The Natural Heritage Inventory Methodology

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

Since its inception in 1950, TNC has maintained a strong science-driven approach to biodiversity and natural areas conservation. As the organization became more active in the protection of biological diversity through direct land purchase, it became obvious that there was a need for better information on which to base its conservation decisions. TNC wished to ensure that scarce funds were invested in areas that were true priorities from the standpoint of biological diversity, and not simply attractive open spaces. Unfortunately, there was no source for well-organized, easily accessible information on the condition, status, and location of species and ecosystems deemed important for conservation. To meet its needs, TNC pioneered a unique private-public partnership -- the Natural Heritage Network.

After developing a standardized methodology for collecting and organizing data, TNC set about establishing a series of locally-based programs to operate as a unified network of permanent biological resource databases. The first "strand" of the network took hold in 1974 with the establishment of the South Carolina Natural Heritage program. The Wisconsin NHI program was formally established in 1985. As of 1997, there are 85 "primary" data centers operating in the western hemisphere, covering all 50 states, six provinces of Canada, and 13 countries in Latin America and the Caribbean. In addition, there are more than one hundred secondary or "satellite" data centers housed in cooperating agencies and operating units such as National Parks and National Forests.

Of course, inventories of areas containing exceptional natural resources or features have been conducted for many years by a variety of organizations, universities and agencies. Many inventories have been, and continue to be, focused on one resource group such as timber stand composition, game animal population status, and surface water location and description. Inventories of high-quality natural areas in the U.S. have been conducted since the early part of this century. In Wisconsin, in-depth statewide natural area surveys conducted by the Department of Natural Resources from the late-1960s through the early-1980s attempted to identify sites retaining the most natural and native (pre Euro-American settlement) conditions. The Department's goal with this inventory was to incorporate the best of these sites into the State Scientific Areas (now the State Natural Areas) program.

Because these inventories had different goals and objectives, their analyses of resources were viewed through different "lenses". Although it did not prevent these inventories from reaching their individual desired objectives, as a group they suffered from a compatibility problem. Not only did the scale of these inventories vary from a local to national view, but each inventory had different criteria in characterizing an area's biological and ecological diversity making it very difficult to meld the results.

The approach used by the Heritage Network is different in that it "atomizes" biological diversity into discrete, common, workable data units for the purpose of analysis. That is, rather than attempt to assess the overall composition, structure, and function of an ecosystem, the Heritage method evaluates the biologic components of the system at a simpler scale. The Heritage system refers to these biological components as "elements," and they are grouped into three categories: species, natural communities, and "others" (a conveniently broad category encompassing an eclectic mix of natural features that a particular Heritage program believes are worthy of attention.) In Wisconsin, the NHI program's "other" category includes animal concentration areas (hibernacula, mussel beds, and migratory bird concentration points) and special geological features (bedrock glades, interior beaches, and open cliffs)

Although each Heritage program is expected to expend some time and resources documenting the occurrences of the common elements occurring in their area, each program's primary focus is on the rare or declining species, the high-quality or rare natural communities, and the unique or significant natural features. In Wisconsin, these three types of elements comprise the NHI Working List.

One of the strongest attributes of the Heritage approach is that by classifying and characterizing these elements, and then collecting specific information about their occurrences in the landscape, each Heritage program amasses comparable data. These data can be used to determine (at different scales) the relative endangerment of the elements and to ascertain which occurrences are the best examples of each element. The other primary strength of the Heritage approach is that by recording data as discrete facts, not only does each datum remain subject to continual rechecking and updating, but the data can be used for a wide range of analyses and applied to the broadest possible array of users. Furthermore, previously collected information does not lose its usefulness as our perceptions of significance change - the data can always be re-analyzed with changed criteria.

The NHI Working List contains native species known or suspected to be rare and/or declining in the state, natural communities, and natural features occurring in Wisconsin. The Working List includes species legally designated as "Endangered" or "Threatened" by either the State of Wisconsin or the federal government, as well as species in the advisory "Special Concern" category. The listing of species as Endangered or Threatened (E/T) in Wisconsin is a legislative action that is typically updated every three or four years (the last update to the state's E/T list became effective August 1, 1997.) Currently, there are 139 species listed as Endangered (74 plants, 65 animals) and 104 species listed as Threatened (65 plants, 39 animals).

Special Concern species are those about which some problem of abundance or distribution is suspected but not yet proven. The main purpose of this category is 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 NHI natural community list 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, forested seep, cobble beach, and sedge fen) 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, there are 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 sands ecoregion 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.

Ideally, from NHI's perspective, these two approaches would be integrated and result in coordinated surveys which inventory different taxonomic groups and geographic areas in a comprehensive and complimentary manner. However, inventory scheduling has been and continues to be dictated primarily by funding sources, development pressures, and individual agendas. The resulting reality is that the NHI database continues to be populated with a variety of survey results. Examples of inventories that generate data incorporated in the NHI database include:

• inventories of federally-listed species funded by the US Fish & Wildlife Service,
  
• status surveys of particular species undertaken for management purposes,
  
• site-specific inventories conducted in conjunction with DNR's regulatory review and permit process,
  
• formation gleaned from theses, dissertations, and other university studies, and
  
• species observations from a variety of naturalists throughout the state who set their own inventory priorities.

More and more of the inventories that the NHI program are involved with are utilizing the "coarse filter-fine filter" approach. Two notable examples are the inventories conducted in partnership with the Southeastern Wisconsin Regional Planning Commission (SEWRPC) in seven southeastern counties and with the Bureau of Forestry in the Northern Highland-American Legion State Forest (NHALSF). In each case, these inventories were driven by the realization that successfully resolving important land use issues requires adequate site-specific data that can be evaluated in a landscape-scale context.

The initial analysis for both the SEWRPC and NHALSF inventories began with an assessment of the entire region where important ecological attributes and the biological processes that supported them were determined. Criteria to evaluate sites were established and then vegetative communities were identified and characterized. Based upon existing habitat characteristics and the habitat preferences of different rare species, sites were identified where species-specific surveys were most appropriate. No doubt several occurrences of rare species exist that were not located through these inventories. However, by concentrating species-specific inventory efforts on those sites most likely to support the populations with the highest conservation value, the organizations involved were able to gather productive information efficiently. As a result, adequate data are now available to formulate appropriate solutions regarding endangered resource protection that face agencies and organizations in these two locations.