The effect of reforestation on climate , it is true, tends to be extremely difficult to measure. In theory, trees absorb CO2, which is good for the climate. However, from a local point of view, trees store heat through what is known as the albedo effect , since the surface is darker when covered with forest.
In tropical areas, this “warming” effect is offset by the density of vegetation, which absorbs a lot of CO2. But a study published in August, and conducted by Princeton University, would show that forests could have a cooling effect , so planting trees in large areas would actually be beneficial in cooling the climate .
As experts indicate, the cooling effect of trees helps reduce the surface temperature of different European cities during the summer months by up to 12 ° C in some regions. While, according to a recently published study, green spaces without trees would have a negligible effect, reinforcing the case for planting trees as a way to help cities adapt to global warming .
To study this effect, Jonas Schwaab of ETH Zurich in Switzerland and his colleagues used satellite-compiled land surface temperature data to compare temperature differences between different areas consisting of treeless urban green spaces. (such as parks), those that were covered by trees and areas corresponding to buildings and roads. In total, they analyzed 293 cities spread across Europe.
It is necessary to keep in mind that the temperature of the Earth’s surface measured by satellites is not the same as the temperature of the air, which tends to be more closely related to what humans would feel. As Schwaab stated, “Typically, the air temperature difference between tree-covered areas and built-up areas would be much smaller than the temperature differences at the surface of the earth.”
The scientists found that the areas that were covered with trees, and that we found in common areas of the main cities, would have a much lower temperature of the Earth’s surface, when compared to the surrounding areas . Specifically, they found that the differences were between 8ºC and 12ºC in Central Europe, and between 0ºC and 4ºC in southern Europe.
The cooling effect of trees comes mainly from shade and perspiration , which is when the water found inside the tree is released as water vapor through its leaves.
This process takes heat energy from the surrounding environment for evaporation, which would help lower the surrounding temperature.
In the warmer climate of southern Europe, the soil is usually drier, so the cooling effect of perspiration is less than in regions further north.
As the study authors state, extreme heat has become a growing problem for cities in Europe and elsewhere in the world, especially as the planet warms.
Hence, the findings show that trees can have a major impact on European cities , although heat mitigation strategies should be tailored to each region, as the size of its effects varies.