environment, Water and Waste. He tells us what he and his team have learned from studying these charismatic and often misunderstood animals over the last ten years, and how they provide a compelling argument for the reintroduction of other species. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Visit name audio.com to learn more. Hello and welcome to Instant Genius. a bite-sized masterclass in podcast form. I'm Jason Goodyear, commissioning editor at BBC Science Focus magazine. Around a decade ago, beavers were spotted in the rivers of South West England for the first time in 400 years.

But exactly what impact have they made on the waterways they live in during this time? In this episode, we speak to Professor Richard Brazier, a researcher based at the University of Exeter and co-director of the Centre for Resilience in Environment, water and waste. He tells us what he and his team have learned from studying these charismatic and often misunderstood animals over the last 10 years and how they provide a compelling argument for the reintroduction of other species.

Okay, so let's kick off with the sort of quickfire beavers 101 then, just so we can all get up to speed. So first off, I imagine a lot of our listeners won't ever have seen one in real life. So what kind of size are they? Beavours can be quite large animals and that's one of the reasons it's really interesting. thing they're coming back into our streams and rivers. They could be the size of, you know, a large Labrador, about three feet long, maybe 25, 30 kilos in weight. So how long do they typically live for? Some of the animals have lived for 15, even 20 years. I mean, it's fairly common for an adult to live for certainly 10 years and for the females to be breeding for that long,

having four or five kits a year, so to be parents of dozens of animals over their lifetime. So you mentioned the kits there. So how does the beaver family unit operate? Well, yeah, family is the right word. If you spend time watching beavers a lot like I do, they do really behave like a family. They'll have parents that are hered for life, that will breed for life, and then they'll have four or five kits a year once they're mature. And they will do all the things that we humans have to do or other mammals have to do with their offspring.

Teach them, in this case, how to swim because, of course, they're spending a lot of time in the water. They will teach them how to forage and fell trees, gather the food that they need, teach them how to build dams. They've got very dexterous front paws, very much like hands. they teach them how to manipulate sticks, strip the bark off the willow trees in particular. So a whole range of sort of learned behaviours emerge within the family unit, which is wonderful to observe. So you've been working on this project to reintroduce beavers into Devon. So when did you start doing that? The work started about 10 years ago.

First off in a small enclosure in mid-Devin where working particularly with Devon Wildlife Trust, We were brought in to build some scientific understanding, to try and to understand if the same things that we had learned about beavers overseas would also manifest in a lowland UK setting. And then we were brought in on the River Otter Beaver trial seven or eight years ago back in 2015 to look at the wilder animals, these animals that had emerged. into the river otter catchment to see if free living beavers would behave in similar ways and also to build the evidence base around how we maybe needed to interact with those animals. So as you said there, you know, there's beavers live in many other different countries. So how long ago was it that they died out in the UK? And why was that? What caused it?

Yeah, it's 400 years ago or thereabouts. We extirpated to them. we hunted them to extinction in the UK. We did so to use the fur. The beaver fur is incredibly waterproof. It felt really well, so it was very useful for making hats of all things and other clothing. We hunted them to eat meat as well.

In fact, the Catholic Church decreed them to be a fish so that they could be eaten on Fridays and Saints days, which seems faintly ridiculous. but the final thing was that the castorium that's produced in their anal glands, it's very concentrated in salacidic acid, which is an active component in aspirin and similar painkillers. So actually hundreds of years ago, certainly back in medieval times, the value of these glands was high.

People say that they were worth a medieval farm labourer's annual wage, just one of those glams. And so there were three main reasons we hunted them to extinction, and then in the UK killed them off. And we nearly did so in mainland Europe and in North America as well. So it's a creature that's very much come back from the brink of extinction, which is good to see. So the ones that were reintroduced into the River Otta, where did they come from? Well, we're not really sure. Right about 2007, 2008, local ones, wildlife photographer spotted these animals, or at least spotted the evidence, gnawed sticks and such like, and then was able to photograph not just adults, but then kits the following year.

Most likely they probably escaped from a private zoo or something similar and lived under the radar with very few people knowing about them for quite a few years. And of course, you know, expanded in population size over those years. But yeah, no one's really sure was. they originally came from. So I think the thing that most people will be interested in when we're talking about beavers is this iconic behaviour that they have of dam building. So first off, do any other animals that we know do things like this? Only really humans. We don't build dam so well, it turns out. No, I mean, you know, in the animal world, beavers are pretty unique in their behaviours. I mean, there's lots of other ecosystem engineers or what we might call keystone species

that adapt habitats for their own benefit, but also for the benefit of many other species, but especially in the riverine setting, beavers are really set apart from any other animals. And as you mentioned, that is because of this ability to build dams. They've been building dams for 40 million years, so they've had plenty of time to adapt, you know, on evolutionary timescales to be incredibly well practiced at dam building or water resource

management in general. I'm not saying they're intelligent, you know, they're not a higher order intelligent species, but they are extremely good at what they do. And they have learned to be good at managing water over such a long time that they, of course, have lived through and much dryer times, much wetter times, a whole range of climate variability, which, of course, we are just starting to try and learn how to adapt to. And they're very good at so doing. So, yeah, remarkable species in terms of how resilient they are. So let's have a look at the process then. What does a beaver do when they start building a dam? The first thing, I mean, beavers build dams because they feel safe in deep water.

So that's the first thing to say. And if they're in a big pond or a, a deep lake, they often won't build dams. But if they're in shallower water, small streams, small lower order rivers, they'll identify locations, particularly where we find confluences between, say, two tributaries, and they have this uncanny knack. I think it's a learned behavior of building their dams just downstream of two tributaries and where two tributaries intersect. They will fell a whole range of different woody species, but willow, hazel, silver birch, poplar, and they'll take the branches from those trees. And to begin with, they will stick them into the banks. They're sharp at the end because of the way they've gnawed them. They'll wedge them into the

banks. And they almost buttress, therefore, against the direction of flow. And once they've done that, the sticks stay there. And then they bring in more material, more sticks, or even, cobbles from the bed of the channel. And after a while, probably a day or two, they will start to swim upstream and use their front paws to push the sediment on the bed of the channel onto the upstream side of the dam.

And that has the effect of not sealing it, but making it into a sort of leaky dam. It holds most of the water, but it allows a small amount of water to leak out. And after a few days, before you know it, instead of a straight, deep channel, you have a wonderful dam structure that's pushing water onto the floodplain, ponding water up that's nice and deep, and, you know, that's where they'll feel safe and live. So as you said earlier, they're pretty big, you know, about as big as a

Labrador. So what sort of size tree can they bring down? Pretty well, any size tree, if they've got long enough. They'll very quickly gnaw through small saplings, the side shoots of larger trees, but they'll sometimes target huge specimens, you know, trees with a circumference of a couple of meters and they will just persistently return at night on night, they're nocturnal animals, so they'll come back nor these trees through periods of the night until eventually they're felled and they're doing that both so they can get the leaves on the tops of the trees that are softer and more nutritious they're doing that so they can get at the the bark as well they'll strip the bark off sometimes entire silver birch trees because in the winter that's a good source

of nutrients and then they'll kind of log the tree up like we would if we were preparing wood for a wood fire or a wood burner in the winter they'll take the side branch off, chop them to size, hold them in the mouths and then swim along, particularly the canals they've cut, floating these logs to where they want to build the dams or where they want to build their lodge. So that sort of brings us neatly onto one of the sort of major purposes of this project. It's about how reintroducing beavers can help with the management of the environment. So you mentioned canals there. First off, how does the appearance of a river environment change when the beavers move in? Well, the most important thing to recognize is that all of our,

pretty well, all of our river catchments, certainly in the UK and in many countries around the world, have been changed radically by humans from what we would call natural stream and river systems. And so the beavers are going to put the stream and river back to a natural structure and function. they're going to swim into a straight, deep channel. Often we've made a stream into a drainage ditch in many locations so that we can farm the land and accelerate the water off that land as quickly as possible. They're going to build dams to bring the water levels up, which will also bring the water tables up and we'll bring the water over onto floatplains.

And they're effectively going to undo that drainage work that we have often put in place, especially on agricultural land. So they changed the structure back to a pre, we might call it a preanthropocene or a sort of pre-human, but pre-human intervention sort of landscape. And in so doing, they often bring the ecosystems back into balance. They often bring water. to these very dry places that we've created,

I would certainly argue from all the evidence, they make them more resilient to both flooding and the sort of drought situations that we've seen all too often recently. So how long does it take a group of beavers to start making an impact on the environment once they're reintroduced? Pretty well overnight.

They're straight in there. I mean, if the water is not deep enough for them to feel safe, they will start building dams that night once they've been dropped into a pond or once they've found a new habitat. And because of that, the hydrological change, this attenuation of flooding that beaver dams give us and slow release of water in dry times that gives us base flow maintenance in droughts. These hydrological changes happen very, very rapidly.

some of the ecological changes, you know, the successional changes of different more aquatic plants or animals coming into the landscape take longer, the water quantity changes happen within a few days. So can the beavers do any harm to the aquatic environment or perhaps even other animals, you know, through the spread of disease or by, I don't know, out-competing them? Most of the things that they do, the changes that they bring about are just reverting ecosystems back to natural functioning. And so pretty well in every direction we look, changes are positive for other species because most of the time they're bringing more water into a landscape. And that tends to be the basis of most life. where there are changes which we perceive to be negative, they're often considered as such because they're different to what we are familiar with.

We often hear nowadays of this concept of shifting baseline syndrome. And for example, if you've walked a river or fished a river for the last two or three decades, you have a notion of how it should look because that is how it's been. in your lifetime. Of course, that river may not be functioning in a natural way. It's just functioning in the way that we have modified it to. And if the beavers, for example, build dams, which catch a sediment in the upstream in the pond location and allow gravels downstream of that dam to be clean, that's a big change. You might say, oh, there's a sediment load where, you know, those fish used to spawn. But of course, downstream of the dam, there's some beautiful, clean,

well-oxygenated gravels that weren't there for the last 20 or 30 years. So those changes can be considered as negative. But if you think about the whole landscape, that there are really only overall benefits from reintroducing this animal. And the main reason goes back to one of my earlier points, which is if we renew coexistence with this animal, it also renews coexistence with all the other species that it has lived alongside for millions of years,

which of course are adapted to the label on certain people. This podcast is sponsored by Name, Audio and Focal. With over 100 years of combined expertise, Name and Focal have been bringing music to listeners just as the artist intended. Since day one, this mantra has shaped every innovation in high-fi design, technology and acoustic engineering, balancing craftsmanship and tradition with pioneering thinking.

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So in addition to the site at Devon, beavers have also been introduced in Plymouth and in Napdale in Scotland. When you're trying to pick a location where you think, oh, that's a good place to reintroduce beavers, what are the considerations that you have to make there? You definitely need to look at the existing habitats.

We have tools or models, New Yorker models that we use to map where are the deciduous woodland? particularly where do they intersect with our streams and rivers, so our riparian zones, because you need both good food resource and water for these animals to thrive. And we've done that mapping work, that modelling across the whole of the UK, and we know that there are hundreds of thousands of kilometres of streams and rivers that have at least good, reasonably good beaver habitat.

We unfortunately know there are probably equal lengths of streams and rivers that don't or couldn't well support beavers at the moment because we've farmed right up to the channel banks or we've made the streams and rivers run through concrete pipes and culverts. But of course there are many efforts, conservation efforts, to improve riparian zones for flood benefit and. bringing nature, making space for water in our environments. And so likely if we see beavers moving into places that are suboptimal, either through human help or through the beavers themselves, re-engineering those places, what's likely to happen is that the land that's available for beavers to live in actually increases with the more beavers coming into the landscape.

So, yeah, we do a lot of work on understanding good habitat. When you put the beavers out, they'll find it. So we sort of can guess, we can predict where they'll go because they go to the places with the best food and the best water. So has the beaver populations sort of grown and spread since the reintroduction? Absolutely. The numbers of animals have, to begin with, increased very, very slowly. Population growth studies of all sorts of animals.

show that when you just have, you know, a pioneering pair, in this case of beavers coming into a catchment, they might have a few kits year and year, and it's a few years until they find other mates. But once you start to have 15, 20 breeding pairs, you really start to accelerate this steep curve of population growth. And in the river Otter catchment, for example, we're right in the steepest part of that growth curve now. So I wouldn't like to guess how many indivisement individual animals there are, probably now since a pair of animals coming into the catchment, maybe 15 years ago, we've got, I would say, at least 30 territories. And a territory could be a pair of animals or it could be four, five or even more.

So, you know, the populations are expanding. And the animals themselves, in response to that, because they're very territorial, are moving around within that catchment and they're actually moving out of that catchment. as well. So it's clear from surveys of neighbouring catchments that they're not just staying in the river Otter, they're moving to find new habitats, new mates, established new territories. And so very slowly but surely they're starting to populate the rivers of the south-west. So just to check, that's 30 different sort of beaver groups that have emerged from just one breeding pair? Yeah, we think it was one breeding pair, certainly a very low number of animals.

and yet that's the kind of number of territories now. As I say, really difficult to pin down how many animals are living in each territory. Might even only be one animal that's just held up in a lodge that it's built. But yeah, certainly of that order of territories nowadays. So what do local residents think about the reintroduction of beavers? You know, if any of the projects come up against resistance of any kind? Yeah, we've done a lot of social science work into this. you know, one of the perspectives on beavers, and one thing we did very early on was a national

survey to understand what people think and, you know, what motivates people, what do people even understand about these animals? And the overwhelming majority of people, we pulled a couple of a couple of thousand people back in 2017, were both positive and very supportive of beaver reintroduction. A lot of folks weren't very knowledgeable, which is not surprising. This is not an animal you come across on a daily basis. It's not even an animal you're educated about at school. So, yeah, that education now we've tried as far as we can and working with other organisations like the Beaver Trust to really bring understanding up to a level. And that's also helped actually with those folks who are perhaps negative about beavers

because they don't necessarily understand what they will do or what kind of an animal they are. And some sectors of society, for example, within the farming communities or perhaps in traditional sort of fishing communities, weren't necessarily as positive about beaver introduction as other sectors of society because they saw them as perhaps imposing some sort of threat

or risk to their ways of life. But actually a lot of the work we've done, to educate, you know, on the basic stuff, for example, to educate people that beavers don't eat fish has really helped fishermen and people associated with fishing as an industry or a pastime to feel less threatened by this animal. I'll be honest, though, I thought they ate fish as well. So what do they eat? They're herbivores. They're generalist herbivores. They'll eat pretty well any vegetation, but absolutely no fish. So, yeah, you don't have to worry about, you know,

your salmon and your trout stocks. So the sort of the key thing to getting people on board with the sorts of projects is just, it's a simple matter of education. Yeah, and that's, as I said just now, not surprisingly, if you don't know a great deal about a new big species, then yeah, you might be anxious or worried or concerned that impacts would be unmanageable or possibly negative. So the learning curve, I would say, society across the whole country has been pretty steep over the last decade.

But now, you know, it's much more common for people to know something about beavers, understand a bit more about them. And, of course, start to be able to see them because it's not just in the River Otter. There's other populations around the country where you can go beaver watching and see for yourself what this amazing animal will do, which of course is going to help a great deal with educating society. Yeah, that's one thing I was going to ask, because obviously they've ever. very sort of charismatic animals. So do you have any advice for someone listening who wants to go out and perhaps spot a beaver? Lots of advice for beaver watchers or potential beaver

watches. Unfortunately, this time of year, as the nights close in, it's harder to see them. As a nocturnal animal, they're emerging about seven in the evening. So you're not so easily going to see that. You can see them in the morning. They'll still be active up until about seven in the morning. But yeah, I mean, the best place to go at the moment in England is the River Otter. There's a number of locations where there's public footpath access along the main river near to Otterton Mill or Ottery St Mary and you can just walk up and down the riverbank. And of an evening, you'll often see some suspicious characters with binoculars and

telephoto lenses lurking on the bank and they'll be there because they know that on the opposite side there's a beaver lodge and they'll be quietly and patiently waiting. And actually, that's one of the wonderful things for me is to see all sorts of people, local people, tourists, people who are interested in the science, people who are just having a casual walk being captured by this animal and then really engaged in proper wildlife, free living beavers in the landscape is a wonderful thing to see.

So I'd thoroughly recommend folks get down to the river Otter, to see those animals if that's of interest to them. Are there any websites that you could direct the listeners to to get a bit more information? Yeah, I mean, the best place to go actually is Devon Wildlife Trust's website. And through that, actually, you can not only learn a lot. There's a great deal of information, but also there's an ability to interact with the Wildlife Trust's rangers

and beaver officers if you want to go on walking tours or you want to see these animals. Another good organisation to Google is the Beaver Trust. So they're a national organisation of charity that's set up to promote understanding and reintroduction of this animal. And again, lots of really detailed information, both on the sort of physiology,

the natural history, the ecology of this animal. So, yeah, Denwar Life Trust and Beaver Trust, two good ports of call for learning. more about beavers. So obviously these projects have been a success. So do you think, perhaps do you think that opens the door for the reintroduction of other species, like people often speak about the links? There are, I think species reintroduction in especially a very nature depleted country like the UK has got an absolutely critical role to play in our nature recovery. If we don't reintroduce species as an island nation, many of the

them will never come back. Many of the other species they used to support will never be seen again. Many of the species we've still got, but that are really struggling, are going to be lost as well. And a good example would be the water bowl. We're really struggling to hold on to probably population of just a couple of hundred thousand water bowls now from the millions we used to have because we've destroyed most of their habitat. The beaver actually creates habitat that is perfect for water voles to thrive in. And we've done some really interesting studies that prove this. So there's a species. Hopefully we won't lose it. We may need to reinforce populations of water voles. And the best places to be to do that would be in beaver lands,

in beaver wetlands. But there's lots of other species, arboreal species that live in woodland that we could, we already are, but we could push on more with reintroducing. Obviously, our iconic species like the Red Squirrel, which has nearly died out in England. There's other woodland-loving, or living species like the Wildcat, Pine Martin, to Middlegill predators that we hunted to extinction again in England and nearly in Scotland, which would bring back balance to our woodland flora and fauna. And the lynx is another one if you brought links back into our woodland. They're such a quiet animal so private in the way they live.

You'd never see them. But they would bring back, like most predators, a climate of fear to the woodland. And we desperately need that because most of our woodlands are overrun with deer. and those deer are significantly hampering the natural regeneration, particularly of deciduous woods, along with grey squirrels. And if we have predators, whether it's Glinks or Pine Martin that would predate and move around grey squirrels, links doing that same role for deer, we would have much healthier, more balanced woodlands. So I absolutely think we should be moving ahead, very positively,

even through introduction of those kind of species. Thank you for listening to this episode of Instant Genius. Brought to you from the team behind BBC Science Focus magazine. That was Professor Richard Brazier. The current issue of BBC Science Focus is out now. Pick up a copy wherever you buy your favourite magazines or download a digital copy from your preferred app store. You can of course also find us online at sciencefocus.com.

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