Impacts from sea-level rise are among the most crucial impacts of climate change. Global sea levels have been rising in the past century, and will almost certainly accelerate through the 21st century and beyond due to global warming (Nicholls, 2010).
The mean rate of sea-level rise from 1993 to 2009 measured by satellites has been 3.3 +/-0.4 mm per year (Ablain et al., 2009). The estimates for future sea-level rises by 2100 diverge, yet have generally increased in projected rises since the publication of the Fourth Assessment Report of the IPCC in 2007. Such newer estimates now range from approx. 30 to approx. 200cm, depending on the assumed future developments that in turn drive climate change.
Regional processes such as sediment accumulation or drainage and groundwater withdrawal can respectively offset or exacerbate these rates.
The main impact of sea-level rise is submergence of land, i.e. “land loss”, and increased flooding in coastal areas. Such direct biophysical impacts can cause a variety of socioeconomic impacts, which are considered to be overwhelmingly negative (Nicholls, 2007). This map focuses on the impact of submergence of wetlands.
Wetland is the area which temporarily but regularly flooded or saturated with water e.g., swamps, marshes, bogs, etc. Wetlands can be broadly divided into inner wetlands and coastal wetlands. Inner wetlands are flooded by fresh water and found near rivers, lakes and artificial reservoirs. Coastal wetlands are flooded by salt water or brackish water due to their vicinity to the sea. The above map demonstrates potential coastal wetland loss due to sea-level rise. Coastal wetlands provide various ecosystem services like fish and fiber, wildlife habitat, flood regulation and recreation, among many other benefits, that contribute to human well-being. The costal wetland ecosystems, such as salt marshes and mangroves are particularly sensitive to rising sea level (IPCC, 2007) as their location is intimately linked to sea. The outer boundary of these wetlands will erode with sea-level rise due to intensified flooding and increased salinity. Vegetation like mangroves cannot survive in higher salinity. Areas that have coastal protection in place, such as bulkheads, dikes, or other structures will resist or limit the formation of new wetlands and also will hinder vegetation migration. As the results of sea-level rise, not only wetlands are at risk but also vital ecosystem services provided by wetlands and the rich biodiversity sustained by wetlands.
The above map displays the area of wetlands (in percentage) that may potentially be lost due to a 2m global mean sea-level rise under the assumption that no protective measures are in place. This means that wetlands, which are currently only temporarily flooded, may be permanently inundated due to sea-level rise and the vegetation in those wetlands will be affected by salt intrusion. This may change present vegetation composition and also alter or hinder the provisioning of ecosystem services presently available. The map displays the area of wetland loss based on second level administrative units. The darker the legend color in the map is, the larger the total wetland area or wetland area lost is relative to the administration units (click on the legend button to visualize it)
Though the map was created using available higher resolution global datasets, it only provides general ideas of wetland losses in the 2nd level administrative units as a whole rather than in local situations, and for comparing such losses across the country. The map displays the scenarios for existing conditions without considering the present and the future adaptation measures. This information is important in order to avoid common misconceptions of such maps. The information presented in the map also embodies uncertainty within itself.
This map builds on the results from estimations of the potential land loss, i.e. land that will be inundated, due to 2m sea level rise. The Globcover 2.2 dataset was utilized to distinguish wetland from other types of land cover due to this dataset’s high resolution with recent information. The wetlands in the Globcover dataset are implicitly categorized into three different classes:
• Closed to open (>15%): broadleaved forest regularly flooded (semi-permanently or temporarily) – Fresh or brackish water.
• Closed (>40%): broadleaved forest or shrubland permanently flooded – Saline or brackish water.
• Closed to open (>15%): grassland or woody vegetation on regularly flooded or waterlogged soil – Fresh, brackish or saline water.
These types of wetlands were re-categorized into a single group that accounts for all types of wetland. This reclassified information was used to generate wetland at risk due to global mean sea-level rise of 2m. This was achieved by looking at the land cover type of the land that will be inundated do due the given global mean sea-level rise. The aggregated information of wetlands potentially inundated was then used to develop the potential wetland loss map.