How We Use Land Contributes To Climate Change

17:37 minutes

white cattle graze in the grass among burnt trees
Burned pastureland in the Amazon. Credit: Frontpage, via Shutterstock.

From cutting back on fossil fuels to planting a million trees, people and policymakers around the world are looking for more ways to curb climate change. Another solution to add to the list is changing how we use land. The United Nations’ Intergovernmental Panel on Climate Change, or IPCC, released a special report this month that emphasized the importance of proper land management, such as protecting forests from being converted to farmland, has on mitigating climate change. 

Cynthia Rosenzwieg, a senior research scientist at NASA Goddard Institute for Space Studies and one of the lead authors of the report, will join Ira to talk about ways we can use land to reduce the amount of greenhouse gas in the atmosphere.

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Segment Guests

Cynthia Rosenzwieg

Cynthia Rosenzwieg is a senior research scientist at NASA Goddard Institute for Space Studies.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow, from cutting back on fossil fuels to planting a million trees. People and policymakers around the world are looking for more ways to curb climate change. Well, another solution to add to the list– how we use land. The UN Intergovernmental Panel on Climate Change, the famous IPCC, released a special report this month that looks at the impact land management has on climate change. And here to tell us about the report is Cynthia Rosenzweig, a senior research scientist at NASA Goddard, for Space Studies and one of the lead authors of the report. Thank you for joining us today.


IRA FLATOW: Give me a few of the main takeaways from the report.

CYNTHIA ROSENZWEIG: For the report overall, the main takeaway is that climate and land are strongly connected, and that land has an enormous role to play in solutions to climate change.

IRA FLATOW: In both how we can recover from what we’ve done, and also actually exacerbating it? Give me an idea.

CYNTHIA ROSENZWEIG: Sure. Well, first of all, let’s just realize, so the land is 30% of the global– global surface area. But the 7 and 1/2 million people, like us, like you and me, live on the land. So we have

IRA FLATOW: A billion people.

CYNTHIA ROSENZWEIG: Billion, billion, billion. 7 and 1/2 billion people, and projected to go up to almost 11 billion by the end of the century. And so we are all strongly connected to the land. So that’s why I think this report has a really strong message for, not only the policymakers, of course, but for everybody who’s so connected to the land. For example, 80%, over 80%, of the food that we eat comes from land based sources.

IRA FLATOW: Give me an idea of how the land interacts with the climate. What is going on in the soil, for instance.

CYNTHIA ROSENZWEIG: Yes. So, the soil is an enormous repository of carbon. And one of the main ways that we can help to solve climate change– the land can’t do it all, there’s a lot of things that we have to do with fossil fuels as well but– the land can be used as a sink for soil carbon. That’s called soil carbon sequestration.

IRA FLATOW: You mean soaking up the CO2.

CYNTHIA ROSENZWEIG: Soaking up CO2 from the atmosphere, excess CO2 from the atmosphere. It can also be used to grow bioenergy, which we need to substitute for fossil fuel. But we have to be careful that we don’t run into a competitive situation between food production and solving climate change. So one of the things that the authors of the report worked on a lot is looking at how we can do both, with the land. Grow enough– grow bioenergy but, at the same time, grow enough food so we make sure that we are able to feed those, nearly, 10 something billion people in 2100.

IRA FLATOW: Our number, 844-724-8255. Our phone number again, 844-724-8255. You can also tweet us @scifri. One of the issues that the report addresses is converting more and more forest land into farmland. And we’re seeing that in the Amazon rainforest. We were just talking about that. Tens of thousands of fires have been started, this year, to burn out the forests for agriculture. And that must be an incredible hit to the environment.

CYNTHIA ROSENZWEIG: Yes, it is. Because when those fires are started and burn, they burn up. When they are on the old growth forest, in particular, then there’s an enormous hit of carbon into the atmosphere. And then it takes a really long time to get that back. So it is– that is a major source of greenhouse gas emissions. But we also, by the way, there’s also air quality and health effects, of course, from the smoke, as well, that we’re seeing in the news, very much in the news, today. So what the report is really saying is that, these different land uses, the importance of the natural ecosystems, such as the Amazon Rainforest as well as food production, they can co-exist. But we need to, wisely, manage them. And we have to start doing that soon. And we’re going to need to scale up those solutions, rapidly.

IRA FLATOW: But that means you’re going to need international cooperation, right?


IRA FLATOW: Isn’t that a challenge? Well, the, certainly, the Intergovernmental Panel on Climate is a body organized by the United– it’s by if by the United Nations. And so this report is approved– the summary for policymakers, which we just got back from Geneva from the approval session with the delegates from the countries. And the scientists and the delegates of the countries work together to bring forward together these key– this key knowledge that can be used to find the solutions.

IRA FLATOW: Well if all these countries, you know, the history is full of wars and things that are fought over oil or treasure, or riches and people, saying, you know, if you do this, you we don’t get enough of that. Why is there not more international pressure on Brazil, for example, for these fires? They’re going to affect the rest of the world’s life, they the lungs of the earth. Why are we not seeing more pressure from all the countries that are going to have to live in this, on the planet, from years on, to stop these fires. I mean, you know?


IRA FLATOW: Is this– is this a diplomatic nicety that, you know, no one wants to take on?

CYNTHIA ROSENZWEIG: Well, Ira, I’m a scientist. And what our role is to really provide the knowledge that is needed, so that other countries can make their own decisions. That’s really how the Paris Agreement for climate change is really organized, that the commitments are nationally determined. And there’s many, many years of ongoing discussion to actually find solutions for the climate change challenges. And that’s what this– and the report offers so many of them.

IRA FLATOW: Give me a few examples of what some of those are.

CYNTHIA ROSENZWEIG: Sure, absolutely. So I’m going to talk about the food part, because I was the–

IRA FLATOW: Food’s– we’re all going to have to eat.

CYNTHIA ROSENZWEIG: We’re all going to have to eat. And we all do eat. And that’s why we all have a role to play. The report takes a food system approach. So it doesn’t just only look at the farmers now, in the production side. Of course, there’s important things that the production side needs to do to both reduce greenhouse gases by, for example, developing paddy rice, since systems that don’t produce as much methane. But at this– but this food system approach then allows us to look at the supply chains.

OK. From the field to the fork, there’s a lot of transportation, there’s a lot of energy use for storage, for grain drying. These are some very high– some of these are very high energy and high fossil fuel using processes. And so we can– we need to look and see how, with a supply chain, as well. But the part then, also, that now this approach, food system approach, really enables us to do, is look at the consumption side as well. What about people’s, two things– diets and, also, food, loss, and waste.

These are two areas that many people have choices about. Not everybody in the world has choices about the food we eat, and we have to be very careful that we’re not making any blanket statement for everybody. But for those who have food choices, the report def– the report brings forward that some diets, in particular those rich in red meat, are higher– have higher greenhouse gas emissions than more diets, plant based diets.

IRA FLATOW: Yeah because, they use also a lot of water as a resource, which is going to be getting scarcer.

CYNTHIA ROSENZWEIG: Yes, exactly. And so focusing on diets that reduce land use, and that have efficient water use, as well as lower greenhouse gases, this is really an important area that we can– that the report brings forward.

IRA FLATOW: You talked about the soil being a sink, a technical term for a sponge. And you have a sink, the water goes down the drain. Sink, [INAUDIBLE], lot of people have trouble with that word?

CYNTHIA ROSENZWEIG: Thank you. You’re the communicator.

IRA FLATOW: But what about having– we’ve tried to talk also about what farmers can do to grow different kinds of crops, or maybe in the off season, what to do with their soil. What are some of the suggestions here?

CYNTHIA ROSENZWEIG: Oh, yes, surely. So there are cover crops. So for a long time there, some farming systems would actually– and this is, I think, part of the problem in Brazil right now, with the burning– so they would burn the residues of the crops and then, and sometimes, even plow up and have just that bare soil. Well that plowing action is just basically providing conduits, pathways, for carbon dioxide to be emitted from the soil. If farmers use cover crops, especially, for example, legumes that provide nitrogen to the soil, they’re simultaneously reducing their greenhouse gas emissions. And they are also enriching the soil for their next crop.

IRA FLATOW: Our farmers must be receptive to these ideas, right?

CYNTHIA ROSENZWEIG: Well, you know, farmers are stewards of the land. And when we think about how farmers can help– and with the report also, we had a great team of policy specialists and policy experts. Again, not telling any country what to do. But one of the things they brought forward was things like incentives for farmers to store up carbon, using their sponge– their soils as sponges for carbon.

IRA FLATOW: I don’t understand why an incentive? A good incentive is your grandchildren.

CYNTHIA ROSENZWEIG: I agree with that, long term.

IRA FLATOW: Why do you need to have such monetary incentives all the time just to know, wouldn’t you like to leave something over for your grandchildren?

CYNTHIA ROSENZWEIG: Absolutely. The long term intergenerational equity, we call that, is very important. But you know we need to get going on these solutions, now.

IRA FLATOW: You think?

CYNTHIA ROSENZWEIG: Are you kidding?


You know, so, this idea of what can we do now, such as soil carbon sequestration. But you know what? Just doing a better job growing crops, because then the roots will store more carbon.

IRA FLATOW: Do we have– I mean, can we do both? Can we feed a growing world, and also be a good steward?

CYNTHIA ROSENZWEIG: The report gives a resounding yes to the answer– as the answer to that question. Not all the scenarios who– as scientists, we use a lot of scenarios into the future. Not all the scenarios have this. If we do bioenergy and very, very large scale mono-crop ways, not paying attention to the environment, we can run into competition between bioenergy for solving climate change and food production.

But if we work on sustainable land management, of both the bioenergy cropping systems, for example, with the second generation of with switchgrass, those C4 grasses, warm season grasses, as well as being very good stewards of our food production, the report comes forward and says yes we can. But we need to start now. When we need to start soon. We need to scale up, and we need to do this really carefully.

IRA FLATOW: I’m Ira Flatow. This is Science Friday, from WNYC Studios, talking with Cynthia Rosenzweig, a senior research scientist at the NASA Goddard Institute for Space Studies, one of the lead authors of the new IPCC report on climate change, about agriculture. I think we have a couple of questions. Yeah. Let’s go to the phones. Well let’s go to Greg in Baton Rouge. Hi, Greg.

CYNTHIA ROSENZWEIG: Hey. How are you doing?

IRA FLATOW: Hi there.

GREG: I just wanted to know if that report touches on aquaculture at all. There are a lot of stories out there about the comparative efficiency and the sustainability of aquaculture versus traditional animal crops. And I just wondered if you guys had a chance to delve into that.

IRA FLATOW: Dr. Rosenzweig, yeah?

CYNTHIA ROSENZWEIG: The report looks at aquaculture on land in freshwater situations, because there is another special report coming out of the IPCC which is going to be, I think, coming out in September, which deals with oceans and the cryosphere. So the marine aquaculture is handled there. But we did look at– in our food security chapter, we included aquaculture. And it certainly is, and can play, an important role.

IRA FLATOW: That’s fish farming.

CYNTHIA ROSENZWEIG: Yes, fish farming.

IRA FLATOW: What about algae, or some alternative sorts of foods? Did you look into those?

CYNTHIA ROSENZWEIG: Yes, we did. In particular, on the meat question. So there are now beginning to be technologies that are looking at cultured meat. They are looking–

IRA FLATOW: Phony meat. I had a great phony hamburger, the other day.

CYNTHIA ROSENZWEIG: They’re looking at cellular, that’s the cultured meat from cellular development. And we even– we also looked at the literature on insects, because insects are high protein sources of food. So what we found was, this is early days for the work on these alternative protein sources. They may play a role in transition. Right now, it’s hard to say what their carbon footprint will actually be. And that’s what in all– in any kind of food production system, you have to look at what the carbon footprint is.

IRA FLATOW: It could be pretty strenuous to find out exactly what that is. Let’s go to a tweet. Diana, on Twitter, wants to know about the potential of regenerative agriculture. You know what she’s talking about?

CYNTHIA ROSENZWEIG: Well, we look at– there’s a whole set of agricultural techniques that have been developed under different rubrics. One of them is conservation agriculture. One is agroecology. One is climate smart agriculture. And we do, in the report, look at that. I’m not sure we looked at regenerative, specifically. But there are all these great techniques that are coming together under these groups who are following these. And those can very much play a role. In particular, diversification in agricultural systems. Getting away from this monoculture commercial, industrial farming that is one end of the spectrum. But diversification can help, in regard to being resilient to the climate changes. Because increased extreme events We also have to–

IRA FLATOW: It’s happening, and we’ve got to–

CYNTHIA ROSENZWEIG: Exactly. So not only do we have to be feeding more people, we have to be reducing our greenhouse gas emissions from our agricultural systems. But we also have to be getting those to be more resilient to the extreme events.

IRA FLATOW: Dr. Rosenzweig, thank you very much for taking the time to be with us today. Cynthia Rosenzweig, senior research scientist at NASA Goddard Institute for Space Studies, lead author on the new UN IPCC report on agriculture. We’re going to take a break. When we come back, we can talk about the iconic features of the summer night skies– fireflies. Everything you wanted to know about them, we’ll talk about it after the break. Stay with us.

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