ETH Zürich researchers have published a new study that is based on observational data from all over Europe. The climate researchers have shown for the first time that forests lead to an increase in precipitation. The study states that if the agricultural land was reforessed, precipitation in Europe could increase by more than seven percent.
Climate researchers have long known that forests affect regional climates. Numerous studies show that usually the temperatures of the surface of the Earth in summer, helping to adapt to the effects of global warming at the local level. It has been less clear how the forests and the reforestation of the agricultural land could affect precipitation at the local and regional level.
Scientists in the project observed precipitation data for more than 5800 measuring stations belonging to different measuring networks. The analysis focused on five regions of Europe due to the availability of data measured in the areas. Regions in the study included in Great Britain, Germany, Netherlands, Sweden and Finland. Pairs of measuring stations were chosen in those regions, with a station in a wooded area and another in agricultural land.
The difference between the forest cover on the ground was at least 20 percent, and the stations should be placed in a similar elevation and no more than 84 kilometers away. For the second phase of the study, the team analyzed the data of the station using statistical models to explain the amount of precipitation and isolate the effect of the station while discards other factors that could affect precipitation.
According to the first author of the study, Ronnie Meier, while there were atypical values, the data showed a clear trend. In wooded areas, precipitation is considerably higher than in agricultural areas. The members of the project team also found that the differences in precipitation were more pronounced in the winter than in summer. The meier hypothesis that the roughness of the forest surface is probably more important than previously thought and is a key factor for greater precipitation.