Chapter 3 North Carolina Species
this in mind, additional rules of thumb will be described below that can help reduce the likelihood of a dire outcome.
Insect populations often undergo extreme fluctuations in numbers, resulting from vagaries in weather or cyclical changes in abundance of their predators or parasites. They are much more prone to local extirpation than either vertebrates or plants. As discussed below, they often survive only where there are enough well-dispersed habitat patches to support metapopulations. Conservation biologists are just beginning to realize how important metapopulations are for animals in general (Chowdhury et al. 2023) . Due to the greater fluctuations their subpopulations experience within a given year or season, invertebrates are often dependent on metapopulation structures. Several insects are believed to have become critically endangered through loss of metapopulation structure, even though habitats within portions of the range of the metapopulations still appear to be high in quality. Examples in the Coastal Plain include the Arogos Skipper, St. Francis’ Satyr, and Venus Flytrap Cutworm Moth. • A metapopulation is composed of several subpopulations, each of which may be relatively unstable, some increasing in a given year, others declining to the point of extirpation. If movement is possible between the sub-populations, declining populations can be “rescued” by immigration from increasing populations elsewhere within the metapopulation.
• A metapopulation can therefore be much more stable than its parts, at least as long as not all subpopulations are affected by the same set of events.
• Metapopulations are most stable when they are spread over a significant area of the landscape.
Preserves can be regarded as islands of habitat to some degree. They are often chosen for conservation as something special in areas where the rest of the landscape has been significantly altered. All too frequently, preserves contain the only remnants of native ecosystems for miles around. While these preserves are intended to remain “natural,” active management is often needed to accomplish this goal, although management, almost by definition, involves some form of artificial disturbance. This disturbance may replace a natural form, such as wildfires, or it may be entirely new, such as spraying an entire preserve with a pesticide to control an exotic pest such as the Gypsy Moth (Hall 1999a, 1999b) . In cases where a management action affects 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 management options can be considered. Even in the worst case, where species are extirpated from the preserve,
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2025 NC Wildlife Action Plan
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