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Advanced machinery has revolutionised agriculture but many tasks, like the harvesting of soft fruit and vegetables, are still done by hand. Manual pickers can select and handle ripe produce more precisely, which minimises damage, while machines require a lot of upfront investment.
But in a warming world, farm labour has its own cost in the form of heat stress and dehydration, which can lead to fatal strokes and kidney failure. Data from the EU's Earth Monitoring Programme show that the seven years preceding 2022 were the hottest on record. According to one report, at least 65 workers died from heat-related illness on US farms between 2002 and 2021. Another study concluded that American crop workers were 20 times more likely to die as a result of heat stress than other civilian employees.
The average number of unsafe summer working days in the US is expected to double by 2050. The threat is worse in Southern Asia and Western Africa where the impact of global warming on human health and productivity is expected to be most extreme. The accumulated global cost in terms of output and working days lost due to heat stress is estimated to reach $2,400bn by 2030, according to the International Labour Organisation.
Some countries have enacted heat illness prevention legislation. California was the first US state to bring in a raft of rules to protect outdoor workers in 2005. On days above 26 degrees celsius, employers have to provide open air or ventilated shade for workers during rest periods. When temperatures rise above 35 degrees, workers must have regular breaks and reminders to drink water and need to be monitored by a supervisor or fellow workers for signs of heat stress.
Since the rules came into force, the number of reported fatalities from environmental heat exposure in California has fallen from 10 in 2005 to three in 2019. A new federal standard to combat heat hazards across the US is currently in the works. But campaigners say many farm workers, especially immigrants, may be afraid to raise concerns for fear of losing their jobs. They also worry that doctors are unaware of or may fail to recognise the long-term damage from repeated exposure to heat stress, an ongoing threat from millions of agricultural labourers around the world.