Chronic drought to become commonplace, scientists warn
Published Monday, July 30, 2012 11:21AM EDT
Last Updated Monday, July 30, 2012 10:42PM EDT
The four-year-long drought that affected western Canada and the U.S. at the turn of the century was the worst to hit the region in 800 years, say scientists who warn that dry spell was nothing compared to the “megadroughts” still to come.
A group of 10 scientists from the University of British Columbia as well as several American universities write in Nature GeoScience that they believe the bone-dry conditions seen between 2000 and 2004 could become the “new normal” in the region.
They say that climatic extremes have increased because of global warming. And as bad as conditions were during the 2000-04 drought, that drought won’t be as severe as the “megadrought” they expect to see during the last half of the 21st century.
“Projections indicate that drought events of this length and severity will be commonplace through the end of the 21st century,” the group of scientists writes.
“Even worse, projections suggest that this drought will become the wet end of a drier hydroclimate period.”
For their research, the scientists looked at historical drought data based on tree-ring analysis. Rings in a tree’s trunk reflect the amount of growth in a given year: wide rings indicate years with good moisture and extensive growth, while narrow rings suggest periods of extreme climactic change and drought.
Based on that data, the scientists say the 2000-04 drought was unlike any since the period between 1146 and 1151.
What’s more, the 2000-04 drought may have made climactic conditions in the region even worse. As trees, crops and vegetation of all kinds dried up and died in those years, the land lost 51 per cent of its ability to capture or “sequester” carbon dioxide.
That means more carbon dioxide was released into the atmosphere in those regions, worsening the problem.
"During this drought, carbon sequestration from this region was reduced by half," Beverly Law, a co-author of the study, professor of global change biology and terrestrial systems science at Oregon State University, said in a statement. "That's a huge drop. And if global carbon emissions don't come down, the future will be even worse."
Many parts of the western and Midwest U.S. are once again facing a drought that’s being called one of the worst since the Dust Bowl.
Last week, the U.S. Department of Agriculture said 45 per cent of the country’s corn crop is in poor or very poor condition. Soybeans are also being hard hit, with more than a third in poor or very poor condition.
It’s unclear whether this current drought is related to these same forces that controlled the 2000-04 drought, Law said, since this study did not look at this most recent period.
But she says her team is certain that droughts are going to continue and worsen, leading to the deaths of large swaths of forest.
"Areas that are already dry in the West are expected to get drier," Law said.
"We expect more extremes. And it's these extreme periods that can really cause ecosystem damage, lead to climate-induced mortality of forests, and may cause some areas to convert from forest into shrublands or grassland."