| Popis: |
Coastal wetlands sequester and bury substantial amounts of atmospheric carbon dioxide (CO2) via photosynthesis. These blue carbon (BC) ecosystems play an essential role in climate change mitigation. Despite the key role that BC ecosystems play, they are increasingly threatened by land use changes (LUC). This may impact their carbon storage and sequestration ecosystem services. We used meta-analysis in ecology to study carbon storage and sequestration within natural and transformed salt marshes and mangroves, across a global scale. Articles published since 2000 on the Web of Science Core Collection, that contained experimental data on carbon storage and sequestration for natural and modified ecosystems, were selected. Case studies were integrated into a database, and standardised. Research on mangroves concentrated on Asia and Oceania, whilst salt marshes concentrated on North America, eastern Asia and Oceania. We found that LUC in BC coastal ecosystems decreased carbon storage and carbon sequestration rates at a global scale. Carbon storage in mangrove sediments significantly decreased from 520.49 ± 388.99 Mg C ha-1 (mean ± SD) in natural systems to 186.81 ± 234.02 Mg C ha-1 in modified settings. Carbon storage in salt marsh sediments also decreased from 97.80 ± 107.69 Mg C ha-1 in natural ecosystems, to 31.42 ± 33.47 Mg C ha-1 in human-managed environments. Biomass carbon storage (aboveground and belowground biomass) averaged 103.07 ± 198.86 Mg C ha-1 in natural mangroves, whereas carbon storage in modified mangroves yielded an average of 29.01 ± 47.40 Mg C ha-1. Within natural salt marshes, biomass carbon stocks had an average value of 3.66 ± 5.24 Mg C ha-1. Carbon sequestration rates, significantly decreased in modified in mangroves, but not in salt marshes, due to inter-site variability. We found that sampling depth may affect the measurement of organic carbon stocks. Conversion of natural coastal ecosystems may decrease their carbon storage capacity. |
