tonight on "nightline" -- inside the melting arctic circle. where the elusive polar bear is clawing for survival. >> their habitat's gone. the world should be interested in this. >> as their environment disappears beneath their feet, these powerful killers are moving inland toward human kind. >> is that the most frightened you've ever been in your life? >> yes. >> our amy robach on a journey to the edge of the earth. >> there are four polar bears right there swimming in the water. that's incredible. >> with the americans who call it home. >> most people here have firearms, just in case. >> and the scientists racing to save this vulnerable species. this special edition of "nightline," vanishing ice, the

last american polar bears, will be right back.

this is a special edition of "nightline," "vanishing ice: the last american polar bears." on the pure white ice they are almost invisible, an enduring. >> of the wild arctic. but in recent years the polar bear's come to embody something

else. a creature caught in a changing world that's disappearing under its feet. there are less than 25,000 polar bears left in the wild, and few ever encounter them. but each year dozens descend on this isolated alaskan village. we're going on a journey to the edge of the earth to understand what's pushing these elusive beasts closer to people. >> you're going to fly right over the arctic circle up to barter island. >> hi. >> this is day 3 of travel. and we have our fingers crossed because we're hopeful that we're actually going to get up there today to see the polar bears. >> here we go. >> we'll check our latitude on

the gps. and yes, we have just crossed the arctic circle. so the burks range is up ahead. they're extremely rugged, as you can see, and it's an extremely remote area. >> reporter: so remote we lose contact with air traffic control. >> we have no radio communication with the outside world right now. definitely a first for me. but this is spectacular. how dicey can it get up here? >> you have to be confident. going up to somewhere as remote as we are. >> reporter: but even from this vantage point our co-pilot says evidence of a warming planet is visible. >> glaciers are receding. the sea ice has shrunk substantially already. permafrost is starting to melt. but the fact things are getting warmer is undisputed. >> reporter: approaching barter island, we get a preview on the stony islands below, a white bear. >> 15 southwest of barter

island, 1,000 feet, inbound. runway. >> wow. we finally made it. >> the village of kaktovik, alaska on barter island. population, 239. a stark and striking landscape but not quite the snow-blafrnted mountains you quite expect from the arctic. a change which has reached into all corners of life here. it's not long before we see what we came for. we left the shore three minutes ago, and already there are four polar bears right there, swimming in the water. that's incredible. i mean, what are we, 50 feet from them? >> we're pretty darn close. >> one, two, three, four polar bears. a mother with her triplets. these bears a drab shade of brown. wearing the signs of spending so

much time on muddy land. >> wow. >> so you often see them playing with each other? >> every day. >> reporter: our captain bruce inglunasak says these bears are here because they're waiting for the sea ice to return. the frozen surface of the arctic ocean where they spend most of the year feeding on seals. >> they're just conserving energy. they know they've got a long wait for freezing. >> reporter: until the freeze-up they scavenge on the remains of the bowhead whales the people of kaktovik must hunt to survive here. >> how long do polar bears linger or stay around these parts? >> every year the fall time they'll hang out here till it's mid november, and then they'll -- when the ice start forming out in the ocean, when that starts happening the seals go on the ice and that's where the polar bears get their seals, it's on the ice. and if that ice is not there, they don't get them.

>> reporter: the bears used to spend just three weeks on land. but today they are stranded for nearly three months because the ice is staying melted longer. scientists say it's due to global warming. in this part of the world the sea ice is declining at a rate of 9% a decade. a dramatic number for polar bear conservationists. scientist dr. todd atwood and his team tranquilize the bears from helicopters, collecting samples. >> this looks like a male. >> reporter: stud yying how climate change is affecting these bears. >> helps with warmth and friction i think. traction. those beautiful claws. >> reporter: we spend about 45 to 50 minutes with each bear that we capture. we collect a variety of samples. a bunch of body measurements so we can measure physical stature and how physical stature might be changing through time. >> probably right on the cusp of being an adult. and we gave him seven ccs, which

is a standard dosage for a bear of this size. >> i think the most surprising thing for me personally has been the complexity of their behaviors. we see them adapt to some pretty dramatic changes in the arctic sea ice ecosystem. we're seeing them use terrestrial habitats to an extent we didn't expect them to be able to use. we're seeing them switch to certain food items that we didn't expect them to switch to. we can characterize stress using hair samples, and we can relate that to how the environment has changed around polar bears to determine if those environmental changes are causing an increase in stress levels. >> currently polar bears are categorized as a vulnerable species, meaning they have a high rix of endangerment in the wild. >> looking for polar bears out here on the sea ice is about learning to read the signs of their passing. and just here behind me are some very, very fresh bear tracks. >> reporter: and in most places of the world polar bears are incredibly difficult to find. >> it's a rare sighting. >> wow. >> reporter: the grueling hunt

demonstrated in the documentary "ghosts of the arctic." but in kaktovik the direct access and sheer number of bears has sparked a tourist boom. visitors like ed bennett fly in, hoping to snap the perfect picture. >> what makes it worth it to me is simply seeing a beautiful white bear walking along a beach who's basically here only because the ice hasn't frozen yet. ice that would have frozen years ago. >> reporter: here we are, unbelievably close to these bears. >> he's so cute. >> he's looking right at us. >> but they believe the water offers us some security. >> so we're safe here on the water? >> we're safe here on the water. >> and brad, i am safely on this boat. >> reporter: on land it can be a different story, as bruce knows all too well. >> and then this happened. i was standing beside him for about a good three seconds. >> reporter: and you you didn't even know he was there? >> i didn't know. >> reporter: he was so quiet when he approached. is that the most frightened

you've ever been in your life? >> yes. >> reporter: i would think so. the opportunity to get a closer look on land is too tempting. so as twilight falls, we set out by suv. >> that's just spectacular right there. it's so pretty. >> reporter: to the bone pile where the hungry polar bears feast. >> we are here right by what the locals call the bone pit, and that's where whale karases have been left for years and years and years. and the polar bears come at dusk and feed on what's left of the bones. >> reporter: our guide tells us we can get a few shots but we have to be ready to make a quick escape. >> we were told we could get out of the vehicle as long as we were near the vehicle and if we heard him say get in we had to run, no hey i need one more shot or i've almost got what i need. he said you'll have to run straight back to the car. you just don't know where they're coming from and they move very quickly. so we would have to move very

quickly as well. >> reporter: though these bears are cute, they can be deadly. in 2013 a bbc wildlife photographer captured the sheer power of a polar bear attack from inside a locked cage. >> one of the most terrifying animals on the planet, one of the most intimidating animals on the planet. one of the few animals that actually see us as food. >> reporter: the male bears can weigh up to 1,500 pounds and stand at over nine feet tall. five times larger than a black bear. they can charge at 25 miles per hour. and their bite force is an astounding 1,200 pounds per square inch. though all they need to kill is one swipe of their massive paw. >> i see some over there too. >> reporter: standing so close to these powerful creatures is awe-inspiring. but our guide, robert thompson, says it is a bittersweet opportunity. >> when i first came here, the pack ice was inside of the shore all summer. now there's 150 miles of water and more in some places. >> and that has a huge impact on

the polar bears. >> that's why we have a lot of polar bears. their habitat's going away. they don't make it. this beautiful population is now down from 1,200 to 900 in the last 10 years. we've been hunting whales for 5,000 or 10,000 years. they're not coming here because of the bones, the remains of whales that we catch. they're coming because their habitat's gone away. the world should be interested in this. >> reporter: but while we're at the bone pile -- >> right over there. >> reporter: -- we become nervous these bears are interested in us. there is mama polar bear with her two cubs. not that far from us. walking through the water. that's pretty close. wow. >> stay with us. ♪ i thought i was managing my moderate to severe crohn's disease. then i realized something was missing... me. my symptoms were keeping me from being there.

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>> announcer: this special edition of "nightline" continues. in the remote alaskan tundra -- >> a little scary. >> reporter: -- a mother polar bear and her cubs are stalking dangerously close to us. >> pretty close. wow. >> reporter: but thankfully, mother bear seems to decide whale meat is a better dinner. >> once in a lifetime. >> reporter: as night falls, our guide robert thompson shows us evidence of a threat we may not be able to escape, signs that the climate is changing. >> you can see where the permafrost is melting. you see the ground cracked over there and it's open. and when it melts more and the water flows out. the fence was here years and

years ago so the wind wouldn't blow it over. they had metal stakes that were driven into the ground. now they're melting and they're not holding the structure up anymore. >> this shows you that the permafrost is melting. it's not permanent. >> reporter: the coastline isn't permanent either. erosion has affected much of alaska's arctic coast, chipping away at beaches, threatening towns and habitats. >> you love this land. >> oh, yeah. >> how does it feel to see the changes that are happening? >> well, i think -- i think the rest of the world should look at this and say it's going to happen more to other people in other areas. it just has well -- an effect on marine life and marine animals and the wildlife on land. >> reporter: dr. james wilder studies the polar bear population in the bufrtd sea near barter island. he says these bears have been coming to these shores for thousands of years but climate change has changed their behavior. >> polar bears are showing up earlier. they used to show up in the

beginning of september. now we see them showing up in the late july, august, and staying for longer and that seems to be correlated with the availability of sea ice. so if sea ice melts earlier, then bears will come to shore sooner. and if it forms later in the fall then itting agreg yates on the coast for longer periods of time. >> it's not good for us. we're used to ice out there hunting the whale. >> reporter: for the people of kaktovik their way of life is at risk as well. >> this is the road i grew up on, the main road. >> reporter: marie rexford is a witness to the changes wrought by rising temperatures. >> good attraction for all the tourists. to us they're a nuisance. they can smell your good food anywhere. they have broken down our door to our cellars. >> reporter: for centuries residents stored the whales they hunted in the permafrost, a natural underground freezer. >> most of the ice cellars

filled up with water, and it's hard to keep them going. >> you used to have natural ice cellars. >> yeah. >> that have now melted? >> they washed out. erosion got all of them. they're all gone. >> and now you've got containers. >> reporter: relying on the earth for sustenance is something the people of kaktovik need to do because even though there is a grocery store here that doesn't mean groceries are accessible for everyone. >> $21 for a bottle of lotion. everywhere you look prices are about three times. $34 for conditioner. it's tough. the prices are a lot higher. >> how challenging is it to keep your store stocked here on barter island? >> the planes are fully loaded with tourists and they're not bringing -- we're slowly getting our mail and our groceries. >> it costs so much for you to get everything here. >> yeah. my prices are just crazy sometimes. >> reporter: another concern here is safety. while the locals know what to do

about bears -- >> most people here have firearms just in case? >> we try to scare them off before anything else. >> reporter: the mayor worries visitors won't. >> they don't really understand that they're wild animals and they can -- their demeanor can change just like that. >> right. i mean, you all live among them with them. you understand. >> it can get crazy when they start coming in, especially when they finish all the blubber at the bone pile, they'll end up -- start coming into the town looking for scraps. >> they're hungry. >> they're smart animals. >> reporter: bears coming into town proving to be such a problem there was a polar bear patrol that sweeps the streets. this bear rummaging through garbage. another peering into a window. >> i used to lock up with a bar that went from across. >> reporter: and our hotel's manager shows us how she locks the bears out at the end of her shift. >> and that's why i do it, so bears can't get in here. >> reporter: but we brave the dark to catch a glimpse of the

northern lights. >> so it's around 3:30 in the morning, and i looked out my window and i saw the northern lights. so i woke everybody up and we're heading outside now to check them out. >> reporter: then the sounds of dogs barking. a warning that polar bears aren't far off. >> we heard some dogs barking. this is the time of night the polar bears are out. we're going to stay close to this door. it's unbelievable because i've seen pictures. i never thought i'd actually see it in person. and there it is. in the sky. and it's surreal, actually. it's just as beautiful as i thought it would be. >> reporter: when we take off from barter island, we're in awe of what we have seen here. the polar bears and the people. the fierceness and the fragility of this arctic world. a once-in-a-lifetime opportunity that may be melting away. tore "nightline" i'm amy robach in kaktovik, alaska. >> our thanks to amy robach and her team for their extraordinary

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finally here tonight, take a look at this incredible high-flying stunt. two french daredevils in wing suits jumping from a mountain about 13,000 feet up, then flying into the cabin of a plane in mid-air over the swiss alps. the duo, known as the soul flyers, say they completed more than 100 practice flights in preparation for this stunt. i want to thank you for watching "nightline" tonight. as always, we're online 24/7 on our "nightline" facebook page. thank you again for watching. and good night.