L - Exceptional Natural Areas

An Exceptional Natural Area is an area composed of relatively intact, species-rich, native plant dominated communities. ENAs are reservoirs of biodiversity. They can vary widely in size and configuration, and often contain more than one type of plant community, including ecotones which are the transition areas between more distinct habitats such as woodland, meadow, or wetland. ENAs may also contain managed landscapes including occasionally mowed or grazed meadows, or utility cuts, which exhibit one or more of the characteristics noted below, and which would disappear without continued management or human intervention. The following are some biological community characteristics used to locate and determine ENAs in New Garden Township:

An Exceptional Natural Area is an area composed of relatively intact, species-rich, native plant dominated communities. ENAs are reservoirs of biodiversity. They can vary widely in size and configuration, and often contain more than one type of plant community, including ecotones which are the transition areas between more distinct habitats such as woodland, meadow, or wetland. ENAs may also contain managed landscapes including occasionally mowed or grazed meadows, or utility cuts, which exhibit one or more of the characteristics noted below, and which would disappear without continued management or human intervention. The following are some biological community characteristics used to locate and determine ENAs in New Garden Township:

  • Communities containing species uncommon or declining in the township, region, or state.
  • Communities that are unusually rich and diverse examples of characteristic plant communities in the township, or are the only remaining examples of these communities in the township.
  • Communities that reflect unusual or regionally uncommon geologic features or structures.
  • Communities with a high number of species with limited ranges of ecological tolerance, or high degree of fidelity to narrow ranges of habitat condition, indicating a specialized or long-established community (“Coefficient of Conservatism” (see below) of 7 or greater).

Starting in the late 1970‘s, two Chicago-area professors developed and expanded a method for evaluating natural areas for quality and environmental integrity. Several years ago, the Bowman‘s Hill Wildlife Preserve adapted this method for use in Pennsylvania. The first and most important step in this method is to assign a Coefficient of Conservatism (CC) to every native plant found in the specified region. Bowman‘s Hill, in consultation with regional botanists, created lists of species with CC‘s for southeastern PA, which is available on their website here. CC‘s are categorized according to the following criteria:

  • 0 to 3: Plants with a high range of ecological tolerances, found in a variety of communities.
  • 4 to 6: Plants with an intermediate range of ecological tolerances, usually associated with a specific plant community.
  • 7 to 8: Plants with a narrow range of ecological tolerances or associated with an advanced stage of plant community succession.
  • 9 to 10: Plants with a high degree of fidelity to a narrow range of habitats.

In New Garden Township, species with a CC of 7 or greater are used as indicators of both high quality habitat and potential ENAs. See Appendix 3: Species with a Coefficient of Conservatism of 7 or Greater.

Due to time and accessibility constraints, not every corner of the Township was thoroughly surveyed, so it is possible that some areas that might qualify as ENAs were not visited. A 1956 aerial photo (select the 1956 woodland checkbox) shows the location of older woods, which are the refuge of woodland species even if they are not of ENA quality. Several interesting areas were only visited once, and a second visit might have led us to include them as an ENA. The following listing of New Garden‘s 14 ENAs is not the “final word” but more of a guide for evaluating natural habitats in the Township. Each of these entries describes the ENA‘s flora, and identifies which botanical survey section (Map 1) in which it is located, and ownership (i.e., private or public). Also identified are the ENA‘s drainage basin, geology, and notable plant species.

The fourteen ENAs are plotted on Maps 3 and 4 found in the appendix. Or, each of the fourteen Exceptional Natural Areas can be viewed in detail using the interactive map.