As the world’s governments look to curb global warming, protecting what’s left of Earth’s tropical forests is crucial. That means REDD+ could have a huge role to play — but debate is currently raging as to whether or not REDD-based projects can actually deliver the level of emissions reductions necessary to avert runaway global climate change.

Many REDD+ projects are built around the idea of carbon offsetting. In a recent investigative article, ProPublica’s Lisa Song writes that, despite their enormous appeal, carbon offsetting programs don’t always lead to the emissions reductions they’re meant to produce.

In “case after case,” Song writes, she found “carbon credits hadn’t offset the amount of pollution they were supposed to, or they had brought gains that were quickly reversed or that couldn’t be accurately measured to begin with.”

However, the ProPublica report has been criticized by advocates of carbon credit schemes who say that Song has failed to tell the whole story.

Earlier this year, it was announced that Indonesia would receive the first installment of a total $1 billion in funds pledged by Norway to preserve the Southeast Asian nation’s tropical forests. Brazil was also set to be paid $96 million, in this case by the UN’s Green Climate Fund, for the emissions avoided by the South American country’s efforts to reduce Amazonian deforestation rates between 2014 and 2015.

Both of these were results-based payouts made under the auspices of the UN’s program for reducing emissions from deforestation and forest degradation, known as REDD+. As the world’s governments look to curb global warming, protecting what’s left of Earth’s tropical forests is crucial. That means REDD+ could have a huge role to play — but debate is currently raging as to whether or not REDD-based projects can actually deliver the level of emissions reductions necessary to avert runaway global climate change.

REDD+ programs can work in a variety of ways. As opposed to wealthy countries and businesses paying developing tropical forest countries directly for proven emissions reductions from reduced deforestation, many are built around carbon offsetting. The idea is that if companies, governments, and anyone else looking to reduce their carbon footprint purchases “carbon credits” to support conservation efforts in forests around the world, those forests will continue to sequester carbon instead of being cut down and releasing their carbon into the atmosphere — and the emissions resulting from the carbon credit-purchasers’ own activities are, in theory, canceled out.

A recent article by ProPublica’s Lisa Song explains that these types of offset schemes have enormous appeal: “The appetite is global. For the airline industry and industrialized nations in the Paris climate accord, offsets could be a cheap alternative to actually reducing fossil fuel use.” But Song writes that she found these offsets do not always lead to the emissions reductions they’re meant to produce: “[T]he desperate hunger for these carbon credit plans appears to have blinded many of their advocates to the mounting pile of evidence that they haven’t — and won’t — deliver the climate benefit they promise.”

A high-profile example cited by Song is the Suruí Forest Carbon Project in the Brazilian state of Rondônia, the world’s first major indigenous-led forest conservation and voluntary offsetting program, designed to prevent five million tons of carbon emissions or more over the course of 30 years. The project was suspended last year, after a surge of illegal miners and loggers invaded the the Paiter-Suruí tribe’s land — sometimes aided and abetted by members of the tribe who felt their community was not receiving a fair share of the benefits of the program.

Though the Suruí Forest Carbon Project was developed entirely outside the framework of REDD+, Song says she looked into REDD-based offset projects “going back two decades and spanning the globe” and considered “findings from academic researchers in far-flung forest villages, studies published in obscure journals, foreign government reports and dense technical documents” in order to examine the track record of voluntary emissions offsetting programs. ProPublica also commissioned an analysis of satellite data to determine how much forest remains in a conservation area in the state of Acre, Brazil that started selling offset credits in 2013. “Four years later, only half the project areas were forested,” Song reports.

In “case after case,” Song writes, she found “carbon credits hadn’t offset the amount of pollution they were supposed to, or they had brought gains that were quickly reversed or that couldn’t be accurately measured to begin with.” In effect, she concludes, these offset programs have given polluters “a guilt-free pass to keep emitting CO₂, but the forest preservation that was supposed to balance the ledger either never came or didn’t last.”

Larry Lohmann, a researcher who has studied carbon credits for two decades, told Song that, “Offsets themselves are doing damage.” Princeton researcher Timothy Searchinger told Song that carbon offsetting is “the worst possible idea — except for everything else.” According to Song, Searchinger added that these offset programs simply haven’t yet been able to generate enough funds to succeed, mainly because carbon credits are currently sold primarily on voluntary markets — a common argument made by proponents of offsets.

Song’s conclusions based on her investigation were far more skeptical of the entire premise of offsets, however: “My visit to Acre suggested that even the best REDD program in the world was running into practical, political and scientific obstacles that couldn’t be fixed with funding alone — another warning sign on top of the reports concluding earlier programs hadn’t worked.”

However, the ProPublica report has been criticized by advocates of carbon credit schemes who say that Song has failed to tell the whole story. David Antonioli and Naomi Swickard, the CEO and Chief Market Development Officer, respectively, of the non-profit organization Verra, posted a response to Song’s report noting that the REDD+ initiative in Acre hasn’t actually obtained third-party certification: “In other words, to date, Acre has not issued a single carbon credit, at least not one that would meet the strict requirements of robust standards like the Verified Carbon Standard (VCS), the standard most often used to certify REDD+ projects around the world.” Verra manages the VCS Program, which was launched in 2006.

Antonioli and Swickard say that the ProPublica article fails to mention other key aspects of offsetting schemes, such as buffer mechanisms that can help ensure carbon credits issued through REDD+ programs are permanent. The article also misses the broader goals of REDD+, which is aimed at more than just conserving forests, they add.

“One of the key insights we have drawn from the more than 150 REDD+ projects certified by the VCS is that successful projects most often work closely with the communities that live in and around forests to address core livelihood needs,” Antonioili and Swickard write. “In short, REDD+ projects have the potential to transform local forest-based economies so that communities can benefit from healthy and thriving forests, rather than being forced to chop them down.”

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