The natural environment is in decline globally. With too few exceptions, environmental indicators are growing worse. For example, water and air pollution are now so poor in some developing countries, such as China and India, that hundreds of millions of people are forced to drink severely tainted water and breathe toxic air. Regionally, acid rain – which has been reduced in North America and Western Europe in recent decades – is on the increase in East Asia and other developing regions, putting ecosystems and agriculture at great risk. The so-called “Asian brown cloud” of smog is so vast that it spreads across the Pacific to the Americas. Coastal seas have been overfished in most oceans, and this phenomenon has extended to regional seas in both the developed and developing worlds. Marine environments are severely degraded by polluting runoff from continents, with the world’s coral reefs shrinking and ocean “dead zones” now extending along the coastlines of all continents. Wildlife around the world is under great threat, with declines and extinctions of species on the rise. These problems are exacerbated by climate change, which is manifested in rising global temperatures, very serious threats to agricultural productivity from droughts and floods, more severe weather events, new threats to species unable to adapt to environmental changes and pollution, declines in marine ecosystems due to warming waters and ocean acidification, and immeasurable dangers posed by sea-level rise, particularly for poor low-lying regions, countries and habitats. These are but a few examples of the environmental challenges that are increasing around the world.