The hair of the bison, a detector of global change in the last virgin forest of Europe

More than a decade ago, a group of scientists began searching for hairs from animals that live in the Bialowieza plain forest (Poland), the last remaining virgin forest in Europe. The team tracked whether the modifications associated with global change had reached this type of natural ecosystems, still primitive, and they found them: there they were imprinted in the carbon and nitrogen isotopes of the hairs of 50 species of mammals collected between 1946 and 2011. To locate these valuable samples of bison, lynx, wolves, shrews, voles or bats (the only flying mammals), among others, scientists investigated museum and private collections, even knocking on the doors of private homes.

With patience and meticulousness, they have shown that animals that live in well-conserved places can “act like canaries in a mine, providing warning signals of environmental changes and becoming sentinels that help detect invisible impacts of global change in a more holistic way.” “, they indicate. The results of the research are have published in Global Change Biology. Scientists also consider that these parameters should be controlled and monitored on a regular basis.

“There are areas of the forest that have never been touched and we have obtained samples that are impossible to find anywhere else in Europe,” says Nuria Selva, researcher at the Polish Academy of Sciences and lead author of the document in which scientists have also participated. from the CSIC and the universities of Seville, Huelva and the University of Ontario (Canada). “If it wasn't for the analysis of the hairs,” she points out, they would never have realized what was happening. The examination concludes that the ratio of carbon isotopes in the fur, for example, of a bison from a collection from 70 years ago is different from that of one living today. This is due to the increase in carbon dioxide (CO₂) – the main greenhouse gas – in the atmosphere, which is incorporated into the vegetation of the Bialowieza forest and from there passes to the animals when they feed. “Although fossil fuel emissions are emitted in China, they reach here,” reflects Selva.

One of the most notable findings of the study was the clear decrease in the proportion of nitrogen isotopes in the hair of the animals tested. This result coincides with the observed decrease in the concentration of nitrogen in the leaves of the trees in the Bialowieza forest, explains Keith Hobson, another of the authors of the study and an expert in stable isotope ecology. Which, at the same time, aligns with other research that has reached similar conclusions in natural forests. For example, a study of North American prairie grasshoppers confirmed that nitrogen availability is declining in plants. “This can have a long-term effect, especially on herbivores, because it lowers the reproductive rate of species, which eat the same amount of leaves, but of poorer nutritional quality,” he adds.

What Selva fears is that important changes will occur in the food webs. [conjunto de cadenas alimentarias de un ecosistema interconectadas entre sí mediante relaciones de alimentación]. “If the basic nitrogen cycles change, it affects the foundations of that network, and it would be a cascade effect whose consequences we do not know,” he says.

The collection held by the Mammal Research Institute of the Polish Academy of Science played a fundamental role in locating the hairs, which began systematically taking samples of animals since the end of World War II and carrying out studies. on the diet through excrement. “We found matchbooks from the 1940s or 1950s with samples of a species of shrew that was new to the forest,” explains Selva. The scientific team took hair from the stuffed mammals, but they had a hard time finding hair from lynxes or wolves. “They told us: 'that hunter has a stuffed lynx in his house' and there we went. Then we were missing shrews and we had to find them,” says Selva, who knows the terrain and the hunters and locals well, having lived there for 22 years. They also encountered problems locating bat samples, which they were assisted by a local researcher.

The Bialowieza Forest covers 150,000 hectares, shared by Poland and Belarus, of which 10,000 form the national park and 6,000 the primeval forest, where human intervention is minimal. Its importance was recognized decades ago, when it was declared a Biosphere Reserve in 1977 and a UNESCO World Heritage Site in 1979. Despite the protections, the enclave has suffered different attacks. The last one occurred with the construction of a huge wall 5.5 meters high and 186 kilometers long, which aims to prevent the influx of migrants from Belarus. The barrier has not only been denounced by human rights organizations, but also by environmental groups and scientists who warn of the attack it constitutes against the fauna of this unique enclave. The barrier crosses the reserve area and blocks the migratory routes of bison, wolves and deer, especially if one takes into account that the border between both countries is one of the corridors used by wildlife between Eastern Europe and Eurasia.

Already in 2016, the Polish Government carried out massive felling of trees in several areas of the reserve – bordering the national park – under the pretext of dealing with a beetle infestation that was killing the most abundant conifer in the forest. Poland suspended work in 2018 following an order from the EU Court of Justice and the threat of a fine of 100,000 euros per day if it failed to comply with the ruling.

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