I would like to point you to this very good article from Le Monde Diplomatique, that explains how african soil is bought by private investors from The US, Europe, Asia and South Africa, in order to grow export crops, e.g. for the production of bio ethanol. The article shows how even countries whose populations suffer from food shortages invite international inverstors to buy arable land, and how 125 years after the african continent was devided by the colonial powers of that time, history repeats.

The article in Le Monde Diplomatique in German language can be found here: http://www.monde-diplomatique.de/pm/2010/01/15.mondeText1.artikel,a0040.idx,11. And here is an automatic translation via Yahoo (as acurate as automatic translations can be...). And finally, another article from the same author on the same topic: http://allafrica.com/stories/200911051028.html (this time in english).