The world’s tropical forests are in such poor shape that they are emitting more climate-warming carbon dioxide into the atmosphere than they absorb, according to a new study.
The paper, published Thursday in the journal Science, quantified the carbon emissions caused by the degradation of tropical forests over the past decade. Its conclusion: In Asia, Africa and Latin America, deforestation has caused tropical forests to be a carbon “source” instead of a carbon “sink.”
The study has made for some grim headlines — but those headlines mask a more nuanced reality, according to one climate expert, who says that the study both confirms what we already knew and points to solutions to a fixable problem.
Before you start panicking about the future of tropical forests, here are five takeaways from the new study.
- The world’s tropical forests were already considered a net source of carbon.
“The idea that forests just magically flipped from sink to source in the past 10 years isn’t true,” said Will Turner, senior vice president of global strategies at Conservation International. Data from the Intergovernmental Panel on Climate Change, a widely cited 2011 paper, and the new study itself showed that carbon emissions caused by deforestation were already outpacing carbon absorption in the tropics, he said.
What the new study does is update what we know about when and how that has happened. “In Africa and Asia in particular, the net carbon emissions of tropical forests were at or around zero in 2003, the beginning of the period studied,” Turner said. “Now they’re very much a source [of carbon emissions].”
Moreover, according to Turner, the 2011 study showed that emissions caused by high tropical deforestation rates of the 1990s had slowed somewhat by the early 2000s, especially in Latin America. The new paper shows that that trend has, unfortunately, reversed.
- As causes of deforestation go, clear-cutting may be exceeded in the tropics by ‘death by a thousand cuts.’
The authors of the new study found that some 70 percent of the carbon emissions they tallied were caused by what is commonly called “forest degradation,” more than from the massive clear-cutting that many people think of when they think of deforestation.
“Think selective logging, or smallholder farmers making small patches of cuts on small plots for their farms,” Turner said. These smaller disturbances tend to thin the forest but can leave some of the forest canopy intact, a phenomenon that some previous studies did not account for, potentially underestimating carbon emissions.
“This paper throws shade on the idea that there’s a substantive difference between deforestation and degradation,” Turner said. “[The authors] put it on a continuum, from massive deforestation all in one place, all the way down to cutting down individual trees. But what they found is that those smaller actions really matter.”
- The actual carbon emissions from tropical deforestation could be worse than what the study reports.
“There’s one thing that this paper doesn’t do,” Turner said. “It looks only at aboveground biomass — trees, essentially — and so the big thing it misses is soil carbon.”
Tropical forests in peatlands and along coastlines can store far more carbon in their soils than they do in the trees themselves, he said. Clearing those forests almost universally leads to loss of carbon from those soils as well, most notably by making peatlands more susceptible to wildfires.
- Gloomy headlines aside, forests aren’t the ‘enemy’ — the enemy is us.
Skimming the headlines is likely to leave an inaccurate impression of the problem.
“These news reports that forests are either good for us or bad for us is completely not the right way to think about it,” Turner said. The paper shows where forest growth and carbon absorption is taking place, and where forest loss is taking place, “and those are different things,” he said.
“Earth’s forests still hold more carbon than the entire atmosphere, and there are still millions of square kilometers’ worth of forests still absorbing carbon,” he said. “They are our friends. The thing that’s not our friend is us, cutting down trees.”
- We know how to solve this problem.
To stop deforestation, you have to know where it’s happening so you can find out who’s doing it, and a number of tools have arisen in recent years to that end. But the rise of small-scale degradation complicates the picture, Turner said.
“You can’t just go to one person and say, You’ve got to stop this,” he said. The study’s finding that 70 percent of the problem is small-scale degradation renders that approach ineffective and points to the need for a big-picture, “landscape approach” to the problem. “What this means is, you have to work with governments, businesses, communities and the farmers themselves to change the systems and incentives that give rise to deforestation,” he said.
“In parts of Indonesia, for example, there have been policies where to maintain land tenure, you have to plant at least one productive crop,” he continued. “So you’ll see these incredibly carbon-rich peatland forests cleared to plant a few trees. There’s just no reason for that. To change these policies, you have to work with all the stakeholders on the ground.”
By deliberately planting and managing tropical forests, Turner said, we can still turn them around from what is now a net source to a sink again, “more than reversing the situation” within a few decades.
“There’s that much potential there. There’s definitely a bright side. We have the knowledge to do it, we just need to bring together the actors to make it happen.”
Bruno Vander Velde is CI’s editorial director.
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