According to a systematic review, dangerous climate conditions could soon be the norm in many parts of the globe.The review authors predict that between 44 and 75% of the world's population will be suffering from heat stress if we don't do anything to reduce greenhouse gas emissions.A staggering number of people will be affected by rising temperatures in the southern regions of Asia. One fifth of the world's population lives near the Ganges or Indus Rivers. In 80 years, these areas will experience deadly heatwaves that exceed 35C (95F) annually.These temperatures can cause severe harm to people, particularly infants, elderly, pregnant women, and those with comorbidities.It is not only us who will be affected. According to the authors, heat stress will affect livestock, poultry, crops and other living organisms in surprising ways.For example, in 2003, the European heatwave claimed the lives and cattle of approximately 70,000 people in Europe. It turned out that this was a sign of things to come.Senthold Asseng, a German biological engineer, says that climate conditions could affect 45 to 70% of the world's land. Without technological support like air conditioning, humans will not be able to survive."Currently, it is 12 percent."This is a significant increase in temperature in a short time. It's too fast for organisms to adjust to long-term. These temperatures can prove fatal even in the short term.Australia's cities could see at least four times as many deaths due to rising temperatures by 2080. Researchers in 2019 forecasted that heatwaves could increase mortality rates by as much as 2,000 percent in some parts of the tropics.This is just for humans. The current review found that all heat thresholds were similar when it came to humans, livestock, poultry and crops.Humans are mildly heat-strained when humidity is high. This is around 23C for humans. It's around 24C for cattle and pigs.However, mild heat strain for humans can occur at around 27C when the humidity is low. For cattle and pigs, stress begins at 29C.Asseng says, "If people are exposed for prolonged periods to temperatures exceeding 32° Celsius at very high humidity or above 45° Celsius at very low humidity, it can prove fatal.""In extreme heat events, where temperatures exceed 40 degrees Celsius, like those occurring on the US Northwest Coast or in Canada, people need technical support. This can be in the form of air-conditioned areas.Crops, livestock and other animals don't have this luxury. Even though heat exhaustion does not cause immediate death in pigs or chickens, it is known that frequent exposure can reduce their growth and lead to lower yields as well as stunted reproduction.For instance, chickens reach extreme heat stress at 37C at which time they start to lay significantly fewer eggs.Dairy cows can produce as much as 20 percent less milk when they are under heat stress.However, wildlife could also be affected. This was not covered in this review. The authors do note that Australia's 2018 heatwave resulted in the death of a third (of one) bat population within two days.The review authors write that "Continued global heating will gradually become fatal to other species if it is not possible for them to avoid, migrate or protect themselves from extreme or prolonged temperature stress.""If the current trajectories towards so-called hothouse Earth continue, many of the creatures discussed in this Personal View could be severely affected, or even disappear entirely."The Lancet Planetary Health published the review.
