Kristin Laidre of the University of Washington, US, reported on polar bears. Speaking at a press conference, she gave the probability of the nearly one-third decline as more than 70%, based on estimates of future reduction in sea ice, which the bears rely upon for travelling, hunting for seals, mating, and, in the case of mothers with cubs, denning.
Currently, the worldwide population of polar bears is around 26,000, composed of 19 subpopulations living in four Arctic ecoregions, Laidre reported, adding that there is great uncertainty due to the difficulty of observing some of the populations. The 35 to 40 year timeframe was equal to three generations. This, she said, was the first study to evaluate the bears’ future status as a function of multiple relationships between abundance and sea ice.
Siberia’s wild reindeer and caribou, two related species, are rapidly declining in the Taimyr region, added Andrey Petrov of the University of Northern Iowa, US, at AGU. From a peak of around one million in 2000, the animals are now down to 600,000, representing about a quarter of the world’s wild reindeer/caribou population.
There are several reasons, Petrov suggested. Climate change is one of them, but revisions to old Soviet-era hunting regulations regarding wolves are another. No longer are bounties paid for unlimited wolf kills, he said, and the growing numbers of wolves result in more reindeer deaths. Other aspects of human activity, including poaching, also reduce reindeer numbers.
But climate factors play a role as well, Petrov said. Reindeer migrate, returning to the same places annually: a winter area, a calving site and a summer area. But the Taimyr herd has been shifting towards the north and east, driven by warmer temperatures, increased harassment by mosquitoes and related climate factors. This has led to drownings, especially among calves, because frozen rivers open earlier now, and the herd has to swim, rather than walk, across them. The trek from calving areas to new summer ranges is also longer than in the past and proves too difficult for some of the calves, who die along the way.
It is not only in the Arctic that climate is affecting wildlife populations. In western North America, both mountain lions and mule deer, which are their principal prey, have been affected. They are often difficult to track in the vast desert regions they inhabit. Satellite imagery of vegetation changes successfully predicts the abundance of both species across climatic zones, reported David Stoner of Utah State University, US, at AGU. Warmer and drier climate reduces vegetation and thereby fragments the populations, leading to declines in these large, wide-ranging species, he said. The reduction in these and other species will, in turn, affect the $150 billion wildlife recreation industry, which includes hunting, fishing, birding and other activities nationwide, Stoner concluded.
Related links
- AGU Fall Meeting 2016
- Kristin Laidre, University of Washington
- Andrey Petrov
- David Stoner, Utah State University