Q What is an ‘alien species’?
A: An alien species has nothing to do with something from outer space. Sometimes also called ‘exotic species’, these are living organisms that invade a new geographical area and thrive in it. They can also wreak havoc with the native species in the area. Most of our common household pests are alien.
An alien species is not always something ugly and vile—if you ask any Australian ecologist, they would tell you that one of their biggest problems have been cute, fluffy rabbits. Rabbits were brought to Australia from England in 1859. But without natural predators, rabbits thrived in Australia. They have become a major threat to the ecosystem by consuming native plants to the point of near extinction.
Invasive alien species are considered one of the main threats to biodiversity on Earth. As transportation around the world has accelerated, more pests have “hitchhiked” with us, spreading around the globe.
The worst alien species, on a global scale, are various kinds of rats. Rats have single-handily caused the extinction of more native birds and other animals than any other alien species. Red fire ants and many other insects, plus brown tree snakes, zebra mussels, water hyacinths, and Nile perch, are among many other alien species that have been especially damaging to native ecosystems globally.