Water scarcity in the Middle East and Africa is likely to be aggravated by climate change, which could increase international tension among countries that depend on water supplies originating outside their borders. Changing Forests and Natural Areas - Climate change could dramatically alter the geographic distributions of vegetation types. The composition of one-third of the Earth's forests would undergo major changes as a result of climate changes associated with a CO2 level of 700 ppm. Over the next 100 years, the ideal range for some North American forest species will shift by as much as 300 miles to the north, far faster than the forests can migrate naturally. Such changes could have profound effects on the U.S. system of national parks and refuges, leading to reductions in biological diversity and in the benefits provided by ecosystems, such as clean water and recreation.
Wetlands are particularly at risk.
The wetlands of the prairie pothole region, which support half the waterfowl population of North America, could diminish in area and change dramatically in character in response to climate change. Model projections indicate that all the Park s glaciers will disappear by 2030 unless temperatures begin to cool instead of warm. Challenges to Agriculture and the Food Supply - Climate strongly affects crop yields. A CO2 concentration of 550 ppm is likely to increase crop yields in some areas by as much as 30 percent to 40 percent, but it will decrease yields in other places by similar amounts, even for the same crop. A warmer climate would reduce flexibility in crop distribution and increase irrigation demands.