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Best Natural Areas

What are they?

The M-NCPPC Department of Parks’ Best Natural Areas contain the best examples of park natural resources in Montgomery County, Maryland. Features such as large wetlands, high quality aquatic resources and forests, diverse native vegetation, uniquely spectacular topography and bedrock formations and/or unique habitats that are scarce and/or fragile help determine an area as the county’s best natural area. The criterion listed illustrates the selection process for each best natural area.

No single factor was determinative, and the areas chosen were not necessarily ranked high in all of the below mentioned criteria. For example, North Branch Stream Valley Park does not have the best quality aquatic resources but contains such an impressively large wetland and has such diverse and exceptional vegetation that it was included as a best natural area. Upper Paint Branch Stream Valley Park, on the other hand, was chosen largely for its extraordinary aquatic resources (although there are portions with high quality vegetation as well). Uniquely spectacular topography and bedrock formations were a dominant factor in the choice of Northwest Branch Stream Valley Park, despite its less than highest quality aquatic resources. Some of the criteria listed below were present in all Best Natural Areas. For example, each of the chosen Best Natural Areas contained a biodiversity area and at least some rare, threatened, endangered or watchlist species.

  • Large Acreage of Contiguous, High Quality Forest
  • Rare, Threatened, Endangered and Watchlist Plants
  • Biodiversity Areas
  • Unique Habitats or Topography
  • Wetlands of High Quality (including Wetlands of Special State Concern)
  • Aquatic Biological Community Rated Good or Excellent
  • Special Trout Management Areas

Criteria for Best Natural Areas

The criteria that were primarily considered when making the decision include the existence of the following resources within the natural area.

 Large Acreage of Contiguous, High Quality Forest

Optimally, the forest area should be large and relatively unfragmented, be composed of a good diversity of native species, and have a varied vertical structure and good canopy development.

  • Size And Shape – As a general rule, 100 acres or greater is needed to sustain a breeding population of forest interior species of birds or other wildlife.  A low edge to interior ratio is preferable; therefore a long, narrow forest area of 100 acres is not very useful for the purpose of sustaining forest interior species, whereas a 100-acre tract that is squarer in shape can sustain such populations. Too much edge allows predatory birds and mammals to penetrate the interior making it more difficult for interior species to survive.  Also, it allows non-native invasive plants, which can out compete and thereby reduce or eliminate native species of vegetation, to penetrate the interior.
  • Contiguous (Unfragmented) – To provide the best habitat the forest stand must be unfragmented; without breaks in the forest canopy.  Wide trails, roads and utility easements allow penetration by predators and invasive plants to the forest interior.
  • Native Species Diversity – An optimal forest area contains a good variety of native species of vegetation.
  • Varied Vertical Structure – The best quality forest has a well-developed overstory with a diversity of tree species, a varied understory with tree species of different heights, shrubs and plants of varying heights and sizes and a variety of good ground cover species.  This offers good habitat to the greatest variety of wildlife species by maximizing the number of available niches for different species, with different needs, to exploit.

Rare, Threatened, Endangered and Watchlist Plants

The Maryland Department of Natural Resources’ “Maryland Natural Heritage Program” uses broadly accepted definitions of the above terms for the classification of a plants status, and these are adopted for purposes of this document. Maryland Natural Heritage Program took the following two definitions directly from the Code of Maryland Regulations (COMAR) 08.03.08.

  • Endangered – A species whose continued existence as a viable component of the State’s flora is determined to be in jeopardy.
  • Threatened – A species of flora, which appears likely, within the foreseeable future, to become endangered in the State.

The following definitions were originally developed and instituted by The Nature Conservancy, an international conservation organization.  This global and state ranking system is used by all state Natural Heritage Programs and numerous Conservation Data Centers in other countries in this hemisphere.  The primary criteria used to define these ranks are the number of known distinct occurrences with consideration given to the total number of individuals at each locality.  Additional factors considered include the current level of protection, the types and degree of threats, ecological vulnerability, and population trends.

  • Highly State Rare (Highly Rare)
    Critically imperiled in Maryland because of extreme rarity (typically 5 or fewer estimated occurrences or very few remaining individuals or acres in the State), or because of some factor(s) making it especially              vulnerable to extirpation.
  • State Rare (Rare)
    Imperiled in Maryland because of rarity (typically 6 to 20 estimated occurrences or few remaining individuals or acres in the State) or because of some factor(s) making it vulnerable to becoming extirpated.
  • Watchlist
    Rare to uncommon with the number of occurrences typically in the range of 21 to 100 in Maryland.  It may have fewer occurrences but with a large number of individuals in some populations, and it may be susceptible to large-scale disturbances.

Biodiversity Areas

These areas are defined in the 1998 PROS (Parks, Recreation and Open Space) Plan as: “Significant natural communities that enhance the biodiversity of the County.      These areas contain one or more of the following natural resources:

  • Populations of rare, threatened, endangered or watchlist plants or animals,
  • Unusual or unique types of habitat,
  • Examples of high quality or otherwise significant natural communities, or
  • Plant or animal species with importance to the County or locality.

Unique Habitats or Topography

A number of unique habitats that are scarce and/or fragile exist in Montgomery County, which can offer exceptional scenic interest, and often support species of plants and animals that can only exist in these special environments.  Examples include:

  • Areas underlain by unusual bedrock such as serpentinite, shale, diabase and limestone, which produce soils that support specific plant communities.
  • Geologic formations such as rock outcrops or escarpments
  • High quality forested and emergent wetlands.
  • Areas with plants that are uniquely preferred by certain important wildlife species such as turtlehead (Chelone glabra), which is the preferred species of the Baltimore butterfly (Maryland’s State Butterfly).

Wetlands of High Quality (Including Wetlands of Special State Concern)

Title 26 of the Code of Maryland Regulations (COMAR) defines “Nontidal Wetland” (referred to as “Wetland(s)” throughout this document) as “an area that is inundated or saturated by surface water or ground water at a frequency and duration sufficient to support, and that under normal circumstances does support, a prevalence of vegetation typically adapted for life in saturated soil conditions, commonly known as hydrophytic vegetation”.

Nontidal wetlands of special State concern” are wetlands “having exceptional ecological or educational value of statewide significance”.  Those areas so designated in COMAR include Little Bennett Regional Park and the Floodplain of Violets Lock which is adjacent to Blockhouse Point Conservation Park.

Aquatic Biological Community Rated Good or Excellent

This rating is established using the criteria set out in the 1998 Countywide Stream Protection Strategy (CSPS).  Stream ratings are determined by comparing data on the diversity and pollution tolerance of the stream’s fish and macroinvertebrates with those found in the County’s highest quality, least impaired streams.  The streams are then divided into the following categories according to how they compare to the reference (highest quality stream) conditions:

  • Excellent – Comparable to the biological community found in reference streams.  Exceptional assemblage of species with a balanced community composition.
  • Good – Decreased number of sensitive species, decreased number of specialized feeding groups, and some intolerant species present.
  • Fair – Intolerant and sensitive species are largely absent; unbalanced feeding group structure
  • Poor – Top carnivores and many expected species absent or rare; general feeders and tolerant species dominant.

Special Trout Management Areas

In Montgomery County, this refers to streams that fall within the definition contained in Title of the Code of Maryland Regulations under the Special Fisheries Management Areas section, as “Catch-and-Return Trout Fishing Areas Limited to Artificial Fly Fishing Only” and “Catch-and-Return Trout Fishing Areas Limited to Use of Artificial Lures Only”.

The applicable stream in Montgomery County with the designation for Fly Fishing Only currently is the Patuxent River from red bank posts located on both sides of the river, approximately 400 yards below Brighton Dam downstream to Mink Hollow Road. The streams currently designated for Artificial Lures Only are 1) Paint Branch and Tributaries upstream of Fairland Road, and 2) The main stem of Patuxent River from the crossing of Maryland Route 97 upstream to the crossing of Maryland Route 27, and in Howard County, 3) Cabin Branch from its confluence with the Patuxent River upstream to Hipsley Mill Road.

It is intended that this effort will help to establish priorities for the development of Natural Resources Management Plans, inventory and monitoring schedules, and habitat enhancement projects, and will help direct methods of protecting and enhancing these resources (Management Strategies).  Since the focus is on areas with outstanding and/or unique natural resources, they generally do not include those that are developed, or proposed for development, with active recreation facilities.


The compiling of this list does not in any way indicate that there are not additional high quality natural areas throughout the County.  In fact, many others were carefully considered when the list was being finalized.  It is important, therefore, not to focus solely on the protection and enhancement of resources in these best natural areas at the expense of other high quality natural areas.  With the inception of the Legacy Open Space initiative, established in the year 2002, privately owned lands in Montgomery County are being scrutinized specifically for their quality as natural areas and as potential addition to the park system.

Finally, it is not intended that the designation as a “Best Natural Area” would necessarily preclude the development of appropriate and needed facilities within its boundaries.    It is hoped that significant consideration and protection would be given, however, to the high quality natural resources contained therein.

The boundaries of each natural area were drawn in an attempt to include the best examples of the exemplary natural resources, which led to the natural area’s selection as one of the best natural areas.  Sometimes these boundaries are drawn broadly, as in the case of Paint Branch Stream Valley Park where the high quality aquatic resources dictate drawing the line to include all the essential tributaries and their subwatersheds, or in the case of Little Bennett Regional Park where an attempt was made to include the broad diversity of high quality aquatic and forest resources that were the reason for its selection.  Conversely, boundaries in some natural areas such as Cabin John and North Branch Stream Valley Park can be drawn more narrowly and still include the best examples of the resources for which they were chosen.