areachange

Areachange is a term used in geography and environmental science to describe the difference in the size of a defined geographic area between two or more time points. It can refer to changes in the spatial extent of land cover, land use, water bodies, or administrative boundaries, and is typically expressed as an area delta (e.g., square kilometers) or as a percentage change relative to an initial area. Areachange is computed by comparing accurate representations of a feature's boundaries across time, often using GIS and remote sensing data. Methods include vector overlay to compute polygon area differences, or raster-based change detection by classifying land cover in each time step and summing pixel counts converted to area.

Applications include monitoring urban expansion, deforestation, glacier or lake area fluctuations, coastline retreat, and habitat changes. Areachange metrics support environmental assessment, resource planning, climate studies, and disaster management. Limitations stem from boundary delineation uncertainties, misregistration, classification errors, and differences in data resolution or projection, which can bias area estimates.

Typical outputs include net area change, annualized change rates, and maps illustrating where change occurred. Data sources range from satellite imagery (for example Landsat or Sentinel data) to aerial photography and cadastral or hydrological records. Software such as GIS platforms and remote-sensing toolkits are used to calculate areachange and to visualize trends.