24 March 2020 12:35
The researchers suggest that introducing large herbivores to different environments could be a means of restoring the planet to an ecological state not seen since many such animals were Through a worldwide analysis comparing the ecological traits of introduced herbivores like Escobar's hippos to those of the past, they reveal that such introductions restore many important traits that have been lost for thousands of years. While human impacts have caused the extinction of several large mammals over the last 100,000 years, humans have since introduced numerous species, inadvertently rewilding many parts of the world such as South America, where giant llamas once roamed, and North America, where the flat-headed peccary could once be found from New York to California. "While we found that some introduced herbivores are perfect ecological matches for extinct ones, in others cases the introduced species represents a mix of traits seen in extinct species," says study co-author John Rowan, Darwin Fellow in organismic and evolutionary biology at the University of Massachusetts Amherst. "For example, the feral hippos in South America are similar in diet and body size to extinct giant llamas, while a bizarre type of extinct mammal - a notoungulate - shares with hippos large size and semiaquatic habitats. These giant herbivores began their evolutionary rise not long after the demise of the dinosaurs, but were abruptly driven extinct beginning around 100,000 years ago, most likely due to hunting and other pressures from our Late Pleistocene ancestors.
The researchers found that by introducing species across the world, humans restored lost ecological traits to many ecosystems; making the world more similar to the pre-extinction Late Pleistocene and counteracting a legacy of extinctions. Erick Lundgren, lead author and Ph.D. student at the UTS Centre for Compassionate Conservation (CfCC), says the possibility that introduced herbivores might restore lost ecological functions had been suggested but not "rigorously evaluated." To this end, the authors compared key ecological traits of herbivore species from before the Late Pleistocene extinctions to the present day, such as body size, diet and habitat. "By doing this, we could quantify the extent to which introduced species make the world more similar or dissimilar to the pre-extinction past. These introduced 'surrogates' for extinct species include evolutionary close species in some places, like mustangs (wild horses) in North America, where pre-domestic horses of the same species lived but were driven extinct. When looking beyond the past few hundred years - to a time before widespread human caused pre-historic extinctions - introduced herbivores make the world more similar to the pre-extinction past, bringing with them broader biodiversity benefits, the authors conclude.
However, a new study published by researchers at the University of Massachusetts Amherst suggests the impact of Escobar's hippos on the environment might be positive, counteracting a legacy of man-made extinctions. The hippos aren't alone, with the study finding many introduced herbivores actually share key ecological traits with extinct species across the world, generally providing balance to ecosystems. "For example, the feral hippos in South America are similar in diet and body size to extinct giant llamas, while a bizarre type of extinct mammal – a notoungulate – shares with hippos large size and semiaquatic habitats. So, while hippos don't perfectly replace any one extinct species, they restore parts of important ecologies across several species," study co-author John Rowan, an evolutionary biologist at the University of Massachusetts Amherst, said in a press release. The researchers compared key ecological traits of herbivore species — things like body size, diet, and habitat — that lived before the Late Pleistocene to the present day. "This allowed us to compare species that are not necessarily closely related to each other, but are similar in terms of how they affect ecosystems," said Erick Lundgren, lead author and Ph.D. student at the University of Technology Sydney Centre for Compassionate Conservation (CfCC). "By doing this, we could quantify the extent to which introduced species make the world more similar or dissimilar to the pre-extinction past. According to the findings, 64% of introduced herbivores are more similar to extinct species than to local native species. But in some cases, foreign species (at least some herbivores) can rewild ecosystems making the world more similar to its pre-extinction past.