August 1st, 2012 by

The U.S. Forest Service estimates that the world’s forests sequester 2-2.8 billion metric tons of carbon annually. A new study published in Nature Geoscience indicates that evergreen forests ranging from northern Mexico to Canada took up a lot less carbon dioxide from the atmosphere during a 2000-2004 drought period, dropping 30-293 million metric tons below normal levels. And, according to the study, this might just be the beginning: Forests in the western U.S. could be facing a 100-year drought.

Just check out this map that shows the current drought situation in the U.S. The destructive impacts of drought are clear with this year’s catastrophic wildfires in Colorado and the ones happening now in Texas, Utah and California. But drought has even longer term impacts that will last longer than one hot, dry summer season. Severe drought may actually convert western evergreen forests into scrubland by the end of the century.

Trees, like all living things, need water to be healthy and functional. I know that I certainly don’t feel well when I’m dehydrated. When trees don’t get enough water, it greatly impairs their ability to sequester carbon dioxide from the atmosphere. Water helps facilitate the leaf development process and the greater the leaf surface area, the greater the ability to sequester carbon. Also, as trees die, the carbon dioxide that is stored within them is released back into the atmosphere. This is bad news not only for forest ecosystems, but the atmosphere.

The research team at Northern Arizona University School of Earth Sciences and Environmental Sustainability that led the Nature Geoscience study thinks that drought may become the new norm. Researcher Christopher Schwalm said the current trends of extreme temperature and droughts could last decades or even a century as a result of global climate change; and drought is just one of the many impacts we have started to see as a result of global climate change. Schwalm noted that although trees are somewhat amenable to change, the type of forests we see in the western U.S. could drastically change over the next century thanks to drought conditions.