There's a lack of evidence that livestock (such as cattle, sheep, and goats) dining on grassland has a lower carbon footprint than that fed on grains, as some environmentalists and "pro-pastoralists" claim, according to a new report by an international group of researchers led by the Food Climate Research Network (FCRN), based at the University of Oxford in the United Kingdom.
"Switching to grass-fed beef and dairy does not solve the climate problem—only a reduction in consumption of livestock products will do that," says one of the report's authors, Pete Smith of the University of Aberdeen in the United Kingdom.
Livestock is responsible for 14.5% of global greenhouse emissions, researchers estimate. The animals emit gases such as nitrous oxide, carbon dioxide (CO2), and methane in amounts that have significantly changed our atmosphere. And the impact is growing. As more people worldwide are lifted out of poverty, many more can afford to eat meat regularly; global demand for animal products, now 14 grams per person per day, is expected to more than double by 2050.
Most modern-day cattle are raised on "landless systems," also known as feedlots, where the cattle have little space, no access to pastures, and are fed a grain-based diet. Proponents of this system argue that it is an efficient way to produce meat that helps prevent conversion of forests and other ecosystems to pasture. But feedlot systems are notorious for producing hydrogen sulfide and polluting waterways with animal waste, ammonia, pathogens, and antibiotics. Moreover, some experts say, because ruminant stomachs evolved to eat grass, feeding them soy or corn results in more greenhouse gas emissions.
Grass fed beef market to grow by $6.3 BN over the next decade
Letting ruminants graze is a better system, some argue. Plants take up CO2 through their leaves and, when they die, leave part of it in their roots, where it remains and is converted to other forms of life; that makes soil a giant carbon sink. But human activities such as deforestation and plowing have released much of the stored carbon, and "pro-pastoralists" suggest that grazing cattle can help restore grasslands and soil, sequestering massive amounts of CO2 in the process. The cows' manure would also recycle nutrients such as nitrogen and phosphorous to the soil, encouraging the growth of new vegetation and sequestering even more carbon.
But the 127-page FCRN report released today, Grazed and Confused, says there is no evidence that grass-grazing cattle will make a difference. Grass-fed cattle do contribute to CO2 sequestration, the international group concluded after sifting through more than 100 papers—but only under ideal conditions. When too many animals roam a field, they will trample plants and soil and impede carbon storage; when it's too wet, carbon uptake is impeded as well. And even under the best of conditions, carbon sequestration is not at levels high enough to counteract the ruminants' own emissions, the report says.
The findings don't sway advocates of grazing. Richard Young of the Sustainable Food Trust in Bristol, U.K., says the report is too quick to dismiss the importance of grazing in some regions. "For me it's very simple," he says. "In countries like the U.K. and Ireland, and on rangelands where rainfall is too unreliable for much crop production, we should continue to encourage and make possible ruminant production." Legislation and policy can help prevent overstocking, he says.
"Farming becomes sustainable when it looks like an ecosystem," adds Richard Manning, the Helena, Montana–based author of Grassland: The History, Biology, Politics and Promise of the American Prairie. "It works when we mimic natural systems. And we have to include animals, because that's what's found in nature." Manning says the report also ignores other services grasslands provide, such as absorbing flood water and filtering runoff. And as the report acknowledges, conventionally raised beef has other environmental issues, Manning points out, such as increasing the demand for grains, and therefore cropland.
In the end, the real solution is reducing global meat consumption, says Tim Benton, who studies sustainable agro-ecological systems at the University of Leeds in the United Kingdom. "Our ever-increasing demand for meat is driving the planet in an unsustainable direction," Benton says. "No one farming system will fix it."
