Trees are a group of about 80,000 species that are distinguished in the plant world by their longevity, might, and the highly developed structure of both their aboveground and underground parts. They are known for their diversity of forms, adaptation to various climatic and soil conditions, and consequently, their primary role in forming the most highly organized terrestrial ecosystems, namely forests. The emergence of trees and the development of forest ecosystems resulted in a significant increase in the oxygen level in the atmosphere and a related decrease in carbon dioxide content, as well as a substantial increase in living space for many other groups of organisms, especially animals. For hundreds of millions of years, forests have been the main natural formation sustaining life on Earth, significantly affecting the composition of the air, climate, water cycle, and biogeochemical cycles. With the increasing population of our planet, the area occupied by this formation has been reduced by more than 50%. Currently, in most areas of Central Europe, they are replaced by plantation agricultural and forestry crops, interspersed tree plantings, and in urban areas – by fragments of undeveloped, partially wild vegetation, parks, squares, allotment gardens, green spaces in recreational areas, historical greenery, residential and home garden vegetation, etc. Although they cannot fulfill all the environmental functions of a forest, they can shape the human environment to mitigate the negative effects of human activity. Well-known properties of tall greenery include protection against strong winds causing air and soil drying and soil erosion, shielding from excessive, direct sunlight, promoting local vertical and horizontal air movements contributing to temperature fluctuation reduction with optimal ventilation of built-up areas.
Tree clusters have a positive effect on increasing and evening out rainfall distribution and retaining water. Well-designed, established, and maintained, they can effectively lower noise levels. Trees act as natural biological filters, as they not only remove carbon dioxide from the atmosphere but also trap large amounts of dust and absorb harmful gases such as sulfur oxides, hydrogen sulfide, sulfuric acid vapors, hydrochloric acid, and nitric acid, or disperse them through constant crown movement. The filtering importance of greenery is particularly significant near streets and other communication routes. It’s also worth mentioning the beneficial effect on human health of substances secreted by trees, known as phytoncides, and negatively charged ions that have a positive impact on the heart, respiratory system, and psyche, among others. The aesthetic role of arranged greenery, especially in softening the unfriendly appearance of construction ugliness (barracks, warehouses, etc.) and the still prevalent concrete sprawl, should not be forgotten. The enormous biocenotic significance of trees and their clusters in the immediate human environment deserves a separate and special discussion.