Decadal Blue Carbon Losses and Gains from Tidal Wetland Reclamation and Restoration in China

Abstract

Tidal wetlands are blue carbon ecosystems, and the restoration of these ecosystems is a natural climate solution due to their remarkable carbon sequestration capacity. However, extensive conversion to aquaculture ponds in China has led to substantial carbon losses. Recent restoration initiatives aim to change the situation. To quantify these impacts, we performed a meta-analysis to assess carbon losses and gains from different pathways, including sediment and biomass carbon storage, carbon burial, carbon emissions, and carbon content changes. We aim to estimate the decadal carbon losses from reclamation and gains from restoration in China’s tidal wetlands. Over the past 30 years, mangrove areas have gradually recovered and are projected to return to 1973 levels by 2052, while tidal marsh loss has slowed, with restoration expected to achieve 1984 levels by 2070. Carbon stock depletion represented the largest loss pathway, accounting for 49.18% of mangrove and 37.33% of tidal marsh losses. Following restoration, biomass recovery contributed significantly to carbon gains: 28.5% for mangroves and 44.4% for tidal marshes. Projections indicate that restoring mangroves to their 1973 extent would yield a carbon gain of 6.8 Tg, while tidal marsh restoration to 1984 coverage would generate 55.2 Tg. These pathways provide a scientific basis for global blue carbon accounting and management strategies.