Mangrove forests, salt marshes and seagrass beds; the blue carbon potential under climate change

Abstract

This thesis aimed to identify how the blue carbon potential of mangrove forests, salt marshes and seagrass beds will change under RCP2.6, RCP4.5 and RCP8.5 scenarios by analyzing the threats posed to these marine ecosystems under each scenario, the potential responses and the measures that can be implemented to preserve their blue carbon potential. This was done by performing a meta-analysis and expert interviews. Human physical activity is the biggest threat all three ecosystems are facing, since it does not only lead to the loss of these systems but also lowers their resilience to climate change pressures. The main climate change stressor mangroves and salt marshes are facing under future climate change is sea level rise, whereas seagrasses are mainly at risk of degradation due to ocean warming and changes in water quality. Regionally blue carbon sinks are expected to respond differently. Some regions of seagrasses and most of salt marshes and mangroves will benefit from warming. In addition some regions and species will be less sensitive to sea level rise, namely high sediment regions and seagrasses. These factors will likely promote an expansion of these systems in those regions and thus an increase of blue carbon potential in some areas of the world. An RCP8.5 scenario would most likely lead to a net decrease of the blue carbon potential, but this is partly contingent on the impacts of human physical activity. Whether the global blue carbon potential will decrease, be a zero net gain, or increase under scenarios RCP2.6 and RCP4.5 strongly relies on whether human physical activity will be decreased in the next few decades. A combination of measures, with a focus on conservation, restoration and adaptation, are important to not only preserve these marine ecosystems under these future climate change scenarios but also enhance their blue carbon potential to make sure they can play a mitigating role.