How much compensation do we need? Replacement ratio estimates for Swiss dry grassland biotopes

Development pressure on reserve networks in densely populated countries may lead to the decision to allow for replacement compensation. Replacement ratios used for specifying replacement compensation are usually based on expert judgment. In contrast, we propose a method to estimate replacement ratios based on the set covering framework. The method is applied to presence–absence data of vascular plants of the dry grassland inventory of Switzerland. For the replacement of 60% of a patch’s high conservation value species by the same vegetation type (“in-kind” compensation), the estimated replacement ratios are <5 for most vegetation types. These ratios are comparable with replacement ratios usually used in practice. Our replacement ratio estimates for replacement by another vegetation type (“out-of-kind” compensation) are considerable higher than proposed by the literature. For oligotroph dry grassland associations, the replacement rations are extremely high, so that these associations have to be considered irreplaceable. The estimated replacement ratios provide a good starting point for designing compensation measures for unavoidable losses in a reserve system. However, additional biodiversity conservation goals should be considered when designing replacement compensation in practice.