04 Mar 2011:
As CO2 Levels Have Risen,
Plants Are Releasing Less Water, Study Says
A study of plant samples from the past 150 years shows that as atmospheric concentrations of carbon
dioxide have steadily increased, the density and size of pores that allow plants to breathe has decreased, also reducing the plants’ transpiration of water
. The undersides of leaves contain pores, or stomata, that enable plants to absorb CO2 and release water into the air. When researchers at Indiana University and Utrecht University in the Netherlands examined leaves from Florida herbarium collections dating back 150 years, and compared them with leaves from the same plant species today, they found that the density of stomata has decreased 34 percent, presumably because greater atmospheric concentrations of CO2 have enabled the plants to absorb sufficient CO2 with fewer pores. That decrease in stomata has led to a “huge reduction in the release of water into the atmosphere,” said one of the researchers. These change have occurred as atmospheric concentrations of CO2 have risen from about 290 parts per million to 390 million today. Should CO2 concentrations double in the future, the researchers — reporting in the journal Proceedings of the National Academy of Sciences
— said that the amount of water released by plants could be cut by half, which would have a profound impact on the global hydrological cycle.
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Tribal people and ranchers join together to stop a project that would haul coal across their Montana land. Watch the video.
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An aerial view of why Europe’s per capita carbon emissions are less than 50 percent of those in the U.S. View the photos.
Ugandan scientists monitor the impact of climate change on one of Africa’s most diverse forests and its extraordinary wildlife. Learn more.
video series looks at the staggering amount of food wasted in the U.S. – a problem with major human and environmental costs. Watch the video.
video goes onto the front lines with Colorado firefighters confronting deadly blazes fueled by a hotter, drier climate. Watch the video.
A three-part series Tainted Harvest
looks at the soil pollution crisis in China, the threat it poses to the food supply, and the complexity of any cleanup. Read the series.