The Arctic seems not to be what it used to be. This area of the Earth, a traditional refuge for migratory animals, today might not represent the happy culmination of an already risky journey. According to a recent study, these animals are more likely than before to starve, be hunted or die of disease upon reaching their destination . Climate change and environmental degradation are behind this.
Arctic ecosystems are changing rapidly with human activity and new evidence suggests that recent decades have brought in more pathogens and parasites , as well as an added increase in predators and a reduction in available food .
The lack of food appears to be due to a seasonal mismatch between the time the animals arrive north and the time their main source of nutrition is available. This mismatch is the result of global warming, which, on the one hand, is causing some plants to bloom earlier or later than usual and the same with insects and, on the other, it is possible that the animals begin their migration sooner or later than normal. In the case of animals that migrate to reproduce, this could lead to higher offspring mortality, as parents are unable to feed their children as well as before.
As for the increase in predators, the problem is that, once again, climate change seems to have reduced the number of rodents that inhabit the Arctic, which implies that carnivores that previously fed on voles and lemmings, now focus its attention on other prey . “Lemmings and voles used to be the main food source for predators like foxes in the Arctic, however milder winters can cause rain to fall on snow and then freeze again, preventing lemmings from reaching. to their food, “explains evolutionary ecologist Vojtěch Kubelka, from the University of Bath (UK). ” With fewer lemmings and voles to feed on, foxes eat the eggs and chicks of migratory birds. We have seen the nest predation rates of migratory Arctic shorebirds have tripled in the last 70 years, largely due to to climate change “. In this sense, hungry polar bears have been observed feeding on colonies of geese, ducks, seagulls and auks, as they now comb the coasts, they do not travel through the sea ice.
Another danger that migratory animals face when reaching the frozen lands of the north is disease. So, even if they have found enough food to feed themselves and have managed to escape predators, they can be victims of parasites, which, although there are no extensive reference records, seem to have increased their numbers. An example of this is the outbreaks of avian cholera that have been recorded in the nests of some birds in the Canadian Arctic . Also the case of the hundreds of thousands of migratory antelopes from Kazakhstan that have died from a deadly bacterial infection of the blood, believed to be due to increased heat and humidity.
“The migration of animals from the equatorial regions to the temperate north and the Arctic is one of the largest movements of biomass in the world,” says evolutionary biologist Tamás Székely of the University of Bath. “But with the reduction in the profitability of migratory behavior and the lower number of offspring that are incorporated into the population, the negative trend will continue and fewer and fewer individuals will return to the North .”
The study authors are concerned that even if only a few migratory animals were to go extinct, it would unleash a series of cascading consequences that would affect the Arctic ecosystem as a whole . They demand greater protection and conservation of migratory breeding grounds in the Arctic.
Referencia: Vojtěch Kubelka, Brett K. Sandercock, Tamás Székely, Robert P. Freckleton, Animal migration to northern latitudes: environmental changes and increasing threats, Trends in Ecology & Evolution. https://doi.org/10.1016/j.tree.2021.08.010
