Taming the Climate Impacts of Cattle and Sheep

Photo: Erik Molvar.

A number of recent climatological reports highlight that the livestock industry is a major source of climate problems. In part, this is due to the livestock industry’s heavy reliance on ruminants – herbivores like cattle and sheep that have a four-chambered stomach that enables them to break down cellulose (think paper or cardboard) and turn it into energy. The byproduct of these mobile bacterial fermentation vats is methane, a greenhouse gas that traps 28 to 84 times more solar heat than carbon dioxide. However, livestock producing 30% of the world’s atmospheric methane is only part of the story. Heavy grazing by domestic livestock destroys vegetation communities with deep-rooted plants that are excellent at sequestering carbon in the soil, and replaces them with weeds that die every year and give up all their carbon to the atmosphere.

From the standpoint of federal policy, the obvious place to start solving this problem is on western public lands, most of which are currently leased to commercial livestock operations for grazing, and which are presently hemorrhaging carbon as a result of overuse. The desertification of western public lands due to excessive livestock numbers, and the conversion of these disturbed lands to flammable invasive weeds that store little if any carbon, is a real issue. Improving the ecological function of 250 million acres of grazed federal lands provides an opportunity to make a big difference in the nation’s carbon balance.

In a natural state, sagebrush steppe is considered superior to coniferous forests for carbon sequestration. While western forests burn every 125 to 700 years (depending on the tree species), releasing the vast majority of their carbon, the carbon in sagebrush grasslands is sequestered underground, in the dense, deep root networks of shrubs and native bunchgrasses. Even when there is a fire, the majority of the carbon stays safely in the soil. One federal scientist has even argued that carbon banking is “the highest and best use” of sagebrush steppe habitats.

Heavy livestock grazing destroys the native bunchgrasses of the sagebrush steppe, and facilitates the invasion of flammable weeds like cheatgrass. The ecology of these more fragile plant communities is now characterized under a “state and transition” model, in which bunchgrasses can only sustain modest grazing pressure until they lose vigor and die out, to be replaced by weeds like cheatgrass. The ecological switch that triggers the shift from healthy bunchgrasses between the sagebrush to flammable weeds is – you guessed it – the domestic cow. And cheatgrass continues to spread rapidly across western public lands under today’s livestock management.

This downward spiral from healthy native vegetation to tinder-dry weeds is readily preventable. All it takes is limiting livestock densities to levels that the environment can sustain. While this sounds simple, land managers are under constant political pressure to maximize the number of cattle and sheep on western public lands. Instead of balancing multiple uses, range managers shift the focus to maximizing the bottom lines of the tenant grazers.

On western public lands, ranchers are commonly authorized to graze off more than half of all of the vegetation that is produced for the entire year. That’s way more damage than native grasses can sustain and still survive (range science says livestock should never be allocated more than one-fourth), and doesn’t leave enough vegetation behind for the native wildlife. This chronic overgrazing for livestock also damages trout streams and the lush plant communities that border them.

The first step to restoring an ecological balance and climate resilience across the West is to dial back this chronic overgrazing. Adding staff to provide rigorous monitoring, instead of the casual eyeballing of the past, will provide further accountability and speed vegetation recovery. With a warming climate and expanding fire seasons, we need to quickly restore cheatgrass-invaded lands to the native bunchgrasses that hold more moisture, and prevent the further advance of this flammable weed by keeping lands that still have some native grasses healthy.

Each day of inaction makes the problem worse, and makes carbon banking solutions harder to achieve.

Erik Molvar is a wildlife biologist and is the Laramie, Wyoming-based Executive Director of Western Watersheds Project, a nonprofit group dedicated to protecting and restoring watersheds and wildlife on western public lands.