The Great Elk Trek
Researchers at Humboldt-Universität zu Berlin were able to show that Central Europe offers an astonishing amount of living space for elk and European bison
They can be up to two metres tall, they have a soft spot for twigs, buds, and water plants, and they have a serious case of wanderlust. Meeting an elk is probably something only people travelling to Scandinavia would expect. However, the large herbivores have now returned to Germany together with the European bison, also known as wisents. Researchers at Humboldt-Universität zu Berlin have now investigated which territories in Central Europe could be used by the migrating species and whether the animals could get there if they wanted to.
Wisents and elk are Europe’s largest land mammals and prefer to live in so-called landscape mosaics – areas where forests, wetlands, and open landscapes exist closely next to each other. Until well into the Middle Ages, the shaggy-brown herbivores were common in Scandinavia, across central Germany, and all the way down to the Pyrenees. “However, they were driven out of Germany through hunting and deforestation,” says Hendrik Bluhm, a biogeographer, who is currently completing his PhD at HU. Several hundred years later, the tide is turning: Migrating moose are increasingly entering Northeastern Germany from Western Poland. Wisents, too, are coming back. The fact that they are reclaiming their ancestral habitat is a real success story, especially since they became extinct only a good hundred years ago. “It was around 1927 when the last individual was shot in the wild. There were only 54 animals left in zoos and wildlife parks,” says Hendrik Bluhm. Emergency breeding programmes succeeded in preserving the species. As of the 1950s, the first herds in Poland were released into the wild.
“Meanwhile, there are more than 7,000 wild wisents in Europe. In addition to the core population in Poland, you can find them in the Baltic States, Belarus, Russia, Romania, Ukraine, and the Rothaar Mountains in Germany. However, the situation of the bison continues to be precarious because of their low genetic diversity – today’s populations hail back to those 54 animals that were still alive in the late 1920s. “Genetic impoverishment increases susceptibility to diseases. The herds are largely isolated from one another and not particularly large. An unforeseen event such as a fire, disease outbreak, or a harsh winter could quickly decimate the population.” Larger herds and more habitats are thus important to ensure the survival of the species.
To open up additional habitats would be desirable not just for the wisents. Like elk, they fulfil important functions in the ecosystems. “Trampling creates hollows in the soil that are used by endangered beetle species. Due to their long migration routes, elk and wisents also spread plant seeds over long distances and ensure that new microhabitats are created through their feeding behaviour, which benefits other animal and plant species. “In collaboration with colleagues from Germany, Poland, the Czech Republic, Austria, and Sweden, Bluhm and his colleagues from the Department of Geography recently investigated which habitats the species is currently using and which still uninhabited areas it could exploit in the future. A large part of the data were provided by about 80 elk and 130 wisents that were equipped with GPS collars. “This enabled us to see: What use do the animals make of certain areas and what are the environmental conditions of these areas?” The researchers combined the information they gained, for example, with spatial environmental data gleaned from satellite images and were able to make predictions about which areas in Central Europe were suitable as new homes.
“Additionally, we looked at the traffic and population density in those habitats that were ecologically suitable. By doing so, we wanted to assess the potential for disturbance and conflict in the possible event of settlement.” Moreover, the researchers investigated which areas could be reached by elk and wisents through migration. “We looked where the landscape was permissive and where barriers limited migration. We aimed to find out where a return could be expected in the medium term, to predict human-wildlife conflict, and to start talking about it with, say, farmers and forest rangers.”
The researchers were surprised at how good the chances were for elk and wisents. “We found areas in a wide variety of Central European regions that could provide suitable habitat – including many in Germany.” However, the research also shows that the potential for conflict increases gradually from East to West. Many more people live in the west of the country and the road and transportation network there is particularly dense. “The largest potential for low-disturbance settlement can be found in Northeast Germany – for example, in the south of Brandenburg, Schorfheide, and the Mecklenburg Lakeland.” Which areas the animals will decide to colonise in the end depends on the number of migration corridors. Here, too, the researchers have identified an east-to-west gradient. “The number of barriers increases towards the west, mainly due to the increasing density of the road and transportation network.”
An increasingly fragmented landscape makes life harder for the animals, not just in Germany. “In Eastern Europe, too, motorways are being expanded and barriers erected. The fence between Belarus and Poland, the EU’s external border, limits migration.” A fence along the German-Polish border has been set up in the summer of 2021 that could also prevent the exploitation of new habitats. It was built to contain the spread of the African swine fever and goes right through the middle of a nature conservation area. It hasn’t yet been researched how the fence impacts the surrounding ecosystems. One general fact is clear: “Migration plays a large role for many species. It has been shown, for example, that red deer populations are becoming more and more genetically impoverished because of a lack of exchange due to landscape fragmentation. These barriers are not only problematic for elk and European bison but also for other species.” Hendrik Bluhm also knows that specifically creating green bridges and passages. “In addition, it is important to assess the ecological impact before erecting more barriers.”
Nora Lessing, Adlershof Journal