Land acquisition is a crucial, expensive part of conservation. As such, accurately accounting for the spatial heterogeneity of conservation costs is a critical part of conservation planning, especially acquisition costs. Studies have revealed that this could lead to large efficiency savings, but they have based this claim on methods of estimation prone to affect the spatial pattern of variation in costs. To date, by lack of data regarding actual acquisition costs faced by conservation organizations, a common approach in systematic conservation planning is to rely on more readily available proxies, such as agricultural land value. However, the lack of mechanistic understanding of what determines actual acquisition costs, as faced by conservation organizations, means that there is a risk that this proxy does not preserve the underlying spatial pattern of variation in those costs, producing cost-inefficient recommendations. The nature of land parcels targeted for conservation or the dynamics of conservation land transactions could be very different compared to those of agricultural lands. The spatial pattern and the variation of one might not accurately reflect those of the other.
Results/Conclusions
With the goal of improving these predictions, we fit data from ~9000 historical land acquisitions by The Nature Conservancy (TNC) over the last 30 years against ecological and socio-economic parameters, to create the first nationwide map of acquisition costs and explain their spatial pattern across the continental U.S. While a useful predictor within our model, we show that agricultural land value used as sole proxy for acquisition costs returns spatially biased estimates. It also underestimates variation in actual acquisition costs, accounts for just 17% of this variation and fails to explain land donations or bargain sales.
Using an original ROI model, we then compare optimized reserve site selection recommendations based on our nationwide acquisition cost model to recommendations based instead on agricultural land value. We describe the type of error that such proxies lead to and illustrate the importance of an accurate land price model in conservation planning, revealing how a better understanding of acquisition costs for conservation land may improve conservation practice.