ALIEN WORLD

About The Project

An alien species is a species introduced by humans outside of its natural distribution. Not all alien species are considered to have negative impacts on local habitats, but some become problematic, and these are known as invasive alien species.

According to the Convention on Biological Diversity, "An invasive alien species (IAS) is a species that is established outside of its natural past or present distribution, whose introduction and/or spread threaten biological diversity”.

Invasive alien species are among the leading threats to native wildlife. IUCN Red List concluded they are one of the most common threats associated with species extinctions, being considered the most important in the case of amphibians, reptiles and mammals. Invasive alien species can lead to changes in the structure and composition of the ecosystems and, unfortunately, there has been a significant increase in invasive species introductions over the years. When a new species is introduced into an ecosystem, it usually does not have any natural predators and it may be able to breed and spread quickly. Native wildlife often have not evolved defences against the invader and may not be able to compete with those species.

Invasive species are primarily spread by human activities, either intentionally or accidentally. Portugal, as most of the European countries, is full of examples: Asian wasp (Vespa velutina), Louisiana crayfish (Procambarus clarkia), silver wattle (Acacia dealbata), American mink (Neovison vison) and many others.