Threats to inland wetlands and uncertainty around global soil carbon stocks and sequestration rates.

Wetlands are vital in climate change mitigation, carbon and nutrient cycling, water quality improvement, flood regulation, wildlife habitat provision, and biodiversity maintenance. However, various threats undermine their integrity and capacity to provide these ecosystem services. In this review and quantitative analysis, we identified the most significant threats to inland wetlands, estimated soil organic carbon (SOC) storage and sequestration rates across regions and climate zones, and pinpointed the sources of uncertainties in global estimates. We found that natural system modification, pollution, biological resource use, agricultural and aquacultural activities, and water regulation are the top five threats, impacting 61 %, 59 %, 59 %, 52 %, and 46 % of Ramsar sites in inland wetlands, respectively. Management plans are lacking in 47-76 % of Ramsar sites globally and over 66 % in Least Developed Countries. Literature data show median SOC stocks of 118.7 Mg ha in temperate and 150.3 Mg ha in the 0-50 cm soil depth of tropical inland wetlands. Our analysis of data from Ramsar sites indicates lower median stocks of 87 Mg ha in temperate and 105 Mg hain tropical wetlands for the 0-100 cm depth, highlighting significant uncertainties. These uncertainties stem from inconsistent definitions of wetlands, inaccurate wetland area data, measurement errors, and variability in sampling and modelling. Addressing these issues requires improved mapping, monitoring, and standardized protocols. Additionally, raising awareness among policymakers and the public about the threats to wetlands, which can destabilize local livelihoods and global carbon and nutrient cycles, is crucial.