The end of cooler forests

Let's face it: climate change is real. If you disagree, then perhaps you are reading the wrong "skeptical" website. In any case, the science behind it is rock solid. I wrote here previously about how sometimes these scientific results show a certain beauty, even when describing the downhill slope we are on. But sometimes scientific studies show how the recent past is better than we thought, and that the future will be worse than expected.

Take for instance the following study by De Frenne from the Belgian University of Ghent and his 44 (!) co-authors. In an in-depth study covering results from over 60 years that got published this week in the Proceedings of the National Academy of Science (PNAS), the authors investigate why certain vegetation is not catching up with rising temperatures. By this they mean that local forest vegetation is showing relatively less warm-loving vegetation than would be expected from the rising temperatures overall.

The authors analyzed several European and North-American forests. According to their methodology, they looked only in "old" forests. Old forests are those which have not been used for agricultural uses (as long as we have maps for the region), presumably because replanted or reclaimed forests show a poor biodiversity.

In these "old" forests, they found a strong indication that there is a "cooler" vegetation mix because they are more dense, and thus give more shadow. This shadow then explains why the local undergrowth vegetation is resisting to the rising overall temperatures. In fact, the detailed statistical analysis is supported by a phenomenon well known by people wandering, hiking or biking in the forest during a hot summer: it is cooler in the forest.

So that is the reassuring part: forest vegetation seems to resist locally the growing temperatures. But that is no longer true according to the authors. They also show that the denser vegetation seems to disappear, according to the authors likely because of the increased need for woody biomass (bioenergy). The risk is not only the loss of this vegetation, but also the loss of cooler, more shadowy areas. The consequences are vegetation that "catches up" to the increased temperatures, with no possibility to return to that earlier mix. And that is not a good thing... Not only are the temperatures changing too rapidly, this catching up might prove even more deadly for certain species.

Science, it is the truth but sometimes it might not be reassuring.