Frederick Kaufman has a very interesting piece (subscription required) on an underreported phenomena in the 2008 spike in food prices – what he calls a “food bubble” caused by commodities investment vehicles structured around wheat futures.
While I think this article is worth reading and considering carefully, it is important to recall that Kaufman is trying to make a particular point about the pervasiveness of problematic investment vehicles in our economy, and the ways in which these vehicles seem to hurt everyone but the people who invent them.  This point is well-made.  However, in making this point Kaufman underplays a couple of really important points:
1) Wheat is but one of the staples that saw a price spike in 2008.  And while price stress on one staple (wheat) can lead people to start shifting into another (corn), driving the prices of the second commodity up, it would take some serious research to substantiate the (implicit) idea that a price spike in wheat could have a dramatic impact on corn prices in Africa (where wheat is the 8th most important crop, at 3.2% of total agricultural production) (via FAOSTAT).  Wheat is important, but maize is the crop that links the world together . . . which leads to my second point:
2) There was a convergence of factors that created the price spike in 2008.  In one sentence, Kaufman acknowledges several important factors:
“By the time the normal buying season began, drought had hit Australia, floods had inundated northern Europe, and a vogue for biofuels had enticed U.S. farmers to grow less wheat and more corn.”
But this is only one sentence in the whole article.  In an effort to point out the impact of investment vehicles on global food security, Kaufman’s narrative underplays just how important these other factors were in driving up the price of other staples like corn (the extra corn was largely rerouted to biofuels, and the drought in Australia removed a great deal of expected production from the world supply).
The point here: food insecurity is enormously complex, and caused by the intersection of processes and events operating at multiple scales.  Even as we tease out some of these processes and events, we must also highlight how each specific process or event intersects with other causes to produce particular outcomes in particular places.