Warmer temperatures in coffee-growing regions are expected to reduce the area that is suitable for growing coffee, according to an article published at Inc.com here.  In addition to the decrease in cultivated area, pests and diseases are also expected to increase in a warmer climate.

Grass food crops like wheat, sorghum, rice and corn are also expected to suffer under warmer conditions, according to the BBC here.  These crops provide almost half of the calories consumed by humans across the planet.  Part of the problem is the rate at which changes occur, which are too fast for the grass species to adapt naturally, and could reduce biodiversity if species cannot change fast enough to match new climate conditions.  The article addresses problems that farmers in less developed countries will have in supplying food to their local areas if the grain varieties they use go extinct.

Source: David Monniaux, Commons Wikimedia
Source: David Monniaux, Commons Wikimedia