Forests Turn Brown in Europe in Summer

Zurich: Droughts and heatwaves are causing Europe’s forests to turn brown in the summer months.

Last year, 37 per cent of Mediterranean and central European forests were affected, a new study revealed.

Researchers from ETH Zurich University and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) have been examining the phenomenon over the past 21 years.

The results, published in the journal Biogeosciences, show that summer forest browning is spreading across Europe. Using high-resolution satellite data, researchers identified periods where areas of forest were not as green as they should be during summer, euronews reported.

While drought played a central role in the browning of forests, its effects were not immediate. Researchers noted a “legacy effect” of intense and persistent dry periods, meaning that the ability of trees to survive heat and drought depends not only on the current weather but on that of previous months and years too. Delving into the history of low-greenness events, researchers identified weather signals that affected trees years down the line.

In particular, frequent periods of little rain over the course of two to three years were a precursor for summer browning. Frequent periods of high temperatures for at least two years in temperate zones also had a significant impact. “Prior to low forest greenness in central Europe, we usually observed two dry, hot summers in a row,” said Mauro Hermann, ETH doctoral student and lead author of the study.

Drought also fosters bark beetle and fungal infestations, as well as forest fires – all of which may indirectly contribute to browning – the researchers noted. The Mediterranean has been suffering from summer forest browning since the early 2000s.

In recent years, the problem has spread to temperate forests in central Europe. With 2022 the continent’s hottest summer on record, Europe experienced its most extensive browning yet with more than a third of forests affected in these regions. This is “far more than any other event in the past two decades,” according to Hermann.

Reduced greenness is a sign of reduced vitality and increased stress in forests. It also indicates forest dieback. In the past, hot, dry summers were less frequent in Europe.

Following the record heatwave in 2003, the colour of Europe’s forests was hardly affected. But since 2018, repeated large-scale droughts and high temperatures have led to extensive browning.

With a repeat of 2022’s record-breakingly hot and dry summer on the cards in 2023, forest browning could become even more widespread in Europe. Germany and Switzerland’s spruces and beech trees, in particular, withered prematurely, as entire forests buckled under constant heat and drought stress. Since weather might not be the only contributor to the phenomenon, the researchers emphasized that it cannot be used to predict the future – but it might offer clues.

“Targeted monitoring of the weather conditions over several seasons could provide valuable information as to whether premature leaf discolouration is likely to occur the following summer,” said Thomas Wohlgemuth,

Head of the Forest Dynamics research unit at WSL and co-author of the study. Forest management could help curb forest browning as temperatures rise, he added.

more recommended stories

Terms of Use:

  • This website Arabian Daily is an individual’s property, not used for any commercial or sales purposes. What you see here are one’s random thoughts in action. I, by no means, endorse any product or party through this, unless stated explicitly.
  • All work you will find here is copyrighted unless stated otherwise. No part of this work can be reproduced in any way with the exception of a) if you share our work, it should link back to this website; b) if you quote any part of our work, it should be properly credited to us with a link to this website.
  • All images used on this website have been taken from open source image websites on the Internet. If any of them are copyrighted to you and you want us to take them down or add credits, please feel free to contact us here, or by using the contact form on this page.
  • The views expressed on Arabian Daily are solely ours. They do not represent any party or any particular school of thought. This website does not promote racism in any form.
  • Privacy Policy:
    This website will respect the readers’ and the writer’s privacy. We do not sell any of their personal or contact information to another company. We do not put your information on spam lists. Also, and more importantly, we are not responsible for the privacy practices of any of our advertisers or website commenters.
  • Reserve Rights: We reserve the right to change the focus on this website, to shut it down, sell it or to change the terms of use at our own discretion.