3.12 Insects
individuals dispersing from one habitat block to another. Since the very existence of a metapopulation depends on dispersal between suitable patches of habitat, any factor that reduces the changes of successful dispersal may doom the whole metapopulation to eventual extirpation, not just individual subpopulations as normally occurs within intact landscapes. Habitat specialists, particularly those dependent on naturally rare types of habitat or on disturbance-maintained habitats, are at greatest risk. Rule of Tumb 3. Insects and other invertebrates should be considered at particular risk from fragmen- tation of native habitats. Even though invertebrate populations can be particularly high within a given subpopulation during a given season, this should not be taken as a sign that, as small species, they only need a limited amount of space to maintain them- selves. Teir long-term survival within a region may depend on as much landscape as is required to support a population (or metapopulation) of Black Bears, Red-cockaded Woodpeckers, or other species of vertebrates. Several insects are believed to have become critically endangered through loss of meta- population structure, even though habitats within portions of the range of the meta- populations still appear to be high in quality. Examples in the Coastal Plain include the Arogos Skipper, St. Francis’ Satyr, and Venus Flytrap Cutworm Moth. Rule of Tumb 4. Wherever possible, management activities should be restricted to only a portion of a given habitat type. Other areas of the same habitat should be set aside as refuge areas (although potentially subject to treatment at a later time). Rule of Tumb 5. In cases where a management action afects an entire preserve, as in treatment for gypsy moths, decisions about the scope, intensity, and alternative treatments should be based according to the proximity of refuge areas beyond the boundary of the preserve. Where other, untreated blocks of habitat are located close by, a wider range of manage- ment options can be considered. Even in the worst case, where species are extirpated from the preserve, recolonization from outside can still be expected. Where external refuges are located far away, however, management decisions should be based on the worst possible case: irrecoverable losses of species from the preserve. 3.12.5 Threats and Problems Te greatest threat to insects comes from habitat loss. Tus conservation eforts aimed at protecting native ecosystems ofers the best hope for the majority of endangered insect species. Even on lands that have been protected to maintain their natural features, man- agement practices need to take the specifc requirements of insects into account.
186
2015 NC Wildlife Action Plan
Made with FlippingBook - professional solution for displaying marketing and sales documents online