This report synthesizes the findings from the Millennium Ecosystem Assessment (MA) global and sub-global assessments of how ecosystem changes do, or could, affect human health and well-being. Over the past 50 years humans have changed natural ecosystems more rapidly and extensively than any comparable period in human history. The findings provide the strongest evidence so far of the ways in which pressures on ecosystems have resulted in the loss of vital ecosystem services, which purify and replenish water, soil and air resources essential to health, and also keep many diseases in check. Loss of these ecosystem services, in turn, affect patterns of communicable and non-communicable disease distribution and transmission. In the future, still-increasing pressures on ecosystems could impact public health in a variety of ways that are unpredictable and potentially severe.