Projected increases in temperature and in the frequency and severity of droughts imply substantial tree mortality in Amazonian forest. With higher temperatures, plants need more water to survive, and many trees would not resist these combined stresses. Higher temperatures also lead to more forest fires, which set in motion a vicious cycle that leads to still more fires and destroys the forest. Invasion of forest by lianas and bamboos is also favored. These phenomena are already spreading in Amazonia. Dead trees from previous droughts, previous fires, or from logging damage make Amazonian forest fires both more likely and more damaging when they occur. With respect to average global temperatures, 2˚C above the global pre-industrial mean is probably beyond the temperature "tipping point" for Amazonian forest.