Geo-Analyst , ISSN 2249-2909 2015 ANALYSIS OF CHANGING LANDSCAPE AND NDVI FOR ASSESSING LANDSCAPE ECOLOGY IN BISHNUPUR SUB-DIVISION, BANKURA DISTRICT, WEST BENGAL,USING LANDSAT TM IMAGES Amborish Das* Abstract Bishnupur sub-division of Bankura District is a part of lateritic ‘Rarh Plain’ of West Bengal and it contains a significant portion of thick Sal forest. The present study shows that various anthropogenic activities, deforestation, monsoonal rainfall erosivity, overuse of land, soil erodibility and water stress enhance progressive loss of topsoil, strain in plant leaf, drought condition and expansion of degraded unfertile land. These phenomena reflect different spectral signatures from the ground, which is well captured by the sensor of Landsat TM in different bands. Therefore using georeferenced satellite images, image processing software, land use classification, NDVI method and GIS, this paper tries to focus on the major spatio-temporal changes in land use and land cover, analyses present condition of natural vegetation, water stress on forest and overall land degradation of Bishnupur sub-division in Bankura District, West Bengal. Keywords: NDVI, Land Degradation, Water Stress, Deforestation and GIS Introduction Agenda 21 has defined Land as a physical entity in terms of its topography and spatial nature including natural resources like the soil, minerals, water and biota existing on the land. These components provide a variety of services essential to the maintenance of life-support systems and the productive capacity of the environment. The multidimensional prospects of land are often threatened by deforestation, misuse and overuse of land, surface and subsurface water depletion, water stress on vegetation, laterisation of soil, rill and gully erosion (Basu, 2002). Those factors are the central causes of land degradation and desertification that means the overall loss of soil quality. It has been found that natural vegetation and its distribution are very much related with the changing surface and sub-surface properties of land and importantly water crisis makes difference in reflectance between red and near-infrared wavelengths ranges (Sabins, 2008). This type of reflectance alteration is well captured by the great sensors of Landsat remote sensing satellites and it appears as distinct signature values in pixels (Sabins, 2008; Guha, 2008). So, to realize the role of changing landscape pattern and land degradation on the natural vegetation this study has been based on forest dominated Bishnupur sub-division of Bankura district, West Bengal using Landsat TM images and Geographic Information System (GIS). *Research Scholar, Dept. of Geography, Visva Bharati, Santiniketan, Birbhum, WB 26 Geo-Analyst , ISSN 2249-2909 2015 Objectives (1) Understanding the geographical set-up of the study area with special emphasize on physical environment. (2) Understanding the land use and land cover characteristics in temporal scale using supervised digital classification of images. (3) Preparing post-monsoon NDVI of two time periods (1991 and 2009) to indentify vegetation stress as well as ecological stress, possibility of drought and its spatial uniqueness. Materials and Methods For assessing the vegetation reflectance difference and land degradation post-monsoonal (November) Landsat TM images of 1991 and 2009 have been taken which have seven distinct bands of 30 meter of spatial resolution (except Thermal Band 6, having 120 meter spatial resolution). These images are directly downloaded from the website of United State Geological Survey The subdivision map of Bishnupur has been taken from Census of India (2001) and it is compared with the topographical sheet 73 M/7, 73M/8, 73M/11, 73M12, 73N/5 and 73N/9 for extracting physical features. The seven bands are stacked in one raster layer and the output layer is reprojected in Geographic latitude/longitude with WGS-84 datum using ERDAS Imagine 9.1 software. Creating a vector layer of Bishnupur subdivision boundary in ArcGIS 10 the study area has been made from images in ERDAS. Using Band 4 (NIR), 3 (Red) and 2 (Green) combinations, Standard False Colour Composite (SFCC) image has been prepared and through training sites and supervised classification land use and land cover change in between 1991 and 2009 has been detected. To find out the vegetation concentration, healthiness of plant leaf and soil moisture availability, NDVI (Normalized Difference Vegetation Index) which is based on Near-Infrared (NIR) band (0.72 – 1.10 micro metre) and red band (0.58 – 0.68 micro metre) has been employed. (Zheng et al., 2004). Chlorophyll absorbs light in the red channel and foliage reflects in the NIR channel (Sabins, 2008). Therefore, higher photosynthetic activity will result in lower reflectance in red band and higher reflectance in NIR band. The formula stands as NDVI = (NIR – Red) / (NIR + Red) NDVI value varies between -1 and +1. The values greater than 0.6 representing dense and healthy vegetation where as the value less than zero is the representative of no vegetation and extreme negative values represent water and values around zero represent bare soil or surface. 27 Geo-Analyst , ISSN 2249-2909 2015 After image processing, thematic map has been prepared using ArcGIS 10 software the changing nature of landscape and NDVI of study area have been analyzed. (fig. 1). Fig. 1: Flowchart of Adopted Methodology Geographical Attributes of Study Area The study area belongs to Bishnupur sub-division of Bankura district and this administrative area is situated over ‘Rarh Plain’ of West Bengal, having deep mantle of Caniozoic laterites and lateritic soils. The sub-division has an area of 1870.05 sq km and it consists of Bishnupur municipality, Sonamukhi municipality and six community development blocks: Indas, Joypur, Patrasayar, Kotulpur, Sonamukhi and Bishnupur. The six blocks have 56 Gram Panchayates. The subdivision has it’s headquarter at Bishnupur. The Sub-Division is bounded by Hooghly district in the east, Burdwan district in the north, Bankura sub-division (Bankura district), Khatra sub-divisions of Bankura district at south-west and Paschim Mednapur district in the south. This Sub-Division and its adjoining region are 28 Geo-Analyst , ISSN 2249-2909 2015 covered under monsoonal deciduous forest, having main concentration of Sal, Teak and Mahua. The lateritic terrain of this area is overlaid on Tertiary sedimentaries and it is a type of low level secondary laterites and detrital origin drifted from western plateau after Pleistocene Ice Age (Prakasam and Biswas, 2009). Bishnupur has a great historical as well as cultural back ground, it was ruled under the Gupta period by local Hindu kings who paid tribute to Samudra Gupta. Damodar, Sali and Dwarakeswar are the main rivers of this region. The optimum physical environment of this area is responsible for dense forest growth which is distinct characteristic of Bishnupur sub-division in Bankura district (Table.1). Fig.2: Location Map of Study Area 29 Geo-Analyst , ISSN 2249-2909 2015 Table.1: Geographical Characteristics of Bishnupur Sub-Division Attributes Description Location 22°53´ 18´´to 23°25´49´´ N and 87°14´52´´ to 87° 46´02´´ E Hydrogeomorphology Lateritic patch located in the both side of river Dwarakeswar, average elevation ranges in these region is 69 metre, rills and gullies, dissected rolling topography having average slope of 3° to 7°, 10 metre of ground water fluctuation. Climate Bishnupur's climate is classified as tropical. In winter, there is much less rainfall in Bishnupur than in summer. This location is classified as Aw by Köppen and Geiger. In a year, the average rainfall is 1552 mm, maximum temperature- 43°C and minimum temperature 8°C, strong seasonal contrast favours laterisation process. Land use, Land cover Total cultivable land- 146210.56 hectare, cultivable waste- 7834.15 hectare, forest-44985.57 hectare. Hazards Drought, heat wave, flood, soil erosion and deforestation Population Total population 906970 out of which 464580 were males and 442280 were females density-553 per sq km, (As per 2001 census) Source: Bankura Zilla Parisad Changing Land Use and Land Cover To understand the anthropogenic pressure on ecological system of a fragile forest area, the analysis of land use and land cover is very much useful. Keeping in mind the behavioural reflectance change of landscape, classification has been made for the post-monsoonal SFCC images of 1991 and 2009 to assess the change in landscape ecology. Census of India (2001) has indicated that the total forest cover of Bishnupur Sub-Division is declining slowly alongside total cultivable land is decreased from 146211 to 124589 hectare in between 2001 and 2011. But, the important thing is that in digital classifications of Landsat TM images (1991 and 2009) set forth the declination of dense forest area from 1991 is quite high, showing adverse effects on landscape ecology of this region. Kotalpur and Indus CD Block experience severe deforestation whereas 30 Geo-Analyst , ISSN 2249-2909 2015 Sonamukhi, Joypur, Bishnupur, Patrashaer CD Block are more covered under dense forest but there are some patches which are completely deforested due to cutting, agricultural expansion and erosion. Comparing the images of 1991 and 2009 Kotalpur and Indus CD Block and eastern part of Joypur, northern part of Bishnupur, northern part of Sonamukhi CD Block have lost its forest cover to a considerable extent from 1991. The lateritic soils are exposed due to forest clearance, as a result water erosion takes place. The dense network of rills and gullies dissect the landscape, transforming barren lands into ravine topography . Importantly, right bank of Damodar and both bank sides of Dawakeswar River are turned into degraded barren land due to sand splays and laterisation. The riverine tract of Sali River is excessively used for agriculture which gradually engulfs the forest fringe situating in lateritic uplands. As per classification of Landsat TM images (1991 and 2009) the dense forest cover is decreased and degraded forest land is increased. So all these information signifies land degradation and desertification.