Background and Research Aims: Mangroves and other blue-carbon ecosystems have recently raised considerable interest for their potential contribution to the mitigation of CO2 emissions. One service of global impact provided by mangrove ecosystems is their role as carbon sinks. Most carbon in mangrove ecosystems is stored belowground as peat, which, unlike shorter-lived aboveground biomass, often remains undecomposed for centuries or millennia. The objective of this study was to estimate the carbon stock (biomass) and its storage in soil in La Cruz Lagoon, at the arid region of the Gulf of California. Methods: Aboveground biomass was estimated based on mangrove structure, pneumatophores, and litter-based primary-productivity; belowground biomass was measured by extracting root cores (45 cm deep), soil cores (1 m deep) and estimating the production of in-growth core roots. Total biomass values were converted to carbon using allometric equations and soil carbon stores by means of laboratory elemental analyzers. Results: The main results showed a low structural development with a litter productivity of 2.21 Mghayear(-1), with a carbon aboveground biomass of 29.8 +/- 3.4 Mg C-orgha(-1) and a belowground biomass of 35.1 +/- 88 Mg C-orgha(-1), with a root:shoot ratio slightly greater than 1, meaning that belowground carbon associated with mangrove biomass is higher than aboveground carbon. The estimated total carbon was 207.21 +/- 42.4 Mg C-orgha(-1). Conclusion: These results suggest a higher content of BGB than AGB is a function of aridity, that is, allocating C belowground rather than aboveground, which helps justifying conservation and restoration strategies to improve or recover the ecosystem services of mangrove ecosystems. Implications for conservation: Implications for conservation of the mangrove ecosystem in tropical and/or subtropical regions has its importance in maintaining forests with high capacity to capture atmospheric CO2 that serves as a carbon sink and storage facility, as a nature-based ecosystem service.