La Jornada: Invasive species affect ecosystems, economies and human communities

Invasive species – such as Pablo Escobar’s hippos in Colombia – are one of the most serious environmental problems on a global scale, since if they are not controlled in time, they affect ecosystems, economies and human communities, warns Germán Leonardo Jiménez Romero, researcher and coordinator of the master’s degree in Ecological Restoration and the Wild Fauna Management hotbed at the Pontificia Universidad Javeriana.

“We have to make an effort of prevention and education with society. If we do not manage to involve it and prevent the possession and growth of invasive species from being promoted, we will continue to face these problems,” he expressed in an interview with The Day in response to the announcement by the Colombian Ministry of the Environment to euthanize 80 hippos.

Hippos arrived in Colombia in the early 1980s, when drug trafficker Pablo Escobar introduced four specimens – one male and three females – from the United States to his private zoo in Antioquia.

After his death in 1993, the animals were abandoned and dispersed along the Magdalena River. In 30 years they reproduced until reaching a population of 160 individuals, and moved about 200 kilometers to the north of the basin. “Little by little they have colonized areas such as pools, streams and ponds, where they have established nuclei,” details Jiménez Romero, who has studied them for 13 years.

Its presence has caused two effects: on the one hand, certain communities near Hacienda Nápoles have developed tourist activities based on its sighting. While, upstream, fishermen and farmers live in fear of being hit by these animals. In 2021, a farmer was attacked and was left with permanent scars.

A study with the University of Florida identified that they have also impacted the environment. Its presence in bodies of water has modified the amount of organic matter in them, due to the fecal load and urine: “This decreases oxygen in aquatic ecosystems and alters the dynamics of plants and animals.”

Their movement and consumption of 70 kilograms of grass per adult specimen in one night also cause effects on the soil and vegetation. “By trampling the soil they can damage its state of conservation and inhibit plants that are yet to be born.”

For the expert, one of the greatest risks of invasive species are the internal or external parasites that they harbor, and that could colonize humans who interact with them. “An example of this, known as zoonosis.”

Added to this situation is the limited genetic variability, which has already led to specimens with morphological differences compared to those from Africa.

“From four animals they begin to interbreed successively, and what we are going to find is that they reproduce between close relatives. After 30 years of this process, known as inbreeding, we begin to notice that the heads are larger, in some cases the vertebral column presents deformations, as does the pelvic girdle, that is, in the hind legs.”

The expert suggests that if this same population existed in Africa, it would have already disappeared due to diseases, predators and environmental conditions. “Nature itself is responsible for purging this decreased genetic variability, but in an environment like the one they are in, that does not happen.”

Although the Colombian government proposed sterilization strategies as a control measure, in 10 years it was only able to sterilize 11 animals. “The need to set up operating rooms in the field and train the personnel involved makes this process slow. Even so, last year they managed to sterilize 20 animals, the record was improved, but it is still slow and expensive.”

Relocation attempts have also not been successful. Countries such as Mexico and India have rejected international mobility offers managed by Colombia. This is due to sanitary and legal restrictions, as well as the lack of adequate conditions to receive animals from wildlife.

In an article published in 2023 in Scientific Reports The time and cost of undertaking sterilization and relocation campaigns for the species were evaluated, and it was concluded that sacrificing them was less expensive and more effective. For the specialist, the case of the hippos in Colombia illustrates a problem that is repeated throughout the world, since when invasive species are not controlled in time, decisions become more costly, complex and controversial.