OOS 14-6 - Reconciling biogeochemical and biophysical impacts of Natural Climate Solutions: towards a cross-scale framework for assessing co-benefits and unintended consequences

Background/Question/Methods
‘Natural Climate Solutions’ (NCS) include reforestation and other managed alterations to land cover designed to mitigate global change by reducing atmospheric carbon dioxide. Private- and public-sector interest surrounding NCS has grown dramatically in recent years, but the CO₂ mitigation potential of NSC remains a topic of substantial scientific debate. However, these managed alterations to ecosystems also have the potential to affect local temperature regimes; when and where these impacts are favorable, natural climate solutions also represent a strategy for local climate adaptation (in addition to global climate mitigation). A holistic approach based in sound ecological science could incorporate local biophysically-driven co-benefits in the design and implementation of NCS policy. We present a potential approach toward a cross-scale framework that integrates biophysical and biogeochemical impacts, using reforestation in the Eastern United States as a model NCS.

Results/Conclusions
Here, we used a multi-scale approach that incorporates ecosystem-scale flux towers and remote sensing to understand where and why reforestation is a promising NCS from both a biophysical and biogeochemical perspective. The adaptive potential of natural climate solutions has been relatively unexplored, due in part to methodological challenges that have historically hindered assessments of how land cover change affects near-surface air temperature. Furthermore, quantifying local biophysical impacts alongside regional and global biogeochemical impacts presents substantial scaling and methodological challenges. Our analytical approach focused on extending land cover effects on surface temperatures to near-surface air temperatures, arguably the more relevant target for climate adaptation. Across much of the eastern United States, forests conferred a substantial adaptive cooling benefit for both surface and air temperature, especially on summer days when climate adaptation is arguably most needed. While our focus here is on reforestation, these approaches could be easily extended to investigate biophysical impacts of other nature-based mitigation strategies. We conclude by introducing a cross-scale framework that integrates local climate adaptation and global climate mitigation that we hope motivates more careful consideration of biophysical impacts in the design and implementation of natural climate solution policy.