Millennium Ecosystem Assessment is a comprehensive study of the world's ecosystems that was conducted between 2000 and 2005 by over 1,300 researchers. It assessed the consequences of ecosystem change for human well-being and provided guidance on how to conserve and sustainably use ecosystems. There are several synonyms for the term, including Ecosystem Assessment of the Millennium, Millennium Ecosystem Report, and Assessment of Ecosystem Change. Other related terms include Ecosystem Health Assessment, Biodiversity Assessment, and Watershed Assessment. These assessments provide critical information on the state of the world's ecosystems and are essential for developing policies and strategies to preserve them for future generations.