Monitoring Natural Sal Forest Cover in Modhupur, Bangladesh using Temporal Landsat Imagery during 1972 2015 Hasan Muhammad Abdullah *, M. Golam Mahboob, Md.Mezanur Rahman, Tofayel Ahmed * Assistant Professor, Remote Sensing and GIS Lab., Department of Agroforestry and Environment, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706 hasan.abdullah@bsmrau.edu.bd
Saturday, January 9, 2016 A vast swathe of Sal forest clear-cut for commercial fruit orchards in Modhupur. Locals allege that influential party people in collusion with some corrupt officials wiped out 250 acres of such forest in the last one year.
Introduction Modhupur Sal (Shorea robusta) forest, the largest natural Sal forest area of Bangladesh It is a threatened ecological resource situated in the central part of the country Rich in biodiversity (flora & fauna) Serve as a sink (absorbed carbon-di-oxide) linked to UN-REDD (United Nations Programme on Reducing Emissions from Deforestation and Forest Degradation) Unfortunately this forest is heavily impacted by human activities Current study investigated and quantified the destruction in areal extent of natural Sal forest using temporal Landsat satellite data
Composition of natural Sal forest associated flora and fauna (Green KM. 1981) Flora Fauna Species type No. Species type No. Climbers 24 Amphibians 12 Grasses 27 Reptiles 25 Palms 3 Birds 148 Herbs 105 Mammals 35 Shrubs 19 Trees 43 Total 221 Total 220
The main driver of natural forest loss is human activities like settlement, commercial plantation, agriculture and agroforestry practices The forest cover change causes elimination of species locally and declination of natural habitats and ecosystem functions, thus affecting, biodiversity and provision of ecosystem services Monitoring land cover changes using multi-temporal remotely-sensed data provides an effective and accurate evaluation of human impact on the forest ecosystem The satellite image is an important data for forest inventory and land use/cover change (LUCC) analysis to assess the variations at different spatiotemporal scales
Description of the study area Modhupur Upazilla (Sub-District) of Tangail District, Dhaka Study area (Modhupur Sub-District) Originally covered with tropical deciduous forest Lies on Plio-Pleistocene terraces. Geologically it is a terrace from 1 to 30 m above the adjacent floodplains Dhaka Division The Sal forest area consists of high lands, locally called "chala", intercepted by an intricate network of narrow depressions, called "baid", which are cultivated for agricultural crops, especially paddy
Materials and Methods Satellite data acquisition and preparation/pre-processing (Landsat is free from USGS) Ground truithing or forest survey using Global Positioning System (GPS) Classification of Landsat imagery using training data(n=45) and subsequent validation using(n=40) validation data DEM data were utilized to understand the topography as mentioned before Hybrid image classification techniques combining supervise and unsupervised classification algorithms were applied Image processing software (R, ErdasImagine, QGIS ) were utilized
Simple scheme of Remote sensing Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on site observation
SRTM (USGS) digital elevation data (90m) of Modhupur Sub-District
Sensor properties of Landsat MSS, TM and OLI satellites. Landsat Multispectral Scanner (MSS) Band and Spectral Resolution (µm) Landsat Thematic Mapper (TM) Band and Spectral Resolution (µm) 4 0.5-0.6 1 0.45-0.52 5 0.6-0.7 2 0.52-0.60 6 0.7-0.8 3 0.63-0.69 7 0.8-1.1 4 0.76-0.90 5 1.55-1.75 7 2.08-2.35 IFOV at nadir 79 x 79m 30 x 30m 30 x 30 m Earth coverage 18 days 16 days 16 days Altitude 919 km 705 km 705 km Swath width 185 km 185 km 185 km Inclination 99 98.2 98.2 Landsat Operational Land Imager (OLI) Band and Spectral Resolution (µm) 1 0.43-0.45 2 0.45-0.51 3 0.53-0.59 4 0.64-0.67 5 0.85-0.88 7 2.11-2.29
Map of Modhupur Sal forest prepared from Landsat imagery showing remnant natural Sal forest coverage in 1972, 1989, 2010 and 2015 (latter dated map overlaid on the older) Legend:
Accuracy Assessment of the classified imagery Year Forest cover(km 2 ) Users accuracy % Producers accuracy % Kappa statistics 1972 90.13 - - - 1989 62.16 - - - 2010 32.49 95.33 94.32 0.87 2015 22.50 96.20 95.55 0.88
Pictorial view of clear forest (left), converted banana (middle) and pineapple (right) based agroforestry system.
Land use/cover map of the Study area of 2015. For better interpretation of the legend, the online version of this article with coloredfigures can be referred. Legend: Sal forest cut and burned for plantation
Different Land use/cover category of the Study area at 2015 Land use category Area (Km 2 ) % of landuse Natural Sal forest 22.50 4.34 Planted forest 39.79 7.67 Wetland Agriculture 208.39 40.18 Dry land Agriculture 73.19 14.11 Agroforestry systems 34.00 6.56 Settlement 140.75 27.14
Conclusion Monitoring natural Sal forest cover changes using multi-temporal remotely-sensed data provides an effective and accurate evaluation of human impact on the local forest ecosystem The study presented a proof of the alarming trend of drastic depletion of natural Sal forest coverage in Modhupur in spite of several attempts to protect Sal forest in Bangladesh This simple and low cost monitoring technique advantaged with freely accessible Landsat data resources would be helpful for decision maker, forest planner, natural resource manager for sustainable management of this invaluable forest and other natural resources of Bangladesh
Thank you.