Humans made an unwitting but fateful choice 10,000 years ago as we started cultivating wild plants: We chose annuals. All the grains that feed billions of people today—wheat, rice, corn, and so on—come from annual plants, which sprout from seeds, produce new seeds, and die every year. The whole world is mostly perennials, yet why did humans cultivate annuals instead of perennials? Not because annuals were better, but because Neolithic farmers rapidly made them better, for example, enlarging their seeds, through selective breeding, by replanting the ones from thriving plants, year after year. As perennials did not benefit from that kind of selective breeding, because they don't need to be replanted, this natural advantage became a handicap to the perennials, causing humans to favour annuals instead.
The main advantage of perennials are the deep, dense root systems that fuel the plants' rebirth each spring and that make them so resilient and resource efficient. However, the yield of perennials is not as high as that of biannials, which benefit greatly from selective breeding.
We pay a steep price for our reliance on high yields and shallow roots as annual root crops mostly tap into only the top foot or so of soil such that that layer gets depleted, forcing farmers to rely on large amounts of fertilizers to maintain high yields. Often less than half the fertilizer in the Midwest gets taken up by crops; much of it washes into the Gulf of Mexico, where it fertilizes algae blooms that cause a vast dead zone around the mouth of the Mississippi. Annuals also promote heavy use of pesticides or tillage because they leave the ground bare much of the year which allows weeds to invade
Above all, leaving the ground bare after harvest and plowing it in planting season erodes the soil. No-till farming and other conservation practices have reduced the rate of soil loss in the U.S. by more than 40 percent since the 1980s, but it's still around 1.7 billion tons a year. Worldwide, one estimate put the rate of soil erosion from plowed fields at ten to a hundred times the rate of soil production. "Unless this disease is checked, the human race will wilt like any other crop," Jackson wrote 30 years ago. As growing populations force farmers in poor countries onto steeper, erodible slopes, the "disease" threatens to get worse.
Perennial grains would help with all these problems. They would keep the ground covered, reducing erosion and the need for pesticides, and their deep roots would stabilize the soil and make the grains more suitable for marginal lands. Perennials capture water and nutrients 10 or 12 feet down in the soil, 11 months of the year, as the deep roots and ground cover would also hold on to fertilizer—reducing the cost to the farmer as well as to the environment.
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