Designed by a partnership of UN agencies, international scientific organizations, and development agencies, the Millennium Ecosystem Assessment (MA) is the most extensive study ever of the linkages between the world’s ecosystems and human well-being. The goal of the MA is to establish the scientific basis for actions needed to enhance the contribution of ecosystems to human well-being without undermining their long-term productivity. With contributions by more than 500 scientists from 70 c...

Nitrogen is indispensable to all life on Earth. However, humans now dominate the nitrogen cycle, and nitrogen emissions from human activity have real costs: water and air pollution, climate change, and detrimental effects on human health, biodiversity, and natural habitats. Too little nitrogen limits ecosystem processes, while too much nitrogen transforms ecosystems profoundly.The California Nitrogen Assessment is the first comprehensive account of nitrogen flows, practice...