While they are appreciated by companies aiming to offset the climate impact of their activities, the effectiveness of carbon credits is increasingly contested. According to a new study, only a small fraction of forest-based carbon credits available actually help prevent deforestation.
As climate change accelerates and pressure mounts on corporations and countries to slash emissions, the market for carbon credits has exploded. The principle is quite simple: to offset the carbon emissions linked to their activities, companies buy carbon credits, which will be used to invest in forest protection or tree planting projects. In carbon markets, a single credit represents one tonne of CO2 that is either removed from the atmosphere by growing trees, or prevented from entering it through avoided deforestation. Such schemes, however, have long been dogged by charges of poor transparency, dodgy accounting practices, and in-built conflicts of interest.
To accurately assess the effectiveness of projects financed by carbon credits, an international team of researchers explored the effects of several projects to reduce emissions from deforestation and forest degradation (REDD) launched in six countries across the world.  The results of the study, which were published Thursday, August 24 in the journal Science, provide a clear conclusion: “Most projects have not significantly reduced deforestation.”
Only 5.4 million out of 89 million credits — about six percent — actually resulted in carbon reduction through forest preservation, the study found.
Although some projects were successful, the reductions were significantly lower than what had been announced. According to the study: “Methodologies used to construct deforestation baselines for carbon offset interventions need urgent revisions to correctly attribute reduced deforestation to the projects, thus maintaining both incentives for forest conservation and the integrity of global carbon accounting.”
“Selling hot air”
“Carbon credits provide major polluters with some semblance of climate credentials,” said senior author Andreas Kontoleon, a professor in the University of Cambridge’s department of land economy. “Yet we can see that claims of saving vast swathes of forest from the chainsaw to balance emissions are overblown.“
“These carbon credits are essentially predicting whether someone will chop down a tree and selling that prediction,” he added in a statement. “If you exaggerate or get it wrong — intentionally or not — you are selling hot air.“
The new study is among the first peer-reviewed assessments across a number of representative projects.
To assess the performance of 18 forest protection schemes in different countries, the researchers identified parallel sites within each region with similar conditions but without forest protection schemes. Of the 18 projects, 16 claimed to have avoided far more deforestation than took place at the comparison sites.
There are several possible reasons that protection schemes have fallen so far short of their carbon sequestration claims. One is that they are calculated on the basis of historical trends that can be inaccurate or deliberately inflated. The operation must also project deforestation or afforestation rates over an extended period of time, which is difficult. In addition, projects may be located in areas where substantial conservation would have occurred in any case. The entire methodology serving as the basis for these carbon credits must therefore be reconsidered!