Time-dependent efficacy of carbon dioxide removal via forest restoration

Forest-based carbon dioxide removal (CDR) is widely promoted as a high-potential, nature-based climate solution, and its efficacy is time dependent because forest CDR follows the growth trajectory of aboveground biomass (AGB). However, this timing is rarely accounted for in CDR assessments, obscuring whether forest restoration can deliver meaningful CDR within 25–55-year climate horizons. Here we provide 1-km resolution, time-dependent estimates of forest CDR across the conterminous US, derived from 113,806 field-based AGB measurements from 74,048 plots. We show that the window for effective forest-based CDR is limited by age-related declines in tree growth. Forest CDR via AGB growth peaks within 9.4–31.2 years, then weakens as forests mature, falling to 1 MgCO2 ha⁻¹ yr⁻¹ within 51.6–108.5 years. Rather than emphasizing full CDR potential, we quantify a more attainable target, achieving 50% CDR potential. This target is reached fastest in the East South Central region within 18.9 ± 5.6 years and slowest in the Mountain region within 75.7 ± 23.9 years. Ignoring time dependence causes IPCC to underestimate CDR in young forests and overestimate it in older ones. Because forest carbon sinks take decades to develop, early action is crucial for restoration to deliver meaningful removals on near-term climate timescales.