19 February 2000
by Kate Melville
Water is something people living in cities generally take for granted, but they shouldn't. As their rural counterparts know very well, insufficient rain can make life very miserable indeed. Recently we have been looking at the impact of weather phenomena such as El Niño and La Niña, but history shows that these events may have been insignificant compared to previous droughts.
A new study by researchers from Arkansas, Arizona, Western Ontario and Valdosta State universities highlights evidence of a "mega-drought" in the 16th century. This event is believed to have impacted on the lives of the early Spanish and English settlers and American Indians throughout Mexico and North America for decades.
The researcher team's findings are based on an analysis of drought-sensitive tree ring chronologies from trees in Great Lakes, North West and the Southeast USA. They established that dry conditions extended from the Mexico and the Rocky Mountains and the Mississippi Valley throughout the last half of the 1500s.
Researchers looked back as far as A.D. 1200, and found no indication of a drought ever having been as long-drawn-out and pervasive as the 16th century megadrought.
Tree ring analysis in not new but the sophistication scientists can now use with computersied equipment and data processing has advanced research enormously over the last decade. Tree cells vary between spring and summer researchers can by analysisng pencil-thin core samples from living trees build up a picture of a region's climatic history. Data from tree rings and weather reports for the last 100 years are then modeled against the older tree ring information to reconstruct the past climate of North America and Mexico.
According to David Stahle, professor of geosciences at the University of Arkansas, "Drought is the most severe natural disaster. Year-in and year-out, over the long haul, drought extracts the most from humanity."
The tree ring records indicate that the drought lasted up to 40 years and records from early English and Spanish settlements tend to confirm these findings. For example records from the Spanish colony of Santa Elena on Parris Island, South Carolina indicate a drought which lasted from 1566-69. The Parris Island colony was abandoned and the tree ring records clearly show that this was the region's worst drought in 800 years!
"If there's any lesson to be taken home from the paleo-record, it's that we need to conserve our water resources. It would help prepare us for the inevitable return of drought," Stahle said.
Interestingly the researchers believe that the mega drought was probably linked to ocean currents, as the drought-affected area looks very similar (but on a much larger scale) than today's La Niña climate phenomenon.
Stahle thinks that cold ocean currents from the equatorial Pacific may have caused the mega drought, "This drought was not a consequence of global warming. We don't know what caused it. The factors that did cause it could return," Stahle said.
To put this research into perspective Stahle says, "If such a drought were to occur today, it would wipe out certain agricultural activities. It would change economic activities on the land. And it would put enormous stress on water resources. This would have a dramatic effect on society."
So next time you leave the tap running while you clean your teeth, just remember the water you waste today may not be there next year, or the year after, or the year after that.....................