While recent research has raised alarm that tropical forests including the Amazon could soon stop serving as carbon sinks, a first-of-its-kind study from 30 experts that takes into account other greenhouse gases suggests the world's largest rainforest may already be contributing to the warming of the planet.
The new analysis, published Thursday in the journal Frontiers in Forests and Global Change, considers not only carbon dioxide (CO2) and its impact on the global climate but also that of methane (CH4), nitrous oxide (N20), black carbon, biogenic volatile organic compounds (BVOCs), aerosols, evapotranspiration, and albedo.
"What the authors do that's important is to expand the conversation beyond carbon dioxide, which is what 90% of public conversation is centered around," Patrick Megonigal, associate director of research at the Smithsonian Environmental Research Center, toldNational Geographic.
"CO2 is not a lone actor," added Megonigal, who was cited in but not involved with the research, which was funded by the National Geographic Society. "When you consider the whole cast of other characters, the outlook in the Amazon is that the impacts of human activities will be worse than we realize."
As 15-year-old climate activist Alexandria Villasenor put it in a tweet about the study: "We're destroying our life-support systems. We're running out of time."
The study notes that "after a transient period of reduced deforestation and increased optimism, rising agricultural conversion and illegal logging activities are again accelerating Amazonian forest loss. This resurgence has renewed concerns that the region is rapidly approaching a catastrophic 'tipping point.'"
Data from the Rainforest Foundation Norway revealed Monday that human activities have destroyed 34% of old-growth tropical rainforests and degraded 30% worldwide. Over half of that destruction since 2002 has been in the Amazon and neighboring South American rainforests. Under Brazilian President Jair Bolsonaro--whose country is home to the majority of the Amazon--deforestation hit a 12-year high in 2020.
"Cutting the forest is interfering with its carbon uptake; that's a problem," Kristofer Covey, lead author of the new study and a professor of environmental studies at Skidmore College, told National Geographic. "But when you start to look at these other factors alongside CO2, it gets really hard to see how the net effect isn't that the Amazon as a whole is really warming global climate."
The study says that despite some uncertainty, "we conclude that current warming from non-CO2 agents (especially CH4 and N2O) in the Amazon Basin largely offsets--and most likely exceeds--the climate service provided by atmospheric CO2 uptake. We also find that the majority of anthropogenic impacts act to increase the radiative forcing potential of the basin."
"Given the large contribution of less-recognized agents," the paper continues--noting that Amazonian trees alone emit about 3.5% of all global CH4--focusing strictly on carbon uptake and storage "is incompatible with genuine efforts to understand and manage the biogeochemistry of climate in a rapidly changing Amazon Basin."
Covey and his colleagues told National Geographic that reversing the damage that's already been done will require halting emissions from fossil fuels around the world and reining in Amazon deforestation, "along with reducing dam building and increasing efforts to replant trees."
The Amazon is among the most biodiverse places on the planet. The ongoing coronavirus pandemic has highlighted the importance of conserving and restoring rainforests not only because of the climate emergency but also to prevent future zoonotic disease outbreaks.
As the pandemic--officially declared a year ago Thursday--has killed more than 2.6 million people and sickened over 119 million worldwide, experts from across the globe have repeatedly called on humanity to heal its "broken relationship with nature."
