The NLCD includes spatial reference and descriptive data for the land surface, such as thematic class (for example, urban, agriculture, and forest), percent impervious surface, and percent tree canopy cover. The database provides cyclical updates of United States land cover and associated changes. Systematically aligned over time, the database makes it possible to understand both current and historical land cover and land cover change and enables monitoring and trend assessments. Sources: The National Land Cover Database Factsheet; Land Cover | Multi-Resolution Land Characteristics (MRLC) Consortium.