Mid-Level Altitude Forests Most Sensitive to Rising Temperatures

September 10, 2012

A new study led by a team of University of Colorado scientists shows that mid-level altitude forests are the most sensitive to rising global temperatures and a decline in snowpack. As KUNC's Kirk Siegler reports, the study was done in California but researchers say its findings apply across the entire West.

Scientists looked at forests from about 6,500 to 8,000 feet in the Sierra Nevada where much of that region’s water supply originates and where many live and recreate. Researchers found that forests’ ability to “green up” during the summer is largely linked with whether there’s been a healthy snowpack the previous winter. As the earth warms, and precipitation comes more in the form of rain than snow, scientists say forests at these altitudes will become even more stressed, and vulnerable for insect outbreaks and wildfires. Noah Molotch of the Institute for Arctic and Alpine Research at CU-Boulder co-authored the study.

"And so in general we’re going to have less water storage in the form of snowpack in the future and our study shows that the forests are quite sensitive to this."

Molotch says one important focus of the study was on the “tipping point,” that is the line between mid-level forests that are sustained by precipitation and snowmelt, and those at higher elevations that are less dependent on precip and more on sunlight and temperature.

"As the region warms, we would hypothesize that that elevation would continue to move up the mountain, and as it does, runoff production from these higher elevations will continue to go down."

Which could have serious implications for water managers and users, as well as the health of the forests. The study was published this week in the journal, Nature Geosciences.