Observing and monitoring land use and land cover change

Understanding the consequences of land use change requires robust documentation on the characteristics of change. Land use change observation and monitoring programs now rely on remotely sensed data coupled with field observations and corroborating information describing the social, economic, and physical dimensions of land use and land cover. Remote sensing approaches for observing and monitoring change vary depending on the geographic scope, ecological complexity, and the information required to understand ecosystem interactions. Strategies based on identifying spectral variability are useful for targeting areas of rapid change. Measuring changes in land cover biophysical properties requires a more complex approach, where different dates of remotely sensed data are transformed to such variables as surface imperviousness, canopy structure, and phenology, and then compared. Mapping the conversion of land use and land cover from one category to another (e.g., forest to urban) requires maps of the land use and land cover for two or more periods. These approaches have been used successfully at local, regional, and global scales using a range of remote sensing data (e.g., aerial photography, Landsat Thematic Mapper, Terra MODIS, Space Imaging's IKONOS), field measurements, and other supplemental sources. Challenges remain, however, and scientific advances in change detection methods, accuracy assessment procedures, and improved strategies for using land cover to more specifically infer land use are needed so that continued improvements in the types and quality of change measures used to study land use and ecosystem interactions can be realized.