Evaporating water supplies
As the global population reaches 7 billion, ecological distortions are becoming widespread. Among the changes are a drop in fresh water supply in more than two dozen of the largest African nations and a net loss of forest in South America and Australia. Nations with stable or declining populations, such as the United States, have seen a rise in acreage and density of temperate forests. Several developing nations with biologically diverse tropical forests have lost ground. Read related article.