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Carbon offset projects claiming to curb deforestation are significantly overestimating their impact, according to a new study published in Science on Thursday.

Sold as a way to lessen the impact of greenhouse gas emissions by allowing polluters or consumers to purchase offsets or credits that allow them to keep emitting in return for funding projects that decrease emissions elsewhere, offsets have become a high-profile model for corporate climate action. 

But a systematic evaluation of 26 carbon offset projects that claim to slow the rate of potential deforestation in six countries on three continents found that the vast majority of projects did not actually slow deforestation, and those that did were significantly less effective than they claimed.

“The main message is that relying on [carbon offset] certification is not enough,” said the study’s lead author, Thales West, an interdisciplinary ecologist and assistant professor at Vrije Universiteit in Amsterdam and a fellow at Cambridge’s Centre for Environment, Energy and Natural Resources. “If you rely 100 percent on offsets, you probably will not do anything positive in terms of mitigating climate change.”

The study focuses on voluntary REDD+, or Reducing Emissions from Deforestation and forest Degradation projects. These are standalone projects that operate independently in the voluntary carbon offset market, outside of the United Nations Framework Convention on Climate Change’s REDD+ framework for national and subnational projects. The authors call for “urgent revisions” to the certification methods used to attribute avoided deforestation to these projects, pointing out major flaws in current practice.

Over the past few decades, carbon offsets have become increasingly ubiquitous, particularly in higher-income countries, where consumers can assuage their climate guilt by paying a little extra for a flight ticket or a rental car, with the understanding that their additional payment will go towards supporting a tree farm, for example. Big, high-emitting companies like Delta, JetBlue, Disney, General Motors and Shell have all bought and sold huge amounts of carbon offsets in the name of climate action. It’s an attractive business model for companies looking to “go green” without significant changes in their operations: purchase some carbon offsets to cancel out your emissions. Or, at least, appear to.

Ever since carbon offsets hit the market, there’s been significant debate over whether or not they’re an effective model for climate mitigation. The Cambridge study illustrates a basic problem: many carbon offsets aimed at reducing deforestation are not nearly as effective as they claim to be. And in a lot of cases, they may not be doing anything at all.

Julia Jones, a PhD conservation scientist at Bangor University focused on conservation impact evaluation, said the study’s unique methods make it especially compelling and set it apart from other research in the field.

“Their study is definitely the largest in scope and using pretty much the most robust methods at the moment,” said Jones, who was not involved in the study.

The study looked at 26 projects in six countries: Cambodia, Colombia, Democratic Republic of Congo, Peru, Tanzania, and Zambia. Researchers found that only eight of the 26 projects selling offsets showed any evidence of reducing deforestation, and even those that did failed to achieve the extent of reductions that the projects claimed.

Only 18 of the 26 projects had sufficient publicly available information to determine the number of offsets they were projected to produce. From project implementation until 2020, those 18 projects were expected to generate up to 89 million carbon offsets to be sold in the global carbon market. But researchers estimate that only 5.4 million of the 89 million, or 6.1 percent, would be associated with actual carbon emission reductions.

West said companies that are buying and selling carbon offsets that have been certified by third-party entities may not be aware that they’re misleading their customers—they might simply trust that the certification is legitimate. But the processes used to evaluate the projects’ effectiveness for certification are deeply flawed, he said.

Most projects look at historical deforestation within a region to forecast a baseline deforestation rate, or the amount of deforestation that would have happened without the project’s intervention, West said. The problem is, it’s all based on hypotheticals.

“They’re not really doing good science,” he said.

West and his colleagues took a different approach. They created a weighted average of regions that are similar to the project area but don’t house any projects, and used that as a “synthetic control.” Then, they compared deforestation in the synthetic control areas with the project areas during the period of time that the project was active. If projects are successfully reducing deforestation, then those project areas should exhibit less deforestation than the synthetic controls. Instead, West and his colleagues found that usually wasn’t the case.

Jones emphasized that the takeaway from the study is that there needs to be increased investment in effective projects for deforestation reduction, not a disinvestment in forest protection. The voluntary carbon market has become a crucial source of funding for forest conservation initiatives, she said, and this funding needs to continue.

“We simply cannot tackle climate change without stopping both tropical forest deforestation and forest degradation now,” Jones said. “It’s a real urgent priority.”

https://arstechnica.com/?p=1963543