Abstract
Lakshmibaur-Nalair Haor, a freshwater wetland ecosystem is situated in the north-eastern region of Bangladesh. This place hosts the second largest freshwater swamp forest in Bangladesh. Containing rich biodiversity, this unique area experiences significant landscape changes. This study examines land-use and land-cover (LULC) changes between 1989 and 2019 in the Lakshmibaur-Nalair Haor area by operating Landsat multispectral imageries through remote sensing (RS) and geographic information system (GIS) techniques. The changing status of the haor was analyzed by initiating normalized difference vegetation index (NDVI) and modified normalized difference water index (MNDWI). The unsupervised classification technique was implemented to classify these images into five major classes (vegetation, cropland, bare soil, shallow water, and deep water bodies) using threshold values of NDVI and MNDWI. After accuracy assessment, the post-classification comparison method was performed to evaluate the change detection. This study demonstrates that this valuable area lost ~ 2208.6 ha (37.54%) of the deep water body and 489.6 ha (8.34%) of vegetation over the last 3 decades. However, it has gained about 1729 ha (29.39%) of cropland, 2673 ha (45.44%) of shallow water and 1124 ha (28%) of bare soil. Such changes indicate significant human interventions such as expansion of croplands with increased population pressure. Gradual change of deep water into shallow water over time is enabling local community to expand agricultural lands and activities during the dry season. This study’s findings are useful in understanding and tracking changes in wetlands in Bangladesh and other similar settings.
Highlights
Wetlands play crucial role in global biodiversity and provide essential support to many species and people’s livelihood across the world
The outcome of satellite image processing shows that the normalized difference vegetation index (NDVI) classifies this area into four classes: bare soil, cropland, vegetation and no-vegetation which includes deep water and shallow water class of the modified normalized difference water index (MNDWI) class
We plotted charts to display the areas in hectares of numerous NDVI and MNDWI classes over the three decades presented in the Figs. 10 and 11
Summary
Wetlands play crucial role in global biodiversity and provide essential support to many species and people’s livelihood across the world. Wetlands often seen as transitional lands between terrestrial and aquatic ecosystems, especially where shallow water covers the land, or the water table is generally at or near the land surface. Such wetlands are classified into seven landscape units, namely, estuarine, open coast, floodplains, freshwater marshes, lakes, peatlands and swamp forest (Cowardin and Golet 1995; Dugan 1990). Over the last 40 years, almost 76% of freshwater animals and plants have disappeared
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