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Climate Witness: Georg Sperber, Germany

Georg Sperber, a 72 year-old forester from Germany, explained the dramatic consequences of higher temperatures for spruce trees in the “Steigerwald” forest in Bavaria. Such trees are the backbone of the German forest industry, but they are suffering more and more from attacks of bark beetle populations which are putting their future at risk.

I am Georg Sperber from Bavaria, Germany. I have worked as a forester for more than 30 years, and the forests I have worked in have changed over these years. Especially in the past 20 years I have seen changes that were remarkable in their nature and intensity. I believe climate change is the main reason.

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You hear a lot about global warming in the media, but out there in the woods you can feel the difference, even without knowing the alarming facts of climate science. The Nineties have been the warmest decade in climate history, and this was obvious to anyone who lives in touch with nature.

In my forests the consequences for spruce trees are especially dramatic. Spruce is the backbone of the German forest industry, covering 28% of Germany's forests. However, higher average temperatures and more frequent droughts due to climate change weaken these trees.

With global warming, spruce is a tree without future in most parts of Bavaria

They are under attack from bark beetle populations, which have massively increased because of the warming. And over past years storms like Vivian, Wiebke and Lothar – probably worse in intensity due to climate change - have wrecked havoc on spruce forests.

Rainfall patterns have also changed significantly. In the Steigerwald forest, rainfall used to peak in spring and early summer when the plants needed the extra water most. But since the Nineties this peak has moved to autumn. All in all the weather has become unpredictable, and the changes affect the forest industry badly. With global warming, spruce is a tree without future in most parts of Bavaria.

The bark beetle is not the only harmful parasite that loves the warmer temperatures. The oak procession moth also spreads heavily and even attacks people with its poisonous hairs, causing painful skin irritations that can last two years. When I studied forestry in the Fifties, the moth was an entomological rarity. But nowadays local authorities in the Mainfranken region are forced to hire fire brigades to battle them. Again and again oak forests – where you find the moth – are sealed off to protect the public. And the fire workers have to wear protective clothing when entering the affected forests.

After I retired 8 years ago, I am out in the woods even more often. Migratory birds always had my special attention, and climate change is also troubling their lives. Each year in spring they return a bit earlier than usual, and they leave much later in autumn. Some Chiffchaffs or Blackcaps don’t leave at all these days, but try to stay over winter. Sometimes I see species I would not have seen in the past. I am excited about these encounters, but they also worry me a lot, because they show that things are changing.

Climate change is the biggest challenge mankind is facing. Currently we are about to put a huge burden on the shoulders of our children and grandchildren. We are absolutely aware that we are doing it, but we know that we shouldn’t be doing it.


The distribution of trees in Germany and most of Central Europe is mainly determined by air temperature and the amount of rain – exactly the factors which are altered by climate change. Rising average temperatures and changes in the water regime have both short and long-term effects on trees and forests across Germany. The degradation in the water supply puts them at particular risk. Less rainfall in summer and water reserves in the soil are insufficient to secure an adequate water supply in some regions. For the trees this results in drying stress, decreased growth and weaker vitality, making them more vulnerable to storm or pest damages. This worrying development also has economic implications.

Timber logged because of such forest damage is usually of less value. As the total amount of timber increases due to so called “unexpected yields”, the price per unit of wood on the market is usually lower. Today, such “unexpected yields” already account for about 40 per cent of the total wood yield in several regions. Harmful parasites benefit from climate change. For them rising temperatures mean more favourable living conditions, resulting in a higher number of individuals, an expanded range of distribution, and immigration of new species.


Scientific review

Reviewed by: Prof. Annette Menzel, Department of Ecology, Chair of Ecoclimatology, Technical University of Munich, Germany

Dr Georg Sperber is a well-known expert in sustainable forest management, in ecological hunting and in questions of different nature and environment conservation issues.

The story Georg Sperber describes here is consistent with scientific findings about climate change impacts on forests observed in northern Bavaria throughout the last decades. Analyses of meteorological data demonstrate that rainfall patterns have been changing with less precipitation in summer putting stress on spruce trees.

It is well documented in scientific literature that insects such as bark beetles and oak procession moth clearly respond to warmer springs and summers. And there is plenty of evidence that bird migration patterns and timings have been altered. The findings thus reflect peer-reviewed literature on climate change related effects on spruce and forest ecosystems in northern Bavaria.

Rosenzweig C, G Casassa, DJ Karoly, A Imeson, C Liu, A Menzel, S Rawlins, TL Root, B Seguin, P Tryjanowski (2007) Assessment of observed changes and responses in natural and managed systems. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 79-131.

All articles are subject to scientific review by a member of the Climate Witness Science Advisory Panel.