The African Sahel-Sudano-Guinean region is one of the largest water limited environments in the world, thus making it highly vulnerable to climate change. Recent studies have shown vegetation greening in the region, but few have investigated the impact of this greening on carbon and water cycles. We used a combination of earth observation (EO) data and a diagnostic model to evaluate the extent of the vegetation greening and its impacts on carbon sequestration potential (i.e., Gross Primary Productivity-GPP) and the water cycle (i.e., Evapotranspiration-ET and Water Use Efficiency-WUE) from 1982 to 2015. Additionally, we evaluated the influence of key climatic variables (i.e., precipitation, temperature, and solar radiation) on vegetation greening, carbon sequestration potential and the water cycle. Our results showed widespread vegetation greening during the first half of the study period (1982–2000), driven mainly by increase in precipitation. However, the rate of greening reduced or became stagnant during the latter half of the study (2000–2015), but did not revert to pre-greening levels of 1980s, implying a persistent ecosystem change. The vegetation greening and increased precipitation resulted in a ~ 17.95% increase in GPP (from ~3.9 PgC/year in 1982 to ~4.6 PgC/year in 2000) and a ~ 21.28% increase in ET (from ~47 mm/year in 1982 to ~57 mm/year in 2015). The WUE showed an overall reduction, mainly attributed to large increases in ET not matched by similar magnitude of increases in GPP. Currently, there is lack of consensus on the magnitude of the contribution of drylands to the global carbon and water cycle. This study shows that drylands undergoing ecosystem change, coupled with climate change, may in future become important contributors to the global carbon and water cycle. Therefore, they could play a key role in future global warming and climate change mitigation strategies.

非洲萨赫勒-苏丹-几内亚地区是世界上最大的水资源有限环境之一，因此非常容易受到气候变化的影响。最近的研究表明该地区的植被绿化，但很少有人调查这种绿化对碳和水循环的影响。我们结合使用地球观测 (EO) 数据和诊断模型来评估植被绿化的程度及其对固碳潜力（即总初级生产力-GPP）和水循环（即蒸发蒸腾-ET 和1982 年至 2015 年的用水效率（WUE）。此外，我们评估了关键气候变量（即降水、温度和太阳辐射）对植被绿化、固碳潜力和水循环的影响。我们的结果表明，在研究期间的前半段（1982-2000 年），植被普遍绿化，主要是由于降水增加。然而，在研究的后半期（2000-2015 年），绿化率下降或停滞不前，但并未恢复到 1980 年代绿化前的水平，这意味着生态系统的持续变化。植被绿化和降水增加导致了  GPP 增加约17.95%（从1982 年的约 3.9 PgC/年增加到2000年的约 4.6 PgC/年） 和约21.28%的 ET 增加（从1982 年的约 47 毫米/年增加到约 57 毫米/年）2015 年）。WUE 总体下降，主要是由于 ET 的大幅增加与 GPP 的类似增加幅度不匹配。目前，关于旱地对全球碳和水循环的贡献程度缺乏共识。这项研究表明，正在经历生态系统变化和气候变化的旱地可能在未来成为全球碳和水循环的重要贡献者。因此，它们可以在未来的全球变暖和气候变化减缓战略中发挥关键作用。