Search

Seagrasses comprise a substantive North American and Caribbean Sea blue carbon sink. Yet fine-scale estimates of seagrass carbon stocks, fluxes from anthropogenic disturbances, and potential gains in sedimentary carbon from seagrass restoration are lacking for most of the Western Hemisphere. To begin to fill this knowledge gap in the subtropics and tropics, we quantified organic carbon (C org ) stocks, losses, and gains from restorations at 8 previously-disturbed seagrass sites around the Gulf of Mexico (GoM) (n = 128 cores). Mean natural seagrass C org stocks were 25.7 ± 6.7 Mg C org ha − 1 around the GoM, while mean C org stocks at adjacent barren sites that had previously hosted seagrass were 17.8 Mg C org ha − 1 . Restored seagrass beds contained a mean of 38.7 ± 13.1 Mg C org ha − 1 . Mean C org losses differed by anthropogenic impact type, but averaged 20.98 ± 7.14 Mg C org ha − 1 . C org gains from seagrass restoration averaged 20.96 ± 8.59 Mg ha − 1 . These results, when combined with the similarity between natural and restored C org content, highlight the potential of seagrass restoration for mitigating seagrass C org losses from prior impact events. Our GoM basin-wide estimates of natural C org totaled ~ 36.4 Tg for the 947,327 ha for the USA-GoM. Including Mexico, the total basin contained an estimated 37.2–37.5 Tg C org . Regional US-GoM losses totaled 21.69 Tg C org . C org losses differed significantly among anthropogenic impacts. Yet, seagrass restoration appears to be an important climate change mitigation strategy that could be implemented elsewhere throughout the tropics and subtropics. [ABSTRACT FROM AUTHOR]

Our results concluded, that deforestation and degradation results in significant losses of TEC stocks from mangroves. While the prevention of deforestation and degradation is the most effective strategy for climate change mitigation and adaptation, it appears that restoration results in mangroves that can continue to combat climate change after 25–30 years. • Deforestation reduced total ecosystem carbon (TEC) stocks of intact mangroves by 60%. • TEC stocks from degraded mangroves forests did not differ from intact forests. • TEC stocks from 25-year-old restored mangroves were similar to intact mangroves. • A gridded sampling approach effectively captured TEC variability across an entire country. Mangrove forest conservation can help reduce global C emissions. Despite this benefit to climate change mitigation and adaptation, mangrove forests are being deforested or degraded at an alarming rate, though restoration efforts may offset these losses. The impacts of deforestation to C stocks are relatively intuitive and result in significant decreases in C stocks. It remains unclear how degradation from selective harvesting of trees affects C stocks or how effective restoration efforts are at restoring C stocks. Furthermore, total ecosystem C (TEC) stocks of pristine mangroves can significantly vary spatially. To address these issues, we conducted an intensive, national assessment of mangrove forests across Cambodia using a grid approach to: 1) examine how land use land cover (i.e., pristine, deforested, degraded, and restored forests) impacts TEC stocks, and 2) how TEC stocks vary spatially across the country. TEC stocks from deforested mangroves were always lower than pristine forests, resulting in an overall loss of 60% C (480 Mg C ha−1). However, TEC stocks from degraded and 25-year-old restored mangroves forests did not differ from pristine forests. Mean TEC in mangroves was 784.7 ± 30.1 Mg C ha−1, decreasing from 957.2 ± 32.8 Mg C ha−1 in the northern region to 628.9 ± 33.1 Mg C ha−1 in the central region to 386.2 ± 19.1 Mg C ha−1 in the southern region of Cambodia. Intensive sampling in mangroves across Cambodia verified impacts of deforestation reported elsewhere, revealed the lack of degradation impacts on TEC stocks, and demonstrated the effectiveness of restoration on TEC stocks after only 25 years. Our gridded sampling approach was able to capture spatial variability across Cambodia and provide a more realistic TEC stock information that can be used for national reporting or participation in C markets. [ABSTRACT FROM AUTHOR]