What would the world look like if humans never existed? We have the ability to dramatically change our environment to meet our needs, altering the landscape in ways unlike any other species. But we also impact the animals that call the land their home, as a recent report showed, by the ruthlessness of our hunting practices. A new study, published in Diversity and Distributions, has attempted to map what the distribution of large mammals would look like if we had never come down from the trees in the first place.
The new study, conducted by researchers at Aarhus University in Denmark, has concluded that the reason Africa is the only place left where large mammal diversity has remained high throughout our history is not because the environment there is particularly favorable, but because they survived the onslaught of human hunting. They then produced a projection of what the mammal diversity would look like in the rest of the world without us. Notably, the diversity in the Americas is much greater than anything like what we see today.
The current distribution of large mammal diversity, with only Africa holding onto a large number of species. Credit: Soren Faurby/Aarhus University
“Northern Europe is far from the only place in which humans have reduced the diversity of mammals – it's a worldwide phenomenon,” explained Professor Jens-Christian Svenning, one of the co-authors of the study. “And, in most places, there's a very large deficit in mammal diversity relative to what it would naturally have been.”
The researchers constructed the new world map by predicting the distribution of now extinct animals based on their ecology, biogeography, and the current natural environmental condition. Their creation provided the first estimate of how mammal diversity would have looked without modern man’s influence. They found that the diversity in the Americas should be much greater, with grasslands not unlike the Serengeti in Africa supporting giant sloths, herds of horses and mastodons, all being preyed upon by short-faced bears and saber-toothed cats.
The predicted large mammal diversity if modern humans hadn't existed, showing particular hotspots in the Americas. Credit: Soren Faurby/Aarhus University
“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,” says Soren Faurby, who led the research. “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 study does, however, presume that the changing climate at the end of the Pleistocene was not sufficient to kill the large mammals off on its own, and that it was man’s influence that delivered the death blow. This area of research is hotly debated and contested, with arguments flying back and forth as to the real reason the world’s large mammals died out. It's generally thought likely to be a combination of climate change and hunting, but it’s impossible to say whether or not all species of mammal would have been able to adapt sufficiently to a changing environment and survive to present.