At what temperature does the climate become a problem?


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When extreme heat becomes more frequent and temperatures remain high for extended periods of time, as is currently the case in Canada and the American Northwest, physiological stress increases in humans, animals, and crops. Professor Senthold Asseng, director of the World Center for Agrarian Systems at the Technical University of Munich (TUM), provides an overview of thresholds and adaptation strategies.

“We have studied which temperatures are preferable and which are harmful in humans, cattle, pigs, poultry and in agricultural crops and we have found that they are surprisingly similar,” says Senthold Asseng, professor of Digital Agriculture at TUM. According to the study, preferable temperatures range from 17 to 24 degrees Celsius.

When is it too hot for humans?

High humidity, mild the strain for humans begins at about 23 degrees Celsius and a low humidity at 27 degrees Celsius. “If people are exposed to temperatures above 32 degrees Celsius at extremely high humidity or above 45 degrees Celsius at extremely low humidity for a long period of time, it can be fatal,” says Professor Asseng. “Durant with temperatures well above 40 degrees Celsius, such as those currently observed on the northwest coast of the United States and Canada, people need technical support, for example in the form of air-conditioned spaces. “

To mitigate the increase in heat stress, Professor Asseng cites a variety of strategies, including increasing the natural shade of trees or structural shading. More cities and buildings can be made -passive, for example, by using wall or ceiling insulation or by lighter, reflective colors of ceiling and wall to reduce thermal pressure.

How do high temperatures affect livestock?

In cattle and pigs, the thermal stress occurs at 24 degrees Celsius and at 29 degrees Celsius with little humidity. Milk yield of cows can decrease by 10 to 20 percent when exposed to heat stress, and fattening yield in pigs is also reduced. The comfortable temperature range for poultry is 15 to 20 degrees. Chickens experience a mild thermal stress at 30 degrees Celsius. At 37 degrees Celsius and above, they experience severe thermal stress and the rate of egg laying decreases.

General thermal stress leads to a reduction in the growth of cattle and , pigs, chickens and other livestock, which means lower yield and reproductive yield. “There are examples of evolutionary adaptations to warm climates in terrestrial mammals. Transylvanian naked chickens are more heat tolerant than other chicken varieties due to a complex genetic mutation that suppresses feather growth. They are naturally conditioned because they have no feathers on their necks, ”says Professor Asseng.

How do crops react to high temperatures?

“In crops, the optimum temperature zone and temperature thresholds appear to be more diverse due to differences between species and varieties,” explains Professor Asseng.

Cold tempered crops, such as wheat, for example, work best in colder temperatures, while warm-temperature crops, such as corn, are sensitive to frost, but can tolerate warmer temperatures. Strategies to reduce heat stress include changes in planting dates to avoid heat stress later in the season, watering (if possible), switching to more heat-resistant crops, and breeding to increase heat tolerance.

How does climate change affect life on Earth?

“By the end of the century, 45 to 70 percent of the world ‘s land surface could be affected in which humans cannot survive without technological support, such as air conditioning. It’s currently 12 percent, “says Professor Asseng. This means that in the future, between 44 and 75 percent of the human population will be chronically stressed by the heat. is expected for livestock, poultry, and other living organisms.

“Genetic adaptation to a changing climate usually takes many generations. The time available is too short for many higher life forms. If current climate trends persist, many living things could be severely affected or even disappear completely from the climate. Earth due to temperature change “. concludes Professor Asseng.

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More information:
Senthold Asseng et al, The upper thresholds of life temperature, Planetary Health Lancet (2021). DOI: 10.1016 / S2542-5196 (21) 00079-6

Citation: At what temperature does the climate become a problem? (2021, July 2) Retrieved July 2, 2021 from

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