In the natural environment, water sustains crucial habitat for plants and animals. As precipitation patterns change, the potential for having too little or too much water threatens ecosystems within and near streams, lakes, and wetlands. In places where precipitation decreases, competition for existing water will increase. This will put the need for water for agriculture and urban uses in direct conflict with the needs of maintaining a sustainable environment. Additionally, increasing temperatures may raise water temperatures and alter stream flows, which can have detrimental effects on aquatic organisms and water-dependent ecosystems.
The impacts of climate change on water for ecosystems will be felt across the nation. In the snowmelt-driven river systems that dominate the western United States, peak runoff is already coming earlier in the year, and creating longer, hotter dry seasons—a trend that is likely to continue in coming decades. In the Southeast, rising temperatures are likely to reduce moisture in the environment by increasing evaporation rates, even if precipitation rates do not change.
Excerpted and adapted from Chapter 1, Section 1 of Climate-Smart Conservation: Putting Adaptation Principles into Practice and the report Climate Change Impacts in the United States: The Third National Climate Assessment (Chapter 3: Water Resources).