VSurrounded by cold ocean currents, Greenland is home to extremely barren flora. Even in the comparatively mild climate on the southwest coast, sparse willow bushes are the most stately wood. Nevertheless, wood from real forest trees can also be found there: driftwood from Siberia and Canada, for example, has always been in demand as firewood. The natives also liked to use it as a material. In the permafrost, products of relevant Inuit craftsmanship have been preserved for millennia.
So far, only a small fraction of the frozen legacy left by Greenland’s indigenous people has been excavated. Whereby something remarkable came to light: Archaeologists have come across a wide range of wooden hunting equipment: spear shafts and associated slings, arrow shafts and bows as well as paddles and frames from boats. Bjarne Grønnow from the Danish National Museum in Copenhagen also identified parts of 4500 year old wooden tires, over which an eardrum was once stretched. Obviously, the first immigrants to Greenland were able to build frame drums like this. As known from historical times, this musical instrument played an important role in the Inuit culture, also as an indispensable piece of equipment for shamans.
It is to be hoped that future generations of archaeologists will also make spectacular discoveries. But climate change, which is more rapid in the Arctic than in Germany, could forestall scientists in many places: The Special Report of the Intergovernmental Panel on Climate Change (IPCC) “The Ocean and Cryosphere in a Changing Climate” from September 2019 not only predicts that rising temperatures will cause Arctic soils to thaw longer and deeper. The warming could also lead to the upper soil layer drying out and allowing more oxygen to penetrate.
Danish scientists working with Nanna Bjerregaard Pedersen from the Danish National Museum in Brede recently discovered that destructive fungi that benefit from such changes are already lying in wait. Together with Robert A. Blanchette from the University of Minnesota in St. Paul and Gry Alfredsen from the Norwegian Institute of Bioeconomy Research in Ås, they examined eleven archaeological sites, from the 61th parallel on the southern tip of Greenland to the 77th parallel high in the north . The age of the wood samples examined ranged from around 4500 years to the present day.
Ashes are the greatest enemy
As the researchers report in the “Scientific Reports”, Most of the woods that have come to light during the excavations can be assigned to spruce or larch. Pine and willow were mostly rare. The researchers were able to identify the majority of the fungal threads that grew out of the wood samples on a suitable culture medium as sac fungi based on their DNA. Among them were many that cause mold rot. Almost all samples from the archaeological context show traces of this wood rot, which is typical of a constantly damp environment. Greenlandic willow wood lying around on damp ground is also attacked by mold rot. This suggests that the corresponding hose mushrooms in Greenland have always been responsible for natural recycling: present everywhere in the soil, these organisms are ready to attack any type of wood.
In contrast to tubular mushrooms, mushrooms usually do not tolerate waterlogging and require more oxygen. No wonder that Pedersen’s researchers were only able to identify representatives of this group of fungi in isolated cases. Forty percent of the wood samples from archaeological sites, however, showed typical signs of brown rot. It is caused by mushrooms, which like to eat cellulose and leave a large part of the brownish lignin. Apparently such species also belong to the inventory of the Greenlandic mushroom flora.
According to Pedersen and her colleagues, fungi that cause mold rot are less dangerous for archaeological objects. They decompose the wood rather slowly and leave the outermost part of the cell wall, including the central lamella between the wood cells, largely undamaged. If a wooden object loses substance in this way, it becomes fragile, but its shape is initially retained. Fungi that cause brown rot are more threatening, but also white rot fungi, which prefer to attack lignin and disdain cellulose. Where, for example, quivers or relatives of the tinder sponge find a suitable atmosphere, they can completely break down wood in a relatively short time. How quickly they progress with their work of destruction depends on how much Greenland will warm up in the future and whether thawed soils dry out temporarily. In any case, Greenland wood is only safe from fungi as long as it remains embedded in the permafrost.