Episode 07: Beaver hydrology and management
“As long as you have enough beaver ponds for a complex, you will start to see broad patches of fire-resistant landscape…They will move into an ordinary stream and through dam building, groundwater raising, channel digging, and spreading; they take that stream ecosystem and turn it into a big wetland patch.”
emily fairfax
A conversation with California State University-Channel Islands Professor Emily Fairfax about her work studying the lives of beavers and their impacts on droughts, fires, and water quality as well as some strategies for beaver management.
guests on the show
Dr. Emily Fairfax
Professor Emily Fairfax leads the BEAVS Research Group — beavers, ecohydrology, and visual storytelling at California State University-Channel Islands. Professor Fairfax’s current research focuses on the ecohydrology of riparian areas, particularly those that have been impacted by beaver damming. She uses a combination of remote sensing, modeling, and field to work understand how beaver damming changes these landscapes and on what timescales those changes operate. She also has an interest in geoscience education research, particularly curriculum development. Learn more on her website and follow her on Twitter @EmilyFairfax.
TRANSCRIPT
Mallika Nocco
Welcome to Water Talk from the University of California Division of Agriculture and Natural Resources. I'm Dr. Mallika Nocco, a cooperative extension specialist in soil plant water relations and irrigation management.
Sam Sandoval
Hi, I'm Sam Sandoval. I'm faculty and an extension specialist in water resources.
Faith Kearns
And I'm Faith Kearns, the academic coordinator for the California Institute for Water Resources.
Mallika Nocco
Thanks for joining us on Water Talk today. I am so excited that we are going to be talking about all things beavers. Our guest is Dr. Emily Fairfax. She's an assistant professor at Cal State University Channel Islands. Emily, I read this quote of yours and it's “when I came face to face with beaver dams for the first time, I had what can only be described as a transformative experience.” To all the people out there who you never know like, what's going to change your life, right? I was wondering if you could share a little bit more about what that moment was like, what that transformative experience was like for you.
Emily Fairfax
I had known for a long time growing up in the Midwest, mostly that beavers were a thing, they existed, but it was just this very peripheral knowledge. I knew it, and that was it. And then when I was in college, I wound up working as a wilderness trip leader for Girl Scouts up in northern Wisconsin. And one of the trips that I was leading was this like three or four week canoeing and backpacking expedition up in the Boundary Waters, and I was really excited and I was like, oh, this is gonna be so great. I can test all my outdoor skills and I love paddling, and I wasn't really expecting anything transformative other than that, like, there's gonna be fun.
And so I'm up there and I am just over and over again portaging my canoe over beaver dams. And I'm like oh my god, these things are huge and they're everywhere, like this one is eight feet tall! This one is 100 feet long, like come on, what are these dams? And the more I looked at them, the more I realized, these are creating lakes, these are holding back so much water. These are structures that are absolutely incredible feats of engineering. Like I could not build these if I tried.
Sam Sandoval
Could you provide us a little bit more of the history of beavers in the landscape. So before European colonization and the numbers that they had, how they were a little bit going down and if they have made any comeback?
Emily Fairfax
Yeah, absolutely. So prior to European colonization, and especially prior to the European fur trade, beavers were everywhere in North America. They were down all the way into the northern parts of what's now Mexico up into, like the Arctic Circle in Canada. They were on the islands off the shore of Washington, they were on the coasts, they were in the inlands. They were in the mountains. They were literally everywhere. It's been estimated that there were up to about 400 million beavers in North America at their peak, although that number is hard to estimate, because we're trying to extrapolate back from trapping journals for the most part. With that kind of population and the amount of stream habitat that exists, there was probably a beaver per kilometer of stream.
Sam Sandoval
I typically tend to understand some of these interactions when I know the life cycle of a beaver.
Emily Fairfax
Yeah, absolutely. Beavers, on average, live about 20 years, maybe up to 25. And they're pretty hardy animals. The parent beavers will mate for life. And something beavers really like to do is fix old dams. And they're really big on like reduce, reuse, recycle. And so they find an old broken dam, and they're gonna fix this. And they get started and start patching it. And they're also like, whoa, smart, because why would you start from scratch when somebody already started the project for you? So they get going, they build the dam. And then as soon as they have a pond, it's big enough for them to feel safe, and a lodge that they can stay in, that's when they're like, alright, we got our starter home. Now let's start family.
So they have babies about once a year, and the kits are born in spring, usually, kits are baby beavers. And then the kits will stay home, on average, about two years. And so in year one, they're like adorable, super small, super useless. They don't do much except like cry and eat food. But then when they get older, they start going out and they start learning with their parent beavers, you know, how do you chew on trees? How do you build dams? It is instinctual for beavers to build a dam. So they will do that without any teaching, but they get much better at it when they follow their parents and they learn from their parents. They practice building food caches, they practice chewing trees. And then by the time they get to be about two or three, lodges getting a little crowded, parents ready to have the next round of kits, and so they send them on their way. And then those beavers will move out and they sort of just go swimming downstream or upstream and they look for a mate and as soon as they find a mate, the cycle starts all over again.
Mallika Nocco
I had read that you started to look into beavers, and hydrology, and drought impacts, and you didn't find that much in the field. And then you started getting into it. Can you tell us a little bit about how you got to this very rich research question. And then what are some of the things that you have found in this area?
Emily Fairfax
Yeah, so I was really surprised that there was not more beaver science going on, I guess. I was working as an actual engineer, not as a beaver person. And I was watching this documentary called Leave it to Beavers made by PBS. And there's this aerial shot of these beaver dams and ponds in Nevada that we're just erupting with green, wildlife, and fauna and flora was amazing. And they were interviewing these hydrologists that were working there. And they were like, oh yes, this is an incredible system, the beavers are storing all this water. And I was like, I need to study this. I started to look into it and there's nothing. Like, there were some news articles. And there's like a speculative thing from the 1940s. And then people would talk about it a lot in like review papers. And they'd say, oh you know, beavers are really good at storing groundwater, that helps with droughts, and there wouldn't be a citation on that statement ever. And I'm like, who put a number to this? How much do I want to know? I really like numbers. I'm kind of big dork about that.
Mallika Nocco
There's these goose chases that you go on. Sometimes it's like, all right, I find this one thing somebody said at some point or this number, and you chase it down and it just leads to nowhere.
Emily Fairfax
Nowhere, or to like some note, that's like personal communication in 1912.
Mallika Nocco
Exactly. Just some person at some point making a conjecture and how is this entered into the scientific literature? But here it is, you know?
Emily Fairfax
Yeah. Yeah. So I was like this has to be studied and I couldn't find anyone who'd studied that. But I could find people who had done work on similar things using remote sensing. So like seeing how bark beetle infestations change plant greenness in riparian corridors, and I was like, oh this is kind of the opposite. I'm looking at how an animal helps the plant greenness instead of hurts the plant greenness. So I wonder if I could apply that method to this system. And I did and it worked. And it was really cool. I actually looked at those specific ones that I had seen in that documentary because I was like so fixated on them. I couldn’t let it go. I needed it.
Mallika Nocco
Where were the ponds that you saw in the documentary?
Emily Fairfax
They were just outside Elko, Nevada, super random. I had never even heard of Elko before that documentary. It seems like a very nice place. I do like Nevada a lot in that region. It's by the Ruby Mountains. So very pretty, but very, very desert in the lowlands. And these streams, they were super incised, and they weren't doing so great from a lot of overgrazing. And then it was actually the land managers and the ranchers in that area that were like, fix this. And so the ranchers were like, we are going to put our cattle on and prescribed grazing plan, and it's going to be a lot better. And as soon as the riparian vegetation started coming back, oh, beavers showed up, and I don't know where they came from.
Mallika Nocco
That’s really interesting to me, because it's kind of like they say that certain creatures, when they show up in your garden, means that you're doing a good job of creating a diverse and intriguing ecosystem. And I wonder if that's what it is, that you know, if the beavers show up, that means that things are starting to look up in that system.
Emily Fairfax
Yeah, I would take it as a compliment. If I was trying to do ecosystem engineering and the ecosystem engineers showed up to help. So these beavers came and then the restoration really accelerated from there and got super green. And everyone's talking about in the news, but not studying it. So I studied it. And I compared these sections of the creeks that had beavers on them to a couple other things in the landscape. So I compared them to sections of creek that didn't have beavers and compared them to the hill slopes in the area that were really disconnected from the surface water hydrology. I compared them to human irrigated alfalfa. It was like beavers are really you know, keeping things green. Let's see how they compare to us. Like we were the ultimate water managers.
I was just looking at how green the plants were staying and their evapotranspiration, so like how much water they were breathing, for all of the things that were disconnected from surface water hydrology, so the hill slopes and then also for the sections of creek that did not have beavers, every year starting in April, they just went brown. Totally died off. Very, very consistent, like these creek zones, they shouldn't be going brown that fast. You expect them to reach peak greenness when you have all the sunlight and you have water coming through the streams, but it wasn't happening. But these places that had beavers, they were like, I'll peak in May, June, July timeframe. It'll be great.
It was just like the alfalfa, exact same patterns, really similar NDVI, greenness, and also evapotranspiration, like water consumption and usage. So these beavers, they were really like pretty close to what we were doing to the alfalfa except they were doing that to the riparian corridor. So they were irrigating this corridor. And the mining company that was nearby, they started looking at groundwater measurements, and they saw every year, groundwater was rising by these beavers, and stream sections that used to not flow suddenly had a very small base flow during the summer. It was like really big changes.
Sam Sandoval
I was thinking about not only the engineering and so on, but I mean, they are good engineers for restoration. I mean, they are doing all this work is helping you know against, or providing some of these ecosystem services. And I've been thinking also in these kind of incised channels, as they are putting all the dams, some sediment will actually start coming in and that incision will start to fill it out. Then you start seeing really a very good time for Mother Nature and you're saying one of the best engineers. I was thinking about restoration. I'm not sure if you have heard about Yellowstone when they reintroduce the wolf and all of the impacts and then they start changing the morphology and at the end beavers come up, could you could you talk a little bit about it?
Emily Fairfax
I love the Yellowstone case study because it is a really good example of two keystone species that were both removed from an ecosystem and then bringing them both back. Bringing one back wasn't enough you had to bring them both back to really get that. So just wolves on their own, when they were removed, the elk kind of went out of control. And they were really grazing hard on all the vegetation along the streams, which made it really hard for beavers to build because they were competing. And, you know, it was basically like having cows overgrazing, except they were elk and there were too many. And so you lost wolves and then you lost beavers. And both of those species are keystones. So whole ecosystems depend on them. So when the wolves were reintroduced and brought back, they started pushing these elk around. And just like I saw in Nevada, as soon as that riparian vegetation started creeping back up, the beavers were like, alright, I'm there. And they showed up. And then when the beaver show up, they accelerate that restoration of their dams.
They do trap sediment, they reconnect incised channels to their floodplains. The beavers themselves will actually dig little channels out into the landscape and really spread that water out. So they're excavating or cutting or building or doing a huge amount of physical engineering. And they need those wolves to keep the elk moving because like, beavers are impressive and they're like really cool, but you know, if you got a whole herd of elk coming in, a little beaver is not going to be able to compete with that, like those are massive consumers. And so through this partnership of the wolves doing what the wolves do, like hunting the elk, keeping them moving, and then the beavers you know, really introducing those physical changes into the streams, you take this very damaged Yellowstone ecosystem and restore it to this beautiful, biodiverse, healthy and resilient ecosystem.
Sam Sandoval
And you know, and that was done not necessarily by Tonka toys, or by bringing all the machinery. I mean, this is the biology at its best bringing all of them back. I mean, it's interesting how, when you're saying about the psychological amnesia, we forget about these two keys species and then all of a sudden they come back and they did modify the landscape, they change the flow of rivers and sediment, which I mean when we do it, it takes a lot of dollars. It takes a lot of time. We invest a lot in restoration, and look at these two doing it for us.
Mallika Nocco
You find, like what you did, this under explored area of science and engineering. And you start to explore it, like what we do when we find just kind of these phenomena without understanding or underlying mechanisms, you start to understand the underlying mechanisms, which it sounds like that's what you've been doing, right? Next step is prediction, control. Can you trick beavers into showing up? You know, are we in that place where we understand like, this is that threshold of greenness? This is that moment, this is the right amount of flow, like do we know those types of, I guess thresholds is the word I would use, but I don't know if that's the word you would use.
Emily Fairfax
We know and we also don't know. So we've got a lot of case studies, but it's still like this different system than beavers had left when they were being trapped out. And so we think like, oh beavers definitely like low gradient streams, too steep and they're not happy, they won't build there. And then I go out into a creek in Colorado and there's a dam on like a 15% gradient stream and I'm like, what is this? Do you follow the rules? And then we are like, okay, well, they have to have, you know, perennial water, they can't deal with ephemeral sources. It's too hard on them. And then there's the beavers in the Mojave Desert, and I'm like, I'm pretty sure you don't have good perennial water where you're building little beavers, or you didn't when you started. Um, now they're doing that. So you have all these things that we know they prefer, but we keep seeing them be like, I can deal with this. I can do something that's a non-ideal environment.
We see them building up in the Yukon Territory, like further north than the treeline. We're like they need trees, like this isn't real. And they're using stones and peat and that's what they're building with. I'm like, what are you doing? Like you totally usurp...how am I supposed to build a model when every single time I think I have a parameter you're like, but what if I changed and they just they can adapt to so many things. So we definitely have models that let us know where it's very likely they could build easily. But these models absolutely do not predict the range of environments that they still wind up building in.
So one thing that you can do though if you want to trick a beaver into building is build a beaver dam, an analog. So you start by building like a kind of crappy human beaver dam. There’s some good ones but like I've never seen a beaver dam analog that's anything like an actual beaver dam. But the beavers see that and they’re like oh, this is an old beaver dam that was poorly built, I can fix this. And humans are a little bit sad on the side because I put so much time into this, this was great. Beavers are like this is garbage, but I'll fix it. And then they will. They love fixing up beaver dam analogs. There's been a lot of studies where people are actually trying to understand the beaver dam analogues themselves. And their study gets derailed because beavers move in and it’s no longer a beaver dam analog study. It’s now a beaver study.
Sam Sandoval
So we were talking about droughts. What about one of the articles you mentioned that they create these kind of not necessarily a fire free zone, but zones that when a fire happened, it can be a good zone to stay to not be harmed by the fire.
Emily Fairfax
Yeah, so that's the work I've been doing most recently. And I was thinking about what I found in the drought work and that, you know, these plants are staying greener, staying wetter. And I was thinking about camping. And when you go camping and you're trying to start a fire, you never pick up like the wet sticks and leaves, that's not gonna start your fire. And I was like, well, if all these things are wet, but the rest of the landscape is really dry, does that mean these little patches aren't going to burn as much? And I approached it the same way. I've been approaching fires with remote sensing, also, because it's not super practical to go to like a burning landscape and try to take data, but I wanted to see if these places stay green? Do they stay cool? Do they stay wet when you have a fire in the area?
I found a bunch of really big fire scars to see you know, these places were large areas, and I know that there's beavers in these places. I wanted to see do they stay green, does the vegetation stay green, around the beavers. And I looked in highlands, I looked in lowlands, low burn intensity, high burn intensity. And across the board, what I'm seeing is that beavers are absolutely capable of creating green patches that stay green during fire. And we've seen this in the field, other scientists have gone out and taken photographs, and are like wow look at this riparian corridor. It's not burning, and it's full of beavers, but there weren't numbers to it. So I've been trying to do the same thing I did for Nevada, which is like, let's get some numbers on this. How much do they help? How long can that work? Does it happen in all fires? Does it only happen in mountain fires, does it happen with pine trees, does it happen with grasslands? And so far what I'm finding is it kind of happens everywhere. And as long as you have enough beaver ponds to make sort of like a complex of them and not just an individual pond, you will start to see these broad patches of fire resistant landscape.
Mallika Nocco
Do you think it's fair to say that beavers are constructing wetlands? Is that fair statement? Beavers make wetlands?
Emily Fairfax
Absolutely, they will move into an ordinary stream that can have a really, really narrow riparian band around it, or even none if it's really incised, and through the dam building and the groundwater raising and the channel digging and spreading, like they take that stream ecosystem and they turn it into a big wetland patch.
Mallika Nocco
Alright, so now I, Sam and Faith please interrupt me, I'm just kind...so my next question is in a former life, I was interested in stormwater impacts, and I looked at rain gardens and biofilters and these types of structures, thinking about water quality. I'm curious if when if you have a beaver, the beaver makes a wetland, you slow the flow of a stream, all of a sudden there are plants, there's maybe nutrient uptake happening. Is there evidence out there already, or is that something that you're thinking about, with improvements to water quality?
Emily Fairfax
Yeah, there's some really incredible work that I've seen going on with that. So out of Georgia, Sara Ledford is a scientist and her research group is looking at how urban beaver ponds can actually purify and clean up streams. You get these beaver ponds in the middle -- there's a playground in the background, there's houses, and there's just this pond. And there's like a doll like on the dam, it's very much like a human wildlife interface. And they're seeing that these ponds can really help remove a lot of the overly high amounts of phosphates and nitrates and things like that. It's been shown that beaver ponds can enhance the nitrification which is really good in agricultural streams.
There's been some very preliminary work coming out of I believe, Ohio. And it's looking at acid mine drainage, and you get some really nasty acidic water coming through these waterways and it goes through beaver pond number one, and your ph goes from one to two, and then it goes to beaver pond number two, you go ph two, three, and you keep going through and then once you get through this chain of beaver dams, it's like, oh, we're at ph seven. And whether that's happening because of you know, the water chemistry is just interacting with the soil differently or if the dam is really driving that water down through the rocks and the rocks are able to suck out some of the acid, the exact mechanism isn't totally understood yet, but when nasty water comes through the beaver ponds, it comes out nice and clean. So I like to call them like the Brita filters of the landscape because people can think about a Brita filter: gross goes in and nice comes out.
Sam Sandoval
What are the natural predators of beavers?
Emily Fairfax
So when they're little, they can get picked off by all sorts of things. Hawks, eagles, coyotes, I mean, they're small, vulnerable little creatures. Adult beavers can be big. They can be 40 pounds up to 110 pounds. So like these are child sized creatures, German shepherd sized creatures. When they're an adult, their predator list is short, because they're so big.
Wolves are a huge predator for them. Especially up in Minnesota and in Canada. You see a lot of wolf predation on beavers, and then grizzly bears and mountain lions. And other than that, you're not going to take down 100 pound beaver. When they're on land, they're really awkward, very round, non-efficient creatures. They're not built to walk on land. That's why they dig these channels on the landscape, it's like their little water highways. So when they see a predator, they jump in and they're like, zoom, this swim past. They swim very fast, they can hold their breath for 15 minutes. You're not going to catch them in the water. So as long as they're in the water, and they're an adult, they are really, really safe.
Mallika Nocco
And I want to know how we can support your work, how can listeners support your work?
Emily Fairfax
That is a great question. There are a lot of ways to support my work. One of the most important things for me, selfishly, is trying to find these beavers and figure out where they are. I am missing beaver dams. I know they're out there, I can find their habitat, but I can't see them themselves. And it is such an effort to hike all these streams, but there's people hiking all the time. And so you see a beaver dam, tell me where it is.
Mallika Nocco
I wonder if this would be something like where it could go into some of the apps and the naturalist things that are out there. I think of iNaturalist where people are able to basically participate as citizen scientists and help you right? Is there something out there like that, is there an app or something where people can tell you?
Emily Fairfax
I use iNaturalist. I think it's really useful. I go on there and I confirm and deny beaver identifications as much as I can. I'm not gonna let another nutria sneak through, that's not going to happen (laughs). And it's really helpful because there are places where I'm like, I don't think there's beavers in this area. And then I go on iNaturalist and two days ago someone posts a photograph of a beaver dam. And there's no way this is not a beaver dam. And they're like, I think this is a dam, can someone confirm and I'm like, I'm gonna confirm this picture. And then I'm going to take a trip and go see that, you know, share it when you see them put it in an app. Or if you don't want to put it in an app, send it to me as an email. I would love to know where they are.
Faith Kearns
I feel like there's a dual thing that happens with beavers in terms of them being intriguing to some people and then also considered a nuisance and having a wildlife human conflict story alongside this story of how incredible they are. And so I'm just wondering if you could talk a little bit about how people view beavers you know, on their land or the flooding problems that they can cause and how people address that?
Emily Fairfax
Yeah, that's a great question. So I obviously love the beavers, but that's not the case with everybody. Um, they, the beavers, they are like, as we've gone over, able to create massive landscape changes. And that can be very much at odds with us when we are also trying to control the landscape that they move into, that we are both creatures that really want to control our environment. And so having that, you know, head butting is not always going to be really productive. They will flood roads if they get by roads, they will flood people's basements if they are in your backyard. So how do you handle that?
I think that, first and foremost, you don't have to like beavers to respect the things that they do that are good, and you don't have to ignore all the things that they do that are bad to still be considered a pro beaver reintroduction or whatever person. We definitely don't need beavers in some landscapes and they shouldn't be in some places, like when they are on someone's property, flooding their house, and it's just causing headache after headache. And I mean that's bad for the beavers, it's not a good habitat for them. And in a lot of states, the best solution is to move the beaver. Take it away. You can't move beavers in California though, it's illegal. So we have a little bit of a tougher situation because your options are lethal management, or some sort of like cooperative management with them. So you have to deal with them on your land. There's not an option to move it without killing it, which is really hard, but you can do it.
So if the issue that you see -- I look at a lot of the depredation permits that come through for beaver and see like, why are people wanting to remove them? What are the concerns? And like half of them are the beaver is chewing down a tree that I care about for some reason, like this is a crop tree, or this is just an important tree to me, or it's my prized pistachio tree. And there are ways to protect the tree and protect most of your trees. And you can kind of nudge the beaver out. If all of your trees are suddenly not accessible to them, that's their food source. That's the building source. And it can be as simple as wrapping your tree in chicken wire, or painting it with a sand paint, the beavers aren't going to want to spend their time doing that. It's too hard for them. And if they have no more building material, they can move on their own, so you can sort of drive them to relocate themselves.
The other issue that comes up a lot is flooding, because they do flood -- that's where all these great benefits come from is the flooding. But you know, you're not wrong if you don't want to have a super lush wetland in your backyard. That's fair. It can be a kind of a messy landscape. So if that happens, you can install different kinds of pond leveling devices, which are basically like a big pipe that you put on one side of the pond and another side downstream of the dam and you drain part of the pond. You don't drain the whole pond, just part of it. And then the beaver doesn't know what's happening, it's like whatever I still have a pond, my dam is fine, I'm good. So then you're controlling the pond level, but you're not totally destroying it. Then you get a nice wetland but it's much smaller and a little bit more packaged.
Faith Kearns
What was the name of that one thing you told me about? The beaver deceiver?
Emily Fairfax
Oh yeah, beaver deceiver is an amazing name. The one thing that beaver people are incredible at is jokes and puns. The beaver deceiver is the original beaver pond leveler and the guy who's been working on it, he developed it 30 years ago, and every year, sees how they're doing and makes a change. It's now, in its current form, is the super robust, extremely inexpensive, and really, like low tech solution to a pretty massive scale problem and he can like save roads because you just divert the flow just enough or you know, they're damming up this culvert, well, now they're not, problem solved. So many of these problems can be dealt with a much later hand than is sometimes our instinct.
Faith Kearns
That seems like a good note to end on there!
Mallika Nocco
Thanks for listening and join us next time on Water Talk.