Integrity concerns in large-scale forest carbon projects
The Kariba REDD+ project, one of the largest forest conservation offset initiatives globally, was designed under the REDD+ mechanism to generate carbon credits by preventing deforestation. These credits were sold on voluntary carbon markets to corporations seeking to offset their emissions.

However, scrutiny intensified in 2023 after investigative reporting suggested that the project may have issued more carbon credits than justified by its actual emissions reductions. Such over-crediting undermines the environmental integrity of offsets, allowing buyers to claim emissions reductions that may not have occurred in reality.

In 2025, these concerns were formally validated when Verra concluded that approximately 57 per cent of issued credits were excess, primarily due to inflated deforestation baselines. This confirmed that a substantial portion of the project’s claimed climate impact was overstated.

According to South Pole, it kept 25 per cent of profits, but documents show it kept 42 per cent; its Zimbabwean partner kept 30 per cent while communities that should have been funded to stop deforestation got only 28 per cent.

Shifting accountability
In February 2023, South Pole publicly defended the Kariba project, asserting that all credits issued during its first 10-year crediting period were valid and rejecting claims of over-issuance.

Yet by October 2023, the company reversed course and terminated its agreement with Carbon Green Investments, citing concerns linked to project management and credibility. The abrupt shift raised questions about due diligence processes, internal oversight, and the robustness of verification standards in the voluntary carbon market.

By 2025, South Pole had fully exited the project and publicly distanced itself from its outcomes, while cooperating with external investigations. The company also committed to cancelling a significant volume of credits it still held, reflecting reputational and liability concerns.

Meanwhile, the project developer, Carbon Green Investments, has disputed aspects of the findings, and the project itself has continued operating locally despite its suspension from major carbon certification systems.

Systemic risks in carbon certification
This case highlights structural weaknesses in the governance of voluntary carbon markets, where private certifiers, project developers, and intermediaries operate with limited regulatory oversight. The Kariba case also exposed challenges in enforcement, particularly when projects exit certification registries, limiting the ability of standards bodies to impose corrective measures.

Key concerns include:

• Incentives for over-crediting: Financial returns are linked to the volume of credits issued, creating pressure to inflate baselines or projections.

• Weak oversight and fragmented roles: Developers, certifiers, and intermediaries operate with overlapping but unclear accountability.

• Limited transparency: Project-level data and methodologies are often inaccessible or difficult to independently verify.

The Kariba controversy has become emblematic of broader concerns surrounding REDD+ and voluntary carbon markets. It adds to growing calls for stronger regulation, standardised methodologies, and independent oversight mechanisms.