With 20 percent of the world’s population but just 7 percent of its available freshwater, China faces serious water shortages as its economy booms and urbanization increases. The government is planning massive water diversion projects, but environmentalists say conservation — especially in the wasteful agricultural sector — is the key.

A dispute between Egypt and upstream African nations has brought to the fore a long-standing controversy over who has rights to the waters of the Nile. The outcome could have profound consequences for the ecological health of the river and for one of the world’s largest tropical wetlands.

Hydro fracturing is a profitable method of natural gas extraction that uses large quantities of water and chemicals to free gas from underground rock formations. But New York City’s concerns that the practice would threaten its water supply have slowed a juggernaut that has been sweeping across parts of the northeastern United States.

As governments, businesses, and homeowners plan for the future, they should assume that the world’s oceans will rise by at least two meters — roughly seven feet — this century. But far too few agencies or individuals are preparing for the inevitable increase in sea level that will take place as polar ice sheets melt.

Bolivia accounts for a tiny fraction of global greenhouse gas emissions. But it will soon be paying a disproportionately high price for a major consequence of global warming: the rapid loss of glaciers and a subsequent decline in vital water supplies.

The coal industry, political leaders, and some environmentalists have high hopes for the concept of carbon sequestration, which takes carbon dioxide emissions from coal plants and buries them underground. But so far, this new technology does not live up to the hype.