In the world of plants, competition for sunlight is fierce. The trees that reach highest with their crowns can capture the most sunlight and win that competition. In beech forests, trees take almost all the sunlight. This means that other, smaller trees and shrubs, such as hazel, cannot grow in a beech forest.
The landscape in Europe was dominated by a variety of different vegetational systems. In this picture it is open wood which lets enough sunlight through the foliage to support bushes, small trees and grasses. Illustration: Brennan Stokkerman
“Hazel thrives in the open countryside and in open or disturbed forest, and tolerates disturbance from large animals. Whereas species like beech and spruce often are severely damaged or killed by cutting or browsing, hazel can manage without problems. Even if you cut down a hazel, it will still produce lots of new shoots,” he says.
“For this reason, hazel was often very common in historical coppice woodlands.”
What pollen can reveal about the past
Almost all trees, flowers and shrubs give off pollen. Pollen is to plants what sperm cells are to animals. In order for a plant to seed, its egg cells must be pollinated.
Pollen is spread by the wind or by insects.
A lot of pollen lands on the ground, where it cannot pollinate other plants. Instead, it is eaten by insects or degraded by microorganisms. However, a small amount of pollen lands in lakes, bogs or streams, where it falls to the seabed.
Below the surface, there is often no oxygen and no life, and the pollen is preserved over hundreds of thousands of years in the soil layers.
By looking at the composition of different types of pollen in the soil layers of ancient, buried wetlands, researchers can deduce what the vegetation looked like more than 100,000 years ago.
Large animals kept the landscape open
So there are indications that Europe was not covered by dense forest before humans came into existence. But what did the landscape actually look like?
According to calculations from the new study, somewhere between 50 and 75 per cent of the landscape was covered by open or semi-open vegetation. And this is most likely due to the large mammals that lived at that time, explains Jens-Christian Svenning.
“We know that a lot of large animals lived in Europe at that time. Aurochs, horses, bison, elephants and rhinos. They must have consumed large amounts of plant biomass and thereby had the capacity to keep the tree-growth in check,” he says and continues:
“Of course, it’s also likely that other factors such as floods and forest fires also played a part. But there’s no evidence to suggest that this caused enough disturbance. For example, forest fires encourage pine trees, but mostly we did not find pine as a dominant species.”
Although the research group cannot be 100 percent certain about the extent to which large animals were behind the open areas, there are strong indications that they were. Firstly, large animals such as bison have exactly that effect in areas where they are still found in European forests. Furthermore, beetle fossils from the last interglacial period also show that many large animals lived at that time.
We have looked at a number of finds of beetle fossils from that time in the UK. Although there are beetle species that thrive in forests with frequent forest fires, we found none of them in the fossil data. Instead, we found large quantities dung beetles, and this shows that parts of the landscape have been densely populated by large herbivores,” he says.
Merck’s rhinoceros with pollen between its teeth
There are many indications that large animals kept the landscape varied before humans came, with large areas of open and semi-open vegetation.
A very special study from Poland further underlines this theory, says Jens-Christian Svenning.
Merck’s rhino was one of the animals that loved to feed on hazel leaves. The animal lived in most of Europe and probably played an important function in keeping the landscapes open and varied. Illustration: Brennan Stokkerman
“In Poland, researchers have taken a closer look at fossils from Merck’s rhinoceros to see what this large animal lived on. They found remnants of pollen and twigs between its teeth, and when they analysed them, they could see that a large amount came from hazel,” he says and continues:
“So the rhinoceros has trudged around eating branches and leaves from hazel bushes. This supports the theory that the large animals have affected the vegetation, perhaps just like historical coppice woodlands. At the same time, marks of its teeth suggest it had foraged a lot on grass and sedges through its life time.”
An argument for rewilding
Not only do we need to rewrite the biology books, but the new findings provide new data to support trophic rewilding, which is the restoration of biodiverse, self-regulated ecosystems via the re-establishment of food-web processes, notably as mediated by wild megafauna species.
The results in the study support that large animals have an essential role to play in restoration, as Elena Pearce explains.
Aurochs are taking a rest in a semi-open forrest. The big animals probably meant that these areas didn’t grow over. Illustration: Brennan Stokkerman
“Now we know that there was a great deal of variation in the landscape. Everything suggests that this variation arose because of large animals affecting the vegetation structure. Many of the large animals from the interglacial period are now extinct, but we still have bison, horses and oxen,” she says and concludes:
“Without large animals, natural areas become dominated by dense vegetation, in which many species of plants and butterflies, for example, cannot thrive. Therefore, it’s important we restore large animals to the ecosystems if we are to encourage biodiversity.”
The study was published in the journal Science Advances
Written by Eddie Gonzales Jr. – AncientPages.com – MessageToEagle.com Staff