This manual was launched by UNEP at a ceremony celebrating the end of the International Year of SIDS. It is seen as a timely and critical tool to enable policymakers to calculate the true value of ecosystems for a transition to a green economy across the world's 52 small island developing states (SIDS). It highlights the strong interdependency between the natural environment and the economy of SIDS and the importance of accounting for the contribution of ecosystem services to human well-being in order to be able to quantify and manage those benefits. The Executive Summary is available in French and Spanish.