We welcome the attempts of Regnery et al. (2013) to apply our global offsetability process (Pilgrim et al. 2012) to the French context: national adaptation is essential for testing and improving this process. We wholeheartedly agree that conserving common biodiversity is crucial for ecosystem functioning. Unfortunately, the authors misinterpret the purpose of our process. Far from recommending that offsets only be undertaken for impacts on rare biodiversity, our process is specifically intended to highlight the risks of offsetting impacts on biodiversity that is particularly vulnerable or irreplaceable, and/or where management opportunities are limited. Our approach thus emphasizes that offsets have a much higher chance of success for more common and widespread biodiversity.
Beyond this general misunderstanding, the assessment of Regnery et al. that 99% of areas developed in France in 2010 would not be subject to our offsetability process is flawed in at least four ways. First, they suggest that our process only applies to species, when we explicitly state that it relates to both species and ecosystems (and suggest that ecological processes be integrated when data permit). Second, they suggest that impacts on LC or NT biodiversity are only considered greater than “Low” if ≥10% of their population is impacted, when in fact this threshold relates to the area of analysis, which we note will “almost always be larger than the predicted project impact area.” Third, Regnery et al. seem not to have assessed which development sites in France in 2010 held ≥10% of Least Concern (LC) or Near Threatened (NT) biodiversity, instead incorrectly assuming that a “Low” categorization applies to any site holding solely LC or NT biodiversity. Last, and most importantly, they directly replace global with national threat categories, despite our advice that there should be “development of national or subnational quantitative thresholds for each issue, via a stakeholder consultation process.”
In summary, far more than 1% of areas developed in France in 2010 would likely be subject to our offsetability process if applied correctly. We suggest that biodiversity of Low Conservation Concern might “be viewed as the lower threshold for offsetting, at which offsets might not be required if cumulative loss is not a significant issue.” Offsetting 100% of impacts to achieve No Net Loss across landscapes would be ideal, but transaction costs would render such a system impractical. Offsetting all small-scale impacts on biodiversity of least conservation concern would only be practicable if a simple compensation system—such as a system of developer contributions or “in-lieu” fees (Treweek et al. 2009)—were established, though this would likely not reach the high bar of No Net Loss offsetting (e.g., BBOP 2012). We encourage further development of our offsetability process for France, given its high global responsibility for biodiversity (Mittermeier et al. 2008). Regnery et al. note that “policy frameworks for the conservation of threatened species and habitats” exist in France, but development in overseas departments and territories has often proceeded without appropriate application of such safeguards (e.g., Bouchet et al. 1995).