Abstract
In recent years, radical changes due to human interference have been observed in the flora of Poland. They consist of: (1) arrival and territorial extension of newcomers introduced by Man, and (2) disappearance of former components of the flora. Some 250–300 of the total of 2,250–2,300 species of vascular plants occurring in Poland have been introduced by Man and have become established in this country, about 100 of them being recent immigrants which have arrived during the sixteenth to twentieth centuries. They grow mostly in ‘ruderal’ places and in cultivated fields. Only 34 species of these newcomers have established themselves in the seminatural vegetation of river-banks, pastures, meadows, etc., and only 9 others have been able to penetrate into natural plant communities. Both native and formerly introduced components of the flora are dying out. It is difficult to estimate the total effect of this process; in some regions more than 10 per cent of the species of vascular plants that formerly occurred are supposed to have become extinct during the last 100 years. Indirect human influence through environmental changes is the main cause of this phenomenon. Direct changing of the whole vegetational cover is also very significant, whereas destruction of particular plant species seems to be of secondary importance.
Published Version
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