Transcript for The Marshall Islands, a nation that fears it's on the brink of extinction
Reporter: In these vast ocean waters -- The Marshall Islands, it's so isolated from the rest of the world. It's a beautiful place. Reporter: From high above, the island of mejuro. It's hard to see there is a battle going on below. A fight for survival between man and nature. It's really life or death for us. Reporter: The Marshall Islands, the front line of climate change. After hours of flying over dark blue pacific waters, through the clouds land appears, a mirage-like vision. A tiny nation of islands and atolls located halfway between Hawaii and Australia. We've traveled here to the Marshall Islands to see a nation on the brink of extinction. The most extreme predictions say as soon as 2030, sea level rise could make this place uninhabitable. We're on the made road, a two-lane highway. Are we going to make it? Yeah. It's really narrow here. From this road, just a matter of feet, water. The capital city of major is 300 feet wide in most places. This thin strip of land is home to over 27,000 people. This is your front yard? Yeah. Reporter: Charlotte jack lives steps from the water's edge. Only 16 years old -- Water's getting worse. It has reached the sea wall. Reporter: She has grown up with the fury of the ocean. You never really know when you could get a surge? No. One day it could be just like this, sunny, windy. Just a perfect day. Tomorrow it could be pouring rain and then water up high. Reporter: Charlotte, this used to be what? We have the laundry. This is where we do our dishes. It's beautiful when the sun sets right there. Yeah. You're literally looking right at the sunset? Doing dishes and looking at the view, yeah. You're not looking out a window, you're just looking out, wow. Charlotte is part of what's called the last generation. Over half of the country's population is under the age of 24. Sometimes I think by the time I graduate and go get my education, try to come back and serve my island, there's no more island, there's no more nation, there's no more culture. I'm just there stuck on the mainland thinking, what could I have ton? Reporter: Earlier this fall united nations reports sounded the alarm about the dire consequences of global warming, stating that if the Earth's temperature rises just half a degree more, there will be longer periods of drought, severe heat waves, more sea level rise. And the nation of the Marshall Islands has been one of the loudest voices on the world stage. We must take every opportunity we can to stay below 1.5-degree limit needed for our survival. Reporter: The government was instrumental in drafting the Paris agreement, a landmark measure to curb carbon emissions and combat climate change worldwide. When Paris came to be, it is really our last hope. To galvanize the entire global community. To say, okay, enough is enough. Reporter: It is this water that has destroyed this coastline. Once many homes stood here. Now most reduced to nothing but rubble. With remnants of lives once lived by people who thought they would be safe. They are working to protect themselves against the wrath of mother nature by building concrete sea walls. You can see right there the old sea wall that was built around parts of the island. It's crumbling now. Where they can, the people of the Marshall Islands have built new walls to help protect them. The question is how much can it really do? The minister of the environment, David Paul, takes us on the water to show the scope of the herculean task at hand. When you look at these sea walls, how much confidence does it give you that it will be safe? Fingers crossed? We are near the smaller islands on the outer edge of Majuro and the lagoon. If the sea level continues to rise, these will be among the first islands to go. We dock on the island of ineko. This is beautiful. Wow. David, when you look all the way down that way and all the way down that way, it's just beaches. Yeah, this used to be all land. And then all the way out it used to be beach. Now the beach is expanding. Sooner or later everything will be beach rather than land. Reporter: This pristine, unspoiled land may one day be lost forever. In local lore, the saying is, if you take away their land, their spirits go too. The land here is owned by families for hundreds of years. It's a really -- it's a feeling of wealth for most. Reporter: Jack is an American expat who's spend decades advocating for the rights of the marshallese. What the U.S. Did out here was horrendous. There's no other way to describe it. Reporter: During the cold war, the United States used the bikini atoll as a strategic military position and a testing ground for nuclear weapons. Zero seconds and the unbelievable explosion detonated! The one weapon that did most of the damage to the northern Marshall Islands was the bravo shot. That was 1,000 times greater than the weapons that were used on Hiroshima and nagasaki. 1,000 times? Reporter: Nuclear fallout from that bomb, so wide, ash rained down on the outer atolls. For years the residents there have suffered from birth defects and high rates of cancer. They had to be evacuated from their homes. It would be a long time before the area of the test could be called safe enough for any kind of life to resume there. Reporter: Today, more than 50 years later, their land is still contaminated by radiation. Describe for me the sacrifice the people here have made for the U.S. Well, they've sacrificed both land and health. Reporter: As a small reparation for their suffering, the marshallese are allowed to live and work in the united States without a Visa. Over one-third of the population has already left, seeking opportunity on the mainland. Soon the more than 70,000 left behind may have no other choice. Just last year, president trump would deliver another crushing blow to the islands with this announcement. The United States will withdraw from the Paris climate accord. The United States government let us down. It's like life and death for us. It really is a death sentence, right? So to speak. Reporter: It's the united States that carries one of the largest carbon footprints. But it's some of the smallest nations that are most affected by their giant neighbors to the north. Are people here day to day, are they aware of the threat from climate change? For us it's really a daily reality. We are seeing our shoreline being eroded. We are experiencing longer drought, more frequent. It is quite challenging to try to cope with it. Reporter: As the sea continues to rise, it's beginning to threaten their fresh water. And will soon kill all plants and trees. Who's next? You know -- What are we going to see? I will say this. We may go first, but -- you're next. Your fight is not just for the Marshall Islands, fair to say? No, it's for the rest of the world. It's for the rest of human doctor. Reporter: Despite the bleak outlook the marshallese are not ready to give up just yet. I'm going to be the last to leave, floating on a kayak, turning the lights out when everything's gone. He has three yep layings to protect. How much hope do you have she'll be able to stay and live and raise a family here on the Marshall Islands? Truthfully? Truthfully. You hear a lot of people talking about, we're going to have all these new emission control things in by 2050. And I'm like, I don't even know if we have till 2030. When it becomes other people's backyard, not just ours, I hope is that maybe they'll actually start trying did do things. Reporter: It's clear this is a battle the marshallese cannot win alone. If you could make one plea about what it's like to live here with global warming, what would it be? Come help us. Come help you? Come help us. We need help. ?????? ??? country road take me home ??? Reporter: Help for the future generations growing up in a land nearly lost. ??? I belong West Virginia ??? Reporter: Their home, the place where they belong. Our thanks to Gloria and her dogged producer, Jasmine brown, who earned support from the international women's media foundation for this story through the Howard G. Buffet fund for women journalists.
This transcript has been automatically generated and may not be 100% accurate.