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What to Eat After the Apocalypse

Engineer Joshua Pearce explains how to feed 7 billion people after a global catastrophe.

In 1841, an invasive water mold began to infect the world’s potatoes. Starting from Mexico, the infectious agent of blight traveled…By Yvonne Bang

In 1841, an invasive water mold began to infect the world’s potatoes. Starting from Mexico, the infectious agent of blight traveled up through North America, then crossed the Atlantic. Eventually it reached Ireland, where, as the journalist Charles Mann described it, “four out of ten Irish ate no solid food except potatoes, and … the rest were heavily dependent on them.”

The Great Famine, as it came to be known, could have been avoided in any number of ways, not least by ceasing the export of food from Ireland to Britain. But the British government failed to take effective action. The question of avoiding starvation becomes harder still if some apocalyptic event causes the whole world to starve. How might a government prepare for a worst-case scenario?

This is a question Joshua Pearce, an associate professor of materials science and engineering, and electrical and computer engineering at Michigan Technological University, began to think about while working on providing low-cost drinking water to the developing world. He found the prospect of disaster terrifying. “This would make us no better off than the dinosaurs, despite all of our technical progress,” he told me. “Humanity is too smart for that.”

It sounds pretty terrifying to say, “cut down the rainforests even faster!”

Pearce partnered with David Denkenberger, a research associate at the Global Catastrophic Risk Institute. They looked around for detailed existing solutions and found just one: storing lots of food. But that, the two engineers realized, would probably feed the global population for a year or less.

So they developed a set of solutions that they believe would provide five years of food for the Earth’s population, and published a book about it called Feeding Everyone No Matter What. I spoke to Pearce to find out some of the very gooey ways we might survive the apocalypse.


What kinds of disasters do you think about?

Let me take the most likely one: the nuclear winter case. Say two countries that both have access to nuclear weapons get very angry at each other, and then retaliate, destroying most of the major cities in the opposite country. The vast bulk of humanity would survive, eventually. Say maybe we lost 5 percent of the population. Ninety-five percent of us would still be alive. But then as those cities burned, you’d end up getting soot in the upper atmosphere that stays there and darkens the entire planet. And all the crops fail.

As the world went dark, you’d have a couple of the more hearty crops survive—the trees would last a little while. But our standard crops? Your wheat, your rice, your corn? That’s all dead. You don’t get that harvest, and that’s what we feed the world with. Vegetable gardens, everything’s just dead. You can’t grow in darkness. As those crops fail, you’ll start to get hungry; you’ll start going into your stored food supplies. The historical assumption is that’s when we all go completely crazy. It’s bad. I’m sure you’ve seen the movies. There’s no good outcome there. That darkness will basically stay for around five years, until it starts to rain out of the atmosphere and then we’ll slowly but surely [get] more and more sunlight and start to rejuvenate agriculture again.

There’d be a little bit of conventional agriculture that survives—like the grow houses. For example, in Japan they have warehouses that just have racks of lettuce growing under LED lights, and that would still work, but what fraction of the population would that feed? I’m sure that the wealthy in whichever culture would still pick tomatoes and lettuce, but the vast majority of the world would not be eating those.

So what would we eat after the sky goes dark?

There are many things that you can eat that we don’t normally consider food, particularly in the west. Leaves are one of them. You can eat leaves. You just have to be careful about how you do it. Leaves are high in fiber and we can’t digest any more than half of it, but if you chew the leaves and spit out the fiber you can draw out nutrients from it. Or you can make teas.

Tea in particular is a relatively easy one to do. Pine needle tea has more than 100 percent of the vitamin C of orange juice. One could actually make pine needle tea from the pine tree in your backyard and get your vitamin C for the day. It’s actually a really good superfood. And in some cultures, like [South] Korea, they even have pop that is flavored with pine. That’s their drink.

The other obvious one is insects. The conversion ratios between biomass and food in insects is much better than say, in cows. Beef production is unbelievably inefficient the way that we do it. In the west, we definitely turn our noses up at eating insects. But there are actually quite a few people throughout the world that eat insects today and, for feeding everyone, it is a very obvious solution. It’s not like you have to eat insects raw. You would never know the difference between say, a sausage patty, a veggie sausage patty, and an insect sausage patty. It’s all the same! It’s just the spices. Let the food scientists go crazy on it.

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Could the oceans feed us?

If you looked at the amount of fish that we currently eat, it’s just a tiny fraction of the human diet. You can expand that much more without wiping out all the fisheries. If you have significant climate change, that will result in more upwelling [seawater rise from the depth of the ocean to the surface], which will be like fertilizing the ocean surface, and you get more fish. Similarly we can purposely fertilize the ocean in order to get more fish. So then we have enough fish to feed everyone. How do you catch it all?

Then we started to look into how many ships exist—and if we converted all of them to fishing vessels, would that be enough in order to get enough fish harvested to meet demand? It turned out you end up with problems such as round trip distance. You can’t have little fishing boats go out and fish and then drive all the way back. The solution to that is ship-to-ship transfers of fish, which luckily, they already do now. So our fish solution is actually one of the better ones under certain circumstances. [But] it won’t work for everything. You still need some light.

You’ve also suggested that we eat bacteria. How would that work?

There are two main sources of bacteria that we looked at. There is a methane-digesting bacteria that you basically grow on natural gas. And then we can either eat that directly or process it or say, feed it to rats and then eat the rats. Then there’s the bacteria that we can grow directly on wood. Or on leftover mushroom waste. And so this would be taking down a tree, pulverizing it, turning it into a slurry, and then letting the bacteria go at it.

When we have full agriculture production—no weird climate stuff going on—we still don’t feed everybody.

So for instance, there are bacteria that secrete sugars they then use to feed themselves. You can pull out the sugars, and eat those ourselves and leave the bacteria and the partially decaying wood pulp. And we can feed that stuff to other things. So for instance, rats digest wood to some degree, particularly after it is partially broken down that way. This makes a fairly good solution. We could feed something similar to chickens. And chicken is something maybe people would maybe be happier to eat than bacteria milkshakes.

Have you tried some of these solutions yourself?

Oh absolutely. A lot of it was just to make sure that the taste wasn’t so bad that it would never happen. Stuff like pine needle tea is really not that bad. Many insects are, I would even go so far as to say, tasty? If you get by the initial sort of gag reflex. Let’s say we grow mushrooms on logs and everybody’s eating mushrooms. Of course, that’s not too scary. And then the waste product from that goes to feed ruminants like cows, and then [you’ve got] beef so you know, you can still have hamburger. It’s not that bad. We might be eating more of the cow than we do now, but it’s not that bad.

In your book, you talk about this need for a lot of chain saws. Why would we need so many?

All the trees would be dead, for lack of light. And so we would need to significantly ramp up our rate of cutting trees down. Plus, temperatures would drop. We looked at a 10-degree and a 20-degree scenario. In the 20-degree scenario, you start having things like say, all of the wood in Canada freezes. That type of problem. Even if we want to do things like chop the wood down and get fields of mushrooms and that kind of thing, frozen wood is much more difficult to deal with. That’s why global cooperation is so important. Because we’d basically be harvesting wood supplies from the equator.

We’re probably the first to ever calculate how many chain saws there are in the world and what their duty cycles were and how fast we can manufacture them in order to make sure that we had enough cutting power. Instead of say, making small handheld devices, we could move that machinery over to making chain saws. Those kinds of technical switches, which are really not that hard for an industry to pull off, would need to be done on a massive global scale in order to give ourselves the tools we need.  And I know from an environmental perspective, it sounds pretty terrifying to say, “cut down the rainforests even faster!”

What was the most surprising thing you discovered?

It turns out that there are several solutions to maintaining the entire global population with things like feedstocks of primarily fossil fuels and wood. The reason that’s so surprising is that right now, when we have full agriculture production—no weird climate stuff going on—we still don’t feed everybody. We still have little kids starving to death every day and yet, I know now that we can feed them on wood pulp. It would certainly be possible. That was very surprising.

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