Icy greeting: Although curious about tourist vehicles, polar bears are far from friendly. The largest of all land predators, the solitary polar bear occasionally hunts humans.

People don't lock their doors in Churchill, Manitoba. That's partly because this town of 900 just south of the Arctic Circle at the western edge of Hudson Bay is safe and friendly, with only one paved road. But it's also because passersby never know when they'll need to duck into the nearest building for safety: Churchill is smack-dab in the migratory path of about 1,000 polar bears. In the past 25 years, Churchill has turned this phenomenon into big business, luring nearly 10,000 tourists each fall to this self-appointed "Polar Bear Capital of the World."

This is about to change. The Arctic is warming nearly twice as fast as the rest of the planet, which is bad news for polar bears, and therefore bad news for Churchill's economy. Normally the ice on Hudson Bay melts in late spring, forcing the bears onto land around Churchill to wait out the summer while living off their fat reserves. When the ice re-forms in the fall, they hustle toward the freezing bay and spend the winter stalking seals and gorging on the pups. Now the sea ice melts earlier and forms later in the year, giving the bears three fewer weeks to feed. Canadian and U.S. biologists have documented a nearly 20 percent decline in the western Hudson Bay polar bear population over the past 20 years. In Alaska, forced to swim longer distances between receding ice sheets, the great lords of the Arctic were actually drowning. Projections show Hudson Bay staying ice-free all year as early as 2050, which would likely doom the bears, and bear tourism.

Ironically, vanishing ice could clear the way for an entirely new industry. Churchill happens to have Canada's only Arctic seaport, but now only a handful of ships slide in each summer. They often arrive dented, having barged through ice cover. For most of the year, the port is frozen shut. Now less ice means the summer shipping season is extending and new trade routes are opening up through the Arctic to northern Russia. This is good news for the American company that bought the Churchill port in 1997 for $10.

Aware of its changing weather, the town also is scrambling to diversify its tourism industry with less spectacular, more dependable attractions. It's now pitching itself as "Bird Watcher's Paradise" in spring, "The Beluga Whale Capital of the World" in summer, and "Nature's Light Show," for viewing the aurora borealis in the middle of winter -- when it's routinely 40 below.