The drought in southern Britain is a reminder of how much we take rain for granted. In fact, drought has probably been responsible for the downfall of more civilisations throughout history than any other single natural disaster.
One of the most spectacular collapses was that of the Mayan civilisation about 1,000 years ago. Despite all their skills in mathematics, farming, architecture and water management, the Mayas abandoned their cities and returned to a life in the jungles.
Exactly why their civilisation collapsed is disputed, but many experts blame a drought spanning 100 years or more. A recent study published in Science has traced the rainfall in the Yucatan from AD800 to 1000, the end of Mayan dominance. This revealed clusters of years with poor rainfalls — but these were fairly short periods of mild drought, only 20 to 40 per cent below normal rainfall, and often ended in very wet spells. So the shortage of rain was fairly modest.
Scientists at the University of Southampton used records of past climate changes gleaned from stalagmites in caves and sediments in shallow lakes. These revealed a lack of summer rainfall. “Summer was the main season for cultivation and replenishment of freshwater storage and there are no rivers in the Yucatan lowlands,” the scientists said. “Societal disruptions and abandonment of cities are likely consequences of critical water shortages.”
The puzzling thing is that the Mayas should have coped because they used an elaborate system for storing rainwater. Perhaps, though, they relied too heavily on rainfalls to replenish their supplies, and when the rains were less plentiful it caused water shortages, possibly drying up their irrigation systems that led to chronic food shortages. “The warning is clear. What seems like a minor reduction in water availability may lead to important, long-lasting problems,” the scientists concluded. The problem is that in Britain we may also be relying too heavily on decent rainfalls to keep us well watered.