Restoration Ecology in Coastal Wetland Ecosystems • iBiology

My name is Alex Moore, and I am a NSF postdoctoral fellow. I do research looking at coastal wetland ecosystems and community dynamics within those ecosystems to help inform restoration and conservation.

00:26 I think that people often think about natural space as being separate and very different from the spaces where we live in urban centers. And so people often themselves think of themselves as being very removed from these natural spaces and things that are less built by humans. And so I think, at least in my work, I try to think about the value that both of these spaces hold separately and then, also, the ways that we can have these spaces be integrated together.

00:55Historically, restoration has focused on the science. We go out, we see the space, we see what it needs, and we just decided to fix it in the ways that we deem best. That often excludes the people who live in those spaces and are impacted by the availability and access to those resources. And so what I'm trying to do is make sure in my work that I'm paying attention to the science and my approaches to it, but also making sure that I'm talking to people thinking about what matters to you, how have you historically used this land, what are the ways that we can take all of that knowledge and combine it together so that we restore it in a way that's healthy and sustainable. Also, not only for the landscape, but then also for the people who live across that system.

01:42Since roughly the 1800s, we've lost about half of the world's global wetlands. And so we've lost them for a number of different reasons. We usually see lots of land conversion, so something that was a wetland is typically converted into something like agriculture or an urban space, like a city. We also have lost them due to climate change and the associated sea level rise. So as those sea levels do increase, the extent of the wetland decreases over time because it can't maintain itself along those coastal regions. And we've also lost them just due to taking out really important species that you find within them.

02:17 Wetlands are incredibly important ecosystems. They have a number of values associated with them, both in terms of what people get from them, and also the services that they provide to people just by their existence. When coastal storms occur, having wetlands there can help buffer the damage that communities that live in those spaces might influence. They're also really important recreationally. People love to go fishing in wetland spaces. They're also important as nursery habitats for other species, or things that might be important economically. So shellfish and other different areas of economic sector also rely quite heavily on wetland ecosystems. So their interests or the uses of them are quite broad, and those are just a handful of things that people get from them.

02:59 So one of the general ideas around restoration that has been quite strong in a lot of different ecological spaces is this idea that if you build a habitat, so if you make sure the soil is there, if you plant some trees, if you plant some grass, if you build it, species will come back to that space. With this, if we build it, they will come idea, we're really focusing on the bottom. We're building this habitat, we're building physical structures and we're saying the top-down elements, or the species that interact with each other, will come all on its own over time. That bottom-up approach gives us certain level of recovery, and then we kind of flatten out over time. And so the average here is that restored wetland ecosystem, where you're really focusing mostly on recovering these physical components, tend to function roughly 30% less well than a natural ecosystem that hasn't been degraded or damaged in any kind of way. So we are seeing this gap in terms of what level of function we see in a restored wetland versus a natural healthy wetland.

04:01 My interest lies in filling that gap. This, essentially, is thinking about, we have this gap in terms of the restored wetland, what its level of function is, a healthy wetland, its level of function. We know that they're different. And so my research is really trying to fill that gap a little bit and thinking about, well, maybe the reason that we're not seeing the kind of recovery that we're hoping for is because we're not thinking about other elements that are also important within that ecosystem. So thinking about these top-down elements, thinking about these different species that play specific roles, maybe we should be incorporating them into the restoration to get better recovery of ecosystem functions.

04:38 For me, when I talk about ecosystem functions within wetlands systems, I'm thinking about nutrient cycling, so nitrogen within the soil, how is it moving from one form to another so that plants can use it for their growth? I'm interested in the rates of decomposition, so if you've got organic dead tissue within the soil, how is that being broken down to make more nutrients available for other species? I'm also interested in growth of vegetation, so how much biomass are we seeing produced over a period of time. So these are all functions that indicate levels of health that you can compare to other historical points in time or other areas that are known to be healthy. And so these are the functions that I'm most interested in when I think about and work in these coastal systems.

05:21 So I just want to give you a brief example of how that might actually go within a coastal system. Here is a very simplified schematic of a salt marsh food web. And so at the top, we've got a predator, so this might be a blue crab, for example, and then beneath that we've got potential prey, so here, this is a Fiddler crab, or a herbivorous purple marsh crab, and then beneath that we can see the vegetation and the soil within the system.

05:47 So in a situation where we remove this top predator, so this might be because of recreational removal or economic incentives to remove this species, this then frees up its prey. So it means that these prey species are no longer concerned about being consumed by predators, and so they're able to eat their food and then reproduce because they don't really have to worry about this control coming from the top-down with this predator influencing their population size. And once that happens, that means that they are now able to consume their vegetation, and so in this situation, what happens is you have all of these crabs. They're now eating all of the vegetation and it's being removed entirely from the system, and depending on how intense this is, what this can lead to is these species will now move to other places because now there's no more vegetation. They've now also consumed it to the point where it's very difficult for it to grow back, and what you end up with is a degraded lost ecosystem where nothing's really productive and it's not functioning very well.

06:48 So in my research, what I do in terms of evaluating the impact that consumers have on ecosystem function is I manipulate the presence and absence of certain species. And so for me, that looks like going into these wetlands systems, identifying certain locations, and then building these cages that either allow me to remove certain species or put certain species within those cages and then measure the effects. And so I'll know certain cages have one combination of species, another set of cages has a separate combination of those species, and then comparing between in terms of measuring soil quality, looking at carbon storage, looking at nutrients between those two different setups can allow us to better understand how different kinds of communities might be influencing different levels of function within those spaces.

Alex Moore: 07:36 The cage setups have been pretty simple. So the idea is that I typically have three or four different experimental treatments within each of the cages, and so one of them might be a situation where the predator is present and the herbivores are present along with the vegetation. One of the other cages might just be that the predator is absent, and so within that cage, you only see the herbivores and their vegetation. And then in other cages, we might only just see the vegetation just to get a sense of looking at if we remove certain species and we measured the same functions across each of these different cages, what are the outcomes going to be and what does this tell us about the importance of those species?

Alex Moore: 08:14 What we found is that the removal of the predator from that ecosystem had impacts on both vegetation growth over time, and then also nitrogen availability in the soil. So having that nutrient available there is important for vegetation growth. And so what we found was that that species, that predator, if you take it out of that system, it has these cascading impacts on these functions that are quite important for the health of that system. And so we also saw that the species that that predator was eating, so the purple marsh crab and the Fiddler crab, their presence also impacted both vegetation growth, and also soil nutrient availability over time. So we know from these experiments that these are really important species and they play a role in levels of function that might be really important when we're thinking about how to conserve and restore these spaces.

Alex Moore: 09:02 What we also saw was that the changes were not consistent across all of the different locations. So at one field site, we saw one change, at another field site, we saw different changes. And so what this means is that the impacts that consumers are having is not just, if you do this one thing, you will see this one thing everywhere, and so that's really dependent on the context, the area, what's the history of the space, what it's being used as right now. So there's lots of variation there, but the overall takeaway is that the consumers are playing a role, just that role looks very different across different sites. Because historically, ecologists have led with the idea that bottom-up control is what's most important within salt marsh system, so any sort of measure of health and function is being driven predominantly by the bottom-up, so by these soil factors, by nutrients, by abiotic features, like the tides or other physical factors within that system.

Alex Moore: 09:59 It turns out, over time we've recognized more and more that top-down factors, so thinking about these interactions between different species, are also quite important for the health and function of these ecosystems. So it's really not driven just from the bottom up, like we have historically been told, but rather we're seeing a lot more top-down control happening within these ecosystems, which indicates that the both of them are important. So a combination of bottom-up and top-down control are really what is driving function within wetland ecosystems.

Alex Moore: 10:28 When you are considering restoration work within these certain spaces, so in this case, in New England coastal salt marshes, and you're trying to get as much recovery as you can over time, it could be really important to not only focus on making sure that physical habitat is present and healthy, but also incorporating species like the purple marsh crab, like the Fiddler crab and also their predators, to help jumpstart additional recovery. And hopefully you'll see that increase the level of function over time, once you add these top-down features back into the system.

Alex Moore: 11:03 Most research studies looking at consumer impacts within wetlands focus on salt marsh ecosystems, and so that means that we don't really have a good understanding of how consumers might impact mangrove ecosystems or seagrass bed systems, or these other coastal ecosystems that we also know are quite important. And so in my work, what that means is I've put a pause on work within salt marshes to really move into these spaces where we haven't seen as much research done so that we can get a better understanding about how these systems function.

Alex Moore: 11:32 So I work now in mangrove ecosystems, and that's partially because of this gap that I recognized from the literature review, so I recognized that we don't really understand how mangrove systems are influenced by consumer interactions. And so for me, that really meant going out and thinking about ways that I can expand my research from these salt mash spaces into these mangrove ecosystems. And so now, in my position, what I do is I work within the Pacific Islands, which are known for their mangrove habitats and working in American Samoa, I do similar experimental studies to see what impacts are being had and how can we get a better understanding of larger scale coastal ecosystem understanding of how consumers impact the function by adding in the sort of mangrove knowledge into what we already know about salt marshes.

Alex Moore: 12:18 So I'm doing these same experimental designs where I have these cages, I remove certain species, or I include certain species and then measure very similar functions, so thinking about soil dynamics, thinking about growth of the vegetation, so the trees themselves and how they function over time. So trying to make sure that my measurements are quite consistent so that when we think about adding these things all together, we can compare across ecosystems using very similar metrics.

Alex Moore: 12:47 So whenever I'm thinking about the work that I do, I'm also very aware of my identity and the roles that I play within the different spaces that I enter. And so right now, working at American Samoa, I think that that stands out in a very unique way for me, in terms of being a Black American citizen working in this space that is an American territory, but the residents themselves are not U.S. citizens. And so the access and the privilege and the resources that are available to me are not available in similar ways to most residents in American Samoa. And so when I enter that space, I'm very aware of the power and privilege that I have because of my background and because of my identity. So I find that it's really important for a scientist to be aware of their identity as they enter these spaces and think about the ways that you influence the work and how that, in turn, it can influence how you think about things and walk through those spaces.

Alex Moore: 13:40 I'm always really interested in thinking about the ways that we can help educate people in terms of not only the science, but also recognizing that science is influenced by people and people are influenced by science. And so whenever I give these kinds of talks, I'm really interested in making sure that people recognize that we do have the scientific information, we have all of this background, we have all of this research, but all of it matters in the context of the people who are being influenced by that work and who all have an ability to influence that work themselves. And so I try to make sure that science is given this more social component to it, so that we recognize that all of these other elements are just as important.

This Talk

Speaker: Alex Moore

Audience:

Educators of H. School / Intro Undergrad
Student
Educators of Adv. Undergrad / Grad
Researcher
Educators

Recorded: October 2020

Talk Overview

Dr. Alex Moore provides an introduction to coastal wetlands, including the functional role they play in our world, as well as the many ways that these ecosystems are used for economic and recreational activities. Dr. Moore discusses the traditional approach to restoring coastal wetlands, and the ways that these efforts can fall short of restoring functional capacity in coastal salt marshes. Incorporating species interactions along with cultural uses and values into restoration efforts may provide an opportunity to further improve outcomes. Dr. Moore finishes with a brief overview of work currently underway in coastal mangroves, another important wetland ecosystem.

Speaker Bio

Alex Moore

Alex Moore

Dr. Alex Moore earned B.S. and M.S. degrees in Ecology and Evolutionary Biology at the University of Michigan, followed by a Ph.D. in Forestry and Environmental Studies from the Yale School of the Environment. Dr. Moore was awarded an NSF Postdoctoral Fellowship at the Center for Biodiversity and Conservation at the American Museum of Natural… Continue Reading

Credits

Sarah Goodwin: Executive Producer
Elliot Kirschner: Executive Producer
Shannon Behrman: Producer
Kevin McLean: Producer, Editor
Eric Kornblum: Videographer
Chris George: Design and Graphics
Maggie Hubbard: Design and Graphics

Leave a Reply Cancel reply