EPOW - Ecology Picture of the Week

Sahara Desert over Niger, northern Africa

Explanation:  On a long flight across Europe and Africa, I awoke as we crossed the largest desert in the world -- the stark and startling Sahara.  

Africa has long been a mostly arid continent.  In the last million years, however, the climate has repeatedly varied from humid to dry and from warm to cool.  Tropical forests have grown and shrunk in central Africa, at times intersected by deserts that actually linked the Sahara in the north to the Kalahari and Namib in the south.  Species of plants and animals closely tied to desert and arid environments have likewise ebbed and flowed from these two great desert centers of endemism.

Today we are in a warm moist cycle where the Sahara is again isolated from southern desert influence.  The Sahara is currently the westerly extension of a vast arid area extending through the Middle East and Central Asia.   Evidence of ancient human occupation has been preserved in these arid environments, and archeological studies such as the Fezzan Project in southwestern Libya are providing new insights into people of the past.  

As I drifted back to dreaming on board the jet liner, I envisioned time speeding up and vast desert dunes once again migrating far across the continent below.

 
Information:
     Kingdon, J. 1989. Island Africa: the evolution of Africa's rare animals and plants. Princeton University Press, Princeton, N.J. 287 pp.
     Le Houerou, H. N.  2001.  Biogeography of the arid steppeland north of the Sahara. Journal of Arid Environments 48(2):103-128.