Do we understand enough about the impact of demographic change on natural resources management (NRM), farm investment and household income strategies in semi-arid areas? Is eco-disaster around the corner, or does land scarcity encourage investment in productivity-enhancing and land-conserving technologies? How should policy initiatives combine poverty reduction with environmental improvement? These questions were raised by a study of Machakos District in Kenya from 1930 to1990. They have now been tested further in four countries – Niger, Nigeria, Senegal and Kenya – in research led by Drylands Research UK and carried out with in-country research teams.