Cows, carbon and climate change


With record heat waves, costly fire seasons, rising sea levels, and superstorms wracking our planet, it is clear that human-caused climate disruption is causing major problems for all of Earth’s inhabitants. Fossil fuels have long (and correctly) been identified as the biggest culprits, with the majority of humanity’s atmospheric carbon contribution coming from burning fossil fuels — oil, coal, and natural gas — and reversing hundreds of millions of years of natural carbon sequestration on the part of swamps and forests. However, there is an increasing global awareness that animal agriculture also plays a major role in accelerating climate change. 

Cattle and other domestic ruminants have a four-chambered stomach, including a fermentation vat (called a rumen) that enables the animal to use microbes to break down cellulose — the main component of wood, paper and cardboard — into sugar. This fermentation process creates methane, which increases atmospheric temperatures  25 to 84 times as much as carbon dioxide. Thus, cattle, sheep and other livestock boost the carbon dioxide absorbed by plants into a far more climate-potent gas. 

Livestock belching, farting and manure emissions of this and other gases has been estimated to account for 14 to 18 percent of the total human-induced greenhouse gases that are responsible for climate change. The remaining 82 to 86 percent of carbon emissions into the atmosphere comes from taking carbon out of the ground and pumping it into the atmosphere, whether through equally-potent methane leaks from natural gas wellfields and pipelines or through burning fuels to produce carbon dioxide. Thanks to the combined effect of greenhouse gases from livestock production and fossil fuel combustion on the world’s climate, the survival of the planet’s life forms, humanity included, is now at risk.

But the livestock also convert and degrade lands, radically reducing carbon sequestration — the natural ability of the biosphere to soak up atmospheric carbon — creating an even greater climate problem than methane emissions themselves. This effect is most obvious in tropical rainforest areas, which are being deforested at an accelerating pace to create pasture lands for livestock. This upsets natural nutrient cycling, as soil nutrients present in rainforest settings quickly leach out of the soil. Following deforestation, the massive carbon banks tied up in rainforest trees, vines and shrubs are gone for the long term. This bankrupting of carbon reserves in the tropics is paired with a catastrophic loss of biodiversity, an environmental crisis co-equal to climate disruption in its severity and significance. 

Less visibly but perhaps more importantly, livestock grazing on the world’s grasslands, shrubsteppes and deserts can cause even greater withdrawals from a carbon banking standpoint than cutting down the forests. Livestock grazing eliminates deep-rooted native grasses and wildflowers, replacing them with shallow-rooted annual weeds that thrive in disturbed environments and die every year, releasing their carbon back to the atmosphere. Annual weeds therefore have little ability to store carbon in the soil.

In addition, once rangelands become degraded through overgrazing, shrubs sometimes increase, but clearing these shrubs to stimulate forage production for livestock further cripples the land’s ability to store carbon.

Throughout the Intermountain West, heavy grazing by livestock flips the ecological switch that converts healthy native habitats to an annual weed called cheatgrass, by suppressing the native perennial grasses and destroying the soil crusts that otherwise prevent cheatgrass invasion. Cheatgrass is highly flammable, and the resulting high-frequency range fires can eliminate deep-rooted shrubs, accelerating carbon loss from the soil.

Restoring the 25 million acres of livestock-degraded and cheatgrass-infested rangelands in the western United States back to native shrubs and grasses could offset some 23 percent of all U.S. carbon emissions. Stopping the livestock-induced damage would allow the land to heal over time and regain its carbon-storing capacity.

Natural areas are the lungs of the planet, breathing in carbon dioxide and exhaling oxygen. Personal choices by consumers (adding rooftop solar panels, eating less meat) can help, but they’re not enough to stem the tide. Returning half the Earth to nature would restore carbon reserves while also addressing the biodiversity crisis. 

We need major policy initiatives like the Green New Deal to force decisive action, stabilize and slash carbon emissions, and restore healthy levels of carbon sequestration through the natural processes of photosynthesis. Major livestock reforms on America’s western public lands would be a key step forward in this effort.

Erik Molvar is a wildlife biologist and serves as executive director for Western Watersheds Project, a nonprofit conservation organization working to protect and restore watersheds and wildlife throughout the American West.

Tags Agriculture Carbon Climate change emissions Erik Molvar Methane

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