Socio-economic and environmental impacts of changing land use pattern of Rangamati District

Abstract

Land is an important resource for the environment, civilization, and every community. Almost all human activity on land is powered by agriculture, housing, and a variety of natural resources. It should be managed appropriately to ensure that this finite resource is put to the best use for the advantage of the most considerable amount of people. Day by day, human involvement and natural phenomena generate changes in land usage. Land use change, in turn, can impact the social and environmental conditions of any area. Many applications require precise land use information, such as natural resource management, planning, and monitoring programs. Land cover change is becoming a critical component of modern natural resource management and environmental change monitoring systems. There has been a rise in research on land use change due to the rapid investment and development of land use mapping. This study aimed to analyze Land Use Land Cover (LULC) changes in the Rangamati district of Bangladesh between 1977 and 2019, the consequences of land use change in socio-economical and environmental situations, and investigate the significant driving forces of land use in the study region. The ‘Normalized Different Vegetation Index’ (NDVI) is a dimensionless index with values between -1 and 1. Higher NDVI values indicate healthy vegetation, whereas lower (0) NDVI values indicate unhealthy vegetation. Values near zero but not negative suggest a settlement, bare land, rock, and sand beach, respectively, while negative values indicate the absence of green vegetation. Landsat Satellite image from five different years (1977, 1989, 2000, 2011, and 2019) was used to calculate the NDVI value for January. To produce a land use land cover map and identify changes, the NDVI values are reclassified using a “Defined Interval” algorithm. The highest NDVI value was discovered in 1977 (0.88), indicating the presence of healthy vegetation at the time. After 1977, it was found that the NDVI value was dropping (0.79 in 1989, 0.74 in 2000, 0.71 in 2011, and 0.53 in 2019), indicating a quickly degrading shift in the plant cover in the studied region. Population growth, migration from plain land, rapid urbanization, the Kaptai Dam, the government's migration policy, high land prices, unplanned development, tourism industry development, firewood collection, and poverty were identified as the significant drivers of LULC changes in the study area. Additionally, analysis of NDVI results confirmed that forest or dense vegetation area is decreasing while settlement area and sparse vegetation area are gradually increasing, which may be a significant threat to ecosystem function and climate change. The accuracy of the NDVI-based classified images is evaluated by computing the overall classification accuracy and the Kappa coefficient using a confusion matrix. Overall classification accuracy ranged from 84 to 90%, with Kappa statistics ranging from 80 to 88% for TM and OLI TIRS images. The study attempts to reconstruct history to comprehend the dynamics of LULC changes for environmental degradation. Land surface temperature (LST) is one of the most important variables of environmental changes. The environmental changes in the Sadar Upazilla of Rangamati were observed using the extracted LST of satellite imagery of January for three different years: 2000, 2011, and 2019 in this study. This was compared to data from the Bangladesh Meteorological Department (BMD) and Google. The retrieved data from satellite imagery is supported by the BMD and Google Data. The NDVI value is significantly associated with the LST taken from the satellite image. As the NDVI value rises, the temperature falls, and as the NDVI value falls, the temperature rises. It revealed that the temperature was low when the vegetation was high and progressively increased when the vegetation was low. The increasing trend of LST in Rangamati is indicative of the district's overall environmental situation. The government and development agencies should view these findings as a critical issue in Bangladesh's southeastern region. The field survey in the Rangamati district gave a clear picture of the socio-economic and environmental change in the locality identifying overpopulation as the significant driving force responsible for land use change.