More Productive U.S. National Forests and Grasslands Could Yield Less Water in a Future Climate

A map shows percent change in average annual water yieldThe U.S. National Forests and Grasslands are public lands that provide important ecosystem services such as clean water and timber supply to the American people. Researchers with the Eastern Threat Center developed a comprehensive Water Supply Stress Index modeling tool to simulate changes in water and carbon cycles on 170 national forests and grasslands based on projections for the next century from 20 global climate models. Even though climate models project higher levels of precipitation in the future, the researchers found that forested watersheds could become drier because forest water use will increase dramatically with higher air temperatures. By 2100, this elevated water use could increase ecosystem productivity – the growth of trees and other vegetation – by 8 to 24 percent, leading to a projected 4 to 7 percent decrease in water yield overall. The most severe declines in water yield could be seen in the Northwest, North Central, and Southwest regions of the United States. The impacts of climate change on water supply and carbon sequestration are expected to intensify under a changing climate in the future, posing greater challenges to managing national forests and grasslands to sustain the broad variety of benefits they provide.

Pictured: A map shows percent change in average annual water yield from the baseline study period (1970-1999) to the future (2070-2099) under global climate model scenarios across 170 national forests and grasslands and nine climate regions. The blue and red dots at national forest and grassland locations indicate positive and negative changes, respectively. Click to enlarge.


Duan, Kai; Sun, Ge; Sun, Shanlei; Caldwell, Peter V.; Cohen, Erika C.; McNulty, Steven G.; Aldridge, Heather D.; Zhang, Yang 2016. Divergence of ecosystem services in U. S. National Forests and Grasslands under a changing climate. Scientific Reports, Vol. 6: 24441.

Forest Service Partners/Collaborators:
Southern Region (Region 8)

External Partners/Collaborators: North Carolina State University

Contact: Ge Sun

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