The set of terrestrial ecosystem core areas (unstratified) is one of two versions of terrestrial and wetland core areas that are part of a suite of products from the Nature’s Network project (naturesnetwork.org). Nature’s Network is a collaborative effort to identify shared priorities for conservation in the Northeast, considering the value of fish and wildlife species and the natural areas they inhabit. While the other version of terrestrial cores (Terrestrial Core-Connector Network, Northeast U.S.) is considered by the planning team to be the primary version for users, this version is also made available for reference and use. A number of additional datasets are also available in the Nature’s Network gallery: https://nalcc.databasin.org/galleries/8f4dfe780c444634a45ee4acc930a055. A detailed technical guide to the terrestrial ecosystem cores is available at: http://jamba.provost.ads.umass.edu/web/lcc/DSL_documentation_tEcoCoreNE.pdf.

Terrestrial and wetland core areas are intact, well-connected places that, if protected, will support a diversity of fish, wildlife, and plants, and the ecosystems they depend upon. Each core area contains important or unique features, including intact, resilient examples of each major ecosystem type in the Northeast and Mid-Atlantic. Core areas contain widespread ecosystems, such as hardwood forests, rare natural communities, such as bogs, and important habitat for a variety of fish, wildlife, and plants. By design, this set of core areas encompasses approximately 20% of the landscape of the region.

The major differences between this “unstratified” version and the other version of core areas (Terrestrial Core-Connector Network, Northeast U.S.) are: 1) this version comprises 20% of the landscape rather than 25%; 2) this version does not use habitat for representative wildlife species to identify core areas; 3) the ecosystem components are not stratified by HUC6 watershed in identifying the areas of highest integrity and resilience for generation of core areas; 4) this version is not associated with core-to-core connectors.

Intended Uses

Core areas can be viewed as among the best places to start for protection of lands and waters in their natural state. It is recommended that this set of core areas be used in conjunction with the “Terrestrial Core-Connector Network, Northeast U.S.” Areas of overlap between core areas in this dataset and the cores that are stratified by watershed are of high priority from both a perspective of the full Northeast region and within the watershed. They may be especially promising locales to investigate for potential conservation action. See the Terrestrial Core-Connector Network, Northeast U.S. for additional descriptions of potential uses.

Description and Derivation

The core areas are based on GIS analyses designed to assess the physical and biological value of resources across the Northeast and Mid-Atlantic, and to identify the most important places for them. This version of terrestrial core areas integrates three components:

1. High integrity examples of more than 90 terrestrial and wetland ecosystem types across the Northeast and Mid-Atlantic. Ecosystem locations have been mapped through a partnership of The Nature Conservancy and the Northeast state fish and wildlife agencies. Their integrity has been assessed using the Index of Ecological Integrity developed by the University of Massachusetts Amherst.

2. Terrestrial sites assessed as having the greatest potential to be resilient over the long term, as identified by The Nature Conservancy.

3. Rare natural communities identified and mapped by state natural heritage programs.

Core areas were built from focal areas (“seeds”) with high value based on one or more of the attributes listed above. These "seeds" were expanded to encompass surrounding areas that provide additional ecological value and resilience to both short- and long-term change. These surrounding areas are typically of high to moderate ecological value. To maintain a coherent shape and size, in some cases core areas contain low-intensity development and minor roads, but high-intensity development and major roads are excluded. Collectively, this version of terrestrial core areas encompasses ~22% of the area of the region, including a total of 17,444 core areas ranging in size from 1.26-155,206 ha, with an average size of 802 ha.

This version of terrestrial core areas does not include stratification of ecosystem components. This ensures that the highest quality examples of ecosystems are represented in the core area network. However, this also results in a less well-distributed and well-connected set of core areas compared to the watershed-stratified version.

Attribute Information and Field Definitions

The attributes listed below are available for each core area (polygon):

• FID = ESRI assigned unique number for each polygon.
  

• Shape = ESRI assigned feature type = “polygon.”
  

• type = indicator designating the polygon as: “core.”
  

• coreID = each core has a unique ID.
  

• areaCount = size of the core area in number of cells (30 x 30 m); this includes any developed cells.
  

• areaHa = size of the core area in hectares; this includes any developed area.
  

• rareCom = percentage of the core comprised of S1-S3 rare communities as defined and mapped by the state Heritage Programs.
  

• system1, system2, system3 = The top three terrestrial or wetland ecological systems for which the core is particularly important. In other words, for these systems the cumulative ecological integrity of the system within the core is greater than expected (from a statistical perspective) given its distribution across the entire core area network. Note, the systems listed here reflect the systems for which the core is especially important, but are not necessarily the most abundant systems in the core.
  

• species1, species2, species3 = The top three representative species for which the core is particularly important. In other words, for these species the cumulative landscape capability index within the core is greater than expected (from a statistical perspective) given its distribution across the entire core area network. Note, the species listed here reflect the species for which the core is especially important, but are not necessarily the species with the highest total landscape capability in the core. We included the species statistics even though these cores were not built based on any species-specific criteria.

ecoURL = contains links to the Ecosystem tables* for each core area.

sppURL = contains links to the Species tables* for each core area.

*The Ecosystem and Species tables contain additional detailed composition statistics, and more information about relative importance, for each core area. See the technical documentation for more information (http://jamba.provost.ads.umass.edu/web/lcc/DSL_documentation_tEcoCoreNE.pdf).

Known Issues and Uncertainties

As with any project carried out across such a large area, the terrestrial core-connector network is subject to limitations. The results by themselves are not a prescription for on-the-ground action; users are encouraged to verify, with field visits and site-specific knowledge, the value of any areas identified in the project. Known issues and uncertainties include the following:

• The results do not incorporate important social, economic, or feasibility factors.

• Users are cautioned against using the data on too small an area (for example, a small parcel of land), as the data may not be sufficiently accurate at that level of resolution.

• The mapping of ecosystem locations and development is known to be imperfect, which consequently affects the mapped values for ecosystem integrity and species habitat. While the ecosystem mapping is anticipated to correctly reflect broad patterns of ecosystem occurrence, errors in classification and placement do occur, as with any regional GIS data. In addition, errors in mapping and alignment of development, roads, traffic rates, and a number of other data layers can affect the model results.

• It is not possible to map all factors affecting ecosystem integrity across the Northeast, and the omission of such factors can be anticipated to create pose some limitations in the results. An example is the limited ability to map the regional impact of invasive species.

• Not all locations of rare natural communities have been mapped by states and therefore may not be components of core areas. The current version of core areas does not reflect rare natural community data from Rhode Island.

The identification of core areas is predicated on the assumption that biodiversity is best supported by intact, well-connected landscapes. While this assumption is soundly grounded in conservation biology theory and findings, it is recognized that many species of conservation concern may depend on habitat currently existing in a less intact state or otherwise missed by core areas. The Core Habitat for Imperiled Species product, in particular, is intended to complement the core areas by focusing on such areas.