According to the 2007 United Nations Global Climate projection, greenhouse gases could accumulate at rates that could effect a 3-5 degree Celsius increase in temperature by the year 2100. What would a rise of 4° Celsius mean to the world in 90 years?
According to experiments conducted at the University of Arizona’s Biosphere 2, the 4° Celsius increase in temperature could trigger large-scale vegetation changes in a very short time. Scientists studying the pinyon pine trees of New Mexico have identified two global warming effects that threaten their survival: drought and carbon starvation.
Global Warming and Drought
Climate scientists have predicted that as temperatures rise, so will the risk of forest fires, droughts and flooding for the next 200 years. Even if emissions from greenhouse gases are stopped now, researchers predict that major areas in eastern China, Canada, Central America and Amazonia will be at risk of forest loss. Unusually intense droughts will be the norm rather than the exception.
To study the effect of heat on the drought tolerance of trees, researchers at Biosphere 2 relocated 20 mature pinyon pine trees to the Arizona desert near Tucson. They placed these trees in two areas, one with conditions resembling those of New Mexico, the other with a temperature higher by 4° Celsius. Researchers stopped watering half of the trees in both areas.
The results came as no surprise. The trees in the warmer area died 30 percent faster on average than trees in the control area, presenting a dire outlook for trees and vegetation in general under global warming.
Carbon Starvation and a World Without Trees
Why do trees die in high temperatures? According to Biosphere 2 director, Travis Huxman, the main cause for tree death under drought conditions is carbon starvation. To prevent water loss, pinyon pine trees close the pores in their pine needle leaves, shutting off all access to carbon dioxide in the atmosphere. They die from carbon starvation which occurs when their carbon store is depleted. Scientists have been reporting that rates of tree death have increased dramatically in the last few years, particularly in the western parts of the United States and in the Amazon forest.
The mechanism behind carbon starvation is also the reason why the Amazon forest has sharply reversed decades of carbon absorption since the 2005 drought. Under normal conditions, the Amazon forest absorbs nearly 2 billion tons of carbon dioxide per year. The 2005 drought triggered carbon starvation in the trees and an excess of 3 billion tons of CO2 in the atmosphere.
Ecological changes have already been triggered by an estimated 0.6°Celsius rise in global temperature over the past 100 years. Already frog species are disappearing at an unprecedented rate; mosquitoes, on the other hand, are thriving in warmer temperatures resulting in an increase in malaria epidemics in parts of Africa. Corals on the Great Barrier Reef are being bleached by acidic seas; marine life and mangrove trees are vanishing.
What will a world without trees mean in 90 years?
No trees, no birds, no animals, no man.
Just dust and a burning sun.
University of Arizona. "Global Warming: Heat Could Kill Drought-stressed Trees Fast." ScienceDaily 15 April 2009. 4 May 2009 <http://www.sciencedaily.com /releases/2009/04/090413180535.htm>.
University of Bristol. "More Fires, Droughts And Floods Predicted." ScienceDaily 17 August 2006. 4 May 2009 <http://www.sciencedaily.com /releases/2006/08/060816083231.htm>.
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