Cooley_et_al_data__Agg_Nov2024_dP.csv

A global 'climate opportunity benefit' of regeneration: meta-analysis shows warming from soil CH4 and N2O is small in forests relative to agriculture Savannah S. Cooley1*, Elisabeth Moore1, Jianna Martinez1, Jocelyn Fahlen1, Erin Maybach1, Maya Gollerkeri1, Anjali Rao Vasa1, Sian Kou-Giesbrecht2, Alexandra M. Huddell3, Linnea Norton1, Kerry Cawse-Nicholson4, Ruth DeFries1, Maria Uriarte1, Duncan N.L. Menge1 1 Department of Ecology, Evolution and Environmental Biology, Columbia University 2 Department of Earth and Environmental Sciences, Dalhousie University 3 Department of Department of Plant and Soil Sciences, University of Delaware 4 NASA Jet Propulsion Laboratory, California Institute of Technology * Corresponding author: [e-mail] AbstractGlobal assessments of ecosystem regeneration as a climate mitigation strategy have traditionally focused on CO2, despite the acknowledgement that methane (CH4) and nitrous oxide (N2O) are also important greenhouse gasses (GHGs). We conducted a meta-analysis of studies that measured soil CH4 and N2O fluxes in unmanaged regenerating forested and savanna ecosystems, with a focus on understanding biome-specific differences in these GHG fluxes compared to a counterfactual of agricultural land use. We expected most regenerating ecosystems to act as small CH4 sinks and relatively larger N2O sources, with a net warming combined CH4-N2O effect. Three of the five forested biomes we studied followed this pattern: subtropical/tropical forest, subtropical/tropical savanna and temperate conifer forest (0.98 ± 0.44, 0.23 ± 0.07, and 0.63 ± 0.37 Mg CO2e ha-1 yr-1, respectively). Results suggest that even after 100 years of regeneration, the radiative cooling of the climate from CO2 sequestration still exceeds the radiative warming driven by the net CH4-N2O effect among all ecosystems on average globally. We also found that the “climate opportunity benefit” of ecosystem regeneration—the difference of the net CH4-N2O effects of agriculture vs. regeneration—yields a net cooling effect for all biomes. However, our results underscore that it is unsound to use ecosystem regeneration as a justification for the continuation of fossil fuel emissions.