Woody vegetation dynamics in the Sahel have been debated since the great droughts of the 1970s–1980s. Here, we combined high-resolution satellite and aerial imagery, field inventory, and historical botanical records to study woody vegetation trends over the years 1965, 1980, 2008, and 2018 in the Ferlo, the Sahelian sylvo-pastoral zone of Senegal. While tree density has decreased from 1965 (14.8 trees ha⁻¹) to 1980 (13.4 trees ha⁻¹) and 2008 (11.9 trees ha⁻¹), tree density has stabilized in 2018 (12.2 trees ha⁻¹). The relatively moderate decrease in tree density over 50 years characterized by extensive human pressure and droughts, as well as the rather stable woody cover following the drought years after the 1980s, do not support narratives of widespread desertification in this region. However, we observed a shift in the composition of species. While the drought-resistant tree Balanites aegyptiaca showed a stable abundance, Acacia tortilis showed strong increases and other species like Sclerocarya birrea and Combretum glutinosum decreased. In addition, recent field surveys show that the ratio between shrubs and trees has increased towards more shrubs. The observed loss of species diversity combined with the increase of drought-resistant species is in line with current observations for savanna ecosystems in the context of an increased aridity.

自1970年代至1980年代的严重干旱以来，萨赫勒地区的木质植被动态一直受到争议。在这里，我们结合了高分辨率的卫星和航空影像，野外清单以及历史植物记录，以研究塞内加尔萨赫勒森林-牧区-费罗地区1965、1980、2008和2018年的木本植被趋势。虽然树木密度从1965年（14.8树木ha ^-1）降低到1980年（13.4树木ha ^-1）和2008年（11.9树木ha ^-1）有所下降，但树木密度在2018年已稳定（12.2树木ha ^-1））。50年来树木密度相对适度的下降（​​其特征是人为压力和干旱加剧）以及1980年代后的干旱年份后相当稳定的木本覆盖，不支持该地区广泛荒漠化的说法。但是，我们观察到物种组成发生了变化。耐旱树Balanites aegyptiaca的树种数量稳定，而Acacia tortilis的树种则表现出强劲的增长，而其他物种如Sclerocarya birrea和Combretum glutinosum减少了。此外，最近的实地调查表明，灌木和乔木之间的比例向着更多的灌木方向增加。在干旱增加的情况下，观察到的物种多样性丧失加上抗旱物种的增加与热带草原生态系统的当前观察相符。