Life is already bad enough for underpaid and overworked crop pickers in the US, but as lethal heat levels rise they will render outdoor labour in the harvest season increasingly impossible.
The men and women who gather melons and strawberries, nuts and grapes, onions and lettuce already find conditions too hot to handle on at least 21 days a year.
By 2050, US agricultural workers will meet unsafe daytime summer temperatures on 39 days each harvest season. And by 2100, this number could triple to 62 unsafe days, according to new research.
Unsafe means that the levels of high thermometer readings and high humidity outdoors could put field workers at risk of heat exhaustion, heat stroke, heat cramps, dehydration, potential kidney injury and even death.
There are roughly one million people in the US officially employed picking crops in states such as Oregon, California, Washington and Florida. The actual number however is estimated to be two million.
“You don’t have to go to the global south to find people who will get hurt with even modest amounts of global warming – you just have to look in your own backyard”
More than three-quarters of them are foreign-born, many from Mexico. Only about half of these have lawful authority to work in the US. Of these, 71% do not speak English well, and on average educational levels are low. Fewer than half have medical insurance, and one third of the families of agricultural workers live below the poverty line.
Their housing and sanitary conditions are often not good, they are often paid on the basis of crops picked, so that to survive they must neglect breaks and work for longer, and they are often deprived of shade, according to data compiled in the journal Environmental Research Letters.
High summer extremes are a hazard, and can cause death on a significant scale. Climate scientists have established that by the century’s end, more than a billion people worldwide will be placed in danger of summer extremes, and the risks are growing.
One enterprising group has even numbered 27 ways in which high temperatures and high humidity can kill. Economists have already counted the price paid in falling productivity in severe conditions in Australia, and – since fruit tends to ripen as the thermometer rises and must be picked at the right moment – the hazards faced by grape-pickers in the world’s vineyards.
When Michelle Tigchelaar began her study of the climate impacts, she was at the University of Washington. She is now at Stanford University in California.
She and colleagues simply followed the climate projections and the impact rising global average temperatures will have on the intensity, frequency and duration of heat waves, and found that with a 2°C rise, expected by 2050, the level of unsafe days leapt from 21 to 39. At 4°C – and there is a high risk on present trends – then unsafe conditions could by 2100 reach 62 days.
“I was surprised by the scale of the change – seeing a doubling of unsafe days by mid-century, then a tripling by 2100. And we think that’s a low estimate,” Dr Tigchelaar said.
“The people who are the most vulnerable are asked to take the highest risk so that we, as consumers, can eat a healthy nutritious diet.”
And her co-author David Battisti of the University of Washington said: “The climate science community has long been pointing to the global south, the developing countries, as places that will be disproportionately affected by climate change.
“This shows that you don’t have to go to the global south to find people who will get hurt with even modest amounts of global warming – you just have to look in your own backyard.”
By Tim Radford
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