We disagree with those who caution against relying on forests as a solution to global warming until the warming effects of trees themselves are better understood (see Nature 565, 280–282; 2019).

Forests are currently the safest, most cost-effective way to avoid dangerous increases in global warming, through their retention, management and restoration (B. W. Griscom et al. Proc. Natl Acad. Sci. USA 114, 11645–11650; 2017). The land sink for carbon (which is made up mainly of intact forests) captures at least 30% of global emissions generated by human activity (C. Le Quéré et al. Earth Syst. Sci. Data 10, 405–448; 2018). And there is almost universal agreement that increased carbon dioxide in the atmosphere will boost the rates of carbon uptake on land (G. Schurgers et al. Geophys. Res. Lett. 45, 4329–4336; 2018).

Simple tree-planting programmes might not simulate the climate-mitigation capabilities attributed to established forests. Until the warming effects of some trees are quantified and explained, forests must be managed to optimize their capacity to act as sinks.