Which crops are most vulnerable to climate change, and in which places? 

[00:00:00] LHF: Hello, and welcome back to Today I Learned: Climate. In our last episode, we went on a whirlwind tour of our global food system—and how it both affects and is affected by climate change. We talked about changes in growing seasons, and extreme weather, and fertilizers, and—well, you should go listen to the episode, we learned a lot.

One thing we didn’t have time to talk about much, though, was… well, food. Yeah, the stuff that actually makes it to our plates. And our guest for that episode was Dr. Cynthia Rosenzweig, who leads the Climate Impacts Group at NASA with a specialty on climate change and agriculture —has a lot to say about food.

[00:00:50] CR: When we think about climate change and food, it brings climate change right into our kitchens and dining rooms. It's very close to us as people. These connections are strong and personal. Food is culture. Food is history, deeply, deeply ingrained and embedded in families and cultures, religions.

[00:01:17] LHF: So we’re bringing Dr. Rosenzweig back to tell us just a little more about the connections between the food we eat and climate change.

let’s start with some stories you may have heard on the news.

[00:01:30] News Clip 1: What if I told you the world is facing a global chocolate shortage? [skip] Scientists blame climate change, disease and a lack of water for a shortage in some of the biggest producing countries like Africa’s Ivory Coast.

[00:01:42] News Clip 2: On the East Coast, it’s clams. Climate change has devastated the shellfish industry in Maine.

[00:01:49] News Clip 3: Okay, so we've all heard about the impact of climate change on the world, but what you may not know, it's also having a big impact on traditional industries like winemaking, affecting everything from where it's made to how it tastes.

[00:02:02] LHF: That was a local ABC station in Los Angeles, NBC News, and CBS. But these statements leave a lot of open questions. Like, why is climate change going to affect certain foods? And why these foods in particular? To understand what’s going on, let’s look at a couple of examples.

[00:02:21] CR: There will be some challenges. You know, avocado. I love avocados. So that one is a bit of a challenge.

[00:02:29] LHF: Avocado is a good example of a food that can use a lot of resources. Avocado trees are largely grown in big plantations—which are thirsty and take up a lot of space. In major avocado-growing regions, like parts of Mexico and Chile, these plantations are depleting local water sources, and contributing to deforestation as they expand. Plus, like many foods, avocados are eaten all over the world, but mostly grown in one area, in this case Latin America—which means if you’re eating avocados in most of the US or Europe, lots of energy was used to ship them to you. And to keep them from getting ruined on those voyages, they’re kept refrigerated, which takes even more energy. This all adds up to a food that well, just takes a lot of resources.

Then there are plants that are very sensitive to a changing environment. Like coffee trees. Coffee is derived from the seeds of coffee cherries, which grow on trees in tropical forests with plenty of rainfall. Scientists expect climate change to make many of these areas warmer and expose them to more frequent and prolonged drought—which is really hard on coffee crops. And we’re seeing hints of this today. In southern Brazil, one of the biggest coffee-growing regions in the world, the past two years have seen the worst drought in almost a century, and many coffee growers are losing their crops or rapidly switching to a different, cheaper variety of coffee that can better withstand heat.

Now, that doesn’t mean these foods are going to go extinct. But these trends definitely make certain foods harder to cultivate—and that’s likely to lead to some changes, like higher prices or farmers switching to different, hardier varieties might pop up on the shelves.

OK so those are two examples. But there’s a good reason to think beyond specific foods.

[00:04:45] CR: Climate change is affecting food availability already through extreme events, which are increasing. So, things such as heat waves, heavy downpours, droughts in some regions and floods in others.

I think we got a taste of this at the beginning of COVID when the supply chains were disrupted and people were not able to get all the foods that they were ordering. We were so used to having anything we want and there was a time—it was short—and the supply chains adjusted, but, but that feeling of okay, you open the cupboard. And eat from the cupboard.

So what's in the cupboard, it's the legumes, it's the beans, right? It's things that are less perishable, because if we have supply chain disruptions, we will need to, I think, be more careful to make sure that we have food in our cupboards at all times.

[00:05:42] LHF: When COVID broke out in early 2020, I stocked up on canned food, you know, soups, beans, stuff like that. Just in case. And we do that when there’s a big storm coming, too. So as weather gets more intense and as our food systems adjust to this and to changing temperatures, we might find ourselves preparing in this way more often.

But for the second half of this episode, I want to come back to the present. What’s on our plates today? And what do those food choices have to do with climate change?

[00:06:18] CR: Let's start at the beginning. If less food is wasted, then we don't have to grow as much food. If we're wasting about 10% of all of our food, that's just all these greenhouse gas emissions that are going up.

[00:06:34] LHF: And in the U.S., we’re wasting a good bit more than that—according to the USDA, more than 30% of the food that makes it to store shelves never gets eaten. Some of that is thrown out by the stores—because it’s past its due date, or because it’s not pretty enough to sell, or other reasons. And some of it is thrown out at home. By cutting down on that food waste, we can also cut down on the land and water and energy that goes into producing it.

And some decisions about what people eat can also affect the food system that we’re a part of.

[00:07:14] CR: I want to be very, very clear that I am not advocating anybody to change their diet. It's really just to begin to think about it. But I think we should engage with climate and food conversations. Since what we choose to eat has a big effect, both on our personal health and planetary health. And this is in part because, some foods, emit a lot more greenhouse gases than others, in particular, beef.

[00:07:48] LHF: Let’s take a minute and look at beef in some detail, because it does get a lot of hype and is one of the foods that creates the most greenhouse gas emissions—though, as someone who enjoys a hamburger from time to time myself, I don’t want you to think this is a lecture about your diet.

So the first thing here is the amount of land that cattle need. We learned last episode that the biggest source of greenhouse gases in our food system comes from cutting down forests to make room for farms and pastureland. In fact, biggest reason that the Amazon rainforest is being cut down today is to make more pastureland for cattle. And we also need a lot of energy, and water and land to grow food for cattle, like soy and hay.

In general, cattle require a lot of land. To illustrate this, I have a little pop quiz for you. According to the USDA, what percentage of all the land in mainland US is used in some way for raising animals for us to eat? Make a guess, even to yourself. Ready for the answer? It’s over 40%. I was shocked by this, more than 40% of all the land here in the lower 48 states is used for livestock. Some argue that this is land that could be used for other purposes, like growing plants for humans to eat directly, or for restoring it back to ecosystems that actually store carbon dioxide, like prairies or forests.

And there’s another thing going on with cows.

[00:09:31] CR: Because of the methane that cows emit, but also through the manure as well, they are, big, big greenhouse gas producers.

[00:09:41] LHF: Yeah, cattle—and some other animals like sheep and goats—produce a lot of the powerful greenhouse gas methane. It’s to do with the way their digestive systems work: it’s really hard to digest grass and hay, so they ferment it in their stomachs, creating methane that they burp out.

So as weird as it may sound, this is actually a big deal. The EPA estimates that more than a quarter of all the methane humans are adding to the atmosphere comes from our livestock burping.

And it’s not just beef. Like, rice fields leave a lot of standing water where oxygen can’t get into the soil—and that creates good growing conditions for bacteria that also release methane.

Why are we talking about this again? Right, food choices.

[00:10:37] CR: So, as we think about our diet choices, there are ways to reduce the causes of climate change. If people eat different food, that then feeds back on what will be produced. And that's where you get the actual reduction in greenhouse gases, for example, from less beef production.

[00:10:58] LHF: This is why you might have heard about people choosing to eat more plants and less meat for the environment. We actually learned while making this episode that our whole team at TILclimate is either vegetarian or just occasional meat eaters. It’s not something we had talked about before, but, like buying green electricity, it’s a choice we were all making to start nudging these bigger systems—the ones that give us our food and our energy—to produce those things in a way that doesn’t add to our climate change problem.

It’s possible to get really into the weeds on food and climate, comparing this vegetable to that one, or digging into exactly where and how your food is grown. But really, if you’re interested in the climate impacts of your own diet, you ca n follow some pretty simple rules.

[00:11:53] CR: Just encourage healthy and sustainable plant-rich diets, especially in developed countries. We always have to say that because it's just so incredibly different in many, many countries and food insecure places. So for those who have choices, more plant-based diets. And try to just be more aware of how much we are scraping food waste into our garbage or our compost bins.

This attention to food has started. So the food is available, affordable, nutritious, reliable, right. And now healthy for the planet as well as for the people.

[00:12:36] LHF: That’s it for our episode, as with all our episodes, we curate websites and articles and papers for you to learn more about this topic, as well as educator guides to help teachers introduce this content in the classroom. Both can be found on our website, tilclimate.mit.edu. Just go to the episode page. Thanks again to Dr. Cynthia Rosensweig for joining us and thank you for listening.