Large grazing mammals such as elephants and rhinoceroses once roamed through Europe, and their presence contributed to sustainable and biodiverse landscape made up of forests and rangeland, and a similar self-managing ecosystem could be reintroduced in Europe's national parks today, researchers contend.

Writing in the Proceedings of the National Academy of Sciences, a research team from Denmark reports on their use of fossilized beetles to paint a picture of ancient ecosystems.

The beetle species the researchers focused on were all types of dung beetles associated with large mammals of the past or with woodlands environments. 

The analysis revealed that these sorts of dung beetles were much more present in the interglacial period that occurred between 132,000-110,000 years ago than they were before the arrival of agriculture in the present interglacial period, roughly 10,000-5,000 years ago.

"Large animals in high numbers were an integral part of nature in prehistoric times. The composition of the beetles in the fossil sites tells us that the proportion and number of the wild large animals declined after the appearance of modern man. As a result of this, the countryside developed into predominantly dense forest that was first cleared when humans began to use the land for agriculture," said Jens-Christian Svenning, a processor at Aarhus University.

"One of the surprising results is that woodland beetles were much less dominant in the previous interglacial period than in the early Holocene, which shows that temperate ecosystems consisted not just of dense forest as often assumed, but rather a mosaic of forest and parkland," said Chris Sandom, a postdoctoral fellow at Aarhus University.

The researchers contend that if large grazing animals were reintroduced to parts of the European landscape, it could be an effective way to restore self-managing landscapes.

"An important way to create more self-managing ecosystems with a high level of biodiversity is to make room for large herbivores in the European landscape -- and possibly reintroduce animals such as wild cattle, bison and even elephants. They would create and maintain a varied vegetation in temperate ecosystems, and thereby ensure the basis for a high level of biodiversity," said senior scientist Rasmus Ejrnæs.