Abstract
Mangroves are known for large carbon stocks and high sequestration rates in biomass and soils, making these intertidal wetlands a cost-effective strategy for some nations to compensate for a portion of their carbon dioxide (CO2) emissions. However, few countries have the national-level inventories required to support the inclusion of mangroves into national carbon credit markets. This is the case for Brazil, home of the second largest mangrove area in the world but lacking an integrated mangrove carbon inventory that captures the diversity of coastline types and climatic zones in which mangroves are present. Here we reviewed published datasets to derive the first integrated assessment of carbon stocks, carbon sequestration rates and potential CO2eq emissions across Brazilian mangroves. We found that Brazilian mangroves hold 8.5% of the global mangrove carbon stocks (biomass and soils combined). When compared to other Brazilian vegetated biomes, mangroves store up to 4.3 times more carbon in the top meter of soil and are second in biomass carbon stocks only to the Amazon forest. Moreover, organic carbon sequestration rates in Brazilian mangroves soils are 15–30% higher than recent global estimates; and integrated over the country’s area, they account for 13.5% of the carbon buried in world’s mangroves annually. Carbon sequestration in Brazilian mangroves woody biomass is 10% of carbon accumulation in mangrove woody biomass globally. Our study identifies Brazilian mangroves as a major global blue carbon hotspot and suggest that their loss could potentially release substantial amounts of CO2. This research provides a robust baseline for the consideration of mangroves into strategies to meet Brazil’s intended Nationally Determined Contributions.
Highlights
Climate change velocity has outpaced models’ predictions spurring the implementation of natural climate solutions policies centered on ecosystems self-organizing properties to mitigate fossil fuels emissions and ensue adaptive capacity to future alterations in the climate system
aboveground biomass (AGB) was lower in São Paulo (84.2 Mg ha−1) and Rio de Janeiro (83.1 Mg ha−1), where extensive mangrove areas have been impacted by industrial activities and urban expansion (Soares, 1999; Ferreira and Lacerda, 2016; Moschetto et al, 2021)
AGB values >100 Mg ha−1 were found in Espírito Santo and Bahia mangroves where the multidecadal stability of more than 70% of the mangrove coverage suggests that the integrity of Mangrove areaa
Summary
Climate change velocity has outpaced models’ predictions spurring the implementation of natural climate solutions policies centered on ecosystems self-organizing properties to mitigate fossil fuels emissions and ensue adaptive capacity to future alterations in the climate system. Brazilian Mangroves: Blue Carbon Hotspots remaining functional over geomorphic timescales (Holling, 1973) Such processes are evident in dynamic coastal sedimentary environments, which alternate between vegetated and unvegetated states (e.g., saltmarshes and mangroves versus mudflats and saltflats) in response to climate and millennialscale changes in sea levels (Gabler et al, 2017; Saintilan et al, 2020). Global estimates generally focus on carbon stocks within either soil or biomass (Hutchison et al, 2014; Jardine and Siikamäki, 2014; Atwood et al, 2017; Rovai et al, 2018, 2021b; Sanderman et al, 2018; Tang et al, 2018; Simard et al, 2019; Kauffman et al, 2020), which are important to determine potential CO2eq emissions from mangrove forest loss (see Adame et al, 2021), but do not provide comparable information in terms of mitigating current emission rates. Global estimates often do not accurately quantify within-country variability, relying, in many cases, on averaged reference values or model-based generalizations to extrapolate predictions to data-poor or dataabsent nations when harnessing national datasets would be more appropriate to inform country-specific conservation targets (Worthington et al, 2020a)
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