4.1. CHANGE DETECTION STUDY
Digital analysis of landsat data of the study area shows that a lot of change of mangrove forest cover has taken place during the last nine years.(1997-2006)
Where as digital image processing and analysis of Landsat TM data of January,2006 ((Figure- 4.3) shows that almost all the forest vegetation has been removed except some patches of mangrove vegetation on the bank of the channels. Only 123.58 ha of poor scrub forest cover are remaining with the forest land . A landuse map has been prepared showing the areas under existing vegetation on cover. It has been shown in((Figure- 4.4).
A year wise deterioration of forest cover has been shown in the table no-3 . This has also been graphical form in ((Figure- 4.5). Then, a change detection map of Mangrove Forest of chokoria sundarbans shown in (Figure- 4.6).
Table No-3 Year wise area of the mangrove cover
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Figure No 4.5 :Graphical represention of the mangrove forest cover.
As the most of the mangroves has been deforested leaving very negligible area of mangrove, we have not attempted to determine the forest density and measure the timber value of the mangrove. The latest TM data of 2006 shows that the Chokoria is no larger a forest area, rather almost whole of its area has been deforestation.
These phenomena occurred because here the environment ensures necessary demands for the existence of all living organisms. Most of the deforestation occurs in Chokoria region at the past century. This loss of forest area occurs due to human activities to provide their needs .Now a days, deforestation plays a vital role for environmental degradation. As a result, global warming, climate change, cyclones, floods, earthquakes and other natural calamities damage life, civilization and creating a threat for the existence of the living beings. It would be worthly mentioned that human generally consider the products of forests useful, rather than the forests themselves. So, they are extracting wood from forests. The enormous collection of wood reduces the forest area. From a secondary information, a statistical view represents that the chokoria mangrove forests area of Cox’s bazar district at 1975 was 7500 hectares, 1981 was 5396 hectares, 1984 was 4940 hectares, 1988 was 973 hectares and in my study at 1997, it has become 271.95 hectares and 2006, it has become 123.58 hectares. We can easily understand that day by day mangrove forests of chokoria sundarbans has been decrease. That day would not be so far when men totally forget the name of chokoria mangrove forest. Such a high loss of forests area results the following adverse environmental impacts in Chokoria mangrove forests:
P Soil erosion: Deforestation increases the rate of soil erosion and landslide.
P Biodiversity: Forests in this region is enriched in biological diversity. Deforestation causes the destruction of habitats. It also damages the composition wildlife.
P Hydrologic cycle: Trees and plants generally affect on hydrological cycle. Precipitation, evapotranspiration and soil moisture content decrease and increase surface runoff and infiltration due to loss of forests.
P Natural calamity: The rate of cyclones and floods increase due to depletion of forests.
P Natural beauty: Chokoria is famous for mangrove forests. Deforestation extracts its charming beauty.
