Spatiotemporal Assessment of Landscape Transformation and Ecological Risk in Halti Beel

Abstract This study investigates the ecological risk of Halti Beel, one of the significant parts of the largest wetland ecosystem of Bangladesh, following the US Environmental Protection Agency (EPA) ecological risk assessment (ERA) guidelines. Physicochemical parameters of water and sediment were analyzed in reference to Environmental Conservation Rules (ECR) and EPA standards. Socio-economic data from local communities and species data from wetland authorities were integrated through questionnaire surveys. Multispectral satellite imageries were used to evaluate the ecological risks associated with LULC changes from 2000 to 2023. ENVI Thematic Change Workflow (TCW) tool was used for LULC change dynamics analysis over 2000-2010, 2010-2023, and 2000-2023. An ecological risk model was developed using Landscape Ecological Risk Indexes (LERI) in Fragstats 4.2; risk zones were mapped, and risk levels were categorized from minimal to severe. A linear regression analysis in SPSS was done to reveal significant relationships between ecological risk and different stressors. The results indicate that the collected samples’ DO, turbidity and electric conductivity exceed the ECR, 1997, and EPA, 2012 standards. The socio-economic prospects of the area largely depend on fishing, farming, and wetland resources, which support local livelihoods despite growing environmental pressure. However, low education levels, poor sanitation, and unregulated land use challenge the local people’s socioeconomic condition. Most of the environmental and anthropogenic factors have strong connections with ecological risk and leave the current status of species highly vulnerable. The significant LULC transformation: from 2000 to 2023, 55.63 % of deep water was converted into shallow water, 11.68 % to agricultural land, and 19.52% of agricultural land was converted to rural settlements, indicating increasing anthropogenic pressure. Between 2000 and 2010, notable changes are that 60.86 % of deep water was converted into shallow water and 18.54 % shifted to agricultural land. From 2010 to 2023, a major transformation of almost half of the deep water area was converted into shallow water and 9.09 % to agricultural land. Ecological risk fluctuated over time; in 2023 ecological risk spread all over the area and middle, highest, and higher risk areas increased synchronously. Major ecological risk areas shifted to the southwest part of the area. The overall results indicate that ecological risk is increasing evidently.