As the Arctic melts due to climate change, its iconic marine mammals are feeling the heat. The Arctic Ocean held less sea ice in June of this year than any previous June on record. For the last four summers, the ice melt has exceeded what even pessimistic climate models predicted only a few years ago.
Yet ice and its inhabitants define this region: Take away the ice, take away the Arctic. Without wildlife conservation measures and a serious attempt to address climate change, the adverse impacts will only grow.
Between 1979 and 2000, the Arctic held an average of 7 million square kilometers of sea ice even in late summer. In 2007, only 4.3 million square kilometers of ice remained, meaning that 40 percent of this habitat was lost. By comparison, about 20 percent of the Amazon rainforest has been destroyed by clear-cutting -- an environmental tragedy that has been widely covered.
Changes this large impose consequences. Since prehistoric times, up to 250,000 walrus have moved northward each summer into the Chukchi Sea, following retreating sea ice. There, off the northern coast of Alaska, walrus feed on clams in the seabed, resting on ice between their dives. Female walrus nurse their young on the ice floes. When the ice rapidly disappeared there during the summer of 2007, thousands of walrus were forced onto land where they risked trampling deaths, predation by bears and depletion of food sources.
As an occasional occurrence, this might not be cause for alarm. A few dozen walrus have often come ashore in Alaska. Along the Russian coast of the Chukchi Sea, thousands of walrus congregate on beaches in late summer before heading south to the Bering Sea. But the conditions in today's Arctic are prompting a major ecological shift and walrus face new pressures as they try to adapt.
Meanwhile, rapidly melting sea ice is opening the region to increased industrial activities, including oil and gas development and more ship traffic, which in turn have the potential to further stress marine mammals. The United States has halted commercial fishing in its Arctic waters for the foreseeable future as a precautionary measure. But commercial shipping plus offshore oil and gas activities are likely to spur extensive coastal infrastructure development and introduce oil rigs to waters where walrus feed. These human impacts must be minimized if walrus are to survive and flourish.
In the eastern Canadian Arctic, the narwhal's future is just as uncertain. Long a source of fascination, Europeans once thought that the creature's long spiral tooth protruding from the front of its head was like the horn of the unicorn. Instead, scientists discovered that the tooth is an extraordinary sensor for temperature, salinity and other ocean conditions and may help with navigation and feeding. Today, up to 60,000 narwhal, or 85 percent of the world's population, migrate in summer through Lancaster Sound, at the eastern entrance to the Northwest Passage. They spend winters feeding on Greenland halibut more than a kilometer below the surface of Baffin Bay.
As sea ice retreats and takes longer to re-freeze each fall, narwhal will also have to respond. Scientists have rated it as the marine mammal most vulnerable to the loss of sea ice. As with walrus, however, habitat changes are not the only risks for narwhal. Increased commercial fishing in Baffin Bay could reduce the species' food sources as well.
The development of a sound, fishery-related ecosystem management plan will allow these marine mammals every chance to adapt as best they can. The Canadian government's promise to create a national marine conservation area in Lancaster Sound also is a crucial step toward helping protect narwhal.
Losing sea ice not only impacts high-profile animals such as walrus and narwhal. Many species have adapted to live only in the Arctic, supporting a food web that begins with tiny algae growing under and in the ice. Conservation measures that encompass wildlife, fishing, shipping and drilling are needed now in Arctic waters, lest its ecology becomes a historical artifact rather than a vital part of our global heritage. And ultimately, if the loss of sea ice is to be slowed or reversed, the human causes of climate change must be addressed. An Arctic without ice deprives not just the narwhal and walrus, but all of us.