Abstract
The climate deterioration after the most recent African humid period (AHP) is a notable past example of desertification. Evidence points to a human population expansion in northern Africa prior to this, associated with the introduction of pastoralism. Here we consider the role, if any, of this population on the subsequent ecological collapse. Using a climate-vegetation model, we estimate the natural length of the most recent AHP. The model indicates that the system was most susceptible to collapse between 7 and 6 ka; at least 500 years before the observed collapse. This suggests that the inclusion of increasing elements of pastoralism was an effective adaptation to the regional environmental changes. Pastoralism also appears to have slowed the deterioration caused by orbitally-driven climate change. This supports the view that modern pastoralism is not only sustainable, but beneficial for the management of the world’s dryland environments.
Highlights
The climate deterioration after the most recent African humid period (AHP) is a notable past example of desertification
This view (Fig. 1a) was embedded in the environmental doctrine of the twentieth century, partly as a consequence of the historical relationship between colonial administrators and traditional pastoralists[1]. This doctrine has led to a recent suggestion that early pastoralism was so unsustainable that it triggered a climatic deterioration in the Sahara around 5500 years ago[2]
We examine the nature of early African pastoralism and its interactions with landscape
Summary
The climate deterioration after the most recent African humid period (AHP) is a notable past example of desertification. This doctrine has led to a recent suggestion that early pastoralism was so unsustainable that it triggered a climatic deterioration in the Sahara around 5500 years ago[2] (at the end of the African Humid Period[3]) This has significant implications for the way in which modern populations living in marginal environments are perceived, and how modern pastoralism is recognised within local and regional ecological and economic policies. The second pulse of northern African human occupancy lasted until 5.5 ka, at which point the Sahara underwent a major population collapse, coinciding with the decline in favourable climatic conditions (Fig. 2) Was this climate–human interaction one way —or was the collapse of the green Sahara an early example of humans interfering with a sensitive environmental system?
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