Science Friday - Beetles, Wildfires, Woodchip Bioreactor. May 7, 2021, Part 2

Episode Date: May 7, 2021

A Beetle’s Chemical (And Plastic) Romance For many species of beetle, the key to finding a mate is scent: Both females and males give off pheromones that signal their species, their sex, and even their maturity level. How do researchers know? In experiments with dead beetles that have been sprayed with female pheromones, live males reliably attempt to mate with the dead insects. But when one team of researchers based at the Chinese Academy of Sciences in Beijing and Syracuse University in New York tried to investigate whether this was true for the flea beetle Altica flagariae, they got a strange result. Males seemed confused when presented with scented dead beetles, leaving the team wondering if the dead beetles were still exuding their original chemicals. What is a research team to do? They attempted the same experiment, but with 3D-printed replicas. This time, the male beetles seemed clearly attracted to the female scent, the researchers wrote in the journal Chemoecology last month. Producer Christie Taylor talks to Syracuse University biologist Kari Segraves about the intricacies of studying beetle intimacy, and the implications for evolutionary biology. Nature’s Early Warning Signs For A Bad Wildfire Season Last year, California saw a record breaking wildfire season. Nearly 10,000 fires burned over four million acres in the state.  Now, wildfire researcher Craig Clements is investigating natural indicators, like the chamise plant, for clues to predict what this wildfire season might look like. Normally, the wildfire season peaks during the late summer. This year, he’s observed a lower moisture content in these plants, possibly indicating the fire season may begin earlier.  Clements joins SciFri to explain how landscape, temperatures, drought, and atmospheric conditions all play a role in wildfire risk.  Arctic Wildfires Are Burning An Important Carbon Sink California wildfires have made national headlines for the last several years, but important—and large—wildfires have also been burning in the forests above the U.S. Canadian border and near the Arctic circle.  A group of researchers wanted to know how these fires affected the northern forests and how this impacted their ability to store carbon. Their results were recently published in the journal Nature Climate Change. Jonathan Wang, an author on that study, discusses what this might mean for future climate change predictions.  Can Woodchips Help The Gulf Of Mexico’s Dead Zone? In the Gulf of Mexico is an ecological dead zone, caused by algal blooms at the mouth of the Mississippi River. Warmer ocean temperatures provide the perfect conditions for algae to grow out of control, suffocating seagrass beds and killing fish, dolphins, and manatees. Fueling this toxic algae’s growth is nitrogen. The Mississippi river empties into the gulf, and drainage water from farms along it carries fertilizer ingredients—straight into the marine ecosystem.  While farmers have tried using practices to reduce fertilizer runoff, like cover crops, no-till farming and conservation buffers, for decades, the problem has only gotten worse. According to a new paper published in the journal Transactions of the American Society of Agricultural and Biological Engineers, a creative new approach involves denitrifying bioreactors—a system that allows bacteria to help convert nitrate in the water to harmless dinitrogen gas. “It’s a complicated name, but it’s really a very simple idea,” says Laura Christianson, assistant professor of crop sciences at the University of Illinois at Urbana Champaign, and lead author on the study. She talks with SciFri producer Katie Feather about how a simple system involving woodchips in a trench can help keep nitrogen out of drainage water from farms across the midwest. Katie also speaks to Shirley Johnson, a farm-owner from Peoria, Illinois, about why she adopted the bioreactor technology, and what farmers can do to help their downstream neighbors.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I am I Refleado. Later in the hour, we're going to talk about the clues scientists look for to predict the wildfire season in California, plus how common woodchips are helping to clean the water all over the world. But first, you know the song, right? Birds do it, bees do it, even beetles do it. Yeah, I'm talking about what else? Mating. And in the insect world, smell is a big part of the process of finding a suitable mate. Sci-Fi producer Christy Taylor is here with a story about the odorous quest for love and an unusual new method for studying it. Hey, Christy.

Hey, Ira. So I'm guessing when we're talking about seductive scents for Beatles, we're not talking about Chanel number five, right? No, I think that's a bit out of their price range. Today, we're actually talking about pheromones. You and I wouldn't be able to smell them, but for the Beatles in this story, they are a highly personalized cocktail of chemicals that can tell a wood. be suitor everything from what species his date is, that's important, to whether she's actually even fertile yet. Yeah, I can see how this is useful for a beetle for sure. And I think I can see why biologists would be interested in studying those chemicals. Yeah, there's a lot to learn there for

sure, not just how they work to convey information, but even how they might be helping new species form. Okay, tell us the rest of the story. Well, for that, we turn to Dr. Carrie Seagraves, a professor of biology at Syracuse University. I talked to her about an unusual innovation her research team just published that might make researching beetle mating and the chemistry involved easier to study. For starters, here she is introducing her main character,

a beetle called the flea beetle. They're called flea beetles because they sort of look like fleas do when they jump. They have really strong hind legs, and they can hop and basically fling themselves through the air to get away from predators. and they are actually gorgeous little beetles. They can be many different kinds of iridescent colors or have little stripes and things on them.

This particular one that we're working on is mostly black with an iridescent thoraxe and head. And the iridescent color comes out really kind of a blue. It's a really beautiful color. These beetles are herbivores. They feed on lots of different plants, particularly in the United States. They can be bad pests of many crops, including things like cabbage. beetles can really cause a lot of destruction. I'm a beetle. I'm looking to reproduce. What is the standard process for locating and wooing a mate? A very common theme is that they use chemicals

in order to seek out and make choices, but beetles also do other crazy things. Like there's, you may have heard of the Hercules beetle. So they have these huge horns on their heads and either heads or thorax as well. And they engage in battles with other males. so the males will fight using these horns and then one will throw another away basically out of the picture. But we have other things like fireflies. Those are actually beetles. And they use these really complex light shows to be able to communicate between males and females. It's like all over the board. It's hard to pinpoint one general system. So for the story that we're going to talk about today, we are going to focus on those that use those chemical signals. So when you're studying that

process, the pheromones themselves, how does that research process usually, go. And projects that we've been working on are generally involved understanding how insects make choices about their mates. That is, you know, how do they find other individuals that are the same species? And then make decisions about which of those individuals they're going to actually mate with. Usually what we'll do is we'll set up arenas that are usually trays or some kind of container and we'll place a mail in with two different models, so things that they need to choose between. So it might be a male versus a female beetle or it might be an immature female versus a mature female beetle. And then we just let the male go and say, all right, in this assay, which of the models do they choose?

In these studies that I've been doing with Kwaijun Shui at the Chinese Academy of Sciences, we've been using dead beetles. We'll kill a beetle. Then we'll let the male go and say which one of these options does it prefer to mate with. They'll mount and attempt to copulate with the dead beetles as odd as that sounds. But essentially, if you do enough males, then you'll be able to figure out overall what the preference is for that species. Okay. That's what usually happens.

But you recently got some results that suggested a new approach might be kind of important. What went wrong? We were looking at three different beetle species. And essentially, we were asking the question, do they recognize the differences between males and females based on their chemistry? So can they find and recognize this chemical signal and do they know which ones are male versus female? So they prefer the females, but we don't actually know why they prefer the females. It could be because of the chemicals or it could be the way the beetles look or the way they feel when they start to mount them.

And so in order to figure out if it was the chemicals versus something else, what we had to do is essentially remove the chemicals from these dead beetles and then swap it. So put the male scent onto the female bodies and put the female scent onto the male bodies. Two of the species, the males preferred to female scent. So they were mounting the males that were coated with the female scent. That third species, it was kind of a mix. It was like they were completely confused. They didn't know which to go to. Some of the males went to the females.

Some of the males went to the males. And they didn't exhibit any preference. That made us question our setup. basically in our experimental design. So you had taken all the scent off these dead beetles and put male scent on dead females and female scent on dead males, and the alive male beetles didn't seem to know which was which still somehow.

So maybe there's some scent that didn't get washed out. Right, right. So this is where 3D printing beetles comes in. How did you come up with the idea to try this? Actually, I took inspiration from one of my colleagues and friends, Rob Burgoso, at Cornell University. He had been using 3D printing to make scent-free flower models. And so it really took Rob's idea to heart and suggested to Quijune that maybe if we made a 3D printed beetle, that means we could have something that didn't already have these chemicals.

We could then paint the chemicals on and then we wouldn't have to worry about maybe having a mixture of signals because those dead beetles might have been leaking out more pheromones. And if they were doing that, then we would have had a mixture of chemical signals. And that would explain why we didn't see a preference. So you 3D imprinted some beetles. How did that go? Well, it was a little tricky because these are tiny beetles. They have very fine legs and very fine antennae. 3D printers aren't quite good enough to be able to print those super fine structures. In the end, our models didn't, they didn't have legs and they were antennae, but they had the overall shape, so they looked pretty much like the beetles. And did the male beetles go for these imitation beetles? Yeah, so you

would be surprised that they were very willing to attempt to mate with these little 3D printed plastic models. Most of them chose the female scented 3D models. So then you took your blank slate of plastic and you spread it with chemicals and you got this pretty strong confirmation then that these male beetles are really drawn to scent. It was really cool because, you know, we had that result before that it said they don't actually have a preference when we swap the chemistry. And so this actually allowed us to be able to show that the beetles do actually queue in on the pheromones and that they are using them to decide whether or not a specific individual is a male or female. What does this get us to understanding on a deeper level? Is there an evolution component,

for example? You know, there's so many beetles in the world. One in four animals is a beetle. Wow. Yeah, there's maybe about 400,000 species of beetles described. People have talked about how important beetles are in the sense that they are really species rich. And so I think we can use this as a model to kind of learn more about how new species form. It's one of the the key questions in evolutionary biology is how do new species form. And the interaction between plants and plant feeding insects might be one of the key ways that we can get new species to form because plants contain a lot of chemistry themselves and talking about chemistry today. And so essentially what this does is it sets up an evolutionary arms race where literally

the plants are gaining defenses and the insects are evolving counter defenses. And they're sort of in this race where they're battling it out to be the one on top, that escalation can drive what we call specialization or where insects tend to have a really narrow diet. And so in this way, we might see actually both groups of plants and plant feeding insects becoming more species rich over time. Well, and you mentioned, you know, one in four animals on earth is a beetle, which is that statistic alone is kind of blowing my mind. But I know personally when I see a beetle, I tend not to find it very easy to tell what kind of beetle it is. There's so many little black and brown beetles. If I can't tell a beetle apart, how does a beetle tell a beetle apart? Right. Especially in this

group that we've been working with, these beetles are extremely similar to one another. They're notoriously difficult to identify by humans, although I think the beetles do a just fine job. We've been working with these three closely related species, and as far as we can tell, despite the opportunities for them to interbreed that it is a very rare thing that happens in nature. So they're really honing in on the cues on the outside of the Beatles, these chemical signals that are distinct between the species and also then within the species, they have these distinctive characteristics that allow them to tell male from female and immature from mature individuals. I'm thinking about beetles like Emerald Ash borer, which are these terrible, terrible pests

that have created a great deal of environmental destruction. Could understanding beetle chemistry help us control them better or manage them? So it's possible that we might be able to co-opt if we understand more about these cues. They're also using these types of chemicals to make choices about what to feed on. In addition to looking at mating in these beetles, we've also looked at their attraction to the host plants. We were doing this one particular study where we were interested in two species. They're each other's closest relatives, and one species feeds on mature elm trees, and another species feeds on young elm trees only.

It's really strained. And so we were asking questions about, well, what is it about old versus young trees that is allowing them to figure out, you know, what they should be feeding on? So we did a similar study to the one we've been talking about, where we took extracts of the chemistry off of the surface of young and old tree leaves and then painted it on to filter paper discs. So literally a piece of paper. And the beetles that were attracted to young trees would go to the filter paper disks

that had the young signals painted onto them, and they would chew on those filter papers. They would lay eggs onto them. It was just like they were sitting on their host plants. And so if you can trick them into doing something that they shouldn't be doing, then you might be able to use that as pest management. Well, I think that's all the time we have. I want to thank you so much for joining me.

Thanks for having me. It's been great. Yeah, it's been really fun. Carrie C. Graves is a professor of biology at Syracuse University in Syracuse, New York. I'm Christy Taylor. We have to take a short break, and when we come back, we'll talk to a scientist in California looking at plant growth to predict what the wildfire season might be like in that state. So stay with us. This is Science Friday.

I'm Ira Flato. Last year, California saw a record-breaking wildfire season. Nearly 10,000 fires scorched over 4 million acres in the state. The wildfire season usually peaks during the late summer, but there are indicators that scientists look for to get an idea about the upcoming season. And my next guest is here to talk about that. Craig Clemens is a professor and director at the Wildfire Interdisciplinary Research Center at San Jose State University.

in California. Welcome to Science Friday. Thanks for having me. Now, I understand that your group has a couple of field sites looking at a shrub called what? What's the shrub called? It's Chamis. It's a common shrub in California. And so we use that to sample what those shrubs are, how they're responding to the climate and the precipitation from the previous winter. And what's so good about this shrub? Well, it's because it's so common across the state, and it's an indicator of what the fuel moisters are of other shrubs. So we basically, it was selected just because of it's from Northern California to Southern California, from the Sierra Nevada, all the way to the coast range.

What does that, I have to stop you for a second and explain to us what fuel moisture is and why you measure that? Yeah, so fuel moisture content is the amount of water in the plant. And what have you observed about the vegetables? this year? Well, because of the low precipitation we had this last winter, our fuel moisture mostly across the state, particularly in northern California, are below normal. And so that's indicative of what we can maybe think about this summer. Generally, April, we have the highest fuel moisture content of this season. And what happened April 1st when we went up to the site,

I was actually training the scientist on how to clip fuels. And it was because it's usually very easy in April because there's new growth. And the new growth is bright yellow, bright green, and you can really determine where that is versus what we call old growth, which is the plant that's from last year. And we went up there in April. We didn't have any new growth. And so that was quite surprising. Eventually, April 15th, we had new growth, so just a couple weeks later, but that new growth moisture content wasn't as high as it was. So fuels just, they didn't get the moisture. The soil moisture is really low. So that's why they're stressed out and struggling. And so how much water is in those living plants? What can it tell you?

It can tell us their flammability. So as you probably know, if you try to start a campfire, you always try to find the most dry kinling and the most dry logs. You know, if you've ever tried to start a campfire with wet logs, it doesn't work very well. And so that's the same thing with the wildfire. If the fuels are wet, if they have a lot of moisture content, then it's harder for them to burn. Wow. So how could this impact the fire? season in California this year? Well, we, you know, typically our peak fire season is in August and then in fall when we have a lot of our, what we call offshore wind events, our Santa Ana winds and the Diablo

winds in northern California. And so that coincides with the minimum in fuel moisture content of these plants. So we're starting off at a deficit already. And so that's the problem. We could have larger fires earlier in the season than we typically would expect. And we're already seeing grass fires take off in early May, when we usually get those late May, June. And we had red flag warning already for Northern California. So we're already getting into fire season. So this is portends for a pretty bad fire season again, if I'm reading you correctly.

It could be. I mean, obviously we have to have the ignitions. Without the ignition, we don't have a fire. But if we do have an ignition, it is anticipated that these fires could get quite large quickly. There are lots of other variables that go into determining how the fire season will go. Can you give us an idea of what other indicators you will be watching for? One thing that we're looking at, and one of our researchers at our center has produced a kind of preliminary model based off some previous research that was published showing that maximum daytime summer temperatures

are an indicator for large fire growth. So we can look actually, we can try to predict what we expect the summer season to be. Is it going to be slightly warmer? Is it going to be slightly cooler? And if that's the case, we can kind of say, well, it looks like it might be more normal. So our indications show that we could expect that slightly above normal summer in terms of area growth, the fires, how large the fire is going to get. But that just depends on how the weather pans out. And one thing about wildfires is that their size and their behavior is a function of the fuels they're burning.

the atmospheric conditions and whether the terrain's very steep and complex, there's a lot of topography. We've always heard in years before when we've talked about the future of California wildfires. We've always looked backwards a bit about the snowpack from the season before in the wintertime. How much effect is that having this year? And was it a good year for snow? And will that affect the fire season? Well, it was not a good year for snow. we had a very low snowpack. I think April 1st, we were around 38 to 40% of what is normal for the snowpack. Wow. And so, yeah. And so obviously areas that don't receive snow aren't affected by

the snowpack. So that would be like coastal California. But when we look at large timber fires, you know, big forest fires in the Sierra Nevada, the snowpack does play a role because that snowpack should melt slowly throughout the summer, that means that there's a lot of water, a lot of soil moisture for those mid-elevation forests. And this year, we don't have that. So I would think that we're going to see, if we do get ignitions in this year, Nevada, those fires could be more intense because there's no, there's no moisture there. Are you able to, with all these factors to create fire prediction systems, you know, that you put this factor, this factor, and we have a prediction? Yeah. So actually, that comes out of a agency called predictive services.

And what they're stating for this year is that June should be slightly normal for most of California, except for Northern California. July, all the mountainous regions are going to be above normal in terms of large fire potential. So that's kind of what the agencies, are predicting, which corresponds to what kind of what we're seeing, what we're thinking about. But there's also other prediction systems that are really related to how we can use high-resolution weather forecasting to model fire behavior if an ignition were to occur. And we interact with other agencies. So it's not just us. It does this. This is a statewide program. All the utilities have a fuel sampling program. For example, PG&E, they have like 26 sites

that they sample twice a month. And so, looking at some of their data and look at some of our data, it's all about the same. Across the state, Northern California and Southern California, our fuel moisters are lower. So if there's an ignition, if there's a fire, it could be severe. But again, we have to have, you know, generally our most severe fires are associated with large wind events. And so without the wind, you can still get a big fire because there's a lot of heat release. And this is something that fire behavior researchers look at, like whether it's a wind-driven fire or what we call a plume-dominated fire. And so there's a lot of differences.

And I think no matter what, if there's ignitions, we will have some pretty big fires this year. Do you have any interaction with the power company? Because aren't they the source, some of those power lines of the wildfires? We do. We actually have a lot of interaction with them. We work with them in a lot of ways. So we actually have contracts for research. We're actually working on a new fuel moisture model for the utilities and using satellite data. We sample the fuels, but there's also new technologies coming online where we can actually look at them using satellite data that gives us a better view versus our point measurement. So that's something that is kind of on the forefront of the research and hopefully that's going to be implemented more widely across the state, but that is used by the

utilities. They have a big reason to have the top science because they have to either shut off their power through public safety power shutoffs, and they have to be aware of what's called situational awareness, like what's going on around their transmission lines. What are the fuels like? Is it going to be windy? They have a lot of sophisticated models and scientists that are a large team of scientists that are looking at this problem daily. Wow. Well, we'll have to just come back and check in on you later and see how that's all going. Yeah, let's see how it happens. I mean, again, you know, things could turn. We could have a slightly cooler summer, and that could really have a positive impact on our fuels and fire behavior. So, you know, we have to hope for the best

and see how things pan out. But yeah, I think Californians need to be cautious this year. Good words to end on, Craig. Thank you very much for taking time to be with us today. Well, thanks for having me. Craig Clemens, professor and director at the Wildfire Interdiscipline Center that's at the San Jose State University in San Jose, California. The California wildfires are the ones that we often hear about, but wildfires occur in many other spots, including in forests above the U.S. Canadian border and near the Arctic Circle. A group of researchers wanted to know how these fires affect the northern forests and how this impacted their ability to store carbon, and of course that means their influence on

climate change. Their results were published in the journal Nature Climate Change. My next guest is one of the authors on that study. Jonathan Wang, a postdoctoral scholar in Earth System Science at the University of California, Irvine. Welcome to Science Friday. Hi, Ira. Thanks. John, what are these northern fires like and how are they different from the ones in California? The forests in the far north are actually quite different from what we're used to seeing in California. So, for example, in California, the fires tend to be, they can be pretty big, but they're usually suppressed. Humans go in and try and prevent the fires from raging too large and causing damage to property and to livelihoods. Whereas in the far north, the forests are so vast and remote that these fires usually don't get attention for a long time.

And so they're just allowed to burn for quite a long time and over in quite a large area. I would say like two or three times the size of the fires I would see in California. They occur in the far north pretty regularly. How do they get started? I know in California we talk about bad power lines or people dropping a cigarette butt, but in these northern fires, how do they get started? Yeah, so the northern fires, they're typically started by lightning strikes, right? Because there aren't that many people living up north.

And so there aren't as many opportunities for campfires or power lines to really cause damage. And so what climate change has been doing has been increasing the likelihood or the incidents of lightning strikes in general. And so that's been leading in part to some of the increased occurrence of large fires in the far north. So then how are these fires impacting these forests? So the forests in Canada and Alaska, they're primarily dominated by this. species of trees called the black spruce. And so these black spruce trees are pretty dry. They're pretty flammable. When fires occur throughout a forest in the north, it tends to burn pretty severely, tends to almost completely torch the forest. And so any carbon that was stored in the above-ground

components, so we're talking like in the leaves or the branches or the trunks of these trees, they're totally annihilated. At the same time, carbon that's stored in the soil burns as well. And so So the Far North is unique in having very dense carbon stores in its soils. And so these increasing fires are starting to threaten these soil stores. One interesting aspect, though, that we found is that after a fire occurs, there's a lot of, let's say, regrowth or chance for regeneration after the fire. And so our study looked at trying to understand how this balance between post-fire regrowth and the initial fire-induced loss, how they add up, how they balance.

balance. And we're finding that because fires are increasing in size and extent and intensity in the far north, forests aren't getting a chance to recover all the way before the fire strike again. Just a quick note, you're listening to Science Friday. And so what is the impact of all of this on carbon sequestration, the absorption of CO2, and climate change? In the far north, we've seen that there's a lot of so-called greening, And we think that because of climate change, because of warming or increased CO2, fertilizing the forest, that there's hope that there might be a net absorption or sequestration of carbon dioxide into northern ecosystems. But what we're finding is that these forests that have been affected by these fires,

the carbon emissions from these fires are really offsetting nearly half, a third to a half of the carbon gained through just normal growth throughout the northern forests. And so these fires really impose, I guess, a strong suppression of the carbon sequestration potential of the far north. These northern forests, are they typical of northern forests around the rest of the world and having the same effect? The forests in Canada and Alaska are, as I mentioned, primarily black spruce. Now, the other far northern forests, for example, in Siberia or in Scandinavia, they're dominated more in Siberia by, tree species called Larch. And so these trees are slightly less slammable. So there's maybe some hope there that the fires don't impact them as much. Now that being said, we've noticed in the past

couple years that Siberia's experienced some of its most dramatic fire years. We've even seen fires survive through the winter and re-adignate in the spring. It's unclear still how much the fire impact in other parts of the far north are influencing the carbon cycle. What surprised you most about what you found in your research? I guess I was surprised by how limited the sequestration of carbon was in the far north. As I mentioned, there's this notion that the far north is greening, and we see this through certain satellite-based studies or certain modeling studies are suggesting that the far north should be greening pretty rapidly.

And so I was expecting to see a much larger carbon sink. What we saw was that about 400 ptrogams of biomass was grown in the Far North during these last 30 or so years. I was really thinking it would be much higher than that, maybe more like a thousand rather than 400. I was just surprised by how, you know, in fact, it felt like the Far North is almost neutral compared to what I was expecting.

You mentioned before that you were surprised by the carbon sequestration that you found or the lack of it. You were surprised by the rate of greening that was not happening at the rate that people thought scientist thought. What does this all mean then for climate change models or predictions that may take this into account and maybe erroneously? Yeah. So we actually, in our study, we compared our carbon sequestration numbers with Earth system models, these computer-based models would

simulate over the same time in the same area. And those models tended to overestimate the growth of biomass by a factor of three. It's a lot bigger. And what we found is that a large reason for that, is that these models do a pretty poor job of simulating fire in Far North. Most of the models didn't even bother to have fire as an explicit process, and the ones that did totally did not capture the rates or trends of burning that was occurring in the study domain. And so that means we have to remodel, right? Yeah, that means we have to improve our models.

Our understanding of fire is really, as you might guess, driven by what happens in temperate ecosystems, like in California. Yeah, but like I mentioned, the fires in the Far North are pretty different. And so if we are expecting the Far North to sequester carbon and to sort of try and maybe offset some of our fossil fuel emissions, we may have to revise how we feel about how much work the Far North might do in helping us prevent this climate crisis. That's really interesting and good to know. Thank you for bringing that to our attention.

Thank you. Jonathan Wang, a postdoctoral scholar in Earth System Science at the University of California, Irvine. After the break, when we come back, how farmers are helping keep polluting nitrogen out of the Missouri River system. It's a new spin on an old process that you're going to want to hear about, so stay with us. This is Science Friday. I am I. Rofleto. Toxic algae blooms are a now common site in the Gulf of Mexico. Warmer ocean temperatures provide the perfect conditions for algae to grow out of control. The other ingredient fueling toxic algae growth is nitrogen.

Drainage water from farms up and down the Mississippi River, which empties into the Gulf, is ferrying fertilizer ingredients straight into the marine ecosystem. And while farmers can't solve warming ocean temperatures on their own, they're testing out a new way to keep nitrogen out of the Mississippi River system. Cyphrates Katie Feather is here to talk more about the solution farmers are finding. Hey, Katie. Hey, Ira. All right, tell us what that solution is.

So the solution is called a denitrifying bioreactor. Can you guess what that is? A denitrifying bioreactor sounds like something out of Iron Man. It does, doesn't it? But a bioreactor is just a reactor where biology is doing the work, in this case, bacteria. So cool. Yeah, it is. Except it's not happening in this big factory-type place.

It's basically just wood chips in a trench. You know, when you say wood chips in a trench, you know, I think I know what that is. I used to use that process in my saltwater fish tank to remove deadly nitrogen from the water. Tell everyone how wood chips in a trench plus bacteria can extract nitrogen from the water. Yeah, it was kind of hard for me to visualize, too, but Dr. Laura Christensen, the lead author on this recent study about the bioreactors, had a really great way of describing it. If a farm had a bioreactor, you wouldn't see it actually in the field where we're growing crops. We call this an edge of field practice. And so as you'd imagine, a bioreactor would be on the edge of the field, catching the drainage water underground, coming from the field.

And then, you know, in some cases, you wouldn't see anything at all because the wood chip trench sometimes is covered up with a soil cap. And sometimes you would actually see the wood chips coming up to the surface. But it would be a pit three or four, maybe five feet deep, filled with two, three, four feet of wood chips. And then the bioreactor itself, I would say, varies in length and width between probably about 10 to 15 feet wide, generally. And usually anywhere from 40 to about 80 or 100 feet long, depending on how much drainage water is coming into the bioreactor. So why do farmers have all this runoff happening in their fields in the first place, especially in the Midwest? Good question. So, you know, if you think about arid environment or out in the western parts of our country, they might have irrigation systems that are very essential for them to be able to grow crops and grow food. But here in the Midwest, we have plentiful rainfall. We're very fortunate for that. But our soils, our fields stay too wet. Rather than having not enough water, we have too much water. And so a critical part, an essential part of how we do agriculture is the practice of tile drainage. The tile drainage, the tile drainage. The tile drain. allow our fields to dry out, especially in the spring, which is important, especially right now,

as we're hot and heavy into planting season here in Illinois, we need to be able to get our tractors into the field to be able to plant. And obviously, if the field is too wet or too muddy, we can't do that. And so tile drains help dry our fields out in the spring so that we can get into the field to plant. And then tile drains also allow the soil and the fields to be dry enough for plants to grow so our crops don't get drowned out during our wet springs. But they also serve as a conduit for moving nutrients like nitrogen and sometimes phosphorus from our field where we need those nutrients for plant growth to downstream waters, like you mentioned, the Gulf of Mexico.

So how do the wood chips extract nitrogen from the water? Tell me about that process. Such a good question. And the way you worded it, wood chips extracting nitrogen, that's not exactly how bioreactors work. Bioreactor's work by enhancing a natural process, a natural part of the nitrogen cycle called denitrification. Now, you mentioned this bioreactor sounded very complicated like something out of Iron Man, but it is actually simple because we're just enhancing a natural process that's been happening all around us for millions and millions of years on its own. And that's the process of denitrification. The process of denitrification is done by

natural little denitrifying bacteria that are good bacteria living in the soil all around us, like I said. And these bacteria convert nitrate, which is a form of nitrogen, into di-nitrogen gas, which is a stable, benign gas that makes 78% of our atmosphere. And so in a bioreactor, we have these denitrifying bacteria that are native and natural in our soil. these denitrifying bacteria live on the woodchips. They eat the carbon in the wood chips as their food. So we're providing them like a super buffet of carbon to eat and fuel them. And then as the nitrate in the water flows by them, they convert that nitrate to nitrogen gas.

And the bacteria, they live on a certain type of wood chip or they're just hanging out on all wood chips. The amazing thing about this process with these wood chip bioreactors is that there are many bacteria that do this process of denitifurification. And so, you know, they're not picky. And so we generally use really any kind of woodchip, the actual physical properties of the woodchip, like how big the woodchips are, tend to be a little bit more important for us compared to like the kind of tree that the woodship is from. And so there's a reaction happening here. are there any byproducts of this reaction that we should be concerned about? Well, you're right. It is a reaction. And the reaction is a conversion of nitrate, which is a form of nitrogen, into dinitrogen gas, which is into, which again, forms 78% of our atmosphere. Dignitrogen gas is a stable, benign gas. It's not a greenhouse gas. But I will say there is a byproduct that we do talk about a lot when we talk about bioreactors.

And that potential byproduct is nitrous oxide. So sometimes when the bacteria maybe aren't as happy, maybe when the water is flowing too fast for these denitripein bacteria to do their job, or if the water is especially cold, under certain conditions, these bacteria are a little less happy, I would say. And there's the risk that we produce slightly more nitrous oxide than we would otherwise. So nitrous oxide, as your listeners will know, nitrous oxide is a greenhouse gas. And so we are concerned about the potential production of greenhouse gas from bioreactors. But the good news is that a number of research groups have looked at this question.

Are bioreactors just transforming a water pollution problem into an air pollution problem? And the resounding results from a number of groups looking at that question is that, no, we're not producing a huge amount of nitrous oxide from our bioreactors. In general, because we're designing these bioreactors very specifically, to do this one very specific job of converting nitrate into dinitrogen gas. In general, we have denitrification operating very efficiently, and so we're not producing a lot of nitrous oxide. And so that's a really good story. There's more work to be done, more research to be done on that.

But we know with good confidence that we're not producing a huge amount of nitrous oxide with this water cleaning technology. What about the impact of these bioreactors? much nitrogen are they removing? If a bunch of farmers were to adopt these bioreactors, would it totally take care of the problem? Like, how many farmers would you need to do that? That's such a good question. The scale of our water quality challenges across the Midwest, across the upper Mississippi River Basin is going to require every conservation practice that we have in our toolbook, and it's going to require at least one conservation practice being applied to

every acre that we have. The scale of water quality challenges is an immense challenge for us in the Midwest. So bioreactors remove anywhere from 20 to about 40% of the nitrogen in the water that you would otherwise send downstream. Our goals for the Mississippi River basin to reduce the hypoxic zone in the Gulf of Mexico are to reduce the amount of nitrogen and phosphorus that we send downstream by 45%. And so a bioreactor, you know, even if every single farm, every single field had a bioreactor, we still wouldn't be meeting that goal. And so that's why I say we need every single practice in our toolkit to make significant headway towards meeting those ambitious 45% nitrogen and phosphorus loss reduction goals in the Midwest. And so we're talking about things like improved

fertilizer management, making sure we soil tests, making sure we do cover crops is one of our best infield practices. We also have practices that have been in our toolbox for a long time, like wetlands or constructed wetlands, and those are some of the best practices that we have. But every practice is different. Every practice has its own cost, benefits, limitations. And so bioreactors is certainly one of our favorites, but it won't work for everyone. I want to bring in someone you've been working with, a farm owner, Shirley Johnson, who just implemented her wood chip bioreactor late last year. Shirley Johnson, welcome to Science Friday. Thank you, Katie. I really appreciate us. How did you find out about a denitrifying bioreactor? So my sister and I own the farm together.

We actually inherited the farm from my father who passed away in 2019. And we are both environmentalists and we want to be good stewards of the land. That includes not only soil health, but also the water exiting the farm. We wanted to make sure that we were not adding more pollution in the form of nitrates to our local streams and then ultimately the Illinois River, the Mississippi River, and the Gulf of Mexico, where there's a big dead zone, as you know. So we were looking around for water conservation practices, and we found several, and we weren't exactly sure which was appropriate for our situation. So we contacted the NRCS, the Natural Resource Conservation Service. and told them that we were interested in trying to clear nitrates from the runoff from the fields.

And NRCS advised a bioreactor. And that was one of the things that we had found when we were looking into this as well. And we were recommended that that was the best thing for our situation. So we had a bioreactor installed. And how was the implementation process for you? A pit with wood chips in it seems very straightforward, but I gather it's not as simple as just digging a pit and putting some wood chips in it. That's right. That's right. So the NRCS actually did the design. They have engineers skilled at doing designs like this. And so I found a contractor who had actually built one before. I was happy to have someone's experience building bioreactors. And so he came out and built it. And it does involve control valves and hooking into the existing tile line. But the main part of it is the pit with wood chips in it that the water runs through.

How do you think more traditional farmers would feel about a denitrifying bioreactor? Do you think someone like your father would have been into the idea or shied away from it because of the investment? No, I think he would have been interested in it. And the reason I say that is dad was always a very progressive farmer. So, for example, he was one of the first farmers in the area to do no-till. And that, of course, is a way to help reduce soil erosion. So he was always interested in the latest, the newest practices, and one thing my sister and I wanted to do was carry on his legacy. But if he were alive today, I'm sure he would be happy to see the farm being used for something that hopefully has a bright future for everybody.

This is Science Friday from WNYC Studios. I'm Katie Feather talking today with my guests, Dr. Laura Christensen, assistant professor of water quality in the Department of Crop Sciences at the University of Illinois at Urbanus. Champaign, and Shirley Johnson, a farm owner in Peoria County, Illinois. What about other people in the ag world? Do they know about this? When you bring it up in conversation, are they confused by it or dismissive of it or excited by it? That's an interesting question. So I don't think it's that well known, but it's interesting because we cited the bioreactor right next to the road. And the NRCS engineer was there looking at it one day and he said that several farmers pulled off and said, hey, what's going on here? So people

are curious. They see it there. They don't necessarily know what it is for sure. But they are curious. And I think that once we get more data and once there's more information from these bioreactors, it will be able to be something that can be implemented on more farms. But I would emphasize that for me as a farmer, it's not going to increase my yield. It's not going to improve my soil health. But what it does is my downstream neighbor is going to be getting cleaner water. The streams, Illinois River, the Mississippi River, the Gulf of Mexico, the dead zone in the Gulf of Mexico. The idea is to be able to reduce the damage downstream. So I feel that I need to take responsibility as a farmer for the effluent from my farm.

Well, thanks so much for joining us today. Thank you so much. Shirley Johnson is a farm owner in Peoria County, Illinois. Laura, I want to get back to you. If we could get the implementation of the bioreactor to be simple enough, then the barrier of entry for farmers would be really low, and hopefully they'd be more likely to use one, right? Yeah, I think there are a number of barriers facing our implementation

and our really our ability to scale the adoption of not just bioreactors, but a variety of conservation practices right now. You know, for bioreactors, in particular, I think one of the first things that we're dealing with still is that there's somewhat of a distrust or a lack of understanding that tile drainage does contain nitrate. We've made a lot of headway on doing, you know, education about the fact that tile drainage does contain nitrate. We are losing nitrogen in the form of nitrate from our field through our tile drains.

But one of the challenges there is that nitrate is a disdain. dissolved pollutant, and so it's clear. So tile drainage water often tends to be very, very clear. It looks very clean, but in fact, it does contain nitrate. And so that's really where we're starting just talking about our nitrogen loss, where nitrogen is coming from in our fields, and how it gets moved through tile drains. You know, and then with bioreactors in particular, it is still a relatively new practice. I would say we've been promoting bioreactors for roughly a decade. And so in terms of, you know, we've been talking about things like conservation tillage, for 20, 30, maybe 40 years. And so it takes some time just for education about the practice

and how the practice works. Let's say a farm owner is out there listening to this and is really interested in getting a bioreactor on their land. What's the best way for them to go about seeing if this is the right thing for them? The best way, the best first step is to go to your local natural resources conservation service, USDA NRCS office. The Natural Resources Conservation Services are premier federal agency that handles agricultural conservation practices. And so there is cost share or incentive payments available for getting some of the bioreactor paid for through USDA environmental quality conservation programs. And so starting with your local NRCS office is absolutely the best place to start. We'll have to leave it there.

Thanks so much for coming on and sharing more about this with us. Oh, it's my pleasure. Thank you so much. Dr. Laura Christensen is assistant professor of water quality in the Department of Crop Sciences at the University of Illinois at Urbana-Champaign. For Science Friday, I'm Katie Feather. Oh, one last thing before we go. We're still going strong on the SciFright Book Club, reading Lenore Newman's book, Lost Feast, Culinary Extinction, and the Future of Food.

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