Climate-induced livelihood transitions in the agricultural systems of Africa are increasingly likely. A recent study by Jones and Thornton (2009) points to the possibility of such climate-induced livelihood transitions in the mixed crop-livestock rainfed arid-semiarid systems of Africa. These mixed systems cover over one million square kilometers of farmland in West Africa, Eastern Africa, and Southeastern Africa. Their characteristically scant rainfall usually causes crop failure in one out of every six growing seasons and is thus already marginal for crop production. Under many projected climate futures, these systems will become drier and even more marginal for crop production. This will greatly increase the risk of cropping and among the several possible coping and adaptation mechanisms, (e.g. totally abandoning farming, diversification of income-generating activities such as migration and off-farm employment, etc.) agro-pastoralists may alter the relative emphasis that they currently place on the crop and livestock components of the farming system in favor of livestock. There has been only limited analysis on what such climate induced transitions might look like, but it is clear that the implications could be profound in relation to social, environmental, economic and political effects at local and national levels. This study sought to identify areas in the mixed crop-livestock systems in arid and semi-arid Africa where climate change could compel currently sedentary farmers to abandon cropping and to turn to nomadic pastoralism as a livelihood strategy, using East Africa as a case study. While the current study found no direct evidence for the hypothesized extensification across semiarid areas in East Africa, it is clear that systems are in transition with associated changes not necessarily climate driven but linked to broader socio-economic trends. Not surprisingly, many of the households in the piloted sites face a wide array of problems including poverty, food insecurity and inadequate diets which will be aggravated by the looming risks posed by climate change.