Global warming affects patterns of rainfall and water distribution. As the Earth warms,
regions that currently receive an adequate supply of rain may shift. Regions of Earth that
normally are low pressure areas may become areas where high pressure dominates. That
would completely change the types of plants and animals that can live successfully in that
region.
In 1995, about 40% of the world’s population faced water scarcity (Figure21.11). Scientists
believe that by the year 2025, nearly half of the world’s people won’t have enough water to
meet their daily needs. Nearly one quarter of the people in the world will have less than 500
m^3 of water per person to use in an entire year. A cubic meter of water equals 1,000 liters.
That means in certain areas of the world, many people will have less water available in a
year than some people in the United States use in one day.
Water Shortages
Water Shortages Projections for 2025
As we continue to use our precious freshwater supplies, scientists expect that we will en-
counter several different types of problems. We currently irrigate our crops using supplies of
groundwater in aquifers underground. When we have used up these groundwater supplies,
we will not be able to grow as many different types of crops or we will have lower yields
of the crops we grow. Using our freshwater often adds many different types of dissolved