Aim: Changes in dryland ecosystem functioning are threatening the well‐being of human populations worldwide, and land degradation, exacerbated by climate change, contributes to biodiversity loss and puts pressures on sustainable livelihoods. Here, abrupt changes in ecosystem functioning [so‐called turning points (TPs)] were detected using time series of Earth observation data. Hotspot areas of high TP occurrence were identified, observed changes characterized and insights gained on potential drivers for these changes. Location: Arid and semi‐arid regions. Time period: 1982–2015. Methods: We used a time series segmentation technique (breaks for additive season and trend) to detect breakpoints in rain‐use efficiency as a means of analysing changes in ecosystem functioning. A new typology to characterize the detected changes was proposed and evaluated, at regional to local scales, for a set of case studies. Ancillary data on population and drought were used to provide insights on potential drivers of TP occurrence. Results: Turning points in ecosystem functioning were found in 13.6% (c. 2.1 × 106 km2) of global drylands. Turning point hotspots were primarily observed in North America, the Sahel, Central Asia and Australia. In North America, the majority of TPs (62.6%) were characterized by a decreasing trend in ecosystem functioning, whereas for the other regions, a positive reversal in ecosystem functioning was prevalent. Further analysis showed that: (a) both climatic and anthropogenic pressure influenced the occurrence of TPs in North America; (b) Sahelian grasslands were primarily characterized by drought‐induced TPs; and (c) high anthropogenic pressure coincided with the occurrence of TPs in Asia and Australia. Main conclusions: By developing a new typology targeting the categorization of abrupt and gradual changes in ecosystem functioning, we detected and characterized TPs in global drylands. This TP characterization is a first crucial step towards understanding the drivers of change and supporting better decision‐making for ecosystem conservation and management in drylands.

中文翻译：

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干旱和半干旱生态系统功能转折点的全球尺度表征

目标：旱地生态系统功能的变化威胁着全世界人类的福祉，气候变化加剧了土地退化，导致生物多样性丧失并对可持续生计造成压力。在这里，使用地球观测数据的时间序列检测到生态系统功能的突然变化 [所谓的转折点 (TP)]。确定了高 TP 发生的热点区域，观察到的变化特征以及对这些变化的潜在驱动因素的见解。地点：干旱和半干旱地区。时间段：1982-2015。方法：我们使用时间序列分割技术（附加季节和趋势的中断）来检测雨水利用效率的断点，作为分析生态系统功能变化的一种手段。针对一组案例研究，提出并评估了一种新的类型学来表征检测到的变化，在区域到地方的范围内。关于人口和干旱的辅助数据用于提供有关 TP 发生的潜在驱动因素的见解。结果：在 13.6%（约 2.1 × 106 平方公里）的全球旱地中发现了生态系统功能的转折点。转折点热点主要在北美、萨赫勒、中亚和澳大利亚观察到。在北美，大多数TPs（62.6%）的特点是生态系统功能呈下降趋势，而其他地区则普遍存在生态系统功能的正向逆转。进一步分析表明：（a）气候和人为压力都影响了北美TPs的发生；(b) 萨赫勒草原的主要特征是干旱引起的 TP；(c) 高人为压力与亚洲和澳大利亚 TP 的发生同时发生。主要结论：通过开发针对生态系统功能突然和逐渐变化的分类的新类型，我们检测并表征了全球旱地中的 TP。这种 TP 特征是了解变化驱动因素和支持更好地制定旱地生态系统保护和管理决策的第一个关键步骤。