Over two decades ago, The Nature Conservancy (TNC) and state natural heritage programs developed the “coarse filter/fine filter” approach to preserving biological diversity (Grossman et al. 1994). This approach involves identification and protection of natural communities (coarse filter) as well as rare species (fine filter). Identifying and protecting representative examples of natural communities ensures conservation of most species, biotic interactions and ecological processes. Those species that “fall through” the community filters are generally the rare species. Identification and protection of viable occurrences of rare species serves as the fine filter for preserving biological diversity. Using communities as a coarse filter assures that conservation efforts are working to protect a more complete spectrum of biological diversity, not just those species whose priority conservation status has been documented. By protecting communities many species not generally targeted for conservation, such as poorly known groups like fungi and invertebrates, are protected. Furthermore, communities are an important tool for systematically characterizing the current pattern and condition of ecosystems and landscapes. The Terrestrial Ecological Systems and Natural Communities of Nebraska (Version IV) was developed primarily as a tool to aid in the conservation of biological diversity by providing a systematic classification of the natural communities found in the state. In some cases, land managers and other conservationists have found natural community classifications too fine-scale and complex for vegetation mapping and other land management projects. In recent years the need for a broader scale ecological classification unit for conservation and resource management efforts on a national and state level became obvious. To fulfill this need, this document, for the first time, includes a classification of the ecological systems of Nebraska (ecological systems are broader scale classification units than natural communities)
