Introduction to Blue Carbon

The consensus in climate change literature has reached a disturbing conclusion. The Intergovernmental Panel on Climate Change (IPCC) warns us in their 2021 report that climate change driven by human activity threatens to bring unprecedented global temperature rises between 1.5℃ and 2℃ during the 21st century, even with massive reductions in current greenhouse gas (GHG) emission levels. Soaring temperatures will be joined by rising sea levels and increased frequency of extreme weather such as droughts, fires and tropical cyclones (IPCC, 2021). In order to limit global warming and mitigate these destructive impacts, humanity must urgently reduce as well as remove enormous volumes of GHG emissions from our atmosphere. To help meet this challenge, we look to nature-based climate solutions. Blue Carbon ecosystems such as coastal wetlands, seagrass meadows, and mangrove forests have been identified as extremely effective, long-term “carbon sinks” that absorb carbon dioxide (Donato et al., 2011). Among these ecosystems, we’ve identified mangroves as the most valuable due to its vast array of ecosystem services which ultimately protect humans and wildlife from the catastrophic effects of climate change (see Figure 1).

Figure 1: Ecosystem functions and services provided by mangrove forests. Figure adapted and modified from Millennium Ecosystem Assessment (2005) and De Groot (1992).

Mangrove Ecosystem Services

Mangroves are renowned for their ability to absorb carbon and store it long-term at faster rates and in greater volumes than any other terrestrial forests by unit area (Donato et al., 2011). Due to the mangrove soils existing within intertidal zones, the tidal flooding enhances collection of carbon-containing sediment and its burial beneath the water (Mcleod et al., 2011). Mangroves also act as a sanctuary for biodiversity, acting as nursery where the young of a species can safely develop. Mangroves, located along saltwater tropical and subtropical coasts, are the home of a diverse number of trees, shrubs, fish, crabs, birds, and tigers (Rog, Clarke and Cook, 2017). All these species play important roles in the functioning and longevity of this unique ecosystem. The dense structure of mangroves also serves to shield coastlines from wearing away due to storms and sea-level rise because the roots of mangroves grip tightly to soil (Guannel et al., 2016; Dasgupta et al., 2019). These abilities are extremely helpful in the fight against climate change, making mangroves an ecosystem of high priority for conservation and restoration.

Ecological Engineering

Our recommendations for restoring and protecting mangroves hinge on ecological engineering techniques, which involves building with nature, such as combining mangroves with seawalls to prevent coastal erosion, porous structures to trap sediment, as well as sediment dredging and nourishment to control the structure of intertidal sediments. These ecological engineering strategies help create an environment where mangroves can persist by ensuring a stable sediment supply so that they don’t drown in water (Kaly and Jones, 1998). These techniques, in conjunction with effective planting strategies for mangroves which aim to mimic nature by replicating patterns of density and species composition, will allow for successful long-term mangrove restoration in the face of adverse climate conditions (Spalding et al., 2014).

Overall, the persistence of Blue Carbon ecosystems like mangroves will be vital in combating climate change, making all restoration and conservation efforts a global priority.

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