After WWII, Mary moved to India, and finished her schooling in Devon, and took a history degree at Girton College, Cambridge (1952).
She carried out fieldwork in Africa and the Middle East; including in Nigeria, Malawi, Kenya, Senegal, Niger, and Iraq (on irrigation).
Leaning on (and improving on) Ester Boserup's work, they discovered environmental enhancement occurred through multicropping and other farming methods, terracing, and strong community organisations.
Mortimore and Tiffen's comparisons of photographs from 1930 and 1990 showed these trends: an improvement in landscapes and in resource management (rather than degradation and impoverishment), albeit with much higher population densities and altered labour regimes.
The 1993 launch of More People, Less Erosion at the ODI in London was electric – several staff members of the UK Department for International Development, the World Bank, and academic researchers from East Africa were there, and the study has echoed through revisionist thinking about African degradation myths and agrarian policy ever since.