Study: Southwest Forests Vulnerable To Swings In Precipitation

Oct 22, 2019

New research from the University of Arizona shows the Southwest is a hotspot for future precipitation swings—and that’s bad news for trees. KNAU’s Melissa Sevigny reports.

A fire scar on a ponderosa pine tree near Flagstaff
Credit Melissa Sevigny

Scientists compared climate data and tree-ring records stretching back decades. They found ponderosa pine, Douglas fir, and pinyon pine trees are especially vulnerable to dramatic swings in precipitation. Ecologist William Smith, one of the study’s authors, says, "They suffer pretty big growth reductions during extreme dry years, but during extreme wet years, they don’t recover fully—they don’t see growth to compensate for the reductions they see during dry years."

In the Southwest wet years are becoming wetter and dry years are becoming drier because of global climate change. Smith says that makes forests vulnerable to mortality events like forest fires and bark beetle outbreaks. The study appeared in the journal Science Advances.