Impacts of Future Crop Tree Release Treatments on Forest Carbon as REDD+ Mitigation Benefits

Sustainable forest management activities, such as future crop tree (FCT) release treatments, became part of the REDD+ strategy to avoid carbon emissions from forests. FCT release treatments are intended to achieve increased growth of FCTs by removing competitor trees. This initially leads to a reduction of the forest carbon pool and represents a carbon debt. We estimated that the time it takes for FCTs to offset the carbon debt through increased growth on experimental sites of 10 km² in Belize, Guyana, Suriname, and Trinidad and Tobago. We further investigated whether the costs of treatment can be compensated by the generated financial carbon benefits. An average of 2.3 FCT per hectare were released through the removal of an average of 3.3 competitors per hectare. This corresponds to an average above ground biomass (AGB) deficit of 2.3 Mg FCT−1. Assuming a 30% increase in growth, the FCT would need on average 130 years to offset the carbon loss. For carbon prices from US$ 5 to 100 Mg CO2e−1 an additional increment between 0.6 and 22.7 Mg tree−1 would be required to cover the treatment costs of US$ 4.2 to 8.4 FCT−1. Assuming a carbon price of US$ 10 Mg CO2e−1, the additional increment required would be between 5.8 and 11.4 Mg tree−1, thus exceeding the biological growth potential of most individual trees. The release of FCTs does not ensure an increase in forest carbon stocks, and refinancing of treatment costs is problematic.