Aquaculture conversion has worst impact on mangrove carbon stocks

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Aquaculture conversion of Indonesian mangrove forests has the largest impact on the ecosystems’ carbon sequestration abilities, removing 60% of soil carbon stocks and 85% of biomass carbon, compared to forest harvesting practices which removed most biomass carbon with minimal impacts on soil stocks. The study, published in Global Change Biology, analysed land-use and land-cover change (LULCC) over a 25-year period and compared carbon stocks between undisturbed forest and areas that had undergone LULCC.

Mangroves left to regenerate recovered previous carbon levels after 25 years. LULCC characteristics need to be incorporated in emission-reduction strategies involving mangrove restoration, the authors said.

Mangroves act as nurseries and feeding grounds for many aquatic and terrestrial species and stabilise shorelines against flooding and extreme weather. They are also excellent carbon sinks, particularly within their soils, and have been found to have greater carbon sequestration potential than terrestrial rainforest per hectare.

Mangroves, therefore, represent an excellent nature-based solution for tackling climate change and offsetting emissions.

Carbon sequestration in mangroves involves many uncertainties, such as variability between species or the impact of methane emissions on net carbon stocks, and a limited number of studies have fully considered the different factors involved. This makes it difficult to accurately valorise mangrove restoration initiatives.

This study adds new information regarding the impact of LULCC on blue carbon stocks in mangrove forests; the location of carbon-rich mangroves within blue mangrove forests; the level of carbon losses from different economic activities; and a timeframe for mangrove regeneration. All of this can inform mangrove conservation decision-making.

Corporates should be mindful that offsetting does not fully consider the complex carbon flows within marine ecosystems and the potential for LULCC to erase carbon savings. Mangrove restoration is not a “quick win” but something that requires long-term attention to achieve consolidated results.

Payments-for-ecosystems and carbon resilience payments, whereby coastal communities are incentivised to conserve mangrove forests, may represent a more sustainable form of corporate action, delegating mangrove guardianship to local stakeholders through a multi-factor approach.

Source: Global Change Biology