Response of terrestrial ecosystems carbon budget to large-scale direct CO<sub>2</sub> removal using Community Earth System Model

<p>The terrestrial ecosystem is a critical carbon reservoir that faces the risk of transitioning from a carbon sink to a source under large-scale carbon dioxide removal (CDR) strategies aimed at mitigating climate change. In this study, we use a fully coupled Earth system model to simulate an abrupt decline in atmospheric CO<sub>2</sub> concentrations from near-current levels to the pre-industrial level of approximately 280 ppm. We find that the CDR-induced reductions in net primary productivity lead terrestrial ecosystems to emit carbon. It takes approximately 14 years after removal for the global land-atmosphere system to reach a new carbon equilibrium, with recovery times varying by region, particularly delayed in the tropics. Boreal ecosystems play a key compensatory role by absorbing the excess carbon released from other regions, thereby helping to restore the global carbon balance. These findings underscore the pressing need for improved land management and a holistic approach that combines natural and technological CDR to achieve net-zero emissions targets.</p>