Fighting Climate Change with Mangrove Blue Carbon
Parties ratifying the Paris Agreement have pledged to ‘achieve a balance between anthropogenic emissions by sources and removals by sinks by 2100’. Considering the economies, which became fuel-dependent; conservation of carbon sinks and reduction of emissions, contributing to such a commitment would not be a wise option. Researchers have stated that the global average atmospheric carbon dioxide (CO2) concentration have rose to 387 parts per million (ppm) by December 2009, the highest level it has reached over the past 800, 000 years. There is a broad consensus among the scientific community that such a rise is driven mainly by the anthropogenic activities and still is in its rise. Human activities and interactions among the major carbon pools like atmosphere, oceans, fossil fuels, and collectively — vegetation- will determine the atmospheric CO2 increase. The Intergovernmental Panel on Climate Change have estimated that, by the year 2050, global CO2 emissions must be reduced by 85% from levels seen in 2000 to prevent a global mean temperature increase of 2oC. This suggests that reduction in emissions is the only possible solution left ahead. Recent approaches have suggested a strategy that combines reducing anthropogenic sources of CO2 coupled with supporting CO2 uptake and storage through the conservation of natural ecosystems that have high carbon sequestration ability.
Plant communities sequester carbon during photosynthesis and store it as biomass in five pools namely aboveground biomass, belowground biomass, leaf litter, dead wood and soil carbon stock. Thus, forests play a critical role in maintaining an equilibrium of carbon between atmosphere, soil and ocean. Conventionally carbon sequestered by the tropical forests is named ‘green carbon’ and that sequestered by coastal and marine ecosystems are termed ‘blue carbon’. Studies show that among the global carob captured through photosynthesis, 45% is stored in terrestrial ecosystems and the rest is stored in marine ecosystems. Mangroves, sea grasses and salt marshes are often conjointly referred to as ‘blue carbon ecosystems’.
Mangrove forests, in particular, are one of the Earth’s finest ecosystem for carbon sequestration and storage, found along the estuaries, seacoasts and river mouths in the tropical and subtropical inter tidal zones. They can store three to four times of carbon on a per area basis than the tropical forests and if undisturbed can retain it for centuries to millennia. Spatial data has estimated that the global coverage of mangroves is 13.8–15.2 million ha and they sequester over two tons of carbon per/ha annually.
Conversely, if they are destroyed or converted to other land uses, the sediment carbon is destabilized or exposed to air (specifically oxygen), which leads to significant loss of carbon emitted back to the atmosphere. Research has found the carbon dioxide emission via mangrove loss contributes up to 10% of the global emissions from deforestation. Hence, mangrove communities can be identified as a crucial tool in climate mitigation strategies. Therefore, carbon stock estimation of mangroves has become a trend during the past years.
Carbon burial rates within a mangrove forest might be affected by variability in hydro period, salinity, nutrient status and suspended sediment supply. This is also linked with decomposition and primary productivity, which are driven by physical, biological and biogeochemical variables.
Most of the services other than carbon sequestration, provided by mangrove communities do contribute to climate adaptation and resilience along coasts, including protection from storm surge and sea-level rise, erosion prevention along shorelines, coastal water quality regulation, nutrient recycling, sediment trapping, habitat provision for enormous commercially important and endangered marine species, and food security for many coastal communities around the world.
Despite of their eminent capability to sequester and store carbon, they have destroyed in an alarming rate. A comprehensive strategy is required to achieve emission reduction targets and encourage climate mitigation policies. However, there is a knowledge gap prevailing due to the lack of scientific data on global coverage of mangroves and their blue carbon stock. Despite the limitation, it should be clearly understood that they drive the marine carbon dynamics and needs protection for the sustainability of life ahead. Thus, actions should be taken not only to conserve the existing mangrove patches but also to plant new mangrove forests.
