Regina scientist warns of potential ‘megadrought’

Feb 24, 2012

REGINA — When a drought hit North America in the 1930s, creating a giant dust bowl and crippling agriculture from Saskatchewan to Oklahoma, it entered history as the Dirty Thirties.

But University of Regina paleoclimatologist Jeannine-Marie St. Jacques says that decade-long drought is nowhere near as bad as it can get.

St. Jacques and her colleagues have been studying tree ring data and, at the American Association for the Advancement of Science conference in Vancouver over the weekend, she explained the reality of droughts.

“What we’re seeing in the climate records is these megadroughts, and they don’t last a decade — they last 20 years, 30 years, maybe 60 years, and they’ll be semi-continental in expanse,” she told the Leader-Post by phone from Vancouver.

“So it’s like what we saw in the Dirty Thirties, but imagine the Dirty Thirties going on for 30 years. That’s what scares those of us who are in the community studying this data pool.”

Tree rings provide the perfect historical record for researchers like St. Jacques, because trees are so sensitive to rain fall.

“If it’s a good, wet year then trees have a thick growth band, but if it’s a bad year, then there’s only a thin band,” she said.

“By taking core samples we can get a record in parts of North America going back 2,000 years.

“Everyone was aware of droughts that hit very hard in their area, but it wasn’t until recently when thousands of people pooled their data ... and we all looked around at each other and said ‘Oh my God.’”

The big concern, she says, is that there’s no reason a megadrought won’t hit the continent again.

“When Europeans settled North America ... we know from tree ring records that it was a very wet period, and so people’s sense of what’s normal is probably not correct,” St. Jacques said.

“We’re certainly very scared in the community, because there’s no reason why these things shouldn’t come back.”

Two societies decimated by megadroughts were the Four Corner region — the area where Colorado, New Mexico, Arizona and Utah meet — and Cahokia, in the central Mississippi Valley.

It was one of the first and certainly one of the largest centres in the area, with more than 20,000 people at its peak in 1075.

“(Cahokia) rose, flourished, it was growing and had major cultural impacts throughout the Mississippi Valley and Midwest, but then they got caught by one of these megadroughts,” St. Jacques said.

“Agriculture collapsed. You just can’t go on when something like this hits.”

While it would be nice to predict when a megadrought is going to occur, St. Jacques says that’s just not possible.

“It’s certainly a very lively area of research, everyone’s very curious why they happen, but we see evidence of these droughts throughout the past 2,000 years in North America and we don’t see why it’s going to change,” she said.

“They could get worse under global warming, for all we know. And that’s juts it — we don’t know.”

St. Jacques said her research into megadroughts has hammered home the role politics plays in being prepared.

“You can’t cope with these things, or prepare for them, on an individual level,” she said.

“You’re either going to have to get people out or get aid in, and you need a functioning political system to do that.

“The important thing is to educate people that their sense of a 10-year drought being the worst they could experience, that’s false. It could well be multi-decadal, and that’s why it’s important to keep political and social systems functioning and taking care of everybody.”

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