Jan Kolen, the director of the Centre for Global Heritage and Development and Professor of Landscape Archaeology and Cultural Heritage at Leiden University, was part of an international research team which researched the impact of humans on the landscape during the last Ice Age. They have discovered that large-scale forest fires started by prehistoric hunter-gatherers are probably the reason why Europe is not more densely forested. A report was recently published in PLOS ONE.
Read more about this research at the website of Leiden University.