CARBON STOCKS IN NORTHEASTERN GABON AND POLICY IMPLICATIONS FOR RUBBER TREE CONCESSIONS

Agricultural activities such as oil palm and rubber production have the potential to grow the economies and increase employment in tropical nations, but measures must be taken to offset the negative environmental effects of converting forests into monocultures. One approach to reconciling agricultural development with environmental degradation is to direct agricultural expansion towards low carbon landscapes such as cleared lands and secondary forests. This approach is tested by estimating carbon stocks and flux in northeastern Gabon, Central Africa at the selectively logged ORG concession that is proposed to be converted to a rubber tree plantation. Gabon is in the process of developing its agricultural sector, thus understanding the implications of converting forest into plantations is critical for implementation of best practices for estimating carbon stocks and reducing carbon emissions.

This study demonstrates that even within degraded secondary forests in Gabon the mean carbon density (123.8 Mg C ha-1) remains relatively high in comparison to degraded forest in other tropical countries. This value is lower than the mean carbon density in Gabon (160-167 Mg C ha-1) (Bombelli et al., 2009; Saatchi et al., 2011), but substantially higher than the 75 Mg C ha-1 carbon threshold recommended by the High Carbon Stock protocol (HCS; HCS Steering Group Committee, 2017). The carbon density distribution within the ORG concession is related to habitat type: forests on slopes had the highest mean carbon density compared to swamps, which were dominated by low-carbon palm species, and flat terra firma forest, the majority of which had been previously cleared for subsistence agriculture.

Through growth and succession, secondary forest should attain carbon densities similar to primary forest, which means there are high environmental opportunity costs of converting secondary forest to plantations. Overall, converting the ORG concession into a rubber plantation will lead to net carbon emissions. If development of the area goes forward, measures should be taken to reduce emissions and prolong carbon retention, such as minimizing soil disturbance, extending harvest rotations, making rubber wood furniture, and setting aside high carbon areas, such as slopes, as offsets.