The vulnerability of Indo-Pacific mangrove forests to sea-level rise

Abstract

Sea-level rise can threaten the long-term sustainability of coastal communities and valuable ecosystems such as coral reefs, salt marshes and mangroves. Mangrove forests have the capacity to keep pace with sea-level rise and to avoid inundation through vertical accretion of sediments, which allows them to maintain wetland soil elevations suitable for plant growth. The Indo-Pacific region holds most of the world's mangrove forests, but sediment delivery in this region is declining, owing to anthropogenic activities such as damming of rivers. This decline is of particular concern because the Indo-Pacific region is expected to have variable, but high, rates of future sea-level rise. Here we analyse recent trends in mangrove surface elevation changes across the Indo-Pacific region using data from a network of surface elevation table instruments. We find that sediment availability can enable mangrove forests to maintain rates of soil-surface elevation gain that match or exceed that of sea-level rise, but for 69 per cent of our study sites the current rate of sea-level rise exceeded the soil surface elevation gain. We also present a model based on our field data, which suggests that mangrove forests at sites with low tidal range and low sediment supply could be submerged as early as 2070.

Projected changes in area of the Sundarban mangrove forest in Bangladesh due to SLR by 2100

“…The high sea-level scenario corresponds to the H++ scenario range which considers high and plausible, but unlikely scenarios (Jevrejeva et al 2014): the 95 % value for RCP8.5 (0.98 m) plus 0.5 m due to Antarctica Ice Sheet melting (Levermann et al 2014). A large value of 1.48 m has been considered to explore a high SLR scenario which is consistent with the extreme scenario of Lovelock et al (2015).…”

“…Loucks et al (2010) estimated that most of the Bangladesh Sundarbans area will be below MSL if a 0.28 m increase above the MSL in the year 2000 occurs in the next 50-90 years, assuming no change in the current local conditions (i.e., the net increase in elevation remains in the range 4-7.8 mm/year). Lovelock et al (2015) developed a model (hereafter referred to as the BLovelock model^) to predict the time to submergence of a mangrove ecosystem subject to accelerated SLR based on the concept of the loss of Belevation capital^, the potential of a mangrove ecosystem to remain within a suitable inundation regime (between Highest Astronomical Tide and MSL). The Lovelock model suggests that the Sundarbans, where there is a relatively high tidal range (4 m) and high sediment supply, will persist beyond 2100 even under the most severe SLR scenario (1.4 m by 2100).…”

Balanced Sediment Fluxes in Southern California’s Mediterranean-Climate Zone Salt Marshes

“…Although 449-664 days was a short sample size for monitoring elevation change (e.g., annual variation in sea level), our results suggest that to keep pace with current and predicted rates of SLR these marshes may require additional inputs of sediment which were not observed during the dry-weatherdominated study period. Lovelock et al (2015) examined whether the length of the SET record was likely to influence their results for mangrove systems. They compared elevation gains over longer periods (mean of 5.5 years) to those over shorter periods (mean record length of 2.1 years).…”

Vulnerability of Fishing Communities from Sea-Level Change: A Study of Laemsing District in Chanthaburi Province, Thailand

“…Meanwhile, the paper used DEM with 5 m of spatial resolution-high resolution showing the vertical distances in meters from mean sea level (MSL) of Thailand (2.50 m)-which was provided by the LDD, Thailand, in 2006, and was extracted from Aerial Photo. In addition, considering land form response, although mangrove soil-surface elevation gains can help coastal systems, such as wetland to avoid the biophysical effects of inundation, the increasing rate of sea level in the long-term in the Gulf of Thailand, especially in the eastern part, is higher than the increasing rate of soil elevation gains in mangrove areas [17]. Thereby, the elevation gains in the study area cannot prevent the inundation and are not considered for inundation mapping for this paper.…”