Science Friday - Carbon Cost Of Urban Gardens And Commercial Farms | Why There's No Superbloom This Year

Episode Date: April 17, 2024

Some food has a larger carbon footprint when grown in urban settings than on commercial farms, while for other foods the reverse is true. Also, what’s the difference between wildflowers blooming in the desert each spring, and the rare phenomenon of a “superbloom”?The Carbon Cost Of Urban Gardens And Commercial FarmsIf you have a home garden, you may be expecting that the food you grow has less of an environmental impact than food grown on large commercial farms. But new research throws some cold water on that idea. A study led by scientists at the University of Michigan examined 73 small urban gardening sites across the U.S., the U.K., France, Poland, and Germany, and found that food grown in urban settings produced six times more carbon emissions per serving than commercially grown food. The bulk of these emissions (63%) came from the building materials used for items like raised garden beds.However, there are some foods that have a smaller carbon footprint when grown at home. They include crops like tomatoes and asparagus, which sometimes need to be flown long distances or require power-hungry greenhouses when grown commercially.Jason Hawes, PhD candidate in the School for Environment and Sustainability at University of Michigan and lead author of the study which was published in Nature Cities, breaks down the results of the research with Ira. They talk about how urban farmers have responded to the findings, the positive social benefits of community gardens, and what home gardeners can do to lessen their carbon footprint.Why There Won’t Be A Superbloom This YearIn California, wildflowers are in bloom.Last year, there was a superbloom. Though there’s no official criteria, a superbloom is when there is an above average number of wildflowers blooming, mostly in desert regions of California and Arizona. It’s an explosion of color in regions that typically have sparse vegetation.About a month ago, a few news articles hinted that maybe, just maybe, we were in for another superbloom year. Turns out we’re not.Who decides when there’s a superbloom anyway? And why did this year turn out not to be a superbloom after all?To answer those questions and provide an update on the state of California’s wildflowers, SciFri producer Kathleen Davis talks with Dr. Naomi Fraga, director of conservation programs at the California Botanic Garden, and research assistant professor at Claremont Graduate University.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

It turns out that the food you grow in your backyard might not be that climate-friendly after all. Are you really telling me that if I build a raised bed and I grow the food, that that has a higher carbon footprint than shipping something in from a distant farm? And the short answer is yes. Hey, Twentee, April 17th, and you're listening to Science Friday. I'm Cyfry producer, D. Peter Schmidt. If you have a backyard garden, you likely want the food you grow to have less of a carbon footprint than the food grown on large commercial farms. Well, unfortunately, new reasons. Research shows that food grown in urban settings produces six times the carbon emissions per serving

compared to commercially grown food. So where's this extra carbon coming from and what can home gardeners do to reduce their footprint? We'll get to that in a minute, but first, guest host Kathleen Davis finds out who decides if there's a super bloom and why there wasn't one this year in California. We're talking about wildflowers. Head out to California and they are blooming. Last year, you may have heard about a super bloom, which is when colorful wildflowers cover the barren desert regions of the state. About a month ago, I was excited to read a few news articles hinting that maybe, just maybe, we might be in for another super bloom year. It turns out that we're not quite there yet. But it made me think, who decides when there's a super bloom anyway?

And why did this year turn out to not be a super bloom after all? joining me now to answer those questions and update us on the state of California wildflowers is my guest. Dr. Naomi Fraga, Director of Conservation Programs at the California Botanic Garden and research assistant professor at Claremont Graduate University in Claremont, California. Dr. Fraga, welcome to Science Friday. Thank you for having me. It's great to have you. So explain to me what is a super bloom, actually? Well, there's no strict definition of a super bloom. It's really a term that's used to describe an above average wildflower year. And so what is an average wildflower year? Well, that's really hard to describe. So it's very difficult to actually quantify super bloom status. When we look at the landscape, what we see in a super bloom are hundreds or thousands of acres of wildflowers simultaneously blooming.

And so the landscape just explodes into color. And we oftentimes have lots of different species coflowering. And it's just a huge, beautiful biological event. I mean, who makes the decision then if there's a super bloom or not? Is there some sort of like regulatory super bloom council out there? Right. Yeah. All of the botanists, we huddle in a room and form a committee.

No, based on people's past experiences with wildflower displays, we can kind of assess what is pretty typical in the environment and what seems more extraordinary. And so while there is no formal declaration, you know, as to when a super bloom happens or when a super bloom is not happening, I think last year we all agreed that there was a super bloom or for the most part botanists agreed. For one is we came out of a very significant drought. And so getting, you know, those series of atmospheric rivers was just really, filled up our souls, you know, and also the flowers did as well. And so I think a super bloom is as much of a biological phenomenon as it is sort of a cultural and an emotional connection with nature.

And so while this year maybe doesn't rise to the same scale or intensity of the flower bloom last year, it's still going to be incredibly beautiful. We still got a fairly significant amount of precipitation in California, which means we're going to have a very significant amount of precipitation in California, which means we're going to have a really nice bloom year. And a really nice bloom year is very super to many people. And so, you know, super bloom or not, it's still a wonderful time to get out and explore flowers. So despite it not being a super bloom, that doesn't mean that there aren't, as you say, some very beautiful and abundant wildflowers to see this year. Can you kind of talk us through what some of those species are? Yeah, there's a lot of different plants out there blooming right now. One of the

The plants that I've seen quite a bit of is desert gold. Its scientific name is Jurea Kinescence, and it's in the sunflower family. This is a plant that's very characteristic of the Mojave Desert and goats into the Sonoran Desert as well. It is making huge gold fields, and it's really incredible. Another plant that I have seen blooming is the brown-eyed primrose and the yellow sun cups. These are both in the evening primrose family. They're both in the genus chylismia.

the desert gold and the primroses benefited both from our summer storms and our winter storms. And it's really been an unusual phenomenon where some of these spring wildflowers actually germinated in the fall season in response to the summer rain and have overwintered and are still going, you know, seven months later here in the spring. So there are many very large and robust blooms out there. And I hear that you have a favorite wildflower, which is the monkey flower. That's not something that I've heard of, I have to say. What are monkey flowers? Tell us a little bit about them, why they're your favorite. Yeah, well, it's a group of plants that I study. So monkey flowers are in the Lopsied family, primacy, and they compose a very rich group of plants that

live primarily in California in Western North America. And so there are, you know, over 100 species. and I study a group of monkey flowers, many of which are rare. And even though they're considered rare, many of them make their own, what you might call many super blooms. They're very small plants, maybe some of them stand only an inch high. They're in this category that we call belly flowers. That means you have to get down on your belly to see them up close. And so in years where we have average to below average rainfall,

we oftentimes don't get very large displays of them, but in years of above average rainfall, we can get whole carpets of these monkey flowers. So it's really pretty spectacular. So I'm going to put my Cynic hat on for just a second. Wildflowers are obviously really beautiful, and it makes it makes it easy to care about them when they look so nice. But what is the role of wildflowers in the ecosystem? I mean, should we care about them, you know, beyond their aesthetic purposes? Wildflowers, while they are, you know, clearly a beautiful component of ecosystems, they also play a really important role, especially to wildlife and pollinators.

So in the Mojave Desert, we have this keystone species called the Desert Tortoise. The Desert Tortoise's primary diet is wildflowers, and it forages on desert plantain and desert primrose and bushmallow and all these really incredible wildflowers that people like to Google at. But also they're really important to pollinators as well. And as we know, pollinators are really at high risk with respect to climate change and other land use changes. And wildflowers provide really important pollen and nectar sources for them. And even though your expertise is in California, I would imagine that, you know, those benefits extend, you know, across the country, Midwest, East Coast, South, all those places.

Yeah, really across the globe. I mean, wildflowers are essential components of ecosystems, and they provide really important resources to wildlife. And they also provide us with a sense of place. I mean, the California poppy is such a characteristic plant that people think of when they think of California. And so they really help us understand where we're living. So what role does climate change?

play in wildflower blooms? Well, these wildflowers are really dependent upon rainfall and cues from temperature as well. And so with changes in precipitation patterns and increases in temperature, we might see that some wildflowers would be greatly affected where the right cues are not there to trigger their germination. We're also seeing some unusual patterns. Earlier, I mentioned that some of these wildflowers are germinated in the late fall. which is really unusual and that they have persisted through the winter season. So that is such an unusual phenomenon because most of those wildflowers usually germinate like in December and not in, you know, August.

And also the temperatures were so mild. They didn't get cold enough to kill off those wildflowers that they persisted over the winter months. So that was just something unusual that I had not personally observed before, that I'm really interested in seeing if I could find evidence that that has occurred before. But then also with increased drought, you know, we might not see some of these wildflowers for, you know, five or more years. And so they have mechanisms to deal with that. They can lay dormant in the soil. So they form a really massive seed bank and they can live, you know, many decades waiting for just the right

conditions. But those conditions might drastically change between the time in which they were born and when, you know, they might be able to germinate. So what can we do to protect these wildflowers? Well, there's a lot of things that we can do. One of the most essential things we need really is land protection. These plants need habitat. They need land to exist on. And so ensuring that we have areas conserved and preserved for the protection is really essential. In Southern California, a lot of development has already occurred, and we have whole preserves dedicated to these wildflowers, like the Antelope Poppy Preserve is dedicated to the California Poppy. Cresolplain is an incredible place to see wildflowers. And so when people go and visit these already protected places,

it's really important that we ensure that we steward those lands and provide the utmost respect to these ecosystems, and we don't trample on them, and we don't implement. their reproduction because they need to produce fruit, set seed in order for them to continue in future generations. Well, that's all the time that we have. I would like to make my guest, Dr. Naomi Fraga, Director of Conservation Programs at the California Botanic Garden and Research Assistant Professor at Claremont Graduate University in Claremont, California. Thank you so much for joining us. Thank you. This is Science Friday. I am Ira Plato. If you have a home garden like I do,

chances are you want the food you grow to have less of a carbon footprint than the food grown on large commercial farms, right? Well, unfortunately, new research throws some cold water on that idea. A study led by the University of Michigan, which examined 73 small gardening sites across five countries, found that food grown in urban settings produces six times the carbon emissions per serving compared to commercially grown food. So where is this extra carbon coming from? And what can we home gardeners do to reduce our footprint? And don't worry, there is some good news here as well. Here to fill us in on this is Jason Haas, PhD candidate in the School for Environment and Sustainability at the University of Michigan. He was the lead author on the study published in Nature Cities. Welcome to Science Friday. Hi, Ira, thanks for having me. You're welcome. Why did you and your team want to do this study? And what was the broad takeaway here?

So this project emerged from a broader assessment of the holistic impacts of urban agriculture on people, places, and the planet. And so among the things that we didn't know was the carbon footprint of urban farms and gardens that grew things in kind of a low-tech way that a lot of folks do, you know, in a Lama Garden, community garden, or even in their backyard. Right, right. So you went out and studied all these little plots of land. Right, right. So we worked with farmers and gardeners, actually, to try to understand what they were investing in their garden spaces, both in terms of time and resources, and then also what they were getting out of it, both in terms of food and social benefits. And we used those data to assess a variety of different kinds of impacts on cities and on people. and one of the last projects that came out of that data set was this carbon footprint paper, which, as you say, the headline maybe is a little bit alarming, but the good news is that we were also able to use that large data set that we generated to figure out what we could do better,

what we could do differently to support low carbon gardening in the future. Interesting. Yeah, because I was just getting my tomatoes ready for the garden and preparing my first attempts at asparagus. and you find that tomatoes and asparagus usually had less carbon footprint than commercial farm. So that's good news. And why is that? Yeah, that's right. That is one of kind of the main takeaways. So as far as we can tell, most urban fruits and vegetables have a relatively similar carbon footprint, at least on the sites we studied. But these sort of things you buy at a grocery store, for example, is much higher. So the examples that we cited in the paper, as you say, were tomatoes and asparagus, although there are plenty of other examples. And the reason those stand

out is because tomatoes in northern cities are often grown in greenhouses on their way to the supermarket. And asparagus is often actually flown in on an airplane because it spoils really quickly. We quantify something we call embodied carbon, which captures basically everything that goes in from, quote, cradle to grave. So from the very beginning of the supply chain, in this case, growing the food, to the very end, in this case, at the supermarket. So if we can start to replace some of those, then that is an automatic good even before we do the sorts of best practices we identified to lower the broader carbon footprint of urban ag. That's cool. Okay.

Let's talk about the major carbon footprint source of home gardening. What was that? So the big thing was what we call infrastructure. So we divided inputs into three categories. We had first irrigation water. And then we had supplies, which were the sorts of things you put into a garden every day. So, you know, fertilizers, compost. And then we had infrastructure, which is all the stuff that we build in order to grow food.

So it could be compost bins, could be raised beds. And what we found is that when you do build those, the carbon invested in those raised beds is actually a substantial portion of the carbon footprint of urban fruits and vegetables throughout the life cycle of a plot of land. So one of the TikTok responses that I saw to this article was someone getting really upset about the idea that they could buy tomatoes or any other crop that had a lower carbon footprint than they could grow in their backyard and saying, are you really telling me that if I go to the hardware store, I build a raised bed and I grow the food, that that has a higher carbon footprint than shipping something in from overseas or from a distant farm? And the short answer is yes, but the more kind of nuanced and interesting answer is if you think about where the wood and the nails and everything else that you used in that raised bed came from, it also got shipped in from somewhere distant, right? Is there an answer to this? Can I make it less carbon intensive by the way I build it? Yeah, absolutely. So the first is, if you're listening to this and you have an urban farm or an urban garden, please don't tear it out.

This article is not intended to discourage urban agriculture. It's just intended to highlight the ways that we can do it in a lower carbon way. And one of those ways is to keep growing food. So if you use a raised bed for longer, for example, if you use it for 20 years versus five years, you're going to grow about four times as much food, right? And so at the end of its life cycle, then that means that more food was produced per unit of carbon invested. Another thing that we identified, which we think is a really exciting opportunity for cities, is to use recycled wood or other materials as inputs to the garden.

And one of the really common examples of this is food waste that becomes compost. But there are other opportunities to recycle things like construction waste into the garden infrastructure. Yeah, you've mentioned the social benefits a couple of times, and that shouldn't be minimized, should it? I mean, that's an important part of having an urban garden is meeting everybody. Yeah, it absolutely is. We've found evidence for actual physical and mental health benefits associated with farming and gardening. There are lots of folks who talk about opportunities for building community resilience, right, and creating these sorts of social networks that stand up strong neighborhoods, which, of course, has opportunities for creating more secure food access in underserved neighborhoods in many cases. Yeah, fresh food out of the gardens instead of in a can. I know you have your own garden. You've said this. Has this made you reconsider any part of that to lessen your own emissions? I actually have to move in a few months. So I'll be building a new garden. And I'm going to do my best

to try to use recycled wood to construct that new garden because I think that's one of the really important things we can do right up front is invest in sustainability by finding reused materials to put in the garden. Well, I want to wish you a good look on your new garden. Thank you for taking time to be with us. Of course. Thank you for having me. And enjoy your garden this year, Iro. Thank you.

Jason Haas, PhD candidate in the School of Environment and Sustainability at the University of Michigan. He was the lead author on a study published in Nature Cities. And that's it for today. Lots of folks help make the show happen, including... Phyllisomeres. Kathleen Davis. Jordan Smudjick. Charles Bergquist.

Next time, the physics and biomechanics of baseball. I'm Cypher producer Dee Petersmith. See you then.