This is what the world would look like without humans
Without humans, the whole world could look like the Serengeti, a large geographical region in Tanzania, Africa.
This is according to a new study conducted by Aarhus University, Denmark, which shows what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts.
The fact that the greatest diversity of large mammals is found in Africa reflects past human activities – and not climatic or other environmental constraints, the report said.
In a world without humans, most of northern Europe would most likely now be home to not only wolves, Eurasian elk (moose) and bears, but also animals such as elephants and rhinoceroses.
In a previous analysis, Aarhus University showed that the mass extinction of large mammals during the Last Ice Age and in subsequent millennia (the late-Quaternary megafauna extinction) is largely explainable from the expansion of modern man (Homo sapiens) across the world.
In its follow-up study, the university investigated what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts, based on estimates of the natural distribution of each species according to its ecology, biogeography and the current natural environmental template.
They provide the first estimate of how the mammal diversity world map would have appeared without the impact of modern man.
The current diversity of large mammals is shown. It can clearly be seen that large numbers of species virtually only occurs in Africa
The natural diversity of large mammals is shown as it would appear without the impact of modern man (Homo sapiens).
The figure shows the variation in the number of large mammals (45 kg or larger) that would have occurred per 100 x 100 kilometer grid cell. The numbers on the scale indicate the number of species.
“Northern Europe is far from the only place in which humans have reduced the diversity of mammals – it’s a worldwide phenomenon. And, in most places, there’s a very large deficit in mammal diversity relative to what it would naturally have been”, said Professor Jens-Christian Svenning, Department of Bioscience, Aarhus University, who is one of the researchers behind the study.
Africa is the last refuge
The current world map of mammal diversity shows that Africa is virtually the only place with a high diversity of large mammals. However, the world map constructed by the researchers of the natural diversity of large mammals shows far greater distribution of high large-mammal diversity across most of the world, with particularly high levels in North and South America, areas that are currently relatively poor in large mammals.
“Most safaris today take place in Africa, but under natural circumstances, as many or even more large animals would no doubt have existed in other places, e.g., notably parts of the New World such as Texas and neighboring areas and the region around northern Argentina-Southern Brazil,” said says Postdoctoral Fellow Soren Faurby, Department of Bioscience, Aarhus University, who is the lead author on the study.
“The reason that many safaris target Africa is not because the continent is naturally abnormally rich in species of mammals. Instead it reflects that it’s one of the only places where human activities have not yet wiped out most of the large animals.”
The existence of Africa’s many species of mammals is thus not due to an optimal climate and environment, but rather because it is the only place where they have not yet been eradicated by humans, the researchers said.
The underlying reason includes evolutionary adaptation of large mammals to humans as well as greater pest pressure on human populations in long-inhabited Africa in the past.
Misinterpretation
The report said that today, there is a particularly large number of mammal species in mountainous areas. This is often interpreted as a consequence of environmental variation, where different species have evolved in deep valleys and high mountains.
According to the new study, however, this trend is much weaker when the natural patterns are considered.
“The current high level of biodiversity in mountainous areas is partly due to the fact that the mountains have acted as a refuge for species in relation to hunting and habitat destruction, rather than being a purely natural pattern. An example in Europe is the brown bear, which now virtually only live in mountainous regions because it has been exterminated from the more accessible and most often more densely populated lowland areas,” said Soren Faurby.
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