The ‘Climate Adaptation Problem’ in Biodiversity Conservation: The Value of Spatial Flexibility in Land Purchase

Existing reserve networks become less suitable as species' ranges shift under climate change and the scarcity and value of habitats change. Reserve sites hence have to be reallocated to reflect these changing values and to remain cost-effective, but restrictions on selling reserve sites limit this adaptation. Under climate change, a novel 'sale' policy that provides resale flexibility by allowing increasingly less cost-effective sites to be sold to free funds for purchasing increasingly cost-effective sites may hence be preferable over a typical 'no sale' policy. Here, we develop a conceptual climate-ecological-economic model to examine under what conditions resale flexibility provides cost-effectiveness advantages. We find that the benefits of resale flexibility provided by the 'sale' policy are particularly high when little funding is available for climate change adaptation. Due to this budget effect, the value of resale flexibility also decreases with increasing interest rates. The value of resale flexibility is particularly high when creating reserves for species that are highly mobile as new reserve sites may then be chosen freely (in comparison to the case that new sites have to be located in the proximity of existing reserve sites). We further examine to what extent the 'sale' policy reduces the permanence of habitat within a specific location ("site habitat permanence"), and identify a new trade-off: 'sale' provides advantages for habitat types that become increasingly rare, while 'no sale' improves site habitat permanence mainly for expanding habitat types.