W e appreciate the opportunity to respond to George Wilhere's comments. We could not find support for Wilhere's first criticism. We addressed different expressions of minimum area in figure 4. In figure 5, we used only those 13 articles (list available from authors) that expressed both predefined, analytical targets and required conservation areas. All 13 required percentages were based on total area.
Regarding Wilhere's second criticism, each review article proposed a value, or range of values, frequently much different from the values given in the original papers. Exclusion of the reviews gives average values for conservation assessments of 30.2 percent (cf. our 30.6 percent) and 42.3 percent for threshold analyses (cf. our 41.6 percent). Our database contains closely related publications (i.e., same author), but all report different objectives and/or results. Our conclusions remain valid.
Wilhere's third criticism is unconvincing. We are not aware that any policy targets stipulate achievement only with strict reserves. Achievement with multiple IUCN protected area categories, varying widely in management intent, is more likely. Similarly, some conservation plans (e.g., in South Africa) achieve targets with a mix of management strategies. It is reasonable that (a) both policy and evidence-based targets assume areas should be managed primarily, but not solely, for bio-diversity conservation; and (b) the particular spatial mix of management and allowable land uses can only be resolved during site-by-site implementation.
We believe Wilhere's fourth criticism misses the point. Clearly, judgment is involved. In many cases, predefined analytical targets were qualified as arbitrary, illustrative, or based on policy. In others, scientists made no pretense about objectivity. Pressey and colleagues (2003) clearly state that targets are interpretations of goals using available data and require periodic revision. Even with spatially explicit population viability analysis (e.g., Noss et al. 2002), there is no objective, universally accepted probability of persistence. Decisions about targets are always subjective, but there is a big difference between subjective decisions based on objective information, logical reasoning, and peer review and those based on political whim.
