Having long been the dominant paradigm in the modernization of agriculture, agricultural intensification following the green revolution is now widely questioned because of its negative impacts on environment and biodiversity, its energy cost, and the risks it entails for human health. At the regional level, however, one must distinguish countries strongly impacted by the Green Revolution, and others less influenced. In sub-Saharan Africa for example, farmers continue to grow grain crops without any pesticide, in a wide diversity of farming practices and landscapes. For the French agronomic research, this distinction is reflected in the two guiding concepts of "agro-ecological transition" and "ecological intensification" whose contours are not necessarily disjoint according to local socio-economic contexts. After giving main features of these two guiding concepts, our presentation will focus on two case studies illustrating the ongoing research efforts in La Reunion and Senegal. In La Reunion Island, where industrial cultivation of sugar cane is a substantial part of the agricultural activity, techniques of Conservation Agriculture have been introduced to limit soil compaction by farm machinery and use of pesticides to control weeds. Diversification of uses is also being studied to produce biomass and fiber (bio-economy). The Serere country in Senegal is characterized by a traditional pesticide free agroforestry system for food and feed production. The impact of natural pest regulation, but also its variability among fields in such an agroecosystem, makes the millet head miner (Heliocheilus albipunctella) a very relevant model system to identify conditions and drivers for boosting ecological processes involved in biological control. In contrast to the single model proposed by the Green Revolution, recent developments in the design of innovative agricultural systems support better consideration of local ecological and social contexts, mobilizing various disciplines su