The first edition of the “Cities and Biodiversity Outlook” (CBO-1) will consist of a global assessment of the links between urbanization, biodiversity and ecosystem services. Combining science and policy, scientists from around the world will analyze how urbanization and urban growth impacts biodiversity and ecosystems, delivering key messages on the conservation and the sustainable use of natural resources to decision-makers. Cities, local authorities and sub-national governments will have the opportunity to showcase their practices on sustainability and biodiversity and learn from existing experiences how to incorporate those topics in their agendas and policies.