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Habitat fragmentation is a threat to the survival of species and causes population decline, as isolated populations are more susceptible to demographic and genetic stochasticity. This can be compensated for by sufficient spatial connectivity between habitat patches to allow dispersal of individuals among populations. In that case such a network of populations may effectively form a metapopulation. In this paper we discuss some aspects of metapopulation theory, notably with respect to maintaining genetic diversity in fragmented forest patches. In addition we will discuss recent studies that explore ways for forest management to anticipate and mitigate the expected climate change, in relation to range shifts and colonisation opportunities.

The distribution of the Eurasian badger (Meles meles, L.) in the Netherlands is fragmented and adult mortality is high in many places because of traffic casualties. Both these facts affect the survival and dispersal of badgers in a negative way and are suggested to be the main causes of the decline of this species. For this reason the speciesreceives special attention from the government in the national Nature Policy Plan and also from the lower administration in the provincesin their policy on physical planning and nature conservation. To evaluate changes in land use by means of spatial scenarios and conservation strategies in favour of the species, an individual-based simulation model was built that describes population dynamics in space and time. The model was used to evaluate three scenarios. The results indicate that the survival of groups benefits strongly from measures directed at lowering adult mortality. Also the (re)colonization of suitable but not inhabited areas increases the survival and is favoured by measures that encourage dispersal. The results indicate that simulation models as described are useful tools for establishing the comparative effectiveness of plans or measures aimed at increasing the viability of the species. [ABSTRACT FROM AUTHOR]