In this part of The State of the Nation’s Ecosystems, we move from background and principles to the indicators themselves. In each of the following seven chapters, we present a suite of indicators, describing, for each one, its significance, current conditions, and historic trends when data are available and, when they are not, why not.

We begin with the core national indicators, which provide a succinct description of ten key aspects of the condition and use of ecosystems in the United States. These core national indicators are followed by chapters that present the indicators for coastal waters, farmlands, forests, fresh waters, grasslands and shrublands, and urban and suburban areas. Each of these ecosystems is described using 14 to 18 indicators.

Each chapter in this part offers a summary table that briefly describes the indicators, including whether data adequate for national reporting are available or not and, if so, whether there are trends or other useful reference points against which to compare the data. This overview table is followed by a summary of the highlights of each indicator, as well as information on the definition of the ecosystem (e.g., “what do we mean by grasslands and shrublands?”). Finally, since data are presented using a variety of regional schemes, we define these for each ecosystem.

The heart of each chapter is the indicators themselves, which are generally presented in one or two pages (given their broad scope, the core national indicators are accorded two pages or more, as are several more-complex indicators throughout the report). Each indicator is linked to technical notes, which provide detail on the indicators and the data sources used to report on them.