Indian Ocean tsunami: The use of MERIS (MTCI) data to infer salt stress in coastal vegetation

Abstract

The Indian Ocean tsunami of 26 December 2004 removed coastal vegetation and inundated large areas of near‐coastal and low lying land with salt water. There were subsequent reports of early vegetation senescence as salt stress reduced the chlorophyll content of plant canopies. The European Space Agency (ESA) uses data from its Medium Resolution Imaging Spectrometer (MERIS) on Envisat to produce an operational product called the MERIS Terrestrial Chlorophyll Index (MTCI). The MTCI values are related to the relative position of the red edge in the reflectance spectrum of vegetation and so can be used to estimate the chlorophyll content of that vegetation. The difference between pre and post‐tsunami MTCI images was compared with elevation data from the Shuttle Radar Topography Mission's (SRTM) Spaceborne Imaging Radar‐C (SIR‐C) for the Phuket region of Thailand. There was a statistically significant (95% confidence level) decrease in the MTCI after the tsunami in near‐coastal and low lying interior regions. It was hypothesized that this decrease was due to a reduction in chlorophyll content as a result of the salt stress produced by salt water inundation. The recovery of this region is to be monitored using the MTCI.