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 applied the mass curve technique (MCT) based on water balance to estimate the global root zone water storage capacity (S_R) using high-quality observation-based data. Our results show that the global average S_R increased by 11%, from 182 to 202 mm in 1982–2020. The total increase of S_R equals to 1652 billion m³ over the past four decades. S_R 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.