The Natural Heritage Inventory Methodology

The Wisconsin Natural Heritage Inventory (NHI) program is part of an international network of NHI programs. The defining and unifying characteristic of this network is the use of a standard methodology for collecting, processing, and managing data on the occurrences of natural biological diversity. This network of data centers is coordinated by Nature Serve (exit DNR), an international non-profit organization.

Natural Heritage Inventory programs focus on natural communities, rare plant and animal species, and other natural features, referred to as Elements of biodiversity. Elements tracked by the Wisconsin NHI Program are listed on the Wisconsin NHI Working List, containing natural communities, as well as Endangered, Threatened and Special Concern plants and animals tracked by the Wisconsin DNR.

Special Concern species are those about which some problem of abundance or distribution is suspected but not yet proven. This category is designed to focus attention on certain species before they become Endangered or Threatened. The NHI program --in consultation with staff from a variety of state and national agencies, organizations, and universities, as well as naturalists throughout Wisconsin-- determines which species to include in the Special Concern category. The Special Concern list is quite dynamic with species added or removed from the list as additional information is collected and consolidated by the NHI program. In some cases, as more data on a species' status and distribution are gathered, it becomes clear that the species is more common than originally thought and the species is dropped from the Working List. In other cases, additional data indicate a decline in a species' status and distribution in the state that warrants proposing it for listing as Endangered or Threatened. The most recent Working List for the State of Wisconsin is available online.

The NHI natural community classification was initially based on the types described by John Curtis in his seminal work, The Vegetation of Wisconsin. The NHI program has subsequently expanded its natural community list to include several less common, or more distinct, types not covered by Curtis (e.g., Algific Talus Slope and Forested Seep) as well as many aquatic communities.

When Heritage programs are initially established, one of the first tasks facing staff is to consolidate existing information on the status and location of rare elements. Beginning with its establishment in 1985, the NHI program gathered this information from museums, herbaria, and a variety of texts, guides, and dissertations describing the state's flora and fauna. After having incorporated much of the available existing data into its database, the NHI program now concentrates its efforts on both conducting inventories and incorporating the results of other ongoing inventories that pertain to endangered resources.

In general, NHI uses two approaches to inventorying biodiversity. The first approach focuses on locating occurrences of particular elements (e.g., where do phlox moths occur in Wisconsin.) The second approach focuses on assessing the components of a particular area (e.g., what rare and endangered resources occur within the Central Sand Plains Ecological Landscape or the Black River State Forest.) The latter approach often employs a "top down" analysis that begins with an assessment of the natural communities present and their relative quality and condition. This information is subsequently used to determine where different species-oriented surveys should be conducted. This second approach, commonly referred to as "coarse filter-fine filter," concentrates inventory efforts on those sites most likely to contain target species. It also allows sites to be placed in a larger, landscape context for broader applications of ecosystem management principles.

The Wisconsin NHI Program conducts coarse filter-fine filter field surveys for rare species and natural communities throughout Wisconsin. Initial inventories take a broad look at the entire region under study to identify and assess ecological attributes and natural communities and habitats present. Then, finer level inventories are carried out that focus on groups of species such as birds, butterflies, aquatic invertebrates, and plants. Inventory results are analyzed along with other information to identify ecologically significant sites. Some of these sites become designated as State Natural Areas while others are purchased by private land trusts or conserved through state and local planning efforts. They all provide some critical function on the landscape (such as corridors for movement, undisturbed habitat, or ecosystem support) or have potential for restoration. Learn more about NHI inventory projects.