Dust Bowls

Excerpts from:

Joseph Romm. 24 May 2012. My Nature Piece On Dust-Bowlification And the Grave Threat It Poses to Food Security.

Human adaptation to prolonged, extreme drought is difficult or impossible. Historically, the primary adaptation to dust-bowlification has been abandonment; the very word ‘desert’ comes from the Latin desertum for ‘an abandoned place’. During the relatively short-lived US Dust-Bowl era, hundreds of thousands of families fled the region.

Dust-Bowl conditions could stretch all the way from Kansas to California by mid-century. America’s financial future and the health and safety of our people are at serious risk…The food security of all of humanity is at risk.

Which impact of anthropogenic global warming will harm the most people in the coming decades? I believe that the answer is extended or permanent drought over large parts of currently habitable or arable land — a drastic change in climate that will threaten food security and may be irreversible over centuries.

The palaeoclimate record dating back to the medieval period reveals droughts lasting many decades. But the extreme droughts that the United States faces this century will be far hotter than the worst of those: recent decades have been warmer than the driest decade of the worst drought in the past 1,200 years.

To make matters worse, the regions at risk of reduced water supply, such as Nevada, have seen a massive population boom in the past decade. Overuse of water in these areas has long been rife, depleting groundwater stores.

Of course, the United States is not alone in facing such problems. Since 1950, the global percentage of dry areas has increased by about 1.74% of global land area per decade. Recent studies have projected ‘extreme drought’ conditions by mid-century over some of the most populated areas on Earth—southern Europe, south-east Asia, Brazil, the US Southwest, and large parts of Australia and Africa. These dust-bowl conditions are projected to worsen for many decades and be “largely irreversible for 1,000 years after emissions stopped.”

Most pressingly, what will happen to global food security if dust-bowl conditions become the norm for both food-importing and food-exporting countries? Extreme, widespread droughts will be happening at the same time as sea level rise and salt-water intrusion threaten some of the richest agricultural deltas in the world, such as those of the Nile and the Ganges. Meanwhile, ocean acidification, warming and overfishing may severely deplete the food available from the sea.

From an ecological perspective, what will be the effects of dust- bowlification on the global carbon cycle? In the past six years, the Amazon has seen two droughts of the sort expected once in 100 years, each of which may have released as much carbon dioxide from vegetation die-off as the United States emits from fossil-fuel combustion in a year. More frequent wildfires also threaten to increase carbon emissions. And as habitats are made untenable, what will be the effect on biodiversity?

“Drought conditions will prevail no matter what precipitation rates are in the future,” said  Michael Wehner, a climate scientist at the Lawrence Berkeley National Laboratory.  “Even in regions where rainfall increases, the soils will get drier. This is a very robust finding.”

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