The North Carolina Natural Heritage Program uses a survey-based approach to identify and evaluate ecologically significant landscape units across the state. We identify and rank occurrences of landscape units according to the biological features they contain, as recorded in ground-based surveys.
Breaking Down Natural Area Components
The Elements of our landscape analysis – analogous to NHP Species or Community Elements – are termed Landscape/Habitat Indicator Guilds. We term the overall process of identifying and ranking these units LHI Guild Analysis, and there are several features that characterize this approach:
Landscape Units
Mapped occurrences of the LHI guilds are termed core areas. These units are intended to represent habitat units that are still large enough and/or well-connected enough to support the entire range of species associated with a particular landscape type (defined by habitats).
Core areas are defined as consisting of residential habitat for these species, including foraging, denning and breeding habitats. Core areas have a connecting function as well as a residential function. The boundaries of a core area occur at the edge of wider habitat gaps that are unlikely to be crossed, including impassable barriers such as four-lane highways.
Habitat-by-Habitat Analysis
LHI guilds are defined according to the habitats they use for residence, foraging, and breeding. Within a given area, species may “see” the landscapes they occupy very differently, depending on their habitat associations. Black bears, red-cockaded woodpeckers, and Venus flytrap moths may all live side by side within a particular longleaf pine savanna, but differ greatly in their use of other adjoining types of habitat, such as sandhills, pocosins, or pine plantations.
Depending on the extent and distribution of these habitats, these species may “see” the landscape as being more-or-less continuous or highly fragmented. Consequently, landscape integrity – or habitat fragmentation – must take habitat associations into account.
Indicator Species
The heart of our survey-based approach is the use of indicator species to determine what habitat units constitute core areas and what priority rank they should receive. These species are selected based on their sensitivity to the integrity/fragmentation of specific types of habitat. They are thus selected on a functional basis rather than on rarity, the main criteria used to define our other types of NHP Elements.
They must be both habitat specialists – the species most likely to be affected by fragmentation, loss, or degradation of a particular type of habitat – and dependent on the presence of large areas or inter-connected blocks of habitat.
Reports on Landscape Habitat Guilds may be downloaded from our searchable Publications Database.