This book documents a decade of research, methodological innovation, and lessons learned in an eco-regional research-for-development program operating in the eastern African highlands, the African Highlands Initiative (AHI). It does this through reflections of the protagonists themselves-AHI site teams and partners applying action research to development innovation as a means to enhance the impact of their research. The book summarizes the experiences of farmers, research and development workers and policy and decision-makers who have interacted within an innovation system with the common goal of implementing an integrated approach to natural resource management (NRM) in the humid highlands. This book demonstrates the crucial importance of "approach" in shaping the outcomes of research and development, and distils lessons learned on what works, where and why. It is enriched with examples and case studies from five benchmark sites in Ethiopia, Uganda, Kenya and Tanzania, whose variability provides the reader with an in-depth knowledge of the complexities of integrated NRM in agro-ecosystems that play an important role in the rural economy of the region. It is shown that the struggle to achieve sustainable agricultural development in challenging environments is a complex one, and can only be effectively achieved through combined efforts and commitment of individuals and institutions with complementary roles.