This paper studies the effects of policy scale for land conservation schemes based on global objectives but implemented at local levels. They are explored in the classical reserve site selection framework for policy efficiency, to which we add the common social objective of equity between spatial units. We first analyze the role of the biophysical attributes of land available for conservation. These natural endowments are then combined with different implementation scales to improve a particular land-based social function: natural habitats for biodiversity. An empirical illustration, based on data from the Provence region of France, is used to explore what we identify as a policy scale trade-off between administrative units. This shows the importance of land availability in predicting the distribution of the costs and benefits of conservation schemes. In terms of equity, we find an interior solution that minimizes an inequality metric (the Gini coefficient) along policy scales. Our approach should lead to more socially acceptable conservation objectives, between the usual two extreme cases of autarky and specialization.