If there are three agricultural products that it's cool to hate right now, they're corn, sugar, and corn syrup. But if we peer into the future — in the very long term — human life on this planet depends on keeping those plants around. Here's why we'll be eating sugar-frosted corn flakes half a billion years in the future.

The last people on Earth will be eating a diet of grasses, corn, and sugar cane, which occasional sorghum supplements. We know this right now. Why? Because human-made carbon dioxide boosting is a temporary problem. Not temporary in the sense that humans might conceive of the word. Not even temporary in the sense that an apocalyptian might conceive of the world, in that the universe will eventually experience heat death. No, the carbon dioxide build up in the atmosphere will end, one way or another, in the final few billions years of habitability on this Earth.


The sun is fueling nearly all life on Earth at present, and apparently thinks that since it gave the Earth life, it should be allowed to take life away again. The center of the sun is heated by atoms of hydrogen fusing to make helium. As more atoms fuse, they make a denser, more compressed center of the sun. This heats the whole thing up, and, ironically, causes the outer layers to expand. Billions of years into the future, the sun will engulf the Earth, but well before that it will expand and heat the planet horrifically. What will be the first casualty of this heating? Our old friend, carbon dioxide.

Carbon dioxide is now involved in what's called the silicate-carbonate cycle. Water and carbon dioxide make acid rain, which is known to dissolve rocks. It dissolves silicate rock into calcium carbonate (CaCO3) and silicon particles, which run down into the oceans and get dropped on the ocean floor. It only leaves the sea floor via geological events that cause the rocks to be exposed to the heat below the Earth's crust. This means it takes a huge amount of carbon dioxide out of the atmosphere. The first part of this cycle will move faster and faster as the Earth heats. The second, which is dependent on geological movements which won't change, will move just as fast as it ever did. Carbon dioxide will almost disappear from the atmosphere.


Botanists, gardeners, and people who paid attention in biology class will have thought of a potential problem with that. The lack of CO2 in the atmosphere will pretty much take out Earth's ecosystem. Trees will go first, then most flowering plants, and eventually the world will de-green itself almost entirely, taking most of the animals with it. But not necessarily human animals. Unlike most other animals on Earth, humans are able to pick and choose which food we subsist on — and we could cultivate one staple and one sweet to keep the last humans on Earth alive.

There are several types of of photosynthesis in plants. Most plants just randomly grab carbon dioxide from the atmosphere. There have been studies done on whether the increase in carbon dioxide in the atmosphere is allowing them to grow more productively. The answer, for the most part, is not really. There were types of plants that weren't even included in the studies, types that had a special process which made the amount of carbon dioxide increase irrelevant.


All plants have an enzyme that collects carbon dioxide, but puzzlingly, that enzyme also collects oxygen. This is useless to the plant, but since there's no scarcity of carbon dioxide, the inefficiency doesn't do any harm to the plant. Some plants, though, have another enzyme, PEP-carboxylase, which occupies a special mesophyll cell in the plant. The enzyme grabs only carbon dioxide, and the cell acts a pump, concentrating the gas before turning it over to the more common enzyme. Scientists are confused as to why these special structures are in place, since there's no reason to put energy into conserving a resource that isn't scarce in the first place. It's an energy drain that make the plants less fit. And really, only a few plants have this special process. A few African grasses have developed the other enzyme. They'll be useless. But humanity lucked out that it's current ubiquitous crop, corn, and its favorite drug, sugar cane, both happen to have this process in place. They're the apocalypse plants. They're going to be the last ones to go.

They will go, though, along with everything else on Earth. The oceans will evaporate and steam off into space. The atmosphere will follow suit. By, conservatively, the year one billion, the Earth won't look much different from Mars or Mercury. If microbes are alive on its surface, they'll have to be tough microbes. Let's hope that by that time we'll have figured out how to go somewhere with a more functional atmosphere. It's amazing, though, that we know what the last humans on Earth - assuming humanity makes it that far - will be eating as they watch their world die around them. These aren't just the food of the future. They're the food of the end of the future.

Solar Images: ESA and NASA

Sugar Cane Image: Rufino Uribe

Via Berkeley, Skeptical Science, PSU and How it Ends.