Influence of the spatial pattern of conserved lands on the persistence of a large population of red-cockaded woodpeckers

Spatial configuration of habitats can affect chances of survival for many r are species, especially those with low dispersal rates or large area requir ements. The red-cockaded woodpecker (Picoides borealis) disperses relativel y short distances and also requires large blocks of habitat-characteristics that make its populations especially sensitive to the distribution of its habitat across a region. We created conservation scenarios for a large popu lation of red-cockaded woodpeckers based on acquisition of conservation eas ements on different properties, and we then estimated the probability of lo ng-term persistence using Geographic Information System technology and a st ochastic demographic model. We considered four broad conservation scenarios : (I) conservation of only those properties that currently have easements ( Status quo); (2) random acquisition of additional conservation properties ( Random); (3) strategic acquisition of additional conservation properties (S trategic); and (4) all properties that have red-cockaded woodpeckers gain p rotection (Total Protection). The data used in the analyses come from the s ixth-largest population (ca. 180 groups), which occurs exclusively on priva te lands in the Red Hills region of north Florida and south Georgia. Chance s of survival exclusively on existing easements were low unless large-scale improvements in habitat quality were realized. Easements acquired in rando m order also did not effectively conserve the large aggregations of active; territories important to population persistence. Even when up to 20,000 ha of new easements were added randomly, densities and distributions of activ e territories generally remained critically over-dispersed. Random acquisit ion of easements did not approximate the additions of habitat based on biol ogical criteria until 30,000 ha were added and an average of 60% of all clu sters was conserved, and even then neighborhood sizes were roughly half the sizes of neighborhoods produced using biological criteria. Alternatively, use of biological criteria to select key properties with a total area < 10, 000 ha better approximated several spatial characteristics associated with population persistence. Overall, scenarios that provided the highest likeli hood of long-term survival conserved core properties and expanded the popul ation on existing easements through habitat improvement and intensive manag ement techniques. This will require ca. 17,000 ha in new easements. We also suggest that management be used to augment populations on existing easemen ts, particularly peripheral regions where populations of ca. 25 territories might eventually be established. (C) 2001 Elsevier Science Ltd. All rights reserved.