The HUC6 terrestrial core-connector network is one of the principal Designing Sustainable Landscapes (DSL) landscape conservation design (LCD) products, and it is best understood in the context of the full LCD process described in detail in the technical document on landscape design (McGarigal et al 2017). This particular product was initially developed for the Connecticut River watershed as part of the Connect the Connecticut project (www.connecttheconnecticut.org) — a collaborative partnership under the auspices of the North Atlantic Landscape Conservation Cooperative (NALCC), and subsequently developed for the entire Northeast region as part of the Nature's Network project (www.naturesnetwork.org). The HUC6 terrestrial core-connector network represents a set of terrestrial core areas and the connectors between them (Fig. 1). In combination with the aquatic core areas, they spatially represent the ecological network designed to provide strategic guidance for conserving natural areas, and the fish, wildlife, and other components of biodiversity that they support within the Northeast.Core areas serve as the foundation of the LCD. They reflect decisions by the LCD planning team about the highest priority areas for sustaining the long-term ecological values of the landscape, based on currently available, regional-scale information. In this product the terrestrial core areas represent the following:1) areas of relatively high ecological integrity across all terrestrial and wetland ecosystem types and geophysical settings, emphasizing areas that are relatively intact (i.e., free from human modifications and disturbance) and resilient to environmental changes (e.g., climate change). Integrity has the potential to remain high in these areas, both in the short-term due to connectivity to similar natural environments, and in the long-term due to proximity to diverse landforms and other geophysical settings;2) areas of relatively high current landscape capability for a suite of representative (a.k.a. surrogate species) terrestrial wildlife species, emphasizing areas that provide the best habitat and climate conditions today; and3) areas of rare terrestrial natural communities that support unique biodiversity, regardless of their landscape context; inclusive of communities listed by state heritage programs as S1 (extremely rare), S2 (rare), and S3 (uncommon), with definitions ofS1-S3 varying slightly among states.Core areas were built from focal areas ("seeds") within each HUC6 watershed that have 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. The surrounding areas were typically of high to moderate ecological value. In some cases the final core areas contained low-intensity development and minor roads, but high-intensity development and major roads were excluded. Collectively, the terrestrial core areas identified in this product encompass ~25% of the Northeast, as decided by the LCD planning team, including a total of 20,358 disjunct core areas encompassing a total of 16,160,371 ha and ranging in size from 3.6 to 107,996 ha, with an average size of 794 ha.Connectors represent "corridors" that could facilitate the movement of plants and animals (i.e., ecological flow) between terrestrial core areas. These connectors increase the resiliency of the core area network to uncertain land use and climate changes. They are wider where more movement between cores is expected because of larger, higher-quality, and closer core areas and where a more favorable natural environment exists between them. Connectors primarily link adjoining core areas along routes that possess the greatest ecological similarity to the ecosystems in the adjoining cores; they do not necessarily represent travel corridors for any individual species. Connectors may traverse through areas of low-density development and cross roads of all classes, but they do not include high-intensity development. Connectors are not identified between core areas that are greater than 10 km apart. Collectively, connectors encompass an additional ~17% of the Northeast.
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