Enlarge / A view of the Pantanal wetlands in Brazil. New research shows a large chunk of global methane emissions are from rotting vegetation in tropical wetlands. (credit: Carl de Souza/AFP via Getty Images)

A 2021 pledge by more than 100 nations to cut methane emissions from anthropogenic sources 30 percent by 2030 might not slow global warming as much as projected, as new research shows that feedbacks in the climate system are boosting methane emissions from natural sources, especially tropical wetlands.

A new trouble spot is in the Arctic, where scientists recently found unexpectedly large methane emissions in winter. And globally, the increase in water vapor caused by global warming is slowing the rate at which methane breaks down in the atmosphere. If those feedbacks intensify, scientists said, it could outpace efforts to cut methane from fossil fuel and other human sources.

Methane traps about 80 times more heat than carbon dioxide over a 20-year period, and scientists estimate it’s responsible for 20 to 30 percent of climate warming since the start of the industrial age, when atmospheric methane was at a concentration of about 0.7 parts per million. It has zig-zagged upward since then, spiking with the first fossil gas boom in the 1980s, then leveling off slightly before a huge surge started in the early 2000s. The amount of methane in the atmosphere reached about 1.9 ppm in 2023, nearly three times the pre-industrial level.

Enlarge (credit: Tony C. French/Getty)

In the urgent quest for a more sustainable global food system, livestock are a mixed blessing. On the one hand, by converting fibrous plants that people can’t eat into protein-rich meat and milk, grazing animals like cows and sheep are an important source of human food. And for many of the world’s poorest, raising a cow or two—or a few sheep or goats—can be a key source of wealth.

But those benefits come with an immense environmental cost. A study in 2013 showed that globally, livestock account for about 14.5 percent of greenhouse gas emissions, more than all the world’s cars and trucks combined. And about 40 percent of livestock’s global warming potential comes in the form of methane, a potent greenhouse gas formed as they digest their fibrous diet.

That dilemma is driving an intense research effort to reduce methane emissions from grazers. Existing approaches, including improved animal husbandry practices and recently developed feed additives, can help, but not at the scale needed to make a significant global impact. So scientists are investigating other potential solutions, such as breeding low-methane livestock and tinkering with the microbes that produce the methane in grazing animals’ stomachs. While much more research is needed before those approaches come to fruition, they could be relatively easy to implement widely and could eventually have a considerable impact.