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Deadly climatic conditions could soon become the norm in most parts of the world, according to a systematic review.
If we do nothing to reduce our greenhouse gas emissions, the authors who conducted the study predict that between 44 and 75 percent of the human population will be chronically heat-stressed by the end of the century. .
Rising temperatures in southern parts of Asia alone will impact an astonishing number of people. A fifth of the world’s population lives around the Ganges and Indus rivers, and in 80 years these areas are expected to experience frequent fatal heat waves above 35 ° C (95 ° F).
Such temperatures can be extremely harmful to humans, especially infants, the elderly, pregnant people, and people with co-morbidities.
It is not us who will suffer either. The authors claim that livestock, poultry, crops and other living organisms will also experience surprisingly similar levels of heat stress.
In 2003, for example, the European heatwave reportedly claimed the lives of 70,000 people across Europe and 24 percent of French livestock. It turns out that was just an omen of what was to come.
“By the end of the century, 45 to 70 percent of the world’s land area could be affected by climatic conditions in which humans cannot survive without technological support, such as air conditioning,” says biologist engineer Senthold Asseng from the Technical University of Munich (TUM) in Germany.
“Currently, it’s 12%. ”
That’s a major increase over a relatively short period of time – far too fast for most organisms to adapt in the long term. Even in the short term, such temperatures can be deadly.
By 2080, Australian cities could experience at least four times as many deaths from rising temperatures alone. In parts of the tropics, researchers predicted in 2019 that heat waves could one day increase the death rate by up to 2,000%.
And it’s just for humans. When the authors of this review compared temperature thresholds for humans, livestock, poultry, crops, and some fish, they found surprisingly similar heat limits for all.
When humidity is high, it is believed that humans are slightly subjected to thermal stress at around 23 ° C. For cattle and pigs, it is around 24 ° C.
On the other hand, when humidity is low, a slight thermal stress reaches about 27 ° C for humans. While for cattle and pigs, stress sets in at 29 ° C.
“If people are exposed to temperatures above 32 degrees Celsius with extremely high humidity or over 45 degrees Celsius with extremely low humidity for a long time, it can be fatal,” says Asseng.
“During episodes of extreme heat with temperatures well above 40 degrees Celsius, such as those currently observed on the northwest coast of the United States and in Canada, people need technical support, for example under the form of air-conditioned spaces.
Crops and livestock do not have this luxury. Even though heat exhaustion does not cause immediate death in pigs, chickens and cattle, frequent exposure is known to reduce their growth, leading to lower yields and delayed reproduction.
Chickens, for example, reach severe heat stress at 37 ° C, at which point they begin to lay significantly fewer eggs.
Under heat stress, dairy cows can produce up to 20% less milk.
Wildlife could be affected in the same way, although it was beyond the scope of this particular review. However, the authors note that the 2018 heat wave in Australia killed a third of a bat population in just two days.
“Continued global warming will gradually become fatal for other species if they cannot avoid, migrate, or protect themselves from extreme or prolonged heat stress,” write the review authors.
“If the current trajectories towards a so-called greenhouse land continue, most of the creatures discussed in this personal view, and many others, could be severely affected or could disappear altogether.”
The review was published in The Lancet’s planetary health.
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