Risks of unavoidable impacts on forests at 1.5 °C with and without overshoot

With global warming heading for 1.5 °C, understanding the risks of exceeding this threshold is increasingly urgent. Impacts on human and natural systems are expected to increase with further warming and some may be irreversible. Yet impacts under policy-relevant stabilization or overshoot pathways have not been well quantified. Here we report the risks of irreversible impacts on forest ecosystems, such as Amazon forest loss and high-latitude woody encroachment, under three scenarios that explore low levels of exceedance and overshoot beyond 1.5 °C. Long-term forest loss is mitigated by reducing global temperatures below 1.5 °C. The proximity of dieback risk thresholds to the bounds of the Paris Agreement global warming levels underscores the need for urgent action to mitigate climate change—and the risks of irreversible loss of an important ecosystem.