Spatial characteristics of the stability of mangrove ecosystems in freshwater and seawater floods in Southeast Asia

Abstract

In tropical regions, mangrove forests are located in the inter-tidal areas between land and sea, and are at risk from both freshwater and seawater floods. Using satellite-derived Normalized Difference Vegetation Index (NDVI) products, this study compared the differences in resistance and resilience of mangrove ecosystems to freshwater and seawater floods in Southeast Asia, and analyzed the spatial characteristics of the stability of mangrove ecosystems under floods in representative areas. Results show that mangroves tended to have lower mean resistance (28.24 vs. 37.32) and higher mean resilience (3.74 vs. 3.56) under freshwater floods, compared to seawater floods. Their resistance increased with the distance from rivers, such that the resistance of coastal areas to freshwater and seawater floods was lower than that of inland areas. These areas with lower resistance showed higher resilience compared to those with higher resistance. Damaged mangroves hardly fully recovered to their normal NDVI levels one year after seawater floods, especially in coastal areas. Although the occurrence of seawater floods was relatively rare in the past, it is likely to increase under more-intense climate extremes in the future, and the threat to the survival of mangroves may also increase. Thus, it is essential to evaluate the stability of mangrove ecosystems under floods.