When it gets hot, many people in industrialized countries cool their homes down to a tolerable temperature.

That they - with a few exceptions, in which the air conditioning is operated with renewable energy sources - still fire up the earth's heating because the process is energy-intensive and releases carbon dioxide, is often neglected in the assessment.

Heat waves, as in 2003 in Europe or currently in North America, bring the human body to the limit of its functionality.

But not only people without air conditioning are exposed to the heat without protection, the entire animal kingdom is too.

Animals have always been exposed to the forces of nature.

Now, in the Anthropocene, human violence occurs - also in the form of heat waves.

Personal experiences and scientific facts

This is what the German biologist Lisa Warnecke, who lives in Australia, focuses on with her book "Tierisch HOT". On the cover, an exhausted-looking koala hugs a tree. According to Warnecke, measurements with thermal cameras have shown that koalas give off heat to the cooler trees. They don't do this with their usual food trees, but special tree species where the effect works particularly well. This tactic is one of many examples of animals trying to adapt to heat. Others hide in underground burrows or adjust their metabolism so that they secrete less water.

The great alternative to such adjustments is to escape the heat.

The author reports on frogs that immediately run away when you play them the crackling of fire from a tape.

But where do you go when it's hot everywhere?

Since Warnecke lives in Australia, she got particularly good visual aids during the fires in early 2020.

They were so huge that it was no longer possible for millions of animals to escape.

The author is noticeably afraid

Warnecke mixes personal experience with scientific facts. The fact that she and her husband research physiological phenomena ensures reliable numbers and data and also ensures that some myths, for example about wombats, which are said to have brought other animals to safety at the mega fire, are exposed. In addition, the author emphasizes that heat and fire are of course not only phenomena of man-made climate change, but part of nature. The fact that there is also an animal in Europe in the form of the black pine jewel beetle that needs burned wood to reproduce and therefore moves in the direction of wood smoke should also surprise some biologically informed readers.

If it weren't for the frequent exclamation marks at the end of sentences, one could say that Warnecke succeeded in conveying her subject matter-of-factly.

Also a little too much creativity in the subheadings, where words like “flying sparks” become “flying sparks”, shouldn't have been.

But that is manageable, because this book reveals an important and at the same time neglected aspect of global heating: its physiological side, the direct and usually brutal effect of heat on living beings.

Stress factors can hardly be played off against each other

If we do not drastically reduce our emissions of greenhouse gases, heat waves on land and in the sea will shape the 21st century and the following centuries. The author is noticeably afraid of such a future. The heat alone can be a tremendous stress factor for wild animals, but we expect a lot more from them: The main reasons for the decline in biodiversity are "clearing, poaching, agriculture, urbanization," writes Warnecke. The loss of habitat would mean that many species would be extinct before they were directly affected by the consequences of climate change.

But the stress factors can hardly be played off against each other; on the contrary, they reinforce each other. Animals can survive heat waves, for example, by cooling down in wetlands or by retreating to higher altitudes. But what if the swamps have been drained and the way into the hills is blocked by highways and cities? Physiological leeway to deal with heat is "still available in many species, but in order to exploit this, animals need a heterogeneous microclimate and space for migration". According to Warnecke, access to buildings and nests, to watering holes and shady places is becoming more and more important so that animals can protect themselves from overheating. It is time to prepare human and animal habitats for the heat waves of the future.

Lisa Warnecke: "Very hot". How the koala, elephant and titmouse are responding to the climate crisis. 

Construction Verlag, Berlin 2021. 232 pp., Hardcover, 22, - €.