Is this a consequence of climate change?
Yes, that is undisputed. We are dealing with longer and more extreme periods of heat, which are also associated with drought. If strong winds are added to this combination, it will be very bad. Worst of all is when the fire itself ignites these winds. This is when the so-called fire tornadoes arise, which are also notorious in the Mediterranean region. A fire that covers a square kilometre can generate its own wind system. This creates a tremendous thermal. And then we find ourselves in a negative spiral of dry and hot weather, with fire and firestorms that transport burning particles for kilometres.
In your research projects you are investigating past forest fires in Europe. Are the present fires also exceptional from a historical perspective?
Among hunter-gatherers, fires were an insignificant phenomenon, but as soon as people started to build up a production economy, this changed. In the lake sediments, where we detect charcoal particles, it is quite clear that the fires increased the moment that people became interested in producing something. One may wonder why this is so. Man had had fire much earlier – since about half a million years, already Homo erectus was familiar with fire – so it wasn’t an achievement of modern man. The increase in fires that we see has to do with the fact that the early farmers built their production systems in the forest...
...you’re referring to slash-and-burn.
Exactly. We see that all over Europe. People are trying to use fire to create favourable conditions for crops that come from the Middle East and need plenty of light and dry conditions. To do this, they have to make clearings. This approach is repeated again and again, because nature has a tendency to close the wounds created by slash-and-burn agriculture. If you want to interrupt this process, you have to clear it with fire again. With the advent of the production economy, there was more and more fire in the system. This started in the Neolithic Age, increased in the Bronze Age, when people settled down, and finally culminated during the Iron Age. There are real fire industries in some places in Europe. In the Lüneburg Heath and in many other areas of Western Europe, the valuable heather was preserved by burning it down a little every year. This is where man has installed proper fire vegetation after clearing.
What role do climate developments play in this fire history of Europe?
At the Oeschger Centre, we try to link the climatic changes with those in the history of vegetation. There was a phase in the Early Holocene around 8,000-10,000 years ago when the Mediterranean region was relatively dry and hot. This had nothing to do with the greenhouse effect as it does today, but rather with the orbital parameters that led to very strong solar radiation in summer. Our investigations of Sicily and Sardinia during this period show that it burned even more than today under the influence of humans. This is worrying. We know from our studies that species that had adapted to fire were more common at that time. Perfidiously, some of these species burn very well themselves because they contain a lot of essential oils...
...like the eucalyptus that’s burning in Australia.
Exactly, in addition to the fire weather, the so-called firewood plays a big role in Australia. Eucalyptus has so many essential oils that it burns almost explosively. This leads to the fire tornadoes I was talking about. In the Mediterranean region it is species such as cistus, sage or rosemary that burn so quickly – all plants that we appreciate so much because they smell good.