An alien species is a species introduced outside its natural past or present distribution and if this species becomes problematic, it is termed an invasive alien species (IAS).
IAS are the most common threat to amphibians, reptiles and mammals. They may lead to changes in the structure and composition of ecosystems detrimentally affecting ecosystem services, human economy and wellbeing of living beings.
The movement of people and goods around the world increases the opportunity for introduction of IAS. Most effective way to stop negative impacts of IAS is through prevention of spread by regulating trade or movement of a species. Once an invasive alien species has arrived, early detection, monitoring and eradication can stop the species from spreading.