Facing the heat: The impact of high temperatures on farm workers, livestock and crops

After months of rain, we’d all welcome sunshine. Farmers most of all.

But there is such a thing as too much sunshine.

Persistent high temperatures gravely affect agriculture as we learned after heatwave after heatwave last summer. (1)

The optimal temperature for humans is between 15°C-20°C. If working outside, as many agri-workers do, people start to suffer heat effects from 27°C, with dangerous conditions coming at any higher temperatures — more so under humid conditions; see table below:

Living in many cities will become increasingly difficult. Already, the average summer temperature in 150 of the world’s megacities is 35°C; i.e. dangerous to human life.

David Wallace-Wells estimates there will be 1.6 billion people living in 950 megacities across the world by 2050 at the current rate — each with summer temperatures of more than 35°C.

Note, too, Europe is heating up at twice the rate of everywhere else outside the Polar regions.

We can therefore expect more frequent and severe extreme weather events affecting all food production, storage and distribution across the continent; see this UN explainer.

The effect of rising temperatures on livestock and crops
All animals, including reptiles and sea creatures, begin to suffer as the ambient temperature gets higher.

Like us, other warm-blooded animals, start to suffer heat stress in upper 20s°C, with potentially lethal consequences as the temperature edges upwards from there.

Many plants don’t thrive in hot conditions, either. Staple crops start to suffer at 30°C, affecting yields. As the temperature rises, the yields are non-linear, with losses on some crops, including wheat, of 4% for each degree above 32°C. Into the high 30s and 40s°C, they wither, possibly die, and more quickly under drought conditions.


How rapidly is the temperature rising?
EU Copernicus data shows that March was the tenth month in a row to be the hottest on record:

Perhaps even more concerning is the record rises in the sea surface temperatures:

Sea surface temperatures have risen by unprecdeneted wide margins (see above).

This will gravely weaken the oceans’ capacity to absorb heat and to redistribute it and freshwater and carbon, too, adding to marine acidification and eutrophication — and ice melt.


On 29th March, the Guardian’s Paul Brown published this article about the data Copernicus is publishing for us all to see: Copernicus on-line portal offers terrifying view of the climate emergency.


(1) A rain-less time will inexorably lead to drought which can have an equally devastating impact on us, on crops and on livestock — and on food processing and distribution.

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