Agriculture is central to the livelihoods of the rural poor and in the attainment of the Millennium Devel op ment Goals (MDGs). Agriculture can be the engine of growth and is necessary for reducing poverty and food insecurity, particularly in sub-Saharan Africa (IFAD 2001; World Bank 2007a). Understanding the dynamic processes of change is crucial to better position the sector for faster growth and sustained development, which is vital for food and livelihoods security for millions of men and women worldwide.