– In many cases this leads to increased competition as space becomes smaller the higher the birds go, says Joséphine Couet, an ecology researcher at the University of Helsinki in Finland.
Together with a large group of European researchers, she examined how a total of 177 bird species in some mountain areas of Europe have changed their habits since the turn of the millennium. The result, now published in the journal Global Ecology and Biogeography, shows that the birds have flown an average of half a meter higher per year since 2001.
– We already know that vegetation is creeping higher due to climate change. Now we can see that it also applies to moving organisms. The birds are probably trying to follow their habitat with food and nesting sites as best they can.
The change is largest in the Scandinavian mountains. The birds there now nest on average a little more than twelve meters higher than at the turn of the millennium. One of the outstanding birds is the little ringed plover, which now nests 33 meters higher than at the turn of the millennium.
What surprised the researchers was that the movement also took place at the same pace on the shady sides of the mountains. It was previously assumed that these slightly cooler areas would form a kind of protective buffer zone for many species as temperatures rose. But that doesn’t seem to be the case.
– Climate change pressure seems to be constant on all sides of the mountains, which we didn’t really expect. We can see that the birds can nest there at a slightly lower altitude, but they are driven upwards at the same speed as on the sunny side. It’s an interesting discovery, says Joséphine Couet
But all birds doesn’t move up. Some go further down instead. This is particularly true for slightly larger birds and may be due to lack of space, explains Joséphine Couet.
– In the Scandinavian mountains, for example, we see how the mountain buzzard has instead moved more than sixty meters down. It probably needs slightly larger hunting grounds than it can find higher up, so there is then a trade-off between comfortable temperature and food availability.
Because mountain areas provide diverse habitats and are in most cases less used than natural areas at lower altitudes, they often contain rich biological diversity. Therefore, researchers believe it is important to study how mountain ecosystems respond to climate change.
– We see that biodiversity in mountain areas is changing and that climate change is driving movements. For some species it can happen very quickly, which can make them more vulnerable and even at risk of extinction. “These are complex patterns that need to be taken into account when we implement conservation measures and manage nature,” says Joséphine Couet.
