On the role of Remote Sensing in environmental impact analysis of shrimp farming
Landsat band1 image (Figure 1) shows the setting
of shrimp farms inside the mangrove areas. These are generally situated near
seacoast and adjoining channels. Figure 2, offers a very detailed view of a
cluster of shrimp farms. Shrimp farms are generally used for a period of five
years for intensive farming. After that, they loose their fertility and are
abandoned or regenerated after dredging the settled waste material. These
abandoned ponds are having large salt deposits and can not be used for
agriculture purpose. Shrimp farming cause following environmental degradation:
 Figure 2 Shrimp farms in mangrove areas(Thailand) In present study the loss of mangrove forest areas has been highlighted using Landsat TM data. The mangrove forest is considered the most important coastal ecosystem in terms of primary production and coastal protection. Thailand's mangrove forests have seriously depleted in last decade. There is strong realization for intensive monitoring using remote sensing techniques and also restrict shrimp farming to non-mangrove areas. Abandoned shrimp farms are easily located on FCC432 due to their dull brown colour which is in contrast to active shrimp farms with blue colour. These abandoned farms have soil laden with thick wastes in farm of nitrogen and phosphorous and salts. It is useless for any fruitful agriculture. During shrimp farming various external additives like feeding pallets, fertilizers, and other chemicals are being added to farm. Those additives can not be utilized by the culture completely for its growth, so they settle down or get dissolved in the water. Frequently this water which is contaminated is dumped in freshwater streams thus making them polluted. Tha main contaminants in this process can be listed as nutrients, dissolved oxygen, dissolved organic matter etc. Conclusion The work presented in this paper is part of the major ongoing project on Ranong area. The priminary investigations have confirmed the usefulness of Landsat TM digital image in delineating degradation in mangrove areas. Active and abandoned shrimp farms have also been located using different false colour composites. On visual interpretation of band 1 it is found that sediment concentration can be monitored. FCC 531 has also shown a yellow colour effluent from shrimp farms entering the streams. Based on the outcome of this study, authors are currently engaged to investigate more on quantitative information extraction on water quality deterioration in shrimp farm areas using multi-band satellite digital image. References
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