Flexibility trade-offs in conservation offsets

Conservation offsets promise cost-effective conservation of biodiversity, especially under economic and environmental change, because they represent a more flexible approach to biodiversity conservation, allowing for the economic development of ecologically valuable land provided that this development is offset by restoration of previously developed areas. The level of flexibility is determined by the trading rules. Lax rules allow for more flexibility, which promises cost savings, but will likely lead to unintended loss of biodiversity. I analyzed the trade-off between economic costs and ecological benefits (biodiversity conservation) in biodiversity offsetting with an ecological-economic model that considered the three main types of offset flexibility: spatial, temporal, and ecosystem type. I sought to examine the influence of ecological and economic conditions on offset flexibility trade-offs. Large variation in the conservation costs and small costs of habitat restoration strongly increased trading activity and reduced the ecological benefit. The ecological benefit was most sensitive to spatial flexibility when a short range of ecological interaction was considered. At a large interaction range, spatial flexibility delivered large cost savings without overly reducing the ecological benefit. Risks and time lags associated with habitat restoration favored an offsetting scheme in which credits are awarded with the initiation of restoration projects rather than their successful completion-given appropriate offsetting multipliers were chosen. Altogether, under scarce resources, the level of flexibility in an offsetting scheme should be chosen by carefully balancing ecological benefits and economic costs.

A framework to measure the wildness of managed large vertebrate populations

As landscapes continue to fall under human influence through habitat loss and fragmentation, fencing is increasingly being used to mitigate anthropogenic threats and enhance the commercial value of wildlife. Subsequent intensification of management potentially erodes wildness by disembodying populations from landscape-level processes, thereby disconnecting species from natural selection. Tools are needed to measure the degree to which populations of large vertebrate species in formally protected and privately owned wildlife areas are self-sustaining and free to adapt. We devised a framework to measure such wildness based on 6 attributes relating to the evolutionary and ecological dynamics of vertebrates (space, disease and parasite resistance, exposure to predation, exposure to limitations and fluctuations of food and water supply, and reproduction). For each attribute, we set empirical, species-specific thresholds between 5 wildness states based on quantifiable management interventions. We analysed data from 205 private wildlife properties with management objectives spanning ecotourism to consumptive utilization to test the framework on 6 herbivore species representing a range of conservation statuses and commercial values. Wildness scores among species differed significantly, and the proportion of populations identified as wild ranged from 12% to 84%, which indicates the tool detected site-scale differences both among populations of different species and populations of the same species under different management regimes. By quantifying wildness, this framework provides practitioners with standardized measurement units that link biodiversity with the sustainable use of wildlife. Applications include informing species management plans at local scales; standardizing the inclusion of managed populations in red-list assessments; and providing a platform for certification and regulation of wildlife-based economies. Applying this framework may help embed wildness as a normative value in policy and mitigate the shifting baseline of what it means to truly conserve a species.