g the circulation of matter in the ecosystem. The red oak also produces a lot of large surface leaves, strongly shading the forest floor. Its leaves decompose very slowly and prevent germination of native plant seeds. This starts a chain of connections: the lack of undergrowth plants will affect the presence of insects and other animals.
PAP: Speaking of alien and invasive species, how to distinguish them?
MD: Geographically alien species are species that have crossed the biogeographic barrier. In other words, man is responsible for their transfer, because even the changing climate would not allow them to cross this barrier. There are alien species, such as yucca, which will grow well in a pot, but in current conditions will not settle in our climate zone, it will not spread on its own, man must help it. A species that settles and begins to reproduce on its own can become an invasive species. According to the International Union of Nature Conservation definition, an invasive species is an alien species that has settled and has a negative impact on any native species. According to this definition, in principle, all invasive species have a negative impact.
PAP: According to this definition, we are obliged to protect native species?
MD: Not according to this definition, but according to other provisions, for example, the Law on Nature Protection or the Regulation of the European Parliament forbids from introducing invasive species to the environment and trading them without permission.
PAP: Does this mean that invasive species must be combated?
MD: There is no obligation to combat them everywhere, but, for example, in nature reserves and national parks, combating invasive species is one of the planned protective tasks. Attempts are made to combat the Jerusalem artichoke, the European goldenrod, the black cherry or the box elder, but we still have a lot to do in terms of the development of effective methods of their removal, which would be harmless to the environment. Today we have chemical, mechanical methods and grubbing up. Each of these methods negatively affects the environment in some way.
PAP: The very human presence affects the spread of alien species. Even scientists carry part of plants on the soles of their shoes and on their clothes, allowing them to settle in previously unreachable areas.
MD: It is impossible to completely eliminate our negative impact on the environment, but it can be minimized. We already have procedures that require scientists to disinfect and change clothing on boats that take them to naturally valuable areas. We also do that when combating the effects of climate change. We know that the return to gas emissions from pre-industrial times is impossible, but we try to strongly reduce these emissions to do as little harm to the planet and ourselves as possible.
PAP: In grocery stores, there are a lot of vegetables and fruits brought from different parts of the world. Are they also 'alien species'?
MD: Vegetables and fruits are settled or non-settled alien species, but usually not invasive ones. But it also depends on the climate zone. In the Polish climate, mango will not be an invasive species, but it can be one in the tropical zone. We are working on analysing the impact of climate change on changes in the range of invasive trees and shrubs in Poland. This analysis shows that even under the influence of the greatest climatic changes, many invasive species from the tropical zone will still be unable to permanently settle in Poland.
PAP: But this does not mean that bringing seeds of fruits, vegetables and flowers in a suitcase from a long journey is a good idea...
MD: This is illegal. The import of plants and their parts from outside the EU requires permission. This is also because the spread of alien species often begins in areas around communication centres - railway stations, ports and airports. Then they appear in the city and if are not contained in time, they can 'escape' to suburban territories and further, to more natural areas. Another way is the purposeful introduction of alien species