Increasing forest cover in the Eifel region 11,000 years ago resulted in the local loss of megafauna

Herds of megafauna, such as mammoth and bison, have roamed the prehistoric plains in what is today's Central Europe for several tens of thousands of years. As woodland expanded at the end of the last Ice Age, the numbers of these animals declined and by roughly 11,000 years ago, they had completely vanished from this region. Thus, the growth of forests was the main factor that determined the extinction of such megafauna in Central Europe.

This is the conclusion reached in a study conducted by Professor Frank Sirocko of Johannes Gutenberg University Mainz (JGU), together with researchers from the Max Planck Institute for Chemistry, the University of Wollongong in Australia, and the University of Göttingen. The project involved the analysis of sediment layers taken from two Eifel maars, i.e., former volcanic craters that had subsequently become lakes. The researchers used these to reconstruct landscape changes and megafauna abundance in the area over the last 60,000 years. The results showed that human hunters and large mammals had actually co-existed here over several thousand years. "The sediments from the Eifel maars have provided us with no evidence that it was humans who were responsible for the eradication of these animals," stated Sirocko. The so-called overkill hypothesis discussed in North America could thus not be confirmed for Central Europe.

Previous vegetation and animal populations can be identified from pollen and fungal spores in sediments

For the purpose of their study, the research partners used sediment cores from the Eifel maars that Sirocko and his team had systematically drilled and archived over the past 20 years. The recent article published in Scientific Reports details the investigation of pollen and spores present in the cores obtained from Holzmaar lake and the infilled maar of Auel located in the Volcanic Eifel. While pollen documents the vegetation of the past, fungal spores provide evidence of the presence of large mammals because certain mold fungi only colonize the dung of bigger herbivores.

On the basis of the grains of pollen, the researchers established that some 60,000 to 48,000 years ago the Eifel region was covered by spruce woods that succumbed to several cold phases, which transformed the landscape into more open forest steppe. This kind of terrain remained predominant from 43,000 to 30,000 years before the present. Subsequently, the forest tundra of the Eifel became an Ice Age polar desert where only grass grew.

The megafauna fecal fungal spores show that it was these environments which were continuously inhabited by large mammals from 48,000 to some 11,000 years ago. Datable bones found in caves in Belgium and gravel deposits in the Rhine valley document that mammoth, woolly rhinoceros, bison, horses, reindeer, and giant deer found the cold phases more accommodating. The sparse forests of the warmer phases were the preferred habitat of red deer, elk, and the European bison.

Development of woodlands deprived megafauna of their food source

The primary cause of the decline and eventual extinction of large mammals in Central Europe was the growth of forests. "As the trees began to take over, the large herbivores lost access to their main staple food, namely grass," explained Sirocko. Neither the extreme climatic fluctuations of the last 60,000 years nor local volcanic activity and associated fire events appear to have played a role in their extinction. At the same time, the arrival of modern humans in Central Europe 43,000 years ago also had little effect on the presence of local megafauna. Instead, times at which extensive numbers of large mammals were living here coincided with periods in which there was a denser population of humans. "This is most apparent some 15,000 years ago. At that time, we find the largest herds of megafauna along with the archaeologically confirmed presence of human hunters in the Rhine valley," Sirocko pointed out. The Magdalenian culture site at Gönnersdorf in northern Rhineland-Palatinate has been extensively excavated by the Römisch-Germanisches Zentralmuseum Mainz -- Leibniz Research Institute for Archaeology (RGZM) in Mainz.

The researchers claim that even in this period, towards the end of the last Ice Age, grassed landscapes were still spreading. This was the era in which the solar irradiation of the Northern Hemisphere began to increase and global sea levels started to rise, eventually flooding the formerly land regions in the English Channel and the North Sea and thus presumably progressively forcing the herds of megafauna away to seek refuge in Central Europe. "The many late glacial maar lakes and silted-up swamps in dried-out maars in the Eifel region must have proved particularly attractive to megafauna," concluded Sirocko. "And it was the resultant large herds that must have enticed the late Ice Age hunters."

Sediments of the Eifel maars do not substantiate the overkill hypothesis

According to the research team, the fact that hunters and megafauna occupied the same region concurrently demonstrates that human beings did not cause the disappearance of large mammals from Central Europe -- in other words, the maar sediments of the Eifel region do not furnish proof that the overkill hypothesis put forward for North America can be corroborated here. The large mammals migrated away only when birch forests began to predominate in the terrain 13,300 years ago. From 11,000 years ago there is no longer evidence of the presence of large herds of megafauna as thick woods had taken over the Eifel, a setting in which large mammals could not survive.