What are exotic and invasive species?
Alien or allochthonous species are all those foreign species that humans have introduced from their areas of origin into new territories. The transport and introduction of these species can take place voluntarily or involuntarily, and has been going on since time immemorial. Thus, organisms as familiar to us as the fig tree or the mouse are in fact species introduced many centuries, even millennia ago. The problem arises when some of these species are able to spread into new territories in a relatively short period of time. These are the so-called invasive species, which can often produce considerable impacts of various kinds. In fact, only a small group of alien species eventually become invasive and cause significant impacts on biodiversity, the economy or human health (#invasivespecies).