The key role of forests in meeting climate targets requires science for credible mitigation

Forest-based climate mitigation may occur through conserving and enhancing the carbon sink and through reducing greenhouse gas emissions from deforestation. Yet the inclusion of forests in international climate agreements has been complex, often considered a secondary mitigation option. In the context of the Paris Climate Agreement, countries submitted their (Intended) Nationally Determined Contributions ((I) NDCs), including climate mitigation targets. Assuming full implementation of (I) NDCs, we show that land use, and forests in particular, emerge as a key component of the Paris Agreement: turning globally from a net anthropogenic source during 1990-2010 (1.3 +/- 1.1 GtCO(2)e yr(-1)) to a net sink of carbon by 2030 (up to 1.1 +/- 0.5 GtCO(2)e yr(-1)), and providing a quarter of emission reductions planned by countries. Realizing and tracking this mitigation potential requires more transparency in countries' pledges and enhanced science-policy cooperation to increase confidence in numbers, including reconciling the approximate to 3 GtCO(2)e yr(-1) difference in estimates between country reports and scientific studies.