The U.S. Environmental Protection Agency's  Report on the Environment (ROE) presents the best available indicators of national trends in the environment and human health. One of these indicators is carbon storage in forests, and the ROE Carbon Storage in Forests tool can be used to explore the trends related to this indicator. The tool is divided into three “exhibits”: a graph of total forest biomass in the contiguous United States, by forest component, 1990–2013; a map of forest biomass in U.S. counties per square mile of land, 2013; and a map of percent change in carbon stored in U.S. forests, by county, 1990–2013.