Coincident with international movements to protect 30% of land and sea over the next decade (‘30x30’), the United States has committed to more than doubling its current protected land area by 2030. While publicly owned and managed protected areas have been the cornerstone of area-based conservation over the past century, such lands are costly to establish and have shown limited capacity to protect areas of highest value for biodiversity conservation and climate change mitigation. Here we examine the current and potential contributions of privately protected land for reaching the 30x30 conservation targets and their corresponding objectives (biodiversity protection and climate change mitigation) at federal and sub-national scales in the U.S. We use a national compilation of spatial data on conservation easements and protected areas, alongside biodiversity distributions, projected biodiversity distributions under climate change, and vulnerable land-based carbon densities, to quantify the capacity of U.S. private land conservation measures to target areas of high conservation priority. We explore how the distributions of protected areas and easements relative to biodiversity and carbon priorities vary spatially (across subnational boundaries) and temporally (over the past two decades). We situate our findings in relevant federal and sub-national conservation policy.
Results/Conclusions
We show that private land conservation instruments (conservation easements) better target areas with high species richness and high climate mitigation potential relative to federal and state-owned protected areas managed for biodiversity across the U.S. Additionally, the average conservation value of public and private lands shows that private lands hold most currently unprotected land with high biodiversity and climate mitigation value. However, we find that these patterns are more nuanced at the subnational scale, providing insight into how subnational policy influences the adoption and distribution of public and private conservation measures. Further, we find that private land conservation measures have improved their targeting of areas with high biodiversity value over the past two decades, and that this pattern is in contrast to federal and state protected areas. Taken together, our analyses provide a view into the potential of private lands to complement traditional protected area contributions to meeting qualitative elements of 2030 conservation targets and highlight the necessity of mechanisms that engage private landholders in enduring conservation partnerships. Our findings also suggest that the scale at which we observe the distribution of conservation measures relative to conservation priorities is critical to understanding the policy implications of those patterns.
