‘Tree expert’ investigates whether trees can help save the environment
Although the spread of invasive species harms biodiversity, all methods of combatting it will also damage the environment in one way or another.
How to best tackle it is the subject of new research entitled 'The effect of invasive tree species on ecosystem services: plant biodiversity, coal and nitrogen circulation and climate regulation’.
Project leader Dr. Marcin K. Dyderski from the Institute of Dendrology of the Polish Academy of Sciences spoke to PAP about how and at what cost trees can help:
PAP: Do trees help protect the climate and prevent climate changes?
MD: It's hard to say because trees are not equal. Their environmental impact varies as well. For example, an oak has dense wood and accumulates more carbon than a poplar. There are species of trees that can dry the soil heavily or shadow the forest floor, preventing the development of other plants, and thus disrupt the local ecosystem. That's why you do not just say: let's plant a million trees. You need to know what trees to plant and where. I would say that it is rather the soil that can save the climate, because it is a more permanent carbon storage. The tree also absorbs carbon, but in the process of decomposition of its tissues, some of this carbon goes to the atmosphere, and some to the soil. A tree that grows quickly and dies quickly, does not affect the climate as positively as a tree that grows slowly.
PAP: Carbon accumulation is one of the most important processes in the age of climate change, but trees also have many other functions.
MD: Of course, trees regulate microclimate. But here the situation is similar: depending on the species of trees, the features of the crown and the leaves, they will affect the access of solar energy to the forest floor. Black cherry, limiting the availability of light at the forest floor, not only reduces the undergrowth biodiversity, but does not allow the native tree species to renew. It also changes the circulation of elements, accelerating 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 gr