Abstract Mangrove degradation in Cambodia, driven by selective logging, hydrological alteration, and chronic anthropogenic pressure, represents a critical dual environmental crisis. This nano-review synthesizes evidence on how these pathways not only release significant stored "blue carbon"—converting forests from carbon sinks to sources—but also function as an extinction trap for rare, functionally unique mangrove taxa such as Heritiera littoralis. Degradation disproportionately impacts rare species through direct exploitation, habitat fragmentation, and altered biotic interactions, while simultaneously driving long-term carbon emissions through biomass loss and the destabilization of ancient soil carbon stocks. The review argues that emissions from chronic degradation may rival those from deforestation in long-term carbon debt. Addressing this double jeopardy requires integrated strategies, including protecting degraded but recoverable forests, implementing biodiversity-smart restoration, and leveraging policy instruments like blue carbon financing with explicit biodiversity co-benefits. Effective conservation must concurrently secure carbon stocks and safeguard rare species to ensure ecosystem resilience and service provision. Keywords Mangrove degradation; Blue carbon; Biodiversity loss; Rare species; Heritiera littoralis; Soil organic carbon; Selective logging; Hydrological alteration; Cambodia; Conservation strategies