The importance of trees – forests and climate
A forest is not only an accumulation of trees placed next to each other, but must be understood as a complex system consisting of the sum of a very large number of interactions, while being able to interact with outside as a single organism.
It is a very rich ecosystem capable of assuming a wide range of ecological functions (ecosystem services) that play a vital role for humans. In addition to wood production, they are a reservoir of biodiversity and habitats for a large number of species. The high biomass production of these ecosystems allows the creation of a very rich soil with a thick layer of humus. Also, these soils are consolidated by the presence of roots, which has the effect of reducing their vulnerability to slope and natural hazards such as avalanches or landslides.
Forest ecosystems also greatly influence the quality of the air. They produce a significant amount of oxygen in the air we breathe, but are also able to capture dust or other non-degradable pollutants.
The importance of forest ecosystems is not limited to the local scale. On the contrary, forests play a role in major terrestrial biogeochemical cycles, particularly those of water and carbon. In the growth phase, a forest fulfils the function of a natural reservoir of carbon, called a sink. It uses the carbon present in the atmosphere (in the form of carbon dioxide) and fixes it in the wood and in the soil. This carbon is found there and blocked in another reservoir that the atmosphere, and therefore does not participate in the increase of the greenhouse effect.
For the water cycle, their role is even more significant. The concept of evapotranspiration is important: it defines the amount of water transferred to the atmosphere depending on the type of surface. This concept includes evaporation at ground level, the interception or not of precipitation by this surface and the transpiration of organisms found there. Through these processes, a large amount of water vapor is transferred to the atmosphere. This water vapor will then condense (due to the lower temperature) and fall back on the forest as precipitation.