When thinking of the term, ‘invasive species’, it’s unlikely that you imagine innocent, harmless creatures that pose no threat to their environment. Instead, ‘invasive’ implies a level of interference, pointing towards a species that has adverse effects on the ecosystems it enters. And indeed, despite most often being moved mistakenly, these populations can grow incredibly fast, oftentimes waging war on the ecosystems in which they end up. They have the potential to cause harm in many ways: introducing new diseases, destroying native food sources, preying on local species and interrupting natural food chains.
Take the grey squirrel in Europe, for example. Belonging to the Eastern and Mid-western United States, the grey squirrel was brought over to Europe in the late nineteenth century. As a result of their size, the grey squirrel is much better equipped to survive the winter months than the European red squirrel. Consequently, the red squirrel’s numbers have dropped drastically in Great Britain, Ireland and Italy over the past few decades. This is just one example of where an invasive species has impacted upon the land where it was introduced; wild pigs, domestic cats and ferrets are all known to have caused damage to native prey populations or crops.
For years, biological and ecological research has leaned mainly towards this negative view of invasive species. However, a group of researchers hailing from eight different universities and research centres worldwide, such as the University of Technology in Sydney and the University of Massachusetts, have put together a study on ‘introduced species’ that suggests that their invasions could be more beneficial than detrimental.
One of the present-day introduced species that the study focused on was the hippos that can be found grazing for food in the Magdalena River, in Colombia. Nicknamed the ‘Cocaine Hippos’, these animals were just one of the things left behind after the death of Pablo Escobar in 1993.
With his grand fortune, Escobar was able to build Hacienda Nápoles, an estate that provided home to a Spanish colonial house, a sculpture park, and a complete zoo. Four hippopotamuses, whose native home was over 6000 miles away in sub-Saharan Africa, were kept in a private menagerie there. Upon seizure of the estate, the hippos were deemed far too difficult to move. Soon, they became feral and escaped into the surrounding areas. Their numbers, which have grown immensely, are now estimated to be between 80 and 100.
The opinion of their human neighbours is split. Whilst the local tourist industries and conservationists have supported their continued presence, there have been some calls for their population to be culled due to the hippos’ impact upon the fishing in the river.
This new study suggests that the accidental spread of the hippos, along with many other introduced species across the continents, could help restore ecological function not seen since the Late Pleistocene era. This is due to the similarities shared between the introduced species and species that were made extinct hundreds of thousands of years ago. Assessing traits such as body mass, diet, fermentation type and habitat, the study then compared each of the present-day species and their unique traits with those that came centuries before. Overall, the researchers concluded that many of these introduced species are almost identical to extinct species of the Late Pleistocene.
Escobar’s ‘Cocaine Hippos’ were shown to be similar in many ways to giant llamas and the semiaquatic notoungulate (visually akin to a kind of prehistoric hippo). Resultingly, their similar grazing style has the potential to restore the land of South America upon which they roam. Likewise, the grazing of several introduced species in Australia could mirror that of the extinct large-bodied browsers.
These herbivores may, therefore, help to reduce shrub cover, reducing the intensity of the highly damaging wildfires that destroy much of Australia’s wildlife year after year. Other examples of introduced species studied include the aforementioned wild pig in North America, the sambar deer in Australia and the wild water buffalo in South America. With overwhelmingly positive results, the study found that 64% of these ‘invasive’ species shared more similarities with extinct species than their native, living neighbours. A small proportion of the species studied, two in Australia and one in Europe, were even found to contribute novel functionality unseen even in the Late Pleistocene Era.
Lead author of the study Erick Lundgren is aware that this study goes against received scientific opinion in science. His interest in introduced species started when he began observing them ‘doing really interesting, facilitative things despite their status as ‘pests’.’ The study, he says, ‘is a culmination of a decade of questioning invasion biology’s premise.’
For Lundgren, the extinctions of the Late Pleistocene provoked him to question what was ‘natural’. And of course, the world we live in today is hugely different from the one inhabited by our early ancestors.
Yet, this study suggests we are perhaps not as far from the ‘natural’ world as scientific opinion has often argued. There may still be conclusions to draw – unfortunately, many of the traits that the extinct species possessed remain unknown and it’s too early to know, for sure, whether trait similarities between them and introduced species will have a lasting impact upon the Earth – but the findings of the study are promising. Ultimately, these ‘invasive’ species could be one of the ways that we may begin to repair the damage done by human-caused extinctions.
For The Yucatan Times
Erin Sharrocks is a features writer currently focusing on environmental stories across Latin America.