Actions that sustain and restore diverse and functioning ecosystems are essential for human safety, health and prosperity. With 2021–2030 declared as the United Nations Decade on Ecosystem Restoration, efforts are scaling up to halt, reverse and prevent future degradation of ecosystems worldwide, including natural, semi-natural, managed, production and urban ecosystems. Sustaining and restoring ecosystems requires public support and leadership from nation-states and civil society, underpinned by sound science, and is driven by the collective action of multiple actors whose actions impact and are impacted by ecosystems. To move the goals of the UN Decade on Ecosystem Restoration forward, the Science Task Force of the Decade presents this think piece, which addresses four fundamental questions, presents five key messages to bring effective and long-term action, and provides recommendations on how to build the ecosystem restoration movement.