by Chloe Rodman
Jeff Tietz (2015) reports for Rolling Stone magazine on the work postdoctoral student Park Williams has been conducting in the past decade. After surveying thousands of trees, Williams created the forest-drought stress index, which determined that, due to climate change, the average forest stress caused by drought will, by 2050, surpass what it has been in the past 1000 years. Conifer forests in the Southwest United States will die, along with many other species across the globe.
Trees are very important in mitigating climate change. Of the 36 billion tons of carbon dioxide gas that we send into the atmosphere each year, trees absorb 25%, while the ocean absorbs an additional 25%. However, in a warming world, trees are beginning to die more frequently. To trees, excessive heat is equivalent to a lack of water, so as the climate warms, trees begin to dry out and die. When trees dry out, they produce less of the sap that helps keeps insects away. Global warming will therefore result in an infestation of insects and wildfires due to the dried out trees. These insects, such the bark beetle, and fires kill trees in addition to the ones that are already dead, which is a major problem because dead trees release the their stored carbon dioxide into the atmosphere. This starts a vicious cycle; forests die, not only taking less carbon out of the air but also emitting carbon dioxide into the atmosphere. This addition of new carbon dioxide aids in global warming, resulting in higher temperatures. These higher temperatures cause more forests to die and the cycle repeats itself.
Forest fires will cause a whole other problem on their own. They are predicted to burn more frequently and severely in the north due to the continuous temperature increase. The soot and ash from forest fires settle over the Arctic permafrost causing it to turn black and absorb solar radiation from the sun. Climate change is already causing this permafrost to melt, releasing huge quantities of carbon dioxide and methane into the atmosphere, and because of soot deposition, the solar radiation absorption is speeding up the process.
Scientist do not believe the world will be barren of trees however. They predict that with every degree Celsius that the world warms, global rainfall will increase by two percent. This means that already wet areas will still thrive. However, as for the moderate-to-dry regions of the world, trees are expected to die at an increasing rate because the evaporation of water will be too great for forests to handle. Forests will be replaced with more water-efficient grasses and shrubs and the landscape will look completely different from how it appears now.
Tietz, J. 2015. The Fate of Trees: How Climate Change May Alter Forests Worldwide. Rolling Stone. http://www.rollingstone.com/politics/news/the-fate-of-trees-how-climate-change-may-alter-forests-worldwide-20150312