American southwest hit hard by climate change

Climate change will severely affect water supplies in major agricultural regions in the US. Cotton farmers will be the hardest hit, finds a new study. The US could face a 0.7% drop in GDP for every half a degree increase in temperature. John Dyer reports from Boston.

Climate change could deplete water basins in some parts of the US, dramatically reducing crop yields by 2050. (Image credit: Carl Wycoff, flickr/Creative Commons)

Growing cotton in Arizona and the southwestern US will become more and more difficult as climate change makes the region drier, according to American and Canadian researchers.

The Massachusetts Institute of Technology, or MIT, and University of Montreal researchers’ study published on Wednesday in the journal Earth’s Future foresees severe reductions in agriculture due by 2050 to water shortages and other problems.

Cotton and other crops will be affected

“In the Southwest, water availability for irrigation is already a concern,” said the study’s lead author, Elodie Blanc, a scientist at MIT’s Joint Program on the Science and Policy of Global Change. “If we mitigate, this could prevent added stress associated with climate change and a severe decrease in runoff in the western United States. But it will be even worse in the future if we don’t do anything at all.”

The American Southwest’s cotton crop would decrease by 10 per cent, the study predicted. Corn yields in the region would drop by the same amount. Hay and other feed for livestock is also set to suffer.

But the scientists noted that sorghum and soybean grown in Kansas and other states in the southern Plains would likely improve as more rain fell on that region.

The researchers applied a model that prognosticates economic, demographic, commercial and technological trends to 99 river basins in the US.

“We’re looking at a more integrated world, and how all these interactions will drive changes in irrigation,” said study co-author and MIT researcher Erwan Monier.

Partly funded by the U.S. government, the study illustrates how researchers have mapped out climate change’s trajectory as the effects of the phenomenon – more drastic swings in the weather, rising sea levels and other changes – become clearer, said Monier.

“The biggest finding is that it really makes a difference in specific regions, whether you take into account how irrigation availability will change in the future and how that will impact yields,” Monier said.

Massive financial losses predicted

Other recent research has suggested similar conclusions.

On Monday, a team of American, Chinese and South Korean scientists published a study in the journal Nature Geoscience that found that warmer temperatures in the Arctic Ocean led to colder temperatures in the US, particularly in the South.

“Crop success depends on a complicated interplay between temperature, precipitation amount, and even timing of snowmelt, and it appears from this work that recent Arctic warming may be disrupting normal patterns,” said Rutgers University Atmospheric Scientist Jennifer Francis, who was not involved in the study but is an expert in Arctic climate patterns.

Late last month, American researchers put a price tag to the changes, saying milder weather might improve the economy in northern states like Maine but harm Florida and other southern states.

The US could face a 0.7 per cent drop in gross domestic product by the 2080s for every 0.56 degrees Celsius temperature increase, according to the study published in Science. In 2015 figures, that’s equivalent to USD 125 billion.

In Arizona, Texas, Florida and Southern California, losses could rise to as much as 20 per cent of GDP, however, in part due to expected deaths during intense heat waves.

“The reason for that is fairly well understood: A rise in temperatures is a lot more damaging if you’re living in a place that’s already hot,” said University of California, Berkeley Public Policy Professor Solomon Hsiang, the study’s lead author.

California fears rising sea levels

The effects of climate change on California alone could be catastrophic.

Golden State officials are worried that salt water could pollute the Sacramento-San Joaquin Delta that feeds the aqueduct that irrigates the state’s Central Valley, one of the most productive agricultural regions in the world.

“With rising sea levels, with climate change, that creates additional pressure coming in from the ocean,” said California State Climatologist Michael Anderson. “Sea level rise is going to become more of an influence.”

The MIT and University of Montreal researchers are now looking further into how the agricultural sector might change as irrigation patterns shift, said Monier.

“In the real world, if you’re a farmer and year after year you’re losing yield, you might decide, ‘I’m done farming,’ or switch to another crop that doesn’t require as much water, or maybe you move somewhere else,” he said. “That’s the next step: How would the agricultural sector adapt?”

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