Mangrove production and carbon sinks: A revision of global budget estimates

TLDR

Mangrove forests are highly productive but globally threatened coastal ecosystems, and their contribution to the coastal carbon budget remains debated, with processes such as CO₂ efflux and dissolved inorganic carbon export potentially significant yet poorly constrained. The study aims to synthesize available data on carbon fluxes in mangrove ecosystems. The authors compiled literature estimates of primary production, organic carbon export, sediment burial, and mineralization to reassess global mangrove carbon budgets. The synthesis estimates global mangrove primary production at ~218 ± 72 Tg C yr⁻¹, yet more than half of fixed carbon remains unaccounted for, with an estimated unaccounted sink of ~112 ± 85 Tg C yr⁻¹ (~30–40 % of global riverine organic carbon input), largely driven by underestimated mineralization and dissolved inorganic carbon export, with CO₂ efflux from sediments and tidal DIC export as major sinks.

Abstract

Mangrove forests are highly productive but globally threatened coastal ecosystems, whose role in the carbon budget of the coastal zone has long been debated. Here we provide a comprehensive synthesis of the available data on carbon fluxes in mangrove ecosystems. A reassessment of global mangrove primary production from the literature results in a conservative estimate of ∼218 ± 72 Tg C a −1 . When using the best available estimates of various carbon sinks (organic carbon export, sediment burial, and mineralization), it appears that >50% of the carbon fixed by mangrove vegetation is unaccounted for. This unaccounted carbon sink is conservatively estimated at ∼112 ± 85 Tg C a −1 , equivalent in magnitude to ∼30–40% of the global riverine organic carbon input to the coastal zone. Our analysis suggests that mineralization is severely underestimated, and that the majority of carbon export from mangroves to adjacent waters occurs as dissolved inorganic carbon (DIC). CO 2 efflux from sediments and creek waters and tidal export of DIC appear to be the major sinks. These processes are quantitatively comparable in magnitude to the unaccounted carbon sink in current budgets, but are not yet adequately constrained with the limited published data available so far.