The Millennium Ecosystem Assessment (MA) is a major international scientific initiative to analyze the status, dynamics and interaction of ecosystems with human society as we enter the third millennium. Building on the general approach pioneered by UNEP's Global Environment Outlook (GEO), the MA combines the retrospective analysis of ecosystem services and their impacts on human well-being with an assessment of expected changes in ecosystem conditions and impacts on society in the future. The audience of the MA includes, among others, four international conventions, the Convention on Biological Diversity; the Convention to Combat Desertification;, the Ramsar Convention on Wetlands; and the Convention on Migratory Species.

Completed in 2005, the MA is a product of intensive collaboration of more than 1,300 scientists in 95 countries. Its process and products explored ecosystem-human system interactions on multiple scales, from the global scale down to the level of specific ecosystems. Its results are published in a series of global and sub-global reports over 2005 and 2006. Besides the four conventions, the target audience of the MA's reports include decision-makers in public and private organizations and civil society around the world.

IISD contributed to the development of the conceptual framework of the MA and the integrated assessment of poverty-ecosystem linkages based on the freedoms and capabilities approach in both global and sub-global contexts.