The Omnivore's Dilemma - Michael Pollan [100]
And yet if I could actually see everything that was going on right here in this pasture, could trace all the ecological connections involved, the scene unfolding directly before me was not nearly as simple as it looked. In fact, there was easily as much complexity present in a single square foot of this pasture as there is in the whole industrial complex into which 534 was plugged; what makes this pasture’s complexity so much harder for us to comprehend is that it is not a complexity of our making.
But try anyway. Focus in for a moment on just the relationship between Budger and the tuft of fescue she’s tearing from its crown. Those blades of grass have spent this long June day turning sunlight into sugars. (The reason Joel moves his cattle at the end of the day is because that’s when sugar levels in the grass hit their peak; overnight the plant will gradually use up these reserves.) To feed the photosynthetic process the grass’s roots have drawn water and minerals up from deep in the soil (some grasses can sink their roots as much as six feet down), minerals that soon will become part of this cow. Chances are Budger has also chosen exactly which grasses to eat first, depending on whatever minerals her body craves that day; some species supply her more magnesium, others more potassium. (If she’s feeling ill she might go for the plantain, a forb whose leaves contain antibiotic compounds; grazing cattle instinctively use the diversity of the salad bar to medicate themselves.) By contrast 534, who never got to pick and choose his dinner, let alone his medications, depends on animal nutritionists to design his total ration—which of course is only as total as the current state of knowledge in animal science permits.
So far the relationship between Budger and this square foot of pasture might seem a little one-sided, since viewed at least from where I stood, Budger’s bite appears to have diminished the pasture. But if I could view the same event from underground and over time, I would see that that bite is not a zero-sum transaction between cow and grass plant. The moment Budger shears the clump of grass, she sets into motion a sequence of events that will confer a measurable benefit on this square foot of pasture. The shorn grass plant, endeavoring to restore the rough balance between its roots and leaves, will proceed to shed as much root mass as it’s just lost in leaf mass. When the discarded roots die, the soil’s resident population of bacteria, fungi, and earthworms will get to work breaking them down into rich brown humus. What had been the grass plant’s root runs will become channels through which worms, air, and rainwater will move through the earth, stimulating the process by which new topsoil is formed.
It is in this manner that the grazing of ruminants, when managed properly, actually builds new soil from the bottom up. Organic matter in a pasture also builds from the top down, as leaf litter and animal wastes break down on the surface, much as it does on a forest floor. But in a grassland decaying roots are the biggest source of new organic matter, and in the absence of grazers the soil-building process would be nowhere near as swift or productive.
Back up to the surface now. Over the next few days, Budger’s shearing of this grass plant will stimulate new growth, as the crown redirects reserves of carbohydrate energy from the roots upward to form new shoots. This is the critical moment when a second bite would derail the grass’s recovery, since the plant has to live on these reserves until it has grown new leaves and resumed photosynthesis.