When a Eucalyptus, a Rabbit and an Ant Set Out to Take Over the World. Or: Who Are the Invasive Species?

Did you pack your bags by yourself?” you’ll be asked at the airport, referring of course, to the security threats we’re all so used to. But in fact a real threat that we are barely aware of characterizes human migration between continents. This threat reached Israel in the past in old wooden ships in the form of rats and reached Australia in the form of rabbits; we ourselves even planted such a threat to drain the swamps, in the form of Eucalyptus trees.

Meet one of the greatest environmental threats – invasive species.

So what is an invasive species actually?

Invasive species are in fact plants or animals that have spread beyond their natural distribution, due to human activity, and established in their new environment. These species cause significant, devastating damage to humans and natural ecosystems while pushing out and negatively impacting local species and their habitats (definition of the Israel Nature and Parks Authority).

How does it happen?

When humans began moving more freely around the world they brought species with them from place to place. Some species were brought intentionally, such as pets and farm animals, so humans could maintain their old lifestyle in their new country of residence, while others were brought unintentionally (e.g., seeds and fruits brought in clothes and luggage).

A lack of awareness of future damages has turned invasive species into a global problem; the damage from their impact is immense and is felt in many fields from biodiversity to economics (a study conducted in 2000 in the USA estimated the price the USA has paid due to invasion by alien species at 6 billion dollars annually in the USA).

Who’s afraid of invasive species and why?

Invasive species come with humans; they are particularly strong and adaptive, establishing themselves at the expense of local species by competing with them over local resources and food resources, and sometimes even preying on and directly impacting local species. In contrast to slow, long-term processes which take place naturally, in which the environment changes at an evolutionary pace, when an invasive species is introduced artificially due to human intervention its presence in its new habitat often becomes dangerous due to the fact that it spreads rapidly and is difficult to stop and eradicate; often the extent of this ecological disaster is discovered only when it’s already too late.

Invasive species are particularly strong and adaptive, establishing themselves at the expense of local species by competing with them over local resources and food resources, and sometimes even preying on and directly impacting local species

A clear example of an invasive species is the introduction of rabbits into Australia

In 1867 an amateur English hunter asked his cousin for rabbits, which he was used to seeing when he lived in England: “Rabbits will make me feel at home as well as providing an opportunity for rabbit hunting,” he thought. Within just a few years, the same shipment of rabbits to “Brown Park” near Winchelsea, Victoria, reached a real population explosion. The rabbits acclimated immediately to the new environment and reproduced rapidly throughout southern Australia. Rabbits, which are known for their reproductive abilities, found optimal conditions in Australia – no significant local predators or extreme weather, and farmlands with a great abundance of low vegetation. Thus the rabbits reproduced at a massive scale; more than two million rabbits were hunted each year without affecting the tremendous numbers that kept multiplying at an extreme rate.

The rabbits fed on the local vegetation and in fact eliminated many species endemic to southern Australia. Many animals, including marsupials characteristic of the continent, found themselves in distress because all their food was eaten up by the rabbits; the peak of the damage was reflected in a lack of pasture and desertification of a large part of the continent.

In 1901, after numerous, diverse attempts to solve the problem, the Australian rabbit-proof fence was built. This is in fact the longest fence in the world built against invasive species. In the 1950s, more effective methods were developed to cope with the rabbit population and the importance of the fence decreased.

This very same animal seems so innocent in its native England, but human intervention that introduced it to another continent disturbed the natural balance and turned the rabbit into a dangerous, invasive species that caused irreversible damage in Australia.

And if it seems as if the problems are all across the sea… check out the other articles and you’ll discover new sides to the familiar sourgrass, the annoying little fire ant, the chirping and particularly invasive myna bird and the Eucalyptus, which after many years has been heralded a cultural hero, but with a little asterisk at the side – sound interesting? Check out the next article