Issues Surrounding Remote Sensing Based Monitoring of Coastal Ecosystems: A Case Study of Tsunami Affected Andaman and Nicobar Islands Benidhar Deshmukh Defence Terrain Research Laboratory, India Email: benidhar@gmail.com G. Prusty Defence Terrain Research Laboratory, Defence Research & Development Organisation Leena Khumukcham Centre of Remote Sensing & GIS, School of Studies in Earth Science Jiwaji University S.N. Mohapatra Centre of Remote Sensing & GIS, School of Studies in Earth Science Jiwaji University Coastal ecosystems around the world are under increasing pressure due to natural factors such as storms, earthquakes, tsunami, etc. besides various human-triggered threats. Policy decisions for effective coastal zone management including the post-disaster response require comprehensive and accurate data collected over time and space. Remote sensing data have long been established as a quicker and cost-effective means of generating information over a relatively large area of land. However, in the coastal regions in general, and tropics in particular a variety of factors influence quality of the acquired remote sensing data for retrieval of reliable information. The present paper discusses various issues surrounding remote sensing based monitoring of coastal ecosystems by taking a case study of mangrove and coral reef ecosystems of the Andaman and Nicobar islands utilising the pre and post tsunami LISS III data acquired from Indian Remote Sensing Satellites. Most of the Andaman and Nicobar groups of islands suffered heavy losses due to the December 2004 devastating tsunami resulting from the Sumatran earthquake. Regions having undergone major changes were identified by comparing the shorelines of pre and post tsunami periods for assessing change in the mangrove and coral reef ecosystems of the most affected regions. However, factors such as information blackout due to cloud cover, difference in tidal stages at the time of image acquisitions and major changes in the islands were found to be affecting the retrieval of reliable information from the images. Unsupervised method of classification and vegetation indices was employed for quantifying the change in the spatial cover and density of the mangrove habitats, respectively. To assess the changes in the coral reef ecosystem spectral differencing method was adopted. However, influence of intervening water column resulted into confusion of spectral distinction of bottom types in the coral reef habitats. Additionally, the difference in sea state condition had an impact on the spectral response leading to inaccuracy in change assessment. In the present paper, influences of these factors are discussed and solutions are suggested.