Global analysis of constraints to natural climate solution implementation.

Natural climate solutions (NCS) could provide over one-third of the climate mitigation needed between now and 2030 to limit warming below 2°C and support the Sustainable Development Goals. However, large disparities persist between the estimated biophysical climate mitigation potential (CMP) of NCS and their actual implementation. Social, political, informational, and economic factors contribute to this gap, but the spatial distribution of these constraints and their impacts on different NCS pathways remains poorly understood. Understanding these constraints is especially important due to the large uncertainties in NCS CMP and growing research on spatial prioritization of NCS, often based only on biophysical criteria. We identified and mapped nonbiophysical constraints to NCS implementation efficacy by conducting a systematic review of recent peer-reviewed literature across 10 high-CMP NCS pathways. From 1,821 papers, we identified 352 that provided 2,480 observations of 39 unique constraints from 135 countries. We mapped the spatial distribution of these constraints and analyzed patterns across NCS pathways and geographic classifications. Lack of funding, insufficient information on NCS management, and ineffective policies emerged as the most common constraints globally. However, each pathway and geography faced a distinct suite of interrelated constraints spanning multiple categories. These findings highlight the need for context-specific, equitable solutions, likely requiring transdisciplinary approaches and cross-sectoral collaborations. The results could also help increase accuracy of NCS CMP estimates. We discuss how adaptive management may be used for NCS initiatives at any scale to proactively diagnose co-occurring constraints at each implementation phase and to develop integrated, place-based solutions.