Should Habitat Trading Be Based on Mitigation Ratios Derived from Landscape Indices? A Model-Based Analysis of Compensatory Restoration Options for the Red-Cockaded Woodpecker

Abstract

Many species of conservation concern are spatially structured and require dispersal to be persistent. For such species, altering the distribution of suitable habitats on the landscape can affect population dynamics in ways that are difficult to predict from simple models. We argue that for such species, individual-based and spatially explicit population models (SEPMs) should be used to determine appropriate levels of off-site restoration to compensate for on-site loss of ecologic resources. Such approaches are necessary when interactions between biologic processes occur at different spatial scales (i.e., local [recruitment] and landscape [migration]). The sites of restoration and habitat loss may be linked to each other, but, more importantly, they may be linked to other resources in the landscape by regional biologic processes, primarily migration. The common management approach for determining appropriate levels of off-site restoration is to derive mitigation ratios based on best professional judgment or pre-existing data. Mitigation ratios assume that the ecologic benefits at the site of restoration are independent of the ecologic costs at the site of habitat loss. Using an SEPM for endangered red-cockaded woodpeckers, we show that the spatial configuration of habitat restoration can simultaneously influence both the rate of recruitment within breeding groups and the rate of migration among groups, implying that simple mitigation ratios may be inadequate.

Quantifying the importance of patch-specific changes in habitat to metapopulation viability of an endangered songbird

“…This situation is not unique to Fort Hood. Indeed, many regulatory provisions require a means by which detrimental changes in ecological resources can be mitigated at the appropriate level by off-site compensation (Bruggeman and Jones 2008). We demonstrated that sensitivity analysis of a stochastic population projection model could be used to quantify how changes in occupied habitat affect metapopulation viability.…”

“…Indeed, many regulatory provisions require a means by which detrimental changes in ecological resources can be mitigated at the appropriate level by off-site compensation (Bruggeman and Jones 2008). This situation is not unique to Fort Hood.…”

“…Corresponding Editor: R. L. Knight. Typically, a parcel is assigned value based on experts' assessments of habitat area or quality, although more recent approaches have proposed incorporating spatial configuration or demographic rates (Bruggeman andJones 2008, Searcy andShaffer 2008). A major challenge in these programs is determining the conservation value of land parcels included in the conservation bank (Fox et al 2006).…”

“…A major challenge in these programs is determining the conservation value of land parcels included in the conservation bank (Fox et al 2006). Typically, a parcel is assigned value based on experts' assessments of habitat area or quality, although more recent approaches have proposed incorporating spatial configuration or demographic rates (Bruggeman andJones 2008, Searcy andShaffer 2008).…”

“…Applied ecologists have debated the relative conservation value of patches differing in size and connectedness since the development of island biogeography (MacArthur andWilson 1967, Brown 1971) and metapopulation theory (Hanski and Gilpin 1991). But despite the recognition that habitat patches vary in their contribution to viability, the specifics may be hard to generalize, suggesting that the value of habitat losses and gains should be evaluated quantitatively based on species-specific models of metapopulation dynamics Mills 1994, Bruggeman andJones 2008). For example, assuming a classic Levins-type metapopulation, Hanski and Ovaskainen (2000) proposed a straightforward approach for quantifying the contribution of individual patches to metapopulation capacity based on probabilities of extinction and colonization.…”