CHAPTER 6
HOW WE GROW THINGS
19 percent of 51 billion tons a year
Cheeseburgers run in my family. When I was a kid, I’d go on hikes with my Boy Scout troop, and all the guys always wanted to ride home with my dad because he’d stop along the way and treat everyone to burgers. Many years later, in the early days of Microsoft, I scarfed down countless lunches, dinners, and late-night meals at the nearby Burgermaster, one of the Seattle area’s oldest burger chains.
Eventually, after Microsoft became successful but before Melinda and I started our foundation, my dad started using the Burgermaster near his house as an unofficial office. He’d sit in the restaurant, eating lunch while he sifted through requests we had received from people who were asking for donations. After a while, word got out, and Dad started getting letters addressed to him there: “Bill Gates Sr., in care of Burgermaster.”
Those days are long gone. It’s been two decades since Dad traded in his table at Burgermaster for a desk at our foundation. And although I still love a good cheeseburger, I don’t eat them nearly as often as I used to—because of what I’ve learned about the impact that beef and other meats have on climate change.
Raising animals for food is a major contributor of greenhouse gas emissions; it ranks as the highest contributor in the sector that experts call “agriculture, forestry, and other land use,” which in turn covers a huge range of human activity, from raising animals and growing crops to harvesting trees. This sector also involves a wide range of various greenhouse gases: With agriculture, the main culprit isn’t carbon dioxide but methane—which causes 28 times more warming per molecule than carbon dioxide over the course of a century—and nitrous oxide, which causes 265 times more warming.
All told, each year’s emissions of methane and nitrous oxide are the equivalent of more than 7 billion tons of carbon dioxide, or more than 80 percent of all the greenhouse gases in this ag/forestry/land use sector. Unless we do something to curb these emissions, that number will go up as we grow enough food to feed a global population that’s getting bigger and richer. If we want to get near net-zero emissions, we’re going to have to figure out how to grow plants and raise animals while reducing and eventually eliminating greenhouse gases.
And farming isn’t the only challenge. We’ll also have to do something about deforestation and other uses of land, which together add a net 1.6 billion tons of carbon dioxide to the atmosphere while also destroying essential wildlife habitats.
In keeping with such a wide-ranging subject, this chapter has a bit of everything. I’ll tell you about one of my heroes, a Nobel Peace Prize–winning agronomist who saved a billion people from starvation but whose name is largely unknown outside global-development circles. We’ll also explore the ins and outs of pig manure and cow burps, the chemistry of ammonia, and whether planting trees helps avoid a climate disaster. But before we get to any of that, let’s start with a famous prediction that turned out to be historically wrong.
In 1968, an American biologist named Paul Ehrlich published a best-selling book called The Population Bomb, in which he painted a grim picture of the future that was not far removed from the dystopian vision of novels like The Hunger Games. “The battle to feed all of humanity is over,” Ehrlich wrote. “In the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now.” Ehrlich also wrote that “India couldn’t possibly feed 200 million more people by 1980.”
None of this came to pass. In the time since The Population Bomb came out, India’s population has grown by more than 800 million people—it’s now more than double what it was in 1968—but India produces more than three times as much wheat and rice as it did back then, and its economy has grown by a factor of 50. Farmers in many other countries throughout Asia and South America have seen similar productivity gains.
As a result, even though the global population is growing, there are not hundreds of millions of people starving to death in India or anywhere else. In fact, food is becoming more affordable, not less. In the United States, the average household spends less of its budget today on food than it did 30 years ago, a trend that’s being repeated in other parts of the world as well.
I’m not saying that malnutrition isn’t a serious problem in some places. It is. In fact, improving nutrition for the world’s poorest is a key priority for Melinda and me. But Ehrlich’s prediction of mass starvation was wrong.
Why? What did Ehrlich and other doomsayers miss?
They didn’t factor in the power of innovation. They didn’t account for people like Norman Borlaug, the brilliant plant scientist who sparked a revolution in agriculture that led to the gains in India and elsewhere. Borlaug did it by developing varieties of wheat with bigger grains and other characteristics that allowed them to provide much more food per acre of land—what farmers call raising the yield. (Borlaug found that as he made the grains bigger, the wheat couldn’t stand up under their weight, so he made the wheat stalks shorter, which is why his varieties are known as semi-dwarf wheat.)
As Borlaug’s semi-dwarf wheat spread around the world, and as other breeders did similar work on corn and rice, yields tripled in most areas. Starvation plummeted, and today Borlaug is widely credited with saving a billion lives. He won the Nobel Peace Prize in 1970, and we’re still feeling the impact of his work: Virtually all the wheat grown on earth is descended from the plants he bred. (One downside of these new varieties is that they need lots of fertilizer to reach their full growth potential, and as we’ll discuss in a later section, fertilizer has some negative side effects.) I love the fact that one of history’s greatest heroes had a job title—agronomist—that most of us have never even heard of.
So what does Norman Borlaug have to do with climate change?
The global population is headed toward 10 billion people by 2100, and we’re going to need more food to feed everyone. Because we’ll have 40 percent more people by the end of the century, it would be natural to think that we’ll need 40 percent more food too, but that’s not the case. We’ll need even more than that.
Here’s why: As people get richer, they eat more calories, and in particular they eat more meat and dairy. And producing meat and dairy will require us to grow even more food. A chicken, for example, has to eat two calories’ worth of grain to give us one calorie of poultry—that is, you have to feed a chicken twice as many calories as you’ll get from the chicken when you eat it. A pig eats three times as many calories as we get when we eat it. For cows, the ratio is highest of all: six calories of feed for every calorie of beef. In other words, the more calories we get from these meat sources, the more plants we need to grow for the meat.
This chart shows you the trends in meat consumption around the world. It’s basically flat in the United States, Europe, Brazil, and Mexico, but it’s climbing rapidly in China and other developing countries.
Here’s the conundrum: We need to produce much more food than we do today, but if we keep producing it with the same methods we use now, it will be a disaster for the climate. Assuming we don’t make any improvements in the amount of food we get per acre of pasture or cropland, growing enough to feed 10 billion people will drive up food-related emissions by two-thirds.
Most countries aren’t consuming more meat than they used to. China, though, is a big exception. (OECD-FAO Agricultural Outlook 2020)
Another concern: If we make a big push to generate energy from plants, we could accidentally spark a competition for cropland. As I’ll describe in chapter 7, advanced biofuels made from things like switchgrass could give us zero-carbon ways to power trucks, ships, and airplanes. But if we grow those crops on land that would otherwise be used to feed a growing population, we could inadvertently drive up food prices, pushing even more people into poverty and malnutrition while accelerating the already dangerous pace of deforestation.
To avoid these traps, we’re going to need more Borlaug-sized breakthroughs in the years ahead. Before we can look at what those breakthroughs might be, though, I want to explain where exactly all these emissions are coming from and explore our options for eliminating them using today’s technology. Just as I did in the previous chapter, I’ll use Green Premiums to show why getting rid of these greenhouse gases is too expensive today, and to make the case that we need some new inventions.
Which brings me to cow burps and pig manure.
Look inside a person’s stomach and you’ll find just one chamber where food starts getting digested before making its way to the intestinal tract. But look inside a cow’s stomach, and you’ll see four chambers. These compartments are what allow the cow to eat grass and other plants that humans can’t digest. In a process called enteric fermentation, bacteria inside the cow’s stomach break down the cellulose in the plant, fermenting it and producing methane as a result. The cow belches away most of the methane, though a little comes out the other end as flatulence.
(By the way, when you get into this subject, you can end up having some weird conversations. Each year, Melinda and I publish an open letter about our work, and in our 2019 letter I decided to write about this problem of enteric fermentation in cattle. One day, as we were going over a draft, Melinda and I had a healthy debate about how many times I could use the word “fart” in the letter. She got me down to one. As the sole author of this book, I have more leeway, and I intend to use it.)
Around the world, there are roughly a billion cattle raised for beef and dairy. The methane they burp and fart out every year has the same warming effect as 2 billion tons of carbon dioxide, accounting for about 4 percent of all global emissions.
Burping and farting natural gas is a problem that’s unique to cows and other ruminants, like sheep, goats, deer, and camels. But there’s another cause of greenhouse gas emissions that’s common to every animal: poop.
When poop decomposes, it releases a mix of powerful greenhouse gases—mostly nitrous oxide, plus some methane, sulfur, and ammonia. About half of poop-related emissions come from pig manure, and the rest from cow manure. There’s so much animal poop that it’s actually the second-biggest cause of emissions in agriculture, behind enteric fermentation.
What can we do about all this pooping, burping, and farting? That’s a tough one. Researchers have tried all sorts of ideas for dealing with enteric fermentation. They’ve tried using vaccines to cut down on the methanogenic microbes living in the cattle’s gut, breeding cattle to naturally produce fewer emissions, and adding special feeds or drugs to their diets. These efforts have mostly been unsuccessful, though one promising exception is a compound called 3-nitrooxypropanol, which reduces methane emissions by 30 percent. But right now you have to give it to the cattle at least once a day, so it’s not yet feasible for most grazing operations.
Still, there’s reason to believe we can cut down on these emissions without any new technology and without a significant Green Premium. It turns out the amount of methane produced by a given cow depends a lot on where the cow lives; for example, cattle in South America emit up to five times more greenhouse gases than ones in North America do, and African cattle emit even more. If a cow is being raised in North America or Europe, it’s more likely to be an improved breed that converts feed into milk and meat more efficiently. It will also get better veterinary care and higher-quality feed, which means it’ll produce less methane.
If we can spread the improved breeds and best practices more broadly—especially crossbreeding African cows to be more productive and making higher-quality feed available and affordable—it’ll reduce emissions and help poor farmers earn more money. The same is true for handling manure; rich-world farmers have access to various techniques that get rid of the manure while producing fewer emissions. As these techniques become more affordable, they’ll spread to poor farmers, and we’ll improve our odds of driving emissions down.
A hard-core vegan might propose another solution: Instead of trying all these ways of reducing emissions, we should just stop raising livestock. I can see the appeal of that argument, but I don’t think it’s realistic. For one thing, meat plays too important a role in human culture. In many parts of the world, even where it’s scarce, eating meat is a crucial part of festivals and celebrations. In France, the gastronomic meal—including starter, meat or fish, cheese, and dessert—is officially listed as part of the country’s Intangible Cultural Heritage of Humanity. According to the listing on the UNESCO website, “The gastronomic meal emphasizes togetherness, the pleasure of taste, and the balance between human beings and the products of nature.”
But we can cut down on meat eating while still enjoying the taste of meat. One option is plant-based meat: plant products that have been processed in various ways to mimic the taste of meat. I’ve been an investor in two companies that have plant-based meat products on the market right now—Beyond Meat and Impossible Foods—so I’m biased, but I have to say that artificial meat is pretty good. When prepared just right, it’s a convincing substitute for ground beef. And all of the alternatives out there are better for the environment, because they use much less land and water and are responsible for fewer emissions. You also need less grain to produce them, reducing the pressure on food crops and the use of fertilizers too. And it’s a huge boon for animal welfare whenever fewer livestock are being kept in small cages.
Artificial meats come with hefty Green Premiums, however. On average, a ground-beef substitute costs 86 percent more than the real thing. But as sales for these alternatives increase, and as more of them hit the market, I’m optimistic that they’ll eventually be cheaper than animal meat.
Yet the big question on artificial meat comes down to taste, not money. Although the texture of a hamburger is relatively easy to mimic with plants, it’s much harder to fool people into thinking they’re actually eating a steak or chicken breast. Will people like artificial meat enough to switch, and will enough people switch to make a significant difference?
We’re already seeing some evidence that they will. I have to admit that even I have been surprised by how well Beyond Meat and Impossible Foods are doing—especially given their early hiccups. I attended an early demonstration by Impossible Foods at which they burned the burger so badly that it set off the smoke alarm. It’s amazing to see how widely available their products are, at least around the Seattle area and the cities I visit. Beyond Meat had a very successful initial public offering in 2019. It may take another decade, but I do think that as the products get better and cheaper, people who are worried about climate change and the environment will favor them.
Another approach is akin to plant-based meat, but instead of growing plants and then processing them so they taste like beef, you grow the meat itself in a lab. It has somewhat unappealing names like “cell-based meat,” “cultivated meat,” and “clean meat,” and there are some two dozen start-up companies working on getting it to market, though their products probably won’t be on supermarket shelves until the mid-2020s.
Keep in mind that this isn’t fake meat. Cultivated meat has all the same fat, muscles, and tendons as any animal on two or four legs. But rather than growing up on a farm, it’s created in a lab. Scientists start with a few cells drawn from a living animal, let those cells multiply, and then coax them into forming all the tissues we’re used to eating. All this can be done with little or no greenhouse gas emissions, aside from the electricity you need to power the labs where the process is done. The challenge with this approach is that it’s very expensive, and it’s not clear how much the costs can come down.
And both kinds of artificial meat face another uphill battle. At least 17 U.S. state legislatures have tried to keep these products from being labeled as “meat” in stores. One state has proposed banning their sale altogether. So even as the technology improves and the products get cheaper, we’ll need to have a healthy public debate about how they’re regulated, packaged, and sold.
There’s one last way we can cut down on emissions from the food we eat: by wasting less of it. In Europe, industrialized parts of Asia, and sub-Saharan Africa, more than 20 percent of food is simply thrown away, allowed to rot, or otherwise wasted. In the United States, it’s 40 percent. That’s bad for people who don’t have enough to eat, bad for the economy, and bad for the climate. When wasted food rots, it produces enough methane to cause as much warming as 3.3 billion tons of carbon dioxide each year.
The most important solution is behavior change—using more of what we have. But technology can help. For example, two companies are working on invisible, plant-based coatings that extend the life of fruits and vegetables; they’re edible, and they don’t affect the taste at all. Another has developed a “smart bin” that uses image recognition to track how much food is wasted in a house or business. It gives you a report on how much you threw away, along with its cost and its carbon footprint. The system may sound invasive, but giving people more information can help them make better choices.
A few years ago, I stepped into a warehouse in Dar es Salaam, Tanzania, and saw something that thrilled me: thousands of tons of synthetic fertilizer piled as high as snowdrifts. The warehouse was part of the new Yara fertilizer distribution center, which was the largest of its kind in East Africa. Walking around the warehouse, I talked to workers filling bags with tiny white pellets containing nitrogen, phosphorus, and other nutrients that would soon be nourishing crops in one of the poorest regions in the world.
It was the kind of trip I love to take. I know it sounds goofy to say this, but to me fertilizer is magical, and not just because it makes our yards and gardens prettier. Along with Norman Borlaug’s semi-dwarf wheat and new varieties of corn and rice, synthetic fertilizer was a key factor in the agricultural revolution that changed the world in the 1960s and 1970s. It’s been estimated that if we couldn’t make synthetic fertilizer, the world’s population would be 40 to 50 percent smaller than it is.
Touring the Yara fertilizer distribution facility in Dar es Salaam, Tanzania, 2018. I’m having even more fun than it looks.
The world uses a lot of fertilizer already, and poor countries should be using more. The agricultural revolution I mentioned—often called the Green Revolution—largely bypassed Africa, where the typical farmer gets just one-fifth as much food per acre of land as an American farmer gets. That’s because in poor countries most farmers don’t have good enough credit to buy fertilizer, and it’s more expensive than in rich countries because it has to be shipped into rural areas over poorly built roads. If we can help poor farmers raise their crop yields, they’ll earn more money and have more to eat, and millions of people in some of the world’s poorest countries will be able to get more food and the nutrients they need. (We’ll cover this in more depth in chapter 9.)
Why is fertilizer so magical? Because it provides plants with essential nutrients, including phosphorus, potassium, and the one that’s especially relevant to climate change: nitrogen. Nitrogen is a mixed blessing. It’s closely linked to photosynthesis, the process by which plants turn sunlight into energy, so it makes all plant life—and therefore all our food—possible. But nitrogen also makes climate change much worse. To understand why, we need to talk about what it does for plants.
There’s a huge gap in agriculture. Thanks to fertilizer and other improvements, American farmers now get more corn per unit of land than ever. But African farmers’ yields have barely budged. Narrowing the gap will save lives and help people escape poverty, but without innovation it will also make climate change worse. (FAO)
To grow crops, you want tons of nitrogen—way more than you would ever find in a natural setting. Adding nitrogen is how you get corn to grow 10 feet high and produce enormous quantities of seed. Oddly, most plants can’t make their own nitrogen; instead, they get it from ammonia in the soil, where it’s created by various microorganisms. A plant will keep growing as long as it can get nitrogen, and it’ll stop once the nitrogen is all used up. That’s why adding it boosts growth.
For millennia, humans fed their crops extra nitrogen by applying natural fertilizers like manure and bat guano. The big breakthrough came in 1908, when two German chemists named Fritz Haber and Carl Bosch figured out how to make ammonia from nitrogen and hydrogen in a factory. It’s hard to overstate how momentous their invention was. What’s now known as the Haber-Bosch process made it possible to create synthetic fertilizer, greatly expanding both the amount of food that could be grown and the range of geographies where it could be grown. It’s still the main method we use to make ammonia today. In the same way that Norman Borlaug is one of the great unsung heroes of history, Haber-Bosch might be the most important invention that most people have never heard of.*
Here’s the rub: Microorganisms that make nitrogen expend a lot of energy in the process. So much energy, in fact, that they’ve evolved to do it only when they absolutely need to—when there’s no nitrogen in the soil around them. If they detect enough nitrogen, they stop producing it so they can use the energy for something else. So when we add synthetic fertilizer, the natural organisms in the soil sense the nitrogen and stop producing it on their own.
There are other downsides to synthetic fertilizer. To make it, we have to produce ammonia, a process that requires heat, which we get by burning natural gas, which produces greenhouse gases. Then, to move it from the facility where it’s made to the warehouse where it’s stored (like the place I visited in Tanzania) and eventually the farm where it’s used, we load it on trucks that are powered by gasoline. Finally, after the fertilizer is applied to soil, much of the nitrogen that it contains never gets absorbed by the plant. In fact, worldwide, crops take up less than half the nitrogen applied to farm fields. The rest runs off into ground or surface waters, causing pollution, or escapes into the air in the form of nitrous oxide—which, you may recall, has 265 times the global-warming potential of carbon dioxide.
All told, fertilizers were responsible for roughly 1.3 billion tons of greenhouse gas emissions in 2010, and the number will probably rise to 1.7 billion tons by mid-century. Haber-Bosch giveth, and Haber-Bosch taketh away.
Unfortunately, there simply isn’t a practical zero-carbon alternative for fertilizer right now. It’s true that we could get rid of the emissions involved in making fertilizer by using clean electricity instead of fossil fuels to synthesize ammonia, but that’s an expensive process that would raise the price of fertilizer considerably. In the United States, for example, using this process to make the nitrogen-based fertilizer urea would raise its cost by more than 20 percent.
But that’s just the emissions from making fertilizer. We don’t have any way to capture the greenhouse gases that come from applying it. There’s no equivalent of carbon capture for nitrous oxide. That means I can’t calculate a complete Green Premium for zero-carbon fertilizer—which itself is actually useful information, because it tells us that we need significant innovation in this area.
Technically, it’s possible to get crops to absorb nitrogen much more efficiently than they do, if farmers have the technology to monitor their nitrogen levels very carefully and apply fertilizer in just the right amount over the course of a growing season. But that’s an expensive and time-consuming process, and fertilizer is cheap (at least in rich countries). It’s more economical to apply more than you need, knowing that you’re at least using enough to maximize the growth of your crops.
Some companies have developed additives that are supposed to help plants take up more nitrogen so there’s less to wash into groundwater or evaporate into the atmosphere. But these additives are used with only 2 percent of global fertilizers, because they don’t work consistently well and manufacturers aren’t investing much to improve them.
Other experts are working on different ways to solve the nitrogen problem. For example, some researchers are doing genetic work on new varieties of crops that can recruit bacteria to fix nitrogen for them. In addition, one company has developed genetically modified microbes that fix nitrogen; in effect, instead of adding nitrogen via fertilizer, you add bacteria to the soil that always produce nitrogen even when it’s already present. If these approaches work, they’ll dramatically reduce the need for fertilizer and all the emissions it’s responsible for.
Everything you’ve just read about—which I’d broadly describe as agriculture—accounts for roughly 70 percent of emissions from farming, forestry, and other uses of land. If I had to sum up the other 30 percent in one word, it would be “deforestation.”
According to the World Bank, the world has lost more than half a million square miles of forest cover since 1990. (That’s an area bigger than South Africa or Peru, and a decline of roughly 3 percent.) There’s the immediate and obvious impact of deforestation—if the trees are burned down, for example, they quickly release all the carbon dioxide they contain—but it also causes damage that’s harder to see. When you take a tree out of the ground, you disturb the soil, and it turns out that there’s a lot of carbon stored up in soil (in fact, there’s more carbon in soil than in the atmosphere and all plant life combined). When you start removing trees, that stored carbon gets released into the atmosphere as carbon dioxide.
Deforestation would be easier to stop if it were happening for the same reasons in every place, but unfortunately that’s not the case. In Brazil, for example, most of the destruction of the Amazon rain forest in the past few decades has been to clear pastureland for cattle. (Brazil’s forests have shrunk by 10 percent since 1990.) And because food is a global commodity, what’s consumed in one country can cause land-use changes in another. As the world eats more meat, it accelerates the deforestation in Latin America. More burgers anywhere mean fewer trees there.
And all these emissions add up fast. One study by the World Resources Institute found that if you account for land-use changes, the American-style diet is responsible for almost as many emissions as all the energy Americans use in generating electricity, manufacturing, transportation, and buildings.
But in other parts of the world, deforestation isn’t about turning out more burgers and steaks. In Africa, for example, it’s a matter of clearing land to grow food and fuel for the continent’s growing population. Nigeria, which has had one of the highest deforestation rates in the world, has lost more than 60 percent of its forest cover since 1990, and it’s one of the world’s biggest exporters of charcoal, which is created by charring wood.
In Indonesia, on the other hand, forests are being cut down to make way for palm trees, which provide the palm oil you’ll find in everything from movie-theater popcorn to shampoo. It’s one of the main reasons why the country is the world’s fourth-largest emitter of greenhouse gases.
I wish there were some breakthrough invention I could tell you about that will make the world’s forests safe. There are a few things that will help, such as advanced satellite-based monitors that make it easier to spot deforestation and forest fires as they’re happening and to measure the extent of the damage afterward. I’m also following some companies that are developing synthetic alternatives to palm oil so we don’t have to cut down so many forests to make room for palm plantations.
But this isn’t primarily a technological problem. It’s a political and economic problem. People cut down trees not because people are evil; they do it when the incentives to cut down trees are stronger than the incentives to leave them alone. So we need political and economic solutions, including paying countries to maintain their forests, enforcing rules designed to protect certain areas, and making sure rural communities have different economic opportunities so they don’t have to extract natural resources just to survive.
You might’ve heard about one forest-related solution for climate change: planting trees as a way to capture carbon dioxide from the atmosphere. Although it sounds like a simple idea—the cheapest, lowest-tech carbon capture imaginable—and it has obvious appeal for all of us who love trees, it actually opens up a very complicated subject. It needs to be studied a lot more, but for now its effect on climate change appears to be overblown.
As is so often the case in global warming, you have to consider a number of factors…
How much carbon dioxide can a tree absorb in its lifetime? It varies, but a good rule of thumb is 4 tons over the course of 40 years.
How long will the tree survive? If it burns down, all the carbon dioxide it was storing will be released into the atmosphere.
What would’ve happened if you hadn’t planted that tree? If a tree would’ve grown there naturally, you haven’t added any extra carbon absorption.
In what part of the world will you plant the tree? On balance, trees in snowy areas cause more warming than cooling, because they’re darker than the snow and ice beneath them and dark things absorb more heat than light things do. On the other hand, trees in tropical forests cause more cooling than warming, because they release a lot of moisture, which becomes clouds, which reflect sunlight. Trees in the midlatitudes—between the tropics and the polar circles—are more or less a wash.
Was anything else growing in that spot? If, for example, you eliminate a soybean farm and replace it with a forest, you’ve reduced the total amount of soybeans available, which will drive up their price, making it more likely that someone will cut down trees somewhere else to grow soybeans. This will offset at least some of the good you do by planting your trees.
Taking all these factors into account, the math suggests you’d need somewhere around 50 acres’ worth of trees, planted in tropical areas, to absorb the emissions produced by an average American in her lifetime. Multiply that by the population of the United States, and you get more than 16 billion acres, or 25 million square miles, roughly half the landmass of the world. Those trees would have to be maintained forever. And that’s just for the United States—we haven’t accounted for any other country’s emissions.
Don’t get me wrong: Trees have all kinds of benefits, both aesthetic and environmental, and we should be planting more of them. For the most part, you can get trees to grow only in places where they’ve already grown, so planting them could help undo the damage caused by deforestation. But there’s no practical way to plant enough of them to deal with the problems caused by burning fossil fuels. The most effective tree-related strategy for climate change is to stop cutting down so many of the trees we already have.
The upshot of all this is that we’ll soon need to produce 70 percent more food while simultaneously cutting down on emissions and moving toward eliminating them altogether. It’ll take a lot of new ideas, including new ways to fertilize plants, raise livestock, and waste less food, and people in rich countries will need to change some habits—we’ll have to eat less meat, for instance. Even if burgers run in the family.
* Fritz Haber had a complicated history. In addition to his lifesaving work on ammonia, he pioneered the use of chlorine and other poisonous gases as chemical weapons in World War I.