Global Environmental Assessments (GEAs) are intended to gather expert knowledge on a topic of global importance and present it in a useful format to those who could use the knowledge in decision-making. GEAs have disseminated new knowledge, influenced environmental policy, changed the evolution of science, and furthered many careers. The GEA community has always adapted to changing circumstances, often by increasing the complexity of the assessment process. The current level of complexity of most GEAs, alongside today’s increasingly polarized societies, changes in international trade, biophysical changes to the planet, greater interest in cross-sectoral problems and solutions, enhanced technological capacity, and increasingly contested nature of some aspects of environmental science may indicate that we’ve reached a point where further adaptation cannot be achieved merely by adding more complexity. It may be time for more fundamental changes to the GEA scope, process, and delivery. We use the MA as a touchstone in exploring how GEAs have evolved, considering both challenges and possible paths forward to retain legitimacy, credibility, and salience in a changing world. One strong possibility is for GEAs to reorient to serve as support structures for a broader diversity of levels and types of decision-making and a broader array of decision-making actors. In a rapidly changing world, a diverse ecosystem of assessment approaches is likely to be more robust, have more impact, and evolve more quickly. Continuing to experiment with different models for delivering multi-scale environmental information will help GEAs fit the needs of the 21st century.