Long‑term monitoring of cropland transformation in Kolkata Metropolitan Area, India using open‑source geospatial technologies

摘要

Urban and peri-urban agricultural practices are degrading throughout the developing world owing to unprecedentedurban sprawling and consequent expansion of built-up areas. This study attempted to assess the changing land use/landcover patterns of Kolkata Metropolitan Area, India from 1990 to 2020 with special emphasis on the transformation trajectoriesof its urban and peri-urban agriculture as a case study using free and open-source software and multi-temporalgeospatial database. It also aimed to project the transformation scenario of croplands in 2030 through application ofthe artificial neural network algorithm of the freely available Modules for Land Use Change Evaluation plugin. Resultsrevealed a persistent spread of built-up areas by engulfing croplands, wetlands, vegetation and water bodies throughoutthe assessment period. An overall loss of 181.11 sq. km of croplands between 1990 and 2020 was estimated and foundto be more prominent in the northern, eastern, and south-eastern parts of the study area. If the existing socio-economicframework and administrative mechanism would prevail as usual, then the projected land use patterns of 2030 wouldpredict a further decrease of 15.46 sq. km in cropland area thereby culminating to a total 37.39% of it original extent since1990. A theoretical three-stage model of land use conversion was developed from the empirical results as well as fieldobservations and validated with the findings of the projected scenario. It indicated two primary conversion patterns forthe study area, viz. (1) natural area to cropland to fallow land and then to built-up, and (2) natural area to fallow land tobuilt-up. Few necessary management measures were suggested to mitigate this persistent loss of croplands and othernatural areas.