Alien plant species in the flora of the Silesian Voivodship

The transmission of organisms beyond their natural distribution range is one of the effects of human activity, important in terms of nature. Specific plant and animal species behave differently in new areas, where they have been introduced either intentionally or unintentiontally. Some species are definitely unable to compete with local species and they occur only ephemerally (casual species), whilst others can compete so effectively that they establish permanently, or even replace the native species. At the end of the 20’11 century, the spread and establishment of alien flora and fauna became so serious that it is specified as one of the major threats to biological diversity