In this week’s episode, host Margaret Walls talks with Becky Epanchin-Niell, an associate professor at the University of Maryland and a senior fellow at Resources for the Future. Epanchin-Niell discusses how climate change and human land and water use have accelerated the frequency and extent of saltwater intrusion, which is saltwater contamination in freshwater rivers, soils, and aquifers. Epanchin-Niell and Walls also talk about the implications of saltwater intrusion for coastal ecosystems, drinking water, and the agricultural sector. Epanchin-Niell’s recent research examines how saltwater intrusion affects agricultural practices on the Eastern Shore of Maryland.
Listen to the Podcast
- Saltwater intrusion has wide-ranging consequences: “This is an issue, because people, plants, animals—we depend upon freshwater for our survival. So, when these freshwater resources become contaminated with salt, it can affect a lot. It affects our drinking water. It affects water for irrigation. It can cause die-offs of species in different ecosystems.” (4:45)
- Saltwater intrusion drives changes in agricultural practices and land use: “What we see is this shift from rotations with corn to rotations that did not have corn in them … In addition, we also see transitions out of agriculture. So, we are seeing these lands shifting from agricultural uses to, for example, wetland vegetation.” (14:52)
- Sea level rise and saltwater intrusion are settling in: “There’s ways in which you can delay or prolong or reduce the economic impacts for a while, but, in many of these really low-lying areas, we’re unfortunately facing very substantial sea level rise. This [Eastern Shore] region has a relative sea-level-rise rate of twice the global average. So, there’s a lot of areas that have already been lost or already been submerged, and there’s no longer land. There’s a lot of places that are going to be lost in the coming decades and the coming century.” (22:06)
Top of the Stack
- “The Spread and Cost of Saltwater Intrusion in the US Mid-Atlantic” by Pinki Mondal, Matthew Walter, Jarrod Miller, Rebecca Epanchin-Niell, Keryn Gedan, Vishruta Yawatkar, Elizabeth Nguyen, and Katherine L. Tully
- “Coastal Agricultural Land Use Response to Sea Level Rise and Saltwater Intrusion” by Rebecca S. Epanchin-Niell, Alexandra Thompson, Xianru Han, Jessica Post, Jarrod Miller, David Newburn, Keryn Gedan, and Kate Tully
- “The Invisible Flood: The Chemistry, Ecology, and Social Implications of Coastal Saltwater Intrusion” by Kate Tully, Keryn Gedan, Rebecca Epanchin-Niell, Aaron Strong, Emily S. Bernhardt, Todd BenDor, Molly Mitchell, John Kominoski, Thomas E. Jordan, Scott C. Neubauer, and Nathaniel B Weston
- Two Degrees by Alan Gratz
The Full Transcript
Margaret Walls: Hello, and welcome to Resources Radio, a weekly podcast from Resources for the Future. I'm your host, Margaret Walls. My guest today is Becky Epanchin-Niell. Becky is an associate professor in the Department of Agricultural and Resource Economics at the University of Maryland and a senior fellow at Resources for the Future (RFF). Becky's research lies at the intersection of ecology and economics, and she focuses on conservation, invasive species, and the topic we're going to talk with her about today—coastal adaptation to climate change.
Specifically, I'm going to ask Becky about the problem of saltwater intrusion, which people sometimes refer to as the leading edge of sea level rise. Some of you who are regular listeners might remember we had what I thought was a great episode of Resources Radio back in May, where we talked to Skip Stiles of Wetlands Watch about sea-level-rise problems in Virginia. I think that the saltwater-intrusion problem actually got mentioned in that episode, but today, we're going to dive into it a little bit more. Becky's going to tell us about some of the problems it creates and potential solutions to them, and she's going to tell us about some of her research on the issue. Stay with us.
Hello Becky. Welcome to Resources Radio. I'm so happy to have you on the show.
Becky Epanchin-Niell: Thanks, Margaret. It's great to be here with you. I'm really excited to be here.
Margaret Walls: If you're a listener, you probably know we don't like to dive straight into the topic. We want to learn a little bit about you first. Can you share a little bit about your background, and especially how you came to do research at the intersection of ecology and economics, and maybe how that led you to this particular topic we're going to talk about today?
Becky Epanchin-Niell: Yeah, it's always fun to reflect on that. I took a bit of a winding path, I'd say, to where I am now, because I always had a love and fascination of nature and always spent my time outdoors collecting lizards and insects. In fact, you can still find me out there a lot these days, but I actually didn’t discover economics until spring quarter of my senior year in undergraduate. It was the last required class for graduation, so I kind of took it a little bit kicking and screaming. I just sort of saw it as the source of environmental challenges, but it was through that class that I really learned about economics as a framework for understanding decisions and also for helping shape solutions—thinking about how we can do foreign policies and incentives to achieve different societal and environmental outcomes. So, I’m super grateful that I ended up having to take that class at that time.
Since then, I've continued at that intersection of ecology and economics. So, I did my master's in biology and just continuously felt the need to be bringing in people into the discussion and the issues at hand, and so I did my PhD. Most of the work that I do at this point is really at that intersection. I'm really lucky in that I get to do a lot of collaborative work, so I work a lot with different natural scientists and different social scientists, and I also try to engage a lot of policymakers and stakeholders in the research that I do.
And the way I got into saltwater intrusion probably stemmed more from me initially thinking about the ways in which sea level rise and climate change affect ecosystem services provided by coastal habitats, including wetlands; then, also that recognition that it's a lot of the rural landowners and the rural land users that are providing a lot of the land and resources that contribute to those ecosystem services. Then, I actually ended up reaching out to some other collaborators who are now long-term collaborators of mine. I reached out, and they actually brought me in, since they'd already been doing work on saltwater intrusion in these coastal areas, and I have been lucky to be working with them since then.
Margaret Walls: That's great. We're going to talk about some of that work you're doing with them. So, maybe give our listeners a background just on what the saltwater-intrusion problem is and a little bit of detail about it. What are the drivers of it, and how big or widespread of a problem is it, Becky?
Becky Epanchin-Niell: At its simplest, saltwater intrusion is the incursion of saltwater into freshwater resources, such as into aquifers, rivers, or soils, such that it ends up contaminating those freshwater resources with salt. This is an issue, because people, plants, animals—we depend upon freshwater for our survival. So, when these freshwater resources become contaminated with salt, it can affect a lot. It affects our drinking water. It affects water for irrigation. It can cause die-offs of species in different ecosystems. You might've heard of ghost forests, for example, which are coastal forests that have been affected by salinization, and therefore you have these die-offs of trees.
Saltwater intrusion, in a sense, is a natural process, in that anywhere where you have that interface between saltwater and freshwater in these coastal regions, you're going to have the salinization of those freshwater resources in those locations. But the real challenge is that changes in climate and land use and water use all really have shifted and increased the sort of extent and frequency and intensity of saltwater intrusion and how far that salinization is reaching inland. When you have, for example, sea level rise, you're raising the elevation of these coastal sea waters, which can then end up reaching further inland. You can think about that in terms of storm surge, where you're going to have salty waters going further in that way, but you also have increasing pressure belowground that can lead to the intrusion of that saltwater further inland.
But also, you think about a lot of the water-management infrastructure that we have, where you have ditches and canals, for example, in areas where, perhaps historically, we might've been draining the land, trying to move that water off the land. As sea level rises, those are also conduits for that saltwater to be moving further inland.
Margaret Walls: I hadn't thought about that part of it. That's interesting. So, Becky, you mentioned saltwater intrusion into freshwater resources. As I understand it, there's a lot of problems that saltwater intrusion does cause for water supplies and water infrastructure—saltwater intrusion to drinking water aquifers, as an example. Can you talk about these issues a little bit?
Becky Epanchin-Niell: Yeah. In fact, this is happening increasingly often. So, there's a lot of issues with saltwater ending up affecting these freshwater resources. What some listeners might actually be familiar with is hearing recently about some of the concerns about saltwater intrusion into the Mississippi River. There's been a salt wedge working its way up the Mississippi River because, under drought conditions, there's been less freshwater flowing into the river, hence allowing the ocean waters to work their way further up.
Like many cases with saltwater intrusion, you end up with these actual interactions between climate conditions—in this case, drought—but also water use that perhaps is reducing the flow of fresh water, as well as connectivity and how we've changed the landscape; in this case, for example, the dredging of the bottom of the Mississippi to facilitate transport. All of these things are ending up contributing to this issue.
There's concern that some of the drinking-water facilities are going to be affected if the saltwater wedge reaches its way up to the intake for these areas.
There's different interventions that are going on now, for example, in the Mississippi River, but you also have this in a lot of aquifers; particularly, if you have pumping or increasing sea level rise or if there's connectivity between the aquifers and the ocean, then you can end up with salinization of your coastal aquifers. And this is a real problem, particularly when those are being used for drinking and often supporting urban communities. For example, we see that in Florida, where you're having the aquifers being contaminated with saltwater.
Margaret Walls: Interesting. Well, let's talk about agriculture a little bit. You mentioned the water issues, which I think is important for people to understand, but a lot of your work has been focused on agriculture. What problems does the saltwater-intrusion issue create for agricultural lands?
Becky Epanchin-Niell: For agriculture, in particular, we're growing crops and growing plants; therefore, most of the crops that we grow are actually very intolerant to salts. There are a handful of plants that are able to excrete salts and therefore persist in saline conditions, but most crops cannot. So, what we see is a decline in crop productivity, decline in crop yields, and often even failure to germinate in highly salinized areas.
Margaret Walls: I think you've focused a lot of your work on the eastern shore of Maryland. Just so people are familiar with it—they might not be familiar with Maryland geography—that's the peninsula that lies between the Atlantic Ocean and the Chesapeake Bay. It’s part of what's called the Delmarva Peninsula with Delaware and Virginia. First, tell us why you're focused on that region and what makes that region, in particular, worth studying for this problem?
Becky Epanchin-Niell: There's a couple of reasons. One is that agriculture is a really important economic sector on the Eastern Shore and so, in that sense, understanding that saltwater intrusion is one of the big stressors in the eastern coastal areas is really important. The Eastern Shore is very low-lying. There's long stretches of the Eastern Shore where you can go pretty far inland and still be at very low elevation. When you have high-tide events or large storms, you can have overwash of saltwater, and you also have a lot of ditching of the Eastern Shore that, again, is allowing for that connectivity of that saltwater further inland.
So, it's both that it's a high-risk area and there’s lots of agricultural values at risk, but also it's an area of extreme environmental importance. There's a lot of water-quality issues and a lot of loss of coastal wetlands in that region. There's a lot of intersection between what we're thinking about what's happening on these agricultural lands and the different ecosystem-service benefits provided in these regions.
Margaret Walls: I'm very familiar with that region myself, having done some work over there.
So, your research in particular is filling a gap in the literature, I think, and when I say in the literature, I mean climate impacts on agriculture. In one of your papers, you mentioned that there's very little known about agricultural responses to saltwater intrusion. There is a pretty big literature on agricultural responses to heat and drought. I know that, but there's not much on this particular manifestation of climate change. Tell us a little bit about what you and your coauthors did to fill this gap and just what some of your findings are?
Becky Epanchin-Niell: I want to start off by just highlighting that I'm part of a larger interdisciplinary team working on this. We've got a whole bunch of different work going on on the Eastern Shore, including planting different crops and trying to look at how yield is affected across salinity gradients. There's remote sensing going on trying to map soil salinities and a lot of work into, for example, the biogeochemistry.
But the study that I've been leading has been looking at using remotely sensed cropland-cover data—the US Department of Agriculture crop data layer—and using that to try to understand how the land cover, or land use, or the crops on agricultural fields has changed over time in response to saltwater intrusion in this Eastern Shore region.
We took these crop characterizations, and we're then linking them with different information about the fields, including the soil types that are present at those fields, as well as information about the elevation of those fields with respect to sea level and in particular how sea level varies over time. What we can then do is see how these land-cover changes relate to sea level, which is our, in a sense, proxy for saltwater intrusion. Using those statistical models that we develop, we can then also make predictions about how land cover may change in the future with anticipated sea level rise.
Margaret Walls: Tell us what you found when you did that work.
Becky Epanchin-Niell: One of the primary findings with respect to land that remained in agriculture within the study period—those areas that were most affected by saltwater intrusion or, in other words, were the lowest elevation with respect to sea level, were much more likely to have transitioned out of corn rotations. Much of the Eastern Shore is cropped in these rotations of corn and soy or corn, soy, and wheat. Corn is particularly susceptible to salinization and is also a crop that requires a lot of inputs.
So, what we ended up seeing was this shift from these fields that were in rotation with corn to ones where corn was absent from those rotations, and this aligns with what we'd expect, based upon the susceptibility of these crops to salinization.
Margaret Walls: Did you do some predictions of how extensive that would be? If there would be less corn or whatever with sea level rise in the future?
Becky Epanchin-Niell: What we see is this shift from rotations with corn to rotations that did not have corn in them—as expected, based upon the susceptibility of the corn to salinization. In addition, we also see transitions out of agriculture. So, we are seeing these lands shifting from agricultural uses to, for example, wetland vegetation. When we look at the predictions going forward, you see a very distinct shift where a substantial amount of these very low-lying lands are moving out of corn and then also transitioning into wetland vegetation.
Margaret Walls: Wetlands have a lot of value, Becky—right?
Becky Epanchin-Niell: Yes, yes!
Margaret Walls: This is an interesting phenomenon. Can you just tell folks why wetlands are so valuable, for one thing? And then this issue of some of the agricultural land changing into wetland, a cropland changing to wetland—that's in response to sea level rise, like what about that a little bit? There's some interesting aspects to that. I mean, in a way, that's a good thing but also a challenge for farmers.
Becky Epanchin-Niell: It's this really challenging topic, because wetlands are very important. They provide a lot of ecosystem-service values in that they support a large amount of biodiversity. They provide habitat for a lot of species. They provide a lot of recreational benefits, aesthetic values—but also in terms of birdwatching and hunting—hunting being a really big pastime on the Eastern Shore in particular. They also do help filter nutrients, which is really important for water-quality issues in the Chesapeake Bay, carbon sequestration, and also coastal protection. You know a lot about this, Margaret. You've done a lot of work on this—just the ways in which it can help reduce coastal erosion and inland flooding, particularly during storms.
These wetlands are a really important ecosystem in east coastal areas, but we've also historically had a lot of loss of coastal wetlands due to a range of stressors, from conversion to other land uses, but also from sea level rise. As wetlands become inundated by higher sea levels, if they can't accrete vertically at a fast enough rate, then wetlands in particular locations will be lost. So, to maintain those coastal wetlands, they need to be able to migrate or disperse inland—so, move inland—as the sea level is rising. But if you face hard barriers such as roads or development, for example, or very active management such as agricultural cropping, that's going to prevent that movement or that migration of wetlands inland.
There's this idea that we are really relying on some of these more natural land spaces or these less developed lands, such as agricultural lands, as potential pathways for wetland migration. At the same time as these agricultural lands are losing their productivity and losing the profitability of cropping those lands, farmers may abandon those lands, for example, or they may engage in programs such as the Conservation Reserve Enhancement Program or put their land into the Wetland Reserve Program or engage in some of the NGO conservation organizations as a means to transition their land out of agriculture and potentially into wetlands.
Margaret Walls: That brings me to a financial question for farmers, then. What you just described might give them some financial benefits. I guess that's one aspect that's a good thing for them, but they are losing some valuable crop production. Are people talking about this? Well, my first question, I guess, is, did you look at this kind of economic impact on the agricultural sector and any calculations of how much profit they're losing? Then, how much opportunity do we have to replace that with some other thing of value for them?
Becky Epanchin-Niell: I would say that farmers are bearing a lot of burden in these coastal areas, and, with a lot of these rural landowners, they're not the source of the rising seas, and yet they are at the front lines of a lot of those impacts. It can be really hard for farmers, many of whom have been farming for decades or even generations, that are seeing their lands lost to salinization and inundation, and this is the loss of livelihoods and, as you said, the economic impacts in those areas.
In another study with one of my colleagues, we quantified some of the economic impacts of losses in profits just in parts of fields that were affected by salinization as a sort of a snapshot in time. Across the Delmarva, it is estimated that losses amount to about $40–$70 million per year in that study. When we're thinking about how these losses play out, we, in part, are going to depend upon, kind of, What is that pathway? How are farmers responding to that salinization?
There, fortunately, are some programs to help offset some of those costs, such as I was mentioning. Some of the different conservation easement programs have potential to provide at least some offset of that income loss. I know that there's also some farmers that have looked into things like mitigation banks or other more market-based forms, but, in general, these are losses that are being faced in these systems.
Margaret Walls: I could see that. Are there some adaptation solutions that can be taken in the agricultural sector, and if so, what are they?
Becky Epanchin-Niell: What I was noting before in the study is what we were really observing was these adaptation responses, one being that you can change the types of crops that you're planting. We did see, for example, a lot more sorghum being planted in some of these low-lying lands, because that tends to be a crop that is much more tolerant to saline conditions and to inundation, for example. Putting in tide gates can help in some particular contexts where you might be able to at least delay that inland flow of salty waters. Trying to change that connectivity is one option.
There's ways in which you can delay or prolong or reduce the economic impacts for a while, but, in many of these really low-lying areas, we're unfortunately facing very substantial sea level rise. This region has a relative sea-level-rise rate of twice the global average. So, there's a lot of areas that have already been lost or already been submerged, and there’s no longer land. There's a lot of places that are going to be lost in the coming decades and the coming century.
A lot of this is, How do we think about that transition? Both in terms of, How do we support the farmers and landowners through this transition? But then also just thinking about, How do these different potential pathways end up resulting in different outcomes in terms of societal or community impacts or ecosystem-service values? That's one of the things that we're hoping to bring to this. Some of the prediction modeling that we're also doing, in terms of thinking about where salinization is going to happen, is just having better ideas about the timeline and where these things are going to happen. Hopefully, this can help with some of the planning, as we think through what these transitions might be.
Margaret Walls: Right. Just having a sense spatially and temporally what the extent of the problem is is helpful for planning, I guess, is what you're saying.
Becky Epanchin-Niell: Yeah.
Margaret Walls: Well, Becky, that's really interesting, and we'll put some links to some of your work on our webpage when we get this podcast episode up. I'm glad you were able to come on and talk to us about it. You know that we closed the podcast with a regular feature that we call Top of the Stack.
Becky Epanchin-Niell: Yeah.
Margaret Walls: We're going to ask you if you could recommend something for our listeners—a book, an article, a podcast, a movie, or anything, really. What's on the top of your stack?
Becky Epanchin-Niell: Well, I'm going to actually put out a book. Two Degrees by Alan Gratz is a book I recently read with my 12-year-old. I'm not sure how much young adult reading you get on this show, but I think a lot of people have kids, so I think it's nice. I really like this. This is a book about climate change, and it's very appropriate for this episode. It tells an interwoven story of three characters, in different regions of North America, each finding themselves in the midst of a different climate disaster and how they understand climate change and about communication of climate change and the really very real impacts. It's a really good book. It's gripping. It's like a page turner, but it’s also really thoughtful, in terms of thinking about the social and information dynamics. So, I highly recommend it.
Margaret Walls: Okay. A lot of young adult books are good for adults. That's great.
Becky Epanchin-Niell: Exactly. It was great reading it with my son, and just a lot of the discussions that we had coming out of it is always fun.
Margaret Walls: Thank you so much for that. Well, it's been a pleasure having you on Resources Radio. I'm so glad we're able to have you come on and talk about what we call the leading edge of sea level rise saltwater intrusion. Thanks so much for sharing your expertise with our listeners. We appreciate it.
Becky Epanchin-Niell: Thank you so much, Margaret. It's always a privilege to get to interact with you and also really wonderful to be a guest here on Resources Radio. So, thanks.
Margaret Walls: Thanks.
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