On the role of Remote Sensing in environmental impact analysis of shrimp farming
Methodology
Landsat TM bands have been analysed for better understanding and interpretability of marine and coastal vegetation cover. It is found that FCC generated with bands 432 has offered a synaptic coverage revealing the landuse categories such as vegetation species, urban dwellings, shrimp farms, river channels, and suspended sediments. In addition it is found that FCC 531 was more useful in extracting information on minor channels and effluents from shrimp farms. The different vegetation species have also become very distinct in this band combination. Using these two products the areas covered by shrimp farms have been delineated and an inventory has been prepared. By traditional surveying this task is very difficult and often not possible. The pollution control authorities have strict instructions to treat the wastewater and then shrimp farmers are allowed to dump in adjoining channels but rarely such treatment is carried out. There is no check in absence of viable monitoring techniques. In FCC 531 it is evident that effluent from shrimp farms is of different quality showing yellowish shade. This waste is generally a amino compound which are fed to shrimps in form of proteins. The effect of this and other waste regularly dumped in streams is toxic and has adverse effect on fishery and other aquatic life. Environmental Impact Due to Shrimp Farming From the published records and inventory from satellite data an analysis is shown in Figure 3 on degradation of mangrove areas in the study area. It is evident that there is gradual decline in mangrove areas since 1961 till 1996. The reason of loss in mangrove Area is attributed to rapid growth in shrimp farming in the region. Shrimp farms are generally developed by clearing mangroves and using the easily available seawater for the ponds. The effluent from Shrimp ponds find a way to the adjoining channels and are further transported to the sea.  Figure 1 Marine environ of Ranong (Thailand) |