The cost of buying land for protected areas in the United States

Buying land to establish protected areas is a common conservation strategy, particularly in countries with strong private property rights. Accurately accounting for spatial heterogeneity in land cost could lead to large efficiency savings when planning future acquisitions. However, lack of data regarding actual acquisition costs faced by conservation organizations has led planners to rely on more readily available proxies, such as agricultural land value. Using data on nearly 36,000 parcels acquired for conservation by public agencies and land trusts in the continental U.S., we built a model predicting protected area acquisition costs. While costs of land for agriculture or development are useful predictors of variation in protected area acquisition costs, they are not, by themselves, good approximations of those costs. For example, using a more comprehensive combination of variables, our model explained almost four times as much variation in actual acquisition costs as those. We found that agricultural land value loses most of its explanatory power once other predictors are used, confirming that it acts as a partial proxy for actual acquisition costs. We then used an optimization model to compare prioritization recommendations with our new cost estimates to those suggested when relying on agricultural land values alone. Locations of highest conservation return on investment shifted from coastal regions toward the country's center, when using actual cost data. Cost estimates used in conservation planning should be based on actual protected area acquisitions, because the type of properties and motivations of buyers and sellers differ from those of other land transactions.