Thousands of walruses have been forced onto an Alaska beach because of disappearing sea ice, and the Federal Aviation Authority has rerouted flights to avoid startling them and creating a deadly stampede.

The FAA instructed pilots to remain above 2,000 feet and half a mile away from the animals, and helicopters — which pose a greater risk because they're noisier — have been asked to remain above 3,000 feet up and a mile away.

Walruses aren't accustomed to being closely packed together, and they're easily startled. A stampede could put the animals at high risk of being trampled to death.

At this time of year, most of the walruses in the Chukchi Sea are females and calves.

Currently, there's an estimated 35,000 walruses crowded on the barrier island in northwestern Alaska. The marine mammals were spotted by scientists from the National Oceanic and Atmospheric Administration on Sept. 27 during an aerial survey flight.

Until 2007, it was unheard of for walruses to leave sea ice for land for long periods of time. The animals spend 80 percent of their time in the water hunting for clams and shellfish, and they rest on sea ice.

However, climate change has led to a decline in sea ice, causing drastic changes in walrus behavior. Last month a report from the National Snow and Ice Data Center found that summer sea ice fell to its sixth lowest on record.

"Those animals have essentially run out of offshore sea ice, and have no other choice but to come ashore," Chadwick Jay, a U.S. Geological Survey ecologist, told The Guardian.

This year marks the biggest "hauling out" ever observed in Alaska, increasing competition for food in addition to the risk of a deadly stampede.

Last year, a NOAA survey counted about 10,000 walruses on the beach, and in 2011, about 30,000 came ashore.

"The massive concentration of walruses onshore — when they should be scattered broadly in ice-covered waters — is just one example of the impacts of climate change on the distribution of marine species in the Arctic," Margaret Williams, the World Wildlife Fund's managing director of the Arctic program, said in a statement.

The walrus haul-out comes the same month that a NOAA report found that sea surface temperatures across the North Pacific are 5.4 degrees Fahrenheit higher than normal.

"Not since records began has the region of the North Pacific Ocean been so warm for so long," the report reads.

The growing size of walrus haul-outs has prompted the U.S. Fish and Wildlife Service to consider expanding protections for the animals.

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