14 DAY TRIAL // New evidence would appear to suggest that forests can at times support the development of heatwaves, but also show that the trees ultimately promote cooling, if the heatwaves spans a long period of time.
At first, when temperatures soar, trees reduce the amount of evaporation they usually produce. This leads to a rise in temperatures at their location, which in turn contributes to the heatwave itself.
However, in the long run, the correlation is does not hold, experts say. They explain that the lower level of evaporation is what ultimately allows the trees to continue engaging in this process.
This is essential to their survival, and the fact that they can employ this regulatory mechanism is an evolutionary wonder in itself.
In relation to the surrounding area, the ultimate net effect will be one of cooling in both cases, experts say, but the methods used to get to this result vary.
The work was conducted by researchers at the Wageningen University, who were led by expert Ryan Teuling. A paper detailing the findings appears in the latest issue of the top journal Nature Geoscience.
But a large number of researchers in other European countries and research groups also participated in the investigation. The work was prompted by the recent heatwaves that struck Europe.
The experts were interested in learning how land use influences temperature levels and the climate. The new conclusions show that not only a lack of precipitation reduces evaporation, as previously thought.
Land use also plays a major role, and this influence has never been analyzed until now. Additionally, the new paper also looked at varied evaporation patterns, depending on the forest and the heatwave.
It was for example determined that grasslands were capable of evaporating more at higher temperatures, and that they sustained the process until no water was left available.
Conversely, forests evaporated less at higher temperatures, bu continued to do so over a much longer period of time than grasslands. Therefore, this is strictly a matter of preferences and adaptation.
The data the team used in their investigation was collected from a flux tower network in Europe. In areas that lacked such towers, satellite data were used instead.
This allowed scientists to create one of the most extensive databases containing such data in the world. They were then able to analyze the differences in evaporation levels between grasslands and forests.
The team recently received a prestigious VENI innovation grant from the NWO to continue investigating the role of forests in the regional climate system, AlphaGalileo reports.