Hunter Gatherers Burned Down Europe's Forests 20,000 Years Ago

Mass man made ecological destruction is nothing new.

When humans reached Australia, one of the main activities that accompanied this megafauna extinction event was the setting of many large scale wildfires. New research establishes that this also happened in Europe around 20,000 years ago.

Reconstructions of the vegetation of Europe during the Last Glacial Maximum (LGM) are an enigma. Pollen-based analyses have suggested that Europe was largely covered by steppe and tundra, and forests persisted only in small refugia. Climate-vegetation model simulations on the other hand have consistently suggested that broad areas of Europe would have been suitable for forest, even in the depths of the last glaciation. 

Here we reconcile models with data by demonstrating that the highly mobile groups of hunter-gatherers that inhabited Europe at the LGM could have substantially reduced forest cover through the ignition of wildfires. Similar to hunter-gatherers of the more recent past, Upper Paleolithic humans were masters of the use of fire, and preferred inhabiting semi-open landscapes to facilitate foraging, hunting and travel. 

Incorporating human agency into a dynamic vegetation-fire model and simulating forest cover shows that even small increases in wildfire frequency over natural background levels resulted in large changes in the forested area of Europe, in part because trees were already stressed by low atmospheric CO2 concentrations and the cold, dry, and highly variable climate. Our results suggest that the impact of humans on the glacial landscape of Europe may be one of the earliest large-scale anthropogenic modifications of the earth system.

Jed O. Kaplan, Mirjam Pfeiffer, Jan C. A. Kolen, Basil A. S. Davis. "Large Scale Anthropogenic Reduction of Forest Cover in Last Glacial Maximum Europe." 11 (11) PLOS ONE: e0166726 (November 30, 2016).

A press release at Science News is more direct than the abstract about what researchers have concluded:

Large-scale forest fires started by prehistoric hunter-gatherers are probably the reason why Europe is not more densely forested. . . .

Deliberate or negligent 

. . . It may be that during the coldest phase of the last Ice Age, some 20,000 years ago, hunter-gatherers deliberately lit forest fires in an attempt to create grasslands and park-like forests. They probably did this to attract wild animals and to make it easier to gather vegetable food and raw materials; it also facilitated movement. Another possibility is that the large-scale forests and steppe fires may have been the result of the hunters' negligent use of fire in these semi-open landscapes. 

Large-scale impact of humans on landscape 

The researchers combined analyses of Ice Age accumulations of silt and computer simulations with new interpretations of archaeological data. They show that hunters throughout Europe, from Spain to Russia, were capable of altering the landscape. This first large-scale impact of humans on landscape and vegetation would have taken place more than 20,000 years before the industrial revolution. The Ice Age is often presented as an era of extreme cold and snow that was ruled by mammoths, bison and giant bears. But the researchers show that humans were also capable of having a significant impact on the landscape. 

Layers of ash 

Searching for evidence of this human impact explains why there are conflicting reconstructions for this period. Reconstructions of the vegetation based on pollen and plant remains from lakes and marshland suggest that Europe had an open steppe vegetation. But computer simulations based on eight possible climate scenarios show that under natural conditions the landscape in large areas of Europe would have been far more densely forested. The researchers conclude that humans must have been responsible for the difference. Further evidence has been found in the traces of the use of fire in hunting settlements from this period and in the layers of ash in the soil.