About 21% of the African population directly depends on rangeland resources. As this number is predicted to grow, it is important to understand the response of African rangelands to global environmental change and formulate, in turn, better hypotheses on their capacity to support livelihoods. Here we used three decades of satellite data and a dynamic global vegetation model to study the response of rangeland vegetation to recent climate change and to describe changes in the vegetation structure accompanying greening and browning trends. Long-term climate change was the dominant driver of vegetation dynamics in ca. 2,495,000 km² of African rangelands (22.7% of the total extent). Examples of these rangelands are in Mauritania, Senegal, Chad, Namibia, Botswana, and South Africa, where the vegetation greened up due to an overall increase in trees, shrubs, and short herbaceous vegetation. We further identified a more extended different type of rangeland (ca. 2,915,000 km²) where vegetation dynamics appeared to be largely unrelated to long-term climate variations. In these rangelands, we observed opposite trends between woody cover (trees and shrubs) and short vegetation (mostly representative of the herbaceous layer). Greening (West Africa, South Sudan) was associated with an overall increase in woody cover (+4.4%) and a concomitant decline in short vegetation (−3.4%), while browning (Angola, Mozambique) resulted from a decrease in woody cover (−2.6%) and an increase in short vegetation (+4.3%) (total per cent change average during 1982–2015). Our results offer a nuanced perspective to frame greening and browning trends in rangeland systems. While greening may mitigate climate change via higher carbon uptake, the encroachment of less palatable woody species reduces the resources available to pastoral communities. On the other hand, browning due to a reduction in the woody cover attenuates carbon sequestration rates, but the observed increase in short herbaceous vegetation may hint a relative increase in forage resources.

非洲人口中约有21％直接依赖牧场资源。随着这一数字的预计增长，重要的是要了解非洲牧场对全球环境变化的反应，并反过来就其支持生计的能力提出更好的假设。在这里，我们使用了三十年的卫星数据和动态的全球植被模型来研究牧场植被对近期气候变化的响应，并描述伴随绿化和褐变趋势的植被结构变化。长期的气候变化是约旦植被动态的主要驱动力。2,495,000千米²非洲牧场（占总面积的22.7％）。这些牧场的例子有毛里塔尼亚，塞内加尔，乍得，纳米比亚，博茨瓦纳和南非，这些地区的植被由于树木，灌木和短草的总体增加而绿化。我们进一步确定了范围更广的不同类型的牧场（约2,915,000 km ²）那里的植被动态似乎与长期的气候变化无关。在这些牧场中，我们观察到木质覆盖物（树木和灌木）和短植被（主要代表草本层）之间的相反趋势。绿化（西非，南苏丹）与木质覆盖物的整体增加（+ 4.4％）和短植被的同时减少（-3.4％）相关，而褐变（安哥拉，莫桑比克）则由木质覆盖物的减少（ -2.6％）和短植被增加（+4.3％）（1982-2015年间平均总变化百分比）。我们的结果提供了一个细致入微的观点，可以勾勒出牧场系统中的绿化和褐变趋势。绿化虽然可以通过增加碳的吸收来缓解气候变化，但对可口性较低的木本物种的侵占减少了牧民可获得的资源。