Not Easy Being Trees

Southwestern states may lose all of their pine and juniper trees by 2100, according to research recently published in Nature Climate Change.

"We have been uncertain about how big the risk of tree mortality was, but our ensemble of analyses—including experimental results, mechanistic regional models and more general global models—all show alarming rates of forest loss in coming decades," Nate McDowell, a forest ecologist at Los Alamos National Laboratory and lead author of the paper, said in a press release.

McDowell studied piñón-juniper forests in New Mexico and simulated drought-like conditions by depriving trees of 50 percent of rainfall for five years (a 2012 NPR story described the project as a tree torture lab where trees are killed to better understand how to save them). Eighty percent of mature trees in the area died.

The study also ran computer models based on predicted global warming scenarios, and while those led to different precipitation patterns, they consistently produced widespread tree death. The average of the results of those models predicts 72 percent of the region's needleleaf evergreen trees will die by 2050, and nearly 100 percent will be gone by 2100.

New Mexico will likely be joined by California, Colorado, Utah and Texas, among others, in losing millions of acres of forests. Throughout the Northern Hemisphere, more than half of conifers are expected to be dead by 2100.

The study was unable to account for the possibility of vegetation adapting to warmer or drier conditions, or the increase in wildfires, or the effects of insect populations on seedlings. Its calculations were also based on the worst-case scenario: that humans continue burning fossil fuels at their present rate.

Santa Fe Reporter