Future climate impacts on biodiversity trends in major global rivers worldwide

The alteration of global runoff patterns and biodiversity resulting from climate change poses a significant issue. Yet, the future responses of riverine biodiversity remain uncertain, largely attributed to the unavailability of long-term data, especially in downstream river regions. This knowledge gap is addressed by projecting potential shifts in riverine biodiversity through the calculation of the Shannon index (SI) for 32 major rivers under various future climate scenarios. Our findings reveal that runoff patterns are expected to shift by a substantial range of −55.53 % to 254.47 %, leading to intensified flow fluctuations, heightened frequency of high-flow events, and increased flood risks. While the SI generally exhibits a decreasing trend for the majority of rivers (88 %), projections indicate a marginal increase, albeit remaining below historical levels. Under SSP scenarios (SSP1–2.6, SSP3–7.0, and SSP5–8.5), the SI is anticipated to decrease by 53 %, 66 %, and 66 %, respectively, with the most significant decline projected under SSP3–7.0. Biodiversity is forecasted to experience a notable decline during the second and third quarters of the 21st century, with a potential resurgence anticipated in the final quarter. These results emphasize the growing threats to river biodiversity and ecosystem integrity posed by climate change.