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Assessing and Creating Linkages within and beyond protected areas

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Year of publication2010
Publisher(s)Wildlands Network
Publication typeOther
Individual, isolated protected areas are not usually enough to protect biodiversity; species need to exchange genetic material for the population to stay healthy over time and many species also migrate or use widely dispersed habitats. Studies show that small isolated populations can be at risk of disappearing: for example local butterfly extinctions in Finland have been linked to inbreeding (Saccheri et al., 1998). Species populations sometimes disappear even if their immediate surroundings are suitable; for instance a small, well-managed protected area may lose species over time unless it is connected to similar habitat (Bennett, 1999). Furthermore, the theory of "island biogeography" helps explain why patch size and connectivity is important (McArthur and Wilson, 1967), with a general principle that the larger the "island" (which could be an isolated protected area), the more species are likely to occur. In consequence many ecologists believe that one large reserve is worth more than a number of small reserves, although there are also those who reject this hypothesis. The point where a habitat becomes "disconnected" will vary between species, its lifecycle needs, mobility and surrounding context (e.g., proximity and types of neighboring habitats). The degree of genetic isolation involved can also vary. Sometime a single break, like a road, can in effect stop two populations on either side from mixing (functional isolation) in some species. Although conservation planners often talk about "landscapes", habitat isolation and the need for connectivity are equally important inmany freshwater andmarine systems.