Tree mortality in the African Sahel indicates an anthropogenic ecosystem displaced by climate change

摘要: Aim Widespread reports of disappearing tree species and senescing savanna parklands in the Sahel have generated a vigorous debate over whether climate change or severe human livestock pressure is principally responsible. Many taxa decline are closely associated with settlement farming, suggesting that parkland ecosystem may not be natural vegetation assemblage. The aim this study to assess possibility activities promoted spread edible fruit into dry Sudano-Sahelian areas during high-rainfall periods cycle. Location West African savannas (Mali, Burkina Faso, Ghana, Togo, Benin). Methods Cultivated adjacent forests transitional landscapes were inventoried at 27 sites five countries. All trees basal diameters > 10 cm counted within 500-m 2 belt transects. Species composition abundance contrasted between three landscape classes degree influence exerted by traditional management. Twentieth century rainfall data averaged for two sets weather stations encompassing north-south range typical species. Rainfall trends used evaluate putative impact on and/ succulent northern limit zone. Results spatial distribution indicate significantly shaped activities. Indigenous land management favours edible-fruit-yielding from wetter Sudanian Guinean zones Sahelian isohyets limits shifted southwards late 20th century, crossing critical 600-mm mean annual threshold flora. Relict historical records system extended past near 15° N latitude middle Africa, compared 13.5° today. Main conclusions current loss mesic Sudano-Sahel zone appears driven sharp drop since 1960s, which has effectively stranded anthropogenically distributed beyond their tolerance limits.