♪ this is "nightline." >> tonight south korean preppers, emergency kits, fire starters, even luxury underground bunkers, under threat of nuclear war. a small but growing group bracing for the worst. we travel across the fractured peninsula to feel the pressure on the ground. >> both sides have big guns, nuclear weapons. >> plus the monarch migrations in the mountains of mexico millions of monarch butterflies taking their winter break. >> is it still on my head. >> yes it's nice. >> we go deeper and closer than

mi tourists are allowed. with their migration threatened what can be done to help these butterflies fly. first the "nightline" five. line" five. ♪ ♪ there are two types of people in the world. those who fear the future... and those who embrace it. the future is for the unafraid.

♪ ♪ ♪ good evening, thanks for joining us.

for more than 70 years south korea has been threatened by a nileation by the north but now kim jong-un with heated receiptrhetoric with president trump are on the shores of south korea. we're taking inside the somewhat secret stigma ma advertised world of south korea preppers where worried mothers are preparing for disaster. [ speaking foreign language ]. >> a seoul businessman. [ speaking foreign language ]. >> he's building luxury underground bunkers. and south korea most famous survivalist, carries a small go bag everywhere he goes. they're part of a tiny but growing community quietly bracing them seflts for the

unthinkable. war with north korea. parks fired as north korea fired intercovenant internetal missiles thought to reach united states. >> it will be met with fire and fury and frankly power the likes of which this country never seen before. >> if it is forced itself or its alleys we will have no choice but to totally destroy north korea. >> with the latest show of force this morning south korea are left in the cross fires between two nuclear powers. >> we have been anxious about north korea provocations since

korean war more than 17 years. >> the bulls eye has been on south korea for decades. >> main target is south korea i think. >> we asked the prepper to run us through hypothetical evacuee uation. >> it geo tags you and tells you where the nearest evacuation center is. >> because north korea is only 70 kilometers away he estimates five minutes to get to evacuation center he wouldn't even stop to call his family. this sign says shelter. >> rather than the first floor he would want to the go deeper. >> but on the surface the rest of seoul like the ritzy district looks like this. you would never sense the geo politics swirling across this fractured peninsula. >> in fact a surprising majority of south koreans say they

believe there's zero chance their neighbors to the worth would start a war. foreign policy analyst a warned an attack on this teeming capital would be catastrophic if there's need to evacuate there's basically just one major route saiding south. >> it's only two and half hours by bullet train from seoul to the southern coast the city most my parents generation fled to and don't want to think of having 10 million people in seoul trying to leave at the same time. >> and most koreans don't want to think about it either. it's business as usual. part bravado, part avoidance but even here president trump's rhetoric does not go unnoticed. [ speaking foreign language ]. >> do you think that president trump's rhetoric has made things

more dangerous. >> i think the biggest thing with president trump's commentary he's normalizing the idea of using force against north korea. >> this is a regular tv pundit here . >> question is how do democracies respond to those scandals. >> now famously known as the bbc dad from this video one of the top ten viral moments last year. a rare bit of humor in his otherwise sobering day job talking about the risks of nuclear armageddon. >> the idea is we hold guns to each other's head, long as we both pull the trigger we're both okay. >> that's classic arms control. >> it's nuclear deterrent. >> the kellys have a lot on the line, his wife is korean and this is home for their family. >> they invited us to a

home-cook home-cooked korean meal. >> looks amazing. kimchi is very much the national dish. >> our conversation what it's like to live under threat of war. >> in a nuclear blast what we have to do most korean people don't know how to do. >> actually surprised how much my students know, if the sound goes off what are you going to do they're like i don't know, go home. >> why do you think koreans don't think about it or to prepare. >> boy who cried wolf problem. the north korea's have been saying since the 60s they will turn seoul into a sea of fire nobody believes them any more. >> they know if we have a war it will be a big war and both countries will zblaps which may be why kim jong-un sent delegation rare face to face talks ahead of the pyeongchang olympic games and two countries

agree to joint women's hockey team. >> some people have mixed feeling s about the intentions. >> former u.n. secretary general sees it as a step forward. >> in the united states during the nixon administration we called it ping pong diplomacy. >> yes. >> this in some ways hockey diplomacy. >> i've seen such a power instantly mobilize passion and friendship through sports. >> even kim jong-un's own sister is attending the olympics, the first time a member of the ruling family will step foot in the south. >> there's a lot of mistrust of north korea. >> you see all of the behavior which north korea has been doing for the last many declaration a decades. >> are you concerned thees clatsing rhetoric could lead to nuclear at indicatialtercation. >> it is unsettling.

i think it has psychological impact against north korea regime. >> like fighting fire with fire. >> of course. >> but she says her 11-year-old son is having trouble sleeping after seeing images of warfare. >> yet while citizens may be anxious the south korea government sees value in the combative exchanges. >> maybe we can give the credit . >> politicians like him warn that military action even a limited strike targeting north korea's nuclear weapons would be colossal mistake. >> could trigger international

conflict. >> one option is left, negotiation. diplomacy. no other way. >> for him prepper, combat with north korea is something he's seen close in 1996 was a paratrooper in south korea army when north korea sent dozens to infiltrate the south. wu says it inspired him to become a survivalist. and he's not alone. >> thank you. >> these underground bunkers are attracting attention. equip with everything from oxygen to hand cranked generator. he's yet to see booming sells. 20,000 take part in digital

presented bying forum that wu has created and some willing to take classes as well. taking careful note s, yank, that concerned mom, hopes that prepping will ease her son's anxiety. preparation that millions hope will prove unnecessary. >> up next we're in the mountains with millions of butter fliez. flies how they've been migrating this same mexican retreat for at least 500 years. 500 years. touch is how we communicate with those we love, but when your psoriasis is bad, does it ever get in the way? embrace the chance of 100% clear skin with taltz. taltz is proven to help people with moderate to severe psoriasis achieve completely clear skin.

with taltz, up to 90% of patients had a significant improvement of their psoriasis plaques. in fact, 4 out of 10 even achieved completely clear skin. don't use if you're allergic to taltz. before starting, you should be checked for tuberculosis. taltz may increase risk of infections and lower your ability to fight them. tell your doctor if you have an infection or have symptoms, or if you've received a vaccine or plan to. inflammatory bowel disease can happen with taltz, including worsening of symptoms. serious allergic reactions can occur. ready for a chance at 100% clear skin? ask your doctor about taltz today. and go to taltz.com to learn how to pay as little as $5 a month.

sometthat's when he needs the way ovicks vaporub.'s sleep. proven cough medicine. with 8 hours of vapors. so he can sleep. vicks vaporub. goodnight coughs. ♪ strummed guitar

you can't experience the canadian rockies through a screen. you have to be here, with us. ♪ upbeat music travel through this natural wonder and get a glimpse of amazing, with a glass of wine in one hand, and a camera in the other, aboard rocky mountaineer. canada's rocky mountains await. call your travel agent or rocky mountaineer for special offers now.

♪ ♪ there are two types of people in the world. those who fear the future... and those who embrace it. the future is for the unafraid. ♪ ♪

♪ did you know you can fly from doocanada to mexico in eig hours but takes the monarch butterflies two months. still military oniolions followr ancestors making history. >> the monarch butterfly, one, two, a bunch. now listen. now listen. that's the sound of butterflies, millions of butterflies fluttering through sunlight they come here in mexico every year in one of the most in cred

migrations on earth. flying thousands of miles to get here. it's a hazy morning. we're hiking up elrosario reserve to witness this mysterious miracle. >> it's getting thin zbler now under threat. >> just need to catch my breath. >> we're at 9,000 feet above sea level. after hard tracking we finally spot them those dark patches. >> those big black clumps are butterflies and they're still sleeping. millions of sleeping butterflies huddled together for warmth. trademark color owning. orange. when it is 60 degrees they wake up, stretch their wings, shivering in cold not fear.

>> she's shivering. >> because it's still a little chilly. >> yeah. >> you're witnessing extraordinary access. tourists are not allowed in this far. we're only here because we're with the monarch big wig for the world wild life fund. >> they come from as far away as winnipeg, canada. they weigh less than an ounce. >> that's over 2,000 miles clear across the u.s. for passenger plane eight hour flight for monarchs up to two months. to within few hundred feets of where their ancestors went the year before and year before that. >> is he still on my head. >> yeah. >> why does this happen. >> the weather is the key. they escape from winter in canada and states. escaping the winter. >> how's it happen?

no one really knows. >> how the monarchs come to fly a great distance is a mystery. >> monarchs in your yard are short lived but in the northern u.s. and canada a super hero generation, bigger, stronger, capable of living eight months and traveling across the continent. >> that's my hand. sense of scale. >> once of a year this freak generation is born that makes this migration. >> exactly. >> they arrive just before the day of the day if dead in october, legend has it they are the spirits of the departed. talking 500 years but not until 1975 when scientists proved they came from so, so far away, how is still the mystery they're trying to solve. monarch watch tags the insects as they head south. they estimate about 80,000 were

tagged in 2017 of which only 1% will be recovered. >> look. we found a tag. >> against the odds we found one, called it in to hq. >> number is xut 121. >> the very next morning we skyped with pam byrd a tagger in laky, texas. 700 miles away. >> hello i'm nick this is eduardo. >> nice to meet you pam. >> nice to meet you both. >> we found one of your butterflies. >> i know i can't believe this i feel like i won the lottery. >> thank you for yr job it's very, very important this data. >> thank you for your participation on your end as well. it's just magic that we can work together like this. >> another slice of magic monarchs drinking from a stream where tourists mingle with them. >> i mean this is amazing. it's beautiful out here. >> i feel like i'm in heaven. >> just being out here seeing

these is cool, you're one with them. >> 1996 is the year with the largest number of monarchs here covering 44 acres of forest. >> and this is the biggest colony of monarchs in the wrorld. >> in the world, yes. this is the most important spot for monarchs right now. >> in 2013 monarchs covered less than two acres, the lowest area in recorded history. >> experts say it's partially due to climate change more hornet canes on the migration route and freak snow storm in 2016 that killed millions. illegal logging is also a problem exer if. enter eduardo, he rallied the locals teaching them preserving the monarchs could be more profitable and rewarding. ♪ >> tourism is booming there growing trees to reforest and

mushrooms to sell. problem is now in the u.s. herb sides killing milk weed plants along the route, monarchs will only lay their eggs on milk weed if you live on those routes you could make a difference, not only the government, the people. >> are you going to go plant milk weed in your yard. >> we have lot s in our yard. >> back in the forest eduardo is blowing on a monarch to warm her up. >> yeah, well done. you saved one. >> one. i'm trying to save million of them. >> for "nightline" if in michoacan, mexico. >> up next, a lesson in courage from president obama's former senior advisor. jarrett.

bibs on people! lobsterfest is back at red lobster... with the most lobster dishes of the year. new dueling lobster tails has two tails that'll fight to be your favorite. one topped with creamy shrimp and scallops, the other... steamed with lemon and herbs. and no, you're not dreaming, classics like lobster lover's dream are back too, along with decadent new lobster truffle mac & cheese. but enough talking about lobster- let's get to eating! - because lobsterfest won't last. so dive in today at red lobster! advil liqui-gels minis. jarrett valerie jarrett. that's fast, 'cause it's liquid. you'll ask... "what pain?" advil liqui-gels minis. searching for answers may feel overwhelming. so start your search with our teams of specialists at cancer treatment centers of america. the evolution of cancer care is here. learn more at cancercenter.com/experts

but when we brought our daughter home, that was it. now i have nicoderm cq. the nicoderm cq patch with unique extended release technology helps prevent your urge to smoke all day. it's the best thing that ever happened to me. every great why needs a great how.

♪ and finally tonight in celebration of black history month and women, president obama's former senior advisor valerie jarrett shared an encouraging message about courage. >> can't be afraid of failure, just go with it, if your heart tells you to do something, do it. this is what courage is, it's overcoming your fear. >> you had a saying from your momma about lightning. >> my grandmother put yourself in the path of lightning.

don't be afraid of taking chances. put yourself out there. >> when lightning strikes. thanks for watching "nightline" and as always we're online 24/7 online on our facebook page. good night america.

♪ ♪ with the chase mobile app, michaela deprince could pay practically anyone, at any bank, all while performing a grand jeté between two grand pianos. she could... in a commercial. in real life she uses it to pay her sister, from her couch, for that sweater she stained. what sweater? (phone buzzes) life, lived michaela's way. chase. make more of what's yours.