The Millennium Ecosystem Assessment – the most comprehensive assessment to date of the status and trends of Earth’s ecological systems – warned us that 60% of the benefits nature provides to people (‘ecosystem services’) are being degraded or used unsustainably. This triggered widespread efforts, by research groups, conservation organizations and think tanks, to design and use ecosystem services assessments and tools around the world. These efforts aim to integrate the ‘value of nature’ in decision-making, policies, business operations and ultimately to change society’s development trajectory to be sustainable. Yet, recent studies point out that not all new tools and scientific knowledge on ecosystem services are effectively used as a basis for decision and action leading to positive social and environmental outcomes. To create change, new scientific and expert knowledge, even when worrying, robust and empirically grounded, is not enough. It needs to be mobilized by leaders and change agents – researchers, conservation NGO practitioners, motivated policy makers or business – who use the information systems and knowledge as part of a strategy of communication, advocacy and action. Context matters. A good understanding of the context for biodiversity and ecosystem services approaches often determines whether a project has impact or not. Such understanding can be gathered quickly and easily using ‘context diagnostic1’ tools. These can be used by practitioners who are agents of change in real world situations. This report introduces such a context diagnostic tool for conservation and Biodiversity and Ecosystem Services Assessment and Valuation (BESAV) practitioners. The tool includes five approaches based on well-established social science theories. Each approach gives a contrasting perspective and raises a set of thought-provoking questions on social, organizational, institutional and political aspects of context. The tool is illustrated throughout by examples inspired by real- world case studies, gathered through interviews and participatory workshops. The tool can be used at different stages of BESAV projects (scoping, implementation, evaluation and debriefing). We have grounded this context diagnostic method on well-established social science theory to build on their rich insights and empirical studies. The five theories were chosen for their relevance to the management of ecosystems: • institutionalizing treatment of new environmental issues • strategic analysis and strategy development • knowledge and innovation as a lever of change • the mobilization and articulation of multiple values •the well-being of local communities who use the natural environment and the role of institutions and rules in enabling them to do so These theoretical frameworks can enrich the way practitioners reflect on and understand the dynamics of change that they are part of.