The American Southwest has started its predicted shift into a drier climate. A recent study concluded that nearly all needleleaf evergreen trees in the region will die by 2100 because of the combined effects of prolonged drought and climate change.

The prediction covers the forests of Utah, Arizona, Colorado and New Mexico. The research team from the University of Delaware utilized various scenarios and models in the study, including the carbon emission limits set during the Paris climate change conference in late 2015.

"And even with those sort of reduced CO2 emissions, or those reduced scenarios, we still see die off occurring by the end of this century. It's just delayed by a decade or so," says Sara Rauscher, one of the researchers and an assistant professor of geography at the University of Delaware's College of Earth, Ocean, and Environment.

The findings imply that by 2050, 72 percent of the area's forests will perish and by 2100, all of the evergreen forests in the Southwest will die. Rauscher said the predicted forest demise is already visible in the region, for instance, there are already several red trees in Colorado.

Some trees in remote areas could survive because of the micro-climate in which they thrive. For example, the heat is not as intense in higher, elevated areas or on a mountain's north side where it's slightly cooler. The slight difference in climate can help save these trees from the predicted extinction.

"No matter how we investigated the problem, we got the same result. This consensus gives us confidence in this projection of forest mortality," adds Rauscher.

The researchers noted that they did not factor in the possibility of insect plagues and forest fires that could affect their predictions for the worse. Notably, they are not certain if the trees could eventually adjust to the increased drought.

Still, the loss of Southwest trees come with devastating effects. Trees absorb carbon dioxide from the atmosphere and release it upon death, resulting in increased warming.

The research was published in the journal Nature Climate Change.

Photo: Ken Lund | Flickr