As global temperatures increase, sea levels continue to rise. During this century, global sea level on average will rise between 1 foot and 6.6 feet, depending on the extent to which greenhouse gas emissions are reduced. Coastlines face high risk for flooding, storms, and ecosystem degradation. As some species are forced to migrate inland, landscape connectivity will also be impacted. Coastal ecosystems are likely to experience some of the most drastic effects, and many of those ecosystems, such as mangrove forests, provide critical services and harbor high biodiversity.
Liang, S., Hu, W., Liu, J., Su, S., Chen, G., Chen, S., Xie, B., Du, J., Liu, W. and Chen, B. 2023. Mapping mangrove sustainability in the face of sea level rise and land use: A case study on Leizhou Peninsula, China. Journal of Environmental Management 325: 116554.
Mangrove forests exist in tropical and warm-temperate intertidal zones across the globe, where trees and shrubs have adapted to tolerate salty soil and submerged roots. Mangroves create habitat for coastal species, cycle nutrients, and protect coastlines against tropical storms. Disturbance of mangrove forests has resounding consequences on food webs, biodiversity, and production, consequences which affect reefs and other nearby ecosystems.
Mangroves’ adaptations to tidal fluctuations make them more resilient to sea level rise than most. However, combined with land use pressures, researchers have found that sea level rise poses a threat to mangroves and mangrove connectivity. Researchers mapped future mangrove habitat sustainability on Leizhou Peninsula, China. They modeled eight total sea level rise scenarios, combining two levels of global warming, two land use scenarios (“Gray” and “Green”), and two time spans projecting to 2070 or 2120.
Under all “Gray” scenarios, which preserve development and seawalls, mangrove habitat decreased. Landward migration was hindered, and existing habitat converted to marsh or open waters. However, under all “Green” scenarios, which allow developed areas to be eroded and inundated, mangrove habitat area increased. This emphasizes the possible tension in conservation and infrastructure planning for coastal ecosystems, where plants and people alike are threatened with displacement.
Although all “Green” scenarios resulted in increased habitat area, sea level rise still negatively impacted connectivity. The expanded habitats still displayed fragmented, poorly connected patches. This suggests that mangrove dispersal and connectivity in these habitats will be a serious conservation concern even if sea level rise is the only factor. However, the researchers suggest that strategic land use may help mitigate the effects of fragmentation. For example, habitat converted to urban development may be permanently damaged, while habitat converted to aquaculture areas could be restored more easily.
Finally, this study demonstrates how conservation strategies and policies must adjust. Many mangroves are conserved by protected area designations, but under all scenarios in this case study, the suitable mangrove habitat within protected areas decreased. Spatial climate pressures increasingly require that protected areas be dynamic and adaptable in order to protect ecologically critical ecosystems such as mangrove forests.
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