The Omnivore's Dilemma - Michael Pollan [101]
Yet it’s misleading to speak about any grass plant in isolation, since many different plant species, performing many different functions, occupy even this one square foot of pasture, and Budger’s bite subtly alters the composition of this community. The shearing of the tallest grasses exposes the pasture’s shorter plants to sunlight, stimulating their growth. This is why a well-grazed pasture will see its population of ground-hugging clovers increase, a boon to grasses and grazers alike. These legumes fix nitrogen in the soil, fertilizing the neighboring grasses from below while supplying nitrogen to the grazers above; the bacteria living in the animal’s rumen will use the nitrogen in these clover leaves to construct new molecules of protein.
Side-by-side comparisons of intensive and continuously grazed pastures have demonstrated that intensive grazing increases the diversity of species in pastures. That’s because rotated cattle don’t eliminate favored species by overgrazing them and their equal-opportunity shearing ensures that no one species of grass ever dominates by rising to hog all the sunlight. This biodiversity confers a great many benefits on all parties. At the most fundamental level, it allows the farm’s land to capture the maximum amount of solar energy, since one kind of photosynthesizer or another is occupying every conceivable niche—niches in space as well as time. For example, when the early season grasses slow down in June, the late season grasses step in, and when drought hits, the deep-rooted species will take over from the shallower ones. A diverse enough polyculture of grasses can withstand virtually any shock and in some places will produce in a year nearly as much total biomass as a forest receiving the same amount of rainfall.
This productivity means Joel’s pastures will, like his woodlots, remove thousands of pounds of carbon from the atmosphere each year; instead of sequestering all that carbon in trees, however, grasslands store most of it underground, in the form of soil humus. In fact, grassing over that portion of the world’s cropland now being used to grow grain to feed ruminants would offset fossil fuel emissions appreciably. For example, if the sixteen million acres now being used to grow corn to feed cows in the United States became well-managed pasture, that would remove fourteen billion pounds of carbon from the atmosphere each year, the equivalent of taking four million cars off the road. We seldom focus on farming’s role in global warming, but as much as a third of all the greenhouse gases that human activity has added to the atmosphere can be attributed to the saw and the plow.
The benefits of a food chain rooted in a perennial polyculture are so many and so great that they’ve inspired dreams of converting our agriculture of annual grains into something that would look a lot more like Joel Salatin’s pastures. That particular vision hatched more than thirty years ago in the mind of a graduate student in plant genetics named Wes Jackson. Today breeders at his Land Institute, in Salina, Kansas, are working on a (very) long-term project to “perennialize” many of our principal grain crops (including corn) and then grow them in polycultures that farmers would seldom if ever have to plow or replant. The basic idea is to allow us to live off the land (and the sun) more like ruminants do, by coaxing perennial grasses (which we can’t digest) to yield bigger and more nutritious seeds (which we can). Of course, the same goal would be accomplished by changing us rather than the grasses—giving people rumens, that is, so they could digest grasses. And there are skeptics who believe perennializing the major crops is no