New studies on carbon credit quality

Two new studies recently published in peer-reviewed journals provide important new evidence on the effectiveness of carbon offset projects.

REDD+ in Sierra Leone: Mixed Results

A February 2024 study published in Nature Sustainability evaluated a large-scale voluntary REDD+ project in Sierra Leone's Gola Rainforest National Park. The researchers used a before-after-control-intervention (BACI) framework with both satellite imagery and household surveys to assess the project's impact over its first five years.

The findings present a mixed picture:

- Deforestation reduction: The REDD+ project slowed deforestation by 30% compared to control communities
- Economic impact: No significant change in economic wellbeing or conservation attitudes among local communities
- Cost efficiency: Achieved approximately 340,000 tCO₂ in avoided emissions annually at an estimated cost of $1.12 per averted tCO₂

While the project did reduce deforestation rates, it did not stop or reverse the trend completely. The researchers found evidence suggesting the program may have shifted labor away from forest-dependent farming activities by increasing the value of alternative income sources.

Australian Carbon Offset Projects Fall Short

Even more concerning findings come from a March 2024 study in Communications Earth & Environment that analyzed 182 carbon offset projects under Australia's Human-Induced Regeneration (HIR) program - one of the world's largest nature-based offset types.

These projects, covering 42 million hectares (an area larger than Japan), claimed to induce regeneration of permanent native forests through changes in land management practices like reducing grazing pressure. However, the researchers found:

- Minimal positive change in forest cover (just 3.6%) across credited areas
- Negligible increase in total woody vegetation cover (only 0.8%)
- Changes in vegetation largely mirrored those in adjacent comparison areas outside the projects, suggesting natural factors like rainfall variability - not project interventions - drove any changes

Despite these poor results, the projects received 27.4 million carbon credits, with 22.9 million issued to projects that showed declining or stagnant woody cover. The Australian government alone has spent approximately AU$300 million purchasing these credits and is committed to purchase around AU$1.2 billion more.

Implications for Carbon Markets

These studies highlight critical concerns about carbon offset reliability:

1. Additionality challenges: Many projects claim credit for changes that would have happened anyway
2. Verification limitations: Current monitoring approaches may not adequately measure actual carbon sequestration
3. Permanence questions: Especially in drought-prone regions where climate variability affects carbon storage

The Australian study authors note that these findings "add to the growing literature highlighting the practical limitations of offsets and the potential for offset schemes to credit abatement that is non-existent, non-additional, and potentially impermanent."

Updating Our Knowledge Base

At carboncredits.fyi, we're committed to synthesizing the latest rigorous evidence on carbon credit effectiveness. Based on our previous systematic assessment of studies using experimental or rigorous observational methods (covering nearly 1 billion tons of CO₂e), we're now:

1. Rerunning our search algorithms to incorporate these and other recent studies
2. Updating our database with new findings
3. Refining our recommendations on which offset types demonstrate the strongest evidence of effectiveness

Our goal remains providing data-driven insights to help organizations make informed decisions about carbon credit investments, ensuring climate finance flows to projects that genuinely reduce emissions.

Stay tuned for our updated systematic assessment, which will integrate these important new findings along with other recent research to provide you with the most current evidence-based guidance on carbon markets.

We are currently in the process of re-running the search algorithm to update our systematic assessment.