Terrestrial ecosystems enhanced root zone water storage capacity in response to climate change over the past four decades.

Adaptation of ecosystems' root zones to climate change critically affects drought resilience and vegetation productivity. However, a global quantitative assessment of this mechanism is missing. In this study, we analyzed high-quality observation-based data to find that the global average root zone water storage capacity (S) increased by 11%, from 182 to 202 mm in 1982-2020. The total increase of S equals to 1652 billion m over the past four decades. S increased in 9 out of 12 land cover types, while three relatively dry types experienced decreasing trends, potentially suggesting the crossing of ecosystems' tipping points. Our results underscore the importance of accounting for root zone dynamics under climate change to assess drought impacts.