The Effect of Forests on Climate
Once there were vast forests covering North America and Europe. What happens to the climate if they were returned? Planting trees in an area where there are no trees now, can reduce the effect of climate change by cooling temperate regions finds a study in BioMed Central's open access journal Carbon Balance and Management. Afforestation could lead to cooler and wetter summers by the end of this century if it was done now. Of course doing it now is a problem not only of resources of what it replaces and the effects that may have elsewhere.
Tree forests cover approximately 9.4 percent of the Earth's surface (or 30 percent of total land area), though they once covered much more (about 50 percent of total land area). A forest is an area with a high density of trees. As with cities, depending on various cultural definitions, what is considered a forest may vary significantly in size and have different classifications according to how and of what the forest is composed.
Climate change is projected to lead to summer droughts and winter floods across Europe. Using REMO, the regional climate model of the Max Planck Institute for Meteorology, researchers tested what would happen to climate change in 100 years if land currently covered in non-forest vegetation was converted into deciduous forest. This equates to more than a doubling of forest in Poland, Czech Republic, Denmark, Northern Ukraine, Northern Germany and France.
The large leaf area and low aerodynamic resistance of these types of trees lends itself to enhanced evapotranspiration compared to other vegetation, cooling the surrounding air, and leading to cooler surface temperatures. The model indicates that in the northern part of central Europe and Ukraine afforestation results in 0.3-0.5C decrease in temperature and 10-15% more summer rain by 2071-2090.
Large contiguous forest blocks can have distinctive biogeophysical effect on the climate on regional and local scale. Results of this case study with a hypothetical land cover change can contribute to the assessment of the role of forests in adapting the world to climate change. Thus they can build an important basis of the future forest policy.
Reforestation of this magnitude is unlikely to occur because the land in question is often in use by humans for agriculture or habitat. But i does point out the net positive effect of of forests on climate and allows a prediction of what might be doable to some degree of magnitude.
For further information see Reforestation.
Forest image via Wikipedia.