Introducing the key patch approach for habitat networks with persistent populations: an example for marshland birds

In landscapes where natural habitat is highly fragmented, any method for as sessment of population persistence or potential for biodiversity should be based upon metapopulation theory, taking into account the spatial and tempo ral dynamics of species. We argue that methods based upon species distribut ion data, population viability analyses (PVA), or landscape indices alone a ll have severe flaws. We introduce an approach based upon a combination of the three methods, in which ecologically scaled landscape indices (ESLI) ar e compared to spatial standards derived from both analysis of distribution data and PVA-type simulations. We derive spatial standards, introducing the key patch approach. Key patches are large patches with a stabilizing role in habitat networks. Key patch standards were developed using spatial analy sis of presence-absence data and calibrated metapopulation models for marsh land bird species. We show examples of the application of this approach in land use management at both regional and national planning scales. (C) 2001 Elsevier Science Ltd. All rights reserved.