Polar Bears May Be More Common Than They Used To Be

See The Polar Bear Problem by Matt Ridley.

"Today bears are now far more common in Spitsbergen and the other islands of Svalbard. They are more common all over the Arctic than 33 years ago. The US Fish and Wildlife Service estimated in 2008 that the polar bear population was at a historic high of 20,000-25,000 bears, up from as low as 5,000-10,000 bears in the 1960s. The International Union for the Conservation of Nature estimated in 1966 that there were 10,000 polar bears in the world; in 2006, the same source estimated 20,000-25,000 bears. Just last May the IUCN Polar BearSpecialist Group concluded there has probably been no drop in the numbers since then.

The reason for this boom is no mystery. When I travelled in Spitsbergen in the 1970s and 1980s you could still find old trap guns on remote headlands, dating from decades before: open-ended wooden boxes concealing rusty rifles with wires attached to the triggers so that a bear would shoot itself if it pulled the bait. The trapper would return later for the skin. Until 1973, bears were hunted for their fur and for sport; in that year, an international agreement banned unregulated hunting, shooting from aircraft and shooting from icebreakers. The species then thrived. Russia, Greenland and Canada all still allow some hunting, mainly by indigenous people, but at a much reduced level.

Not all populations are thriving. Some authorities think the numbers are declining in Hudson Bay and parts of the Canadian Arctic, while expanding elsewhere, but these are minor fluctuations compared with the impressive recovery of the species since the 1960s. Al Gore, in his film An Inconvenient Truth, made much of a report of four bears that drowned in open water off Alaska, implying this was a new and deadly fate awaiting polar bears as Arctic ice retreated. But polar bears often swim long distances — one was recorded swimming 400 miles — and nobody knows how unusual it was for four to get caught in a storm and drown.

The polar bear is a specialist seal-eating predator (so it is little wonder that it goes for other elongated six-foot mammals when hungry). It occupies a specific niche: the ice edge. It cannot thrive on unbroken Arctic sea ice, because seals are not found there. Nor can it survive on ice-free sea because it cannot kill seals in open water. In parts of the Arctic, notably Hudson Bay and Wrangel Island, it takes refuge on land for several late summer months when the ice vanishes, fasting — or scavenging ineffectually for young walrus, birds and fish — till the ice re-forms. This is when it is hungriest and most dangerous.

If the ice-free season lengthens in these places because of climate change, the bears might die out. After all, the most southerly polar bear dens in the world, in James Bay in Canada, are on the same latitude as Nottingham: they are at the extreme southerly end of their range. But by the same token, areas further north, currently too solidly frozen for seals, will become more hospitable to bears.

For example Svend Funder of the University of Copenhagen recently published a paper with two colleagues, based on a study of driftwood and beach ridges in north-eastern Greenland, where today year-round ice fastened to the shore prevents waves that can form beach ridges. They concluded that There is now good evidence that this sort of ice retreat has happened in the past.for thousands of years when the Arctic was known to be 2-4°C warmer, beach ridges formed and driftwood failed to make it to Greenland, indicating open water on this coast (driftwood needs multi-year ice to be transported from Siberia without sinking).

In Funder’s words: ‘Our studies show that there have been large fluctuations in the amount of summer sea ice during the last 10,000 years. During the so-called Holocene Climate Optimum, from approximately 8,000 to 5,000 years ago, when the temperatures were somewhat warmer than today, there was significantly less sea ice in the Arctic Ocean, probably less than 50 per cent of the summer 2007 coverage, which was absolutely the lowest on record.’

Much has been made of the 2007 summer ice retreat being the ‘greatest on record’, but records began only in 1979. In the 1920s and 1930s, there were probably still more open seasons; likewise in the medieval, Roman and other warm periods all the way back to the Holocene Optimum. Polar bears certainly survived such warmer spells, presumably by ranging somewhat further north. Indeed, fossils suggest that polar bears already existed in their current form during the last interglacial period, 120,000 years ago, when the Arctic was almost certainly wholly free of ice in late summer.

A total disappearance of sea ice at all seasons would undoubtedly doom thepolar bear’s lifestyle. But no scientist in his wildest exaggerations is suggesting the disappearance of Arctic sea ice in winter. As long as there is pack ice for much of the year with an ice edge, plenty of seals and controls on hunting, thepolar bear is going to thrive — and tent-based tourism to the Arctic is going to be dangerous."