Carbon sequestration in plants and soils can be vulnerable but has additional benefits.
Biosequestration offsets reduce atmospheric CO2 concentration by growing vegetation that will store carbon in plants and soils equivalent to the amount of carbon to be offset.
Biological sinks on land through forestry and agriculture are the most common forms of biosequestration for carbon emissions collectively under the name of land use, land use change and forestry (LULUCF) projects. The most widely available carbon offsets are reforestation projects, although there is an increasing interest in ‘avoidance deforestation’ carbon credits and in projects that promote agricultural best practices that conserve or increase soil carbon.
Biosequestration carbon offsets have the potential to bring multiple secondary environmental and social benefits, including the establishment of long-term sustainable forestry industries, reduced erosion, the preservation and increase in biological diversity, and improved hydrological regulation. For the same reasons, it may have unintended negative consequences, such as the use of limited water resources and biodiversity degradation if exotic species are planted in monocultures. Biosequestration carbon offset projects need to demonstrate a well integrated plan with other environmental resource uses and a framework for sustainable development.
Unintended negative effects
Experiments into the limiting factors of ocean productivity have shown the potential for ocean carbon sequestration by fertilising with iron, one of the most limiting nutrients. Because the likely large and unintended negative changes that iron fertilization produces in marine biodiversity and trophic interactions (Le Quéré et al. 2004), the GCP does not support this type of projects for C offsets.