What do soil carbon, wildflowers and raptors have in common? They benefit from well-managed grazing in our parks and open space preserves.
Grazing is one of those topics that can put a dinner table conversation among friends on edge. Everyone has an opinion. Grazing is good. Grazing is bad. Cows are undoing the planetary environment. Cows are the next salve for conservation.
The real story with grazing is that it’s complicated, and it is both a science and an art. As park managers, we are working hard to learn as much as we can about restoring and stewarding grassland ecosystems with grazing as one of our tools. When you see cows in a Sonoma County park or open space preserve, please know that they are there to get some work done.
So what’s the work? It turns out that grasslands are adapted to pulses of activity that consume the overstory growth. Such disturbance comes from herds of grazing animals or fire or both. This mowing of vegetation is a critical part of the function of the entire system.
Much of California historically looked like the African Serengeti, a vast grassland savannah populated by herds of animals like mammoth, camel, antelope and elk. The herds ate the tall grasses, giving more sunlight to the other plants like wildflowers. They trampled some of the old grass and turned it into the soil to increase organic material and contributed their manure as additional compost. Their hooves created divots and exposed bare soil, action that is needed for many annual plant seeds to germinate and take root.
Added to this were infrequent thunderstorms that brought lightning-ignited fires to the grasslands and intermingled forests. Like grazing, the fires removed the excess dead grass material called thatch and produced a flush of nutrients to the plants’ roots.
Native Americans applied fire all across the California landscape for at least 10,000 years, amplifying the effects of natural fires and keeping the forest from overtaking open hillsides and valleys. Both grazing and fire are largely credited with giving the Bay Area its iconic patchwork of intermingled forests and meadows.
When domestic cattle and sheep were brought to the West, many of the region’s ecosystems were significantly overgrazed. Overgrazing comes in the form of too many animals in one place or animals in one place for too much time. The underlying principle is movement. Grasslands can sustain a lot of disturbance if the animals graze, then move off and the land has time to recover. During times of rest, new plants take root, perennial plants re-sprout, nutrients are absorbed, roots decompact soils, and biomass is recovered and primed for another round of munching.
Conservationists, responding to periods of overgrazing, have often made the mistake of removing grazing from critical grassland ecosystems. In many cases, a rapid decline in bird species, butterflies and native plants followed.
And there’s the rub. Grassland ecosystems do poorly when they have too much disturbance and they also do poorly when they have too little. Too much hoof action compacts the soils, makes water run off and erodes the land rather than percolating through the soil to recharge groundwater. Too little hoof action allows one or two species (these days often weeds) to take over. And so it goes with all of the other effects of grazing: too much or not enough.