The Potential of Blue Carbon Management in Mexico. A Case Study From the Biosphere Reseerve of Sian Ka´an.

Recent scientific and policy research has focused on ‘blue carbon’ ecosystems as a means for countries to achieve their climate change mitigation commitments under the Paris Agreement. Mexico has a great potential in this regard having the 4th largest mangrove area in the world, as well as extensive seagrass meadows. Over the last decades, however, mangrove forests in Mexico have been severely impacted. There has been a growing interest in restoring them, but it is still unknown whether restored mangroves provide ‘blue carbon’ services similar to natural ones. The present study aimed to determine whether a 5-year-old restored mangrove forest in the Biosphere Reserve of Sian Ka’an has similar carbon stocks (plant biomass and soil) to those of intact mangroves. Interstitial salinity and tidal inundation appeared to be the main factors preventing mangrove establishment. Therefore, salinity levels were reduced by reconnecting fresh and saltwater discharge prior to establishing the experimental plots. Sediment samples down to 1m depth and aboveground biomass measurements were collected on a yearly basis since 2015. Also, allometric models of the two main mangrove species found, Rhizophora mangle and Avicennia germinans, were developed. A year after the experimental plots were established, vegetation expansion was observed in all areas. Mangrove restoration also facilitated soil organic carbon sequestration over time and depth (H(2)=47.383, p<0.001). The present study has successfully assessed the early stages of mangrove restoration activities and our results demonstrate the potential for mangrove restoration to effectively sequester carbon. Further studies should be conducted to account for the finer scale variability and longevity of organic carbon in these ecosystems.