Two distant countries, yet there are so many similarities, like cultural or linguistic ones, between Portugal and Romania. Environmental issues, unfortunately, do not escape from these resemblances. The invasion of alien species (IAS) in both countries is something that we are used to seeing and the consequences are often the same, changing all the surrounding ecosystem and in the near future, possibly destroying it. All of this is being verified in the invasion and substitution of autochthonous species that, after their arrival, take advantage of the climate change in that country.