Global changes in climate are due to increased emissions of greenhouse gases, resulting in changes to cold desert ecosystems. This comes as no surprise to those of us living in the Great Basin. We see this man-caused or at the very least man-intensified change all around us.
The Great Basin is characterized by cold winters, hot and dry summers, and highly variable precipitation. Temperature increases in the Great Basin have been clearly documented. Changes in the amount of precipitation are harder to see, although a change in timing of the precipitation is evident. These changes combine to make the Great Basin more arid. Droughts are happening more frequently and lasting longer. Invasive annual grasses are spreading, and wildfire seasons are becoming more intense and lasting longer.
Between 1895 and 2011, Great Basin temperatures increased between 1.2 and 2.5 degrees Fahrenheit. Temperatures in the southern Great Basin have increased more than in the north. Nighttime temperatures have increased more than daytime, and winter temperatures have risen more than summer. We get fewer cold snaps and more heatwaves.
Warmer temperatures have meant less snow and earlier snowmelt. Less precipitation falls as snow and more as rain. Mountain snowpack and snowmelt are very important to area agriculture, industry and urban uses. The amount of water in the snowpack has decreased, more from increasing temperatures than less precipitation.
Streamflow is increasing earlier in spring, leaving lower flows during hot summer months, when the demand for water is high. Annual streamflow in the Humboldt River has increased 12 percent, but peak flows are occurring 10-15 days earlier than during the last century. High elevation country holds most of the stored water as snow and these areas shave shown the greatest shifts in temperature and streamflow timing.
The amount of annual runoff has not changed that much but the driest years contain up to 50 percent lower stream flows. Rain falling on snow causes rapid melt and downstream flooding, especially when rain falls on frozen soil. We saw events like these in 2017.
Next week, I will go into future predictions and possible land management strategies for dealing with a changing climate. The information for these columns comes from an article titled “Effects of Changing Climate on the Hydrological Cycle in Cold Desert Ecosystems of the Great Basin and Columbia Plateau,” 2018, printed in a publication of Rangeland Ecology & Management.