Overview of Ecological Units Data

NatureServe Explorer provides data for ecological units (associations and systems) primarily in the contiguous United States and Hawaii. Canadian data are provided in NatureServe Explorer where available. Ecological systems for Latin America and the Caribbean are provided on InfoNatura. The completeness of ecological unit inventory and classification work varies widely among states, provinces and regions, and NatureServe Explorer reflects these variations. Ecological units are defined by the International Ecological Classification Standard, primarily composed at present of the International Vegetation Classification (IVC) and the NatureServe Ecological Systems Classification. For details on this standard, see Classification of Standard Ecological Units.

The Comprehensive Report for ecological units contains available information in the following categories: classification; related names; global conservation status; distribution; environmental setting; vegetation structure; dynamic processes; authors and contributors; and references. This information is continually reviewed and updated in the NatureServe Central Databases in order to reflect ongoing inventory and classification efforts, and new status assessments. NatureServe Explorer is updated periodically from the NatureServe Central Databases.

Because of the wide variation in ecological units inventory and classification throughout the United States, it is not possible to make a definitive interpretation of the differences in diversity of ecological units among states or regions. Some states or regions focus efforts on those US-NVC associations that are considered imperiled (conservation ranks G1 or G2), while others, like the western U.S. Forest Service Districts, focus on more common units. Also, while the classification system is intended to develop units with consistent scale, associations are more narrowly defined in some regions, resulting in a greater number of associations than average.