Raw J L, Van Niekerk L, Chauke O, Mbatha H, Riddin T, Adams J B
DSI-NRF Research Chair in Shallow Water Ecosystems, Department of Botany, Nelson Mandela University, Gqeberha, South Africa; Institute for Coastal and Marine Research, Nelson Mandela University, Gqeberha, South Africa.
Institute for Coastal and Marine Research, Nelson Mandela University, Gqeberha, South Africa; Coastal Systems and Earth Observation Research Group, Council for Scientific and Industrial Research (CSIR), Stellenbosch, South Africa.
Sci Total Environ. 2023 Feb 10;859(Pt 1):160142. doi: 10.1016/j.scitotenv.2022.160142. Epub 2022 Nov 12.
Blue carbon ecosystems (mangroves, salt marshes, and seagrasses) contribute towards climate change mitigation because they are efficient at sequestering atmospheric CO into long-term total ecosystem carbon stocks. Destruction or disturbance therefore reduces sink capacity and leads to significant CO emissions. This study reports the first national estimates of: 1) total carbon storage, 2) CO emissions from anthropogenic activities, 3) the potential for restoration to enhance carbon sequestration for blue carbon ecosystems in South Africa. Mangrove ecosystems have the greatest carbon storage per unit area (253-534 Mg C ha), followed by salt marshes (100-199 Mg C ha) and seagrasses (45-144 Mg C ha). Salt marshes are the most extensive and contribute 67 % to the national carbon stock of 4000 Gg C. Since 1930, 6500 ha has been lost across all blue carbon ecosystems (26 % of the natural extent), equivalent to losing 1086 Gg C from the national carbon stock. Historic CO emissions were estimated at an average rate of 30,266 t COe yr. Despite losses, a total of 3998 ha could be restored to increase carbon sequestration and CO removals of 14,845 tCOe.yr. Extractive activities have declined rapidly in recent decades, but abiotic pressures on estuarine ecosystems (flow modification, reduced water quality, and artificial breaching) have been increasing. There is an urgent need to quantify the potential impact of these pressures and include them in estuarine management and restoration plans. Blue carbon ecosystems cover a relatively small area in South Africa, but they are valued for their multiple ecosystem services that contribute towards climate change adaptation and biodiversity co-benefits. These ecosystems need to be included in national policies driving climate change response in the Agriculture, Forestry and Other Land-Use (AFOLU) sector, such as incorporating them into the wetland subcategory of the national GHG inventory.
蓝碳生态系统（红树林、盐沼和海草床）有助于缓解气候变化，因为它们能够有效地将大气中的二氧化碳封存到长期的生态系统总碳储量中。因此，破坏或干扰会降低碳汇能力并导致大量二氧化碳排放。本研究首次对以下内容进行了全国性估算：1）总碳储量；2）人为活动产生的二氧化碳排放；3）南非蓝碳生态系统恢复以增强碳固存的潜力。红树林生态系统单位面积的碳储量最大（253 - 534 Mg C/公顷），其次是盐沼（100 - 199 Mg C/公顷）和海草床（45 - 144 Mg C/公顷）。盐沼分布最广，占全国4000 Gg C碳储量的67%。自1930年以来，所有蓝碳生态系统共损失了6500公顷（占自然面积的26%），相当于国家碳储量损失了1086 Gg C。历史二氧化碳排放量估计平均为每年30266吨二氧化碳当量。尽管有损失，但总共3998公顷的区域可以恢复，以增加碳固存并实现每年14845吨二氧化碳当量的二氧化碳清除量。近几十年来，采掘活动迅速减少，但河口生态系统面临的非生物压力（水流改变、水质下降和人工决口）却在增加。迫切需要量化这些压力的潜在影响，并将其纳入河口管理和恢复计划。蓝碳生态系统在南非覆盖的面积相对较小，但因其对气候变化适应和生物多样性协同效益有贡献的多种生态系统服务而受到重视。这些生态系统需要纳入推动农业、林业和其他土地利用（AFOLU）部门应对气候变化的国家政策中，例如将它们纳入国家温室气体清单的湿地子类别。
