Are Declining Stocking Rates Underexplored By Scientists? – Inside Climate News

If you stood in front of a map of the world, subtracted its oceans and threw a dart, you would have about a one-in-four chance of hitting land humans use for grazing livestock. But concentrations of grazing animals used for human consumption across the world have been shifting for the last 25 years, according to a new study, suggesting profound environmental and climate consequences.

In a paper published today in the Proceedings of the National Academy of Sciences, authors from Arizona State University used data from the Food and Agriculture Organization of the United Nations to establish livestock trends from 1999 to 2023. In middle Africa, parts of Asia and Central and South America, livestock numbers are on the rise, while in North America, Europe and Australia their numbers are falling. 

But the environmental changes associated with a decrease in livestock on the land have not always been studied at the same rate as the impacts of an increase in stocking on a landscape. From 1999 to 2023, there were about 10 papers published on overgrazing, the ecological impact of species like cattle eating the same patch of land too frequently, for every one study exploring how landscapes respond in the absence of livestock, said Osvaldo Sala, director of Arizona State University’s Global Drylands Center and one of the paper’s authors.

As a result, scientists do not understand the ecological consequences of decreasing livestock as well as they understand overgrazing’s impacts.

“The mismatch between the patterns of stocking rates and the literature really surprised me,” Sala said. “Policy is determined by what scientists tell the broader community, so if the scientists are [saying] that the major problem is overgrazing, the policy will be to try to study overgrazing, combat overgrazing, while, in fact, that only addresses the challenges in half of the world.”

Increasing concentrations of livestock were driven by factors like regional changes in total meat consumption and the amount of poultry or pork production, and correlated with wealth and population growth.

Fewer livestock in North America and elsewhere in the West brings difficult-to-predict environmental consequences. Sometimes ecosystems can rebound in the absence of cattle, restoring biodiversity, but this is not guaranteed. The paper found that decreased grazing can affect local water cycles, increase a landscape’s wildfire risk or reduce biodiversity if regeneration is not properly managed.

These changes can have climate implications—more plant growth traps more carbon, but can make a landscape more likely to burn more severely, releasing carbon stored in vegetation into the atmosphere. Without more research into these outcomes and their relationship to declining stocking rates, scientists may be missing a key component of agriculture’s connection to climate change.

“It’s not only an opportunity but a need if we want to have a full picture of climate change,” Sala said.

The vast majority of U.S. livestock is in ranges in the American West. Sala emphasized that even though there are fewer cattle on the landscape today than there were in 1999, that doesn’t mean that overgrazing isn’t still an issue.

According to reporting by High Country News, wealthy landowners in the region allow their cattle to overgraze rangeland despite warnings from federal agencies. 

“They’ve highlighted a really important blind spot that exists in general research about livestock trends globally,” said Retta Bruegger, a rangeland ecologist at Colorado State University, who was not involved in the paper. “I think the implications for rangeland health are really important here.”

Drought and wildfire sprang to her mind as potentially fruitful avenues of future research for scientists.

Bruegger, who works with ranchers on Colorado’s western slope, added that the paper underscores researchers’ need to pay attention to historical livestocking trends, particularly in the West. “Sometimes we have this idea [that] the numbers of livestock on our public rangelands in the West are constant or maybe they’re increasing and they’re really not, according to the paper,” she said. The new work “highlights the need to really be engaged with the actual trends that are happening as we think about ecology and landscapes.”

Sala is excited by the many research opportunities his paper suggests. Even something as well-understood as plants’ ability to trap carbon must be explored more, he said. It’s not enough to simply suspect that flora no longer exposed to grazing will store more carbon, he said. “We need to find out how much, where, and when. We don’t know.”