This book synthesises information on an important environmental problem - the invasion of natural ecosystems in Africa by alien Prosopis trees, and how they should be managed. It addresses how the problem came about, what we know about how it works, and how it can potentially be managed at different scales. The book has a focus on eastern Africa but includes studies from elsewhere. Prosopis trees were originally introduced to Africa as early as 1880 (in South Africa), and later to eastern Africa in 1917 (in Sudan). They are difficult to manage due to their ecological features, such as their ability to produce copious amounts of seed, and to compete successfully with native species for resources, but also because they have both beneficial uses and negative impacts, making them conflict species, where people disagree on goals for management and how they should be achieved. In eastern Africa, Prosopis juliflora invades rangeland, cropland, settlements and riparian ecosystems, causing negative impacts on biodiversity and ecosystem services that rural communities depend on. This book considers the perceptions and conflicting interests of different stakeholder groups, and how engagement can be used to co-design management strategies and implement concrete control measures. The book is therefore not only of interest to those working with this invasive tree species, but also to persons involved in policy development and management of other invasive species, or in the wider field of sustainable environmental management.