John D. Sutter is a columnist for CNN Opinion who focuses on climate change and social justice. Follow him on Snapchat , Facebook and email . This story is part of a CNN series called " Vanishing ." Learn more about the sixth extinction and get involved.

Nosy Andragnombala, Madagascar (CNN) It's 2 a.m. when the half-moon wakes Hary. He senses its gravitational pull -- feels the moon coaxing fish out of a nearby reef and into his fishing nets here at the edge of Africa.

The 33-year-old fisherman seems to have an almost-telepathic relationship with the coral that surround this castaway island, which is little more than a heap of sand off the southwest coast of Madagascar. That relationship was passed down from his father, and it's one held by Vezo people here.

That word -- Vezo -- is taken to mean "at struggle with the sea," and residents of Nosy Andragnombala define themselves by that struggle. At birth, their umbilical cords are placed in seashells and tossed as an offering into deep blue waters.

They are part of the reef, and it is part of them.

There's little else: No electricity or freshwater. No industry, no jobs, no school. If you don't know the reef -- can't feel its tides and sense its moods -- then you can't survive.

And that makes what's happening on this island all the more tragic.

The reef is disappearing.

Coral have started turning white and dying. No one here understands why.

Local theories abound. Was it that hurricane? A chemical spill? A curse? Moake, an older neighbor of Hary's, told me white coral snagged his fishing net one day. It spooked him, and now he won't return to that spot. "I've already seen the white coral but I don't know what's caused it to become white," Hary tells me. "I don't know whether it's something in the water that's caused it to turn white."

Hary wakes well before dawn to cast fishing nets into the Mozambique Channel.

Yet, he's seen clues.

"There's a time when you see it," he says. "During the hot season."

Scientists can explain the mystery of the white coral.

But, frankly, I'm starting to see it as a curse, too.

A curse you and I cooked up.

'And then we wept'

By now, the storyline should be familiar: We humans are burning loads of fossil fuels and chopping down the rainforest, and that's causing the atmosphere to heat up rapidly.

That's true regardless of who's in the White House.

What's less understood is that the ocean is actually storing much of that heat.

Beneath the surface, there's evidence of a mass extinction brewing.

Coral are among the silent victims, and the results are undeniable.

This year, amid record heat, 93% of the Great Barrier Reef experienced bleaching , the term used to describe sick coral that eject the bright-colored algae that live on them. Bleached coral turn white, and while they're not dead, they are suffocating. The colorful algae feed the coral with the oxygen and sugar they need to survive. With prolonged or repeated bleaching, coral begin to die, eventually turning to rubble or becoming smothered by plants. It doesn't help that adding CO2 to the atmosphere and ocean also makes the waters more acidic, and worse still for the survival of coral.

CNN Map

The consequences are truly stunning.

Research indicates nearly all the world's coral reefs could be lost by 2050.

This is just one sign of the sweeping changes we humans are inflicting on the natural world, and ultimately on ourselves. Biologists say we are on the verge of the Earth's sixth mass-extinction event -- something akin to the end of the dinosaurs. Anthony Barnosky, a researcher at Stanford, told me we have perhaps 20 years to change course -- including addressing climate change -- or three-quarters of the world's species could vanish in coming centuries.

Overfishing and pollution also threaten coral in Madagascar. But climate change -- and the warming and ocean acidification that come with it -- is expected to land the soundest blow.

To stop that, we need to eliminate net carbon pollution.

Basically, that means purging fossil fuels from the global economy.

If we fail, there will be dire consequences.

Journalists often see the end of coral through the eyes of scientists. "I showed the results of aerial surveys of #bleaching on the #GreatBarrierReef to my students, And then we wept," Terry Hughes, a professor at Australia's James Cook University, wrote on Twitter in April.

Or we focus on losses for the tourism industry, which could be considerable.

Those perspectives matter.

More critical, though, are the 275 million people who depend on coral reefs for survival.

Hary and Lydia are raising six children. They can't afford to send them to school.

They're people like Hary, his wife, Lydia, and the six children they're raising.

Their fates are linked to a catastrophe we are helping to cause.

'My children can't eat'

Hary stops by my tent on his midnight walk to the ocean.

"Ooh-OOH! Ooh-OOH!" he calls.

Translation: Get up, reporter dude. The fish are waiting.

I stumble out of my sleeping bag, groggy and confused. Soon, we push off into the darkness of the Mozambique Channel in an outrigger canoe that Hary built by hand. Hary is in the back; the butt cheeks of his shorts are patched from years spent perched on the rails of the narrow boat. His second eldest son, Harizo, is up front. The 13-year-old is his dad's professional shadow.

A blood-colored moon hangs on the southern horizon. Father and son are faint silhouettes against the midnight sky and charcoal sea. The air tastes of salt, and the lull of the waves feels almost womb-like. Most surreal: The waters are bioluminescent, so each stroke of the paddle causes twinkling constellations of light to swim across the reef below us, as if mirroring the stars. The scene is exhilarating, especially for a city dweller like me.

In this moment I understand how completely tied Hary is to waters around the island.

As we paddle away from shore, sea melting into the distant horizon, I think about the disaster unfolding below the hull of the boat: The reef already is dying.

If we don't find anything out there, my children can't eat. Lydia, Nosy Andragnambala

A local nonprofit called Blue Ventures has been doing scuba surveys of reef health in this area. Their divers found 70% of reefs were bleached in April, at the peak of a heatwave, which is attributed partly to El Niño but also to the warming trend we're causing by burning fossil fuels.

Hary and the other fishermen know their catch is a fraction of what it once was.

"We really suffer when we go a week without catching anything," he says.

Their children cry from hunger, his wife, Lydia, tells me.

"If we don't find anything out there," she says, "my children can't eat."

'Ways of the sea'

Hary and Lydia's response to the crisis? Try harder.

They're nothing if not resourceful.

They moved to this island years ago because the reef on mainland Madagascar was too degraded -- and because the fishing was farther away. Hary lived out here with his father as a boy, and Lydia later joined him. They'd known each other as little kids in school. Neither was able to finish, though. They had to fish.

They have four kids together and care for at least two others; one is the son of a relative who died. The village is home to a few dozen people, and many depend, at least in part, on Hary's catch for their own survival.

Out here, people have to work together to make it.

After putting his net in the water about 3 a.m. Hary makes it back at shore by about 5 a.m. He is out again at dawn to collect his nets, and then spends the afternoon on the water, casting a long line with 50 hooks on it into the deep ocean just beyond the barrier of the reef.

In all, he spends about 12 hours per day at sea.

Lydia and the kids are hard at work, too. If you walk around Nosy Andragnombala, you're sure to see tiny children building and playing with wooden toy boats. They whittle out the hull and mast and then attach scrap-plastic sails. The kids push these little boats out onto the waves, tapping them with sticks so they catch the wind just so. When the children are about 10 years old, Hary says, they'll be ready to fish out on the water. He won't need to teach them to sail, though. They'll already understand how wind and wood work together.

Lydia searches reef flats near the island for octopus.

Like other women on the island, Lydia hunts octopus and cooks. At dusk, she boils fish on a fire while the sun sets and humpback whales perform their lumbering acrobatics on the horizon.

It's an idyllic place, but the struggle to live here is real. Several years ago, locals created an ocean reserve to protect the reef. They work with a village association to police the waters. Those efforts, combined with an intimate knowledge of the reef, make survival possible.

But barely.

One day, Lydia asks me, though an interpreter, if I want her to "teach me the ways of the sea."

I do, of course.

I slap some $12-a-bottle sunscreen on my face, and she leads me onto the ankle-deep reef flats, a spear in her hand and a notebook in mine.

'Hara, John!'

Lydia is a woman defined by brightness. Her shirt is magenta, yellow and blue. Her smile is loud and infectious, and she paints her face with a paste of mashed-up mangrove seeds, turning it orange and protecting it from the sun. Her intellect shines, too. If you duck down and follow her into her home, whose footprint is about the size of three queen mattresses and often sleeps eight, you'll notice two pieces of butcher paper pinned to the thatched walls. On them: English words translated into phonetics and then into Vezo, the local language.

"Water = oatere = rano."

"Fish = fise = fia."

"This is our octopus reserve = Dise ize ore aketapose rezeriva = Ato misy ty rezeriva horita nay."

She has been learning English in case a visitor showed up someday.

"Photo, John! Photo!"

Lydia points at a black urchin in the ankle-deep water. Each time she sees something new -- especially spiky, don't-step-on-that stuff, like an urchin -- she gestures frantically and insists I take a photo and write down the Vezo word for the creature in my notebook.

"John, photo!" A round, pink urchin.

"Photo!" Some greenish blob that apparently will kill you.

"Horita!"

That's an octopus, which she identifies by noticing the way the creature has arranged a pile of rocks, just so, in front of its secret den. The spot is completely unremarkable to me until she dips her spear into the hole and then twists it gently, like a baker rolling bread sticks. A tentacle emerges and wraps itself around the stick. Lydia pulls the creature out, notes that it is large enough to harvest sustainably (she won't take small octopuses because she worries about depleting the reef; and the community has established its own reef management system to try to protect its natural resources) and then stabs the tip of the spear through its Jell-O head.

A black ink cloud puddles in the water.

She ties the octopus to a bright blue string and drags it like a rag doll.

The tour continues.

Local coral is damaged for many reasons, but climate change could deliver the knock-out punch.

"Hara, John!"

Hara means coral.

Lydia points at one piece of healthy coral in a mess of rubble, a vast expanse of reef that looks something like the ruins of an ancient city. It stretches on like almost as far as I can see, a few live coral here and there, but mostly khaki, beige and gray.

It is heartbreaking to see this rubble.

Especially juxtaposed against her enthusiasm.

'Don't touch it'

I struggle with whether or how to engage Hary and Lydia in a conversation about climate change and the white coral -- this foreign curse that understandably makes little sense out here.

How do you tell someone that factories and cars and deforestation on the other side of the world are slowly heating up the entire planet, warming the ocean, making it more acidic, and messing up reefs worldwide? It's a tricky concept even for those of us who are climate culprits, who live in polluted cities and burn coal to pump electricity and air conditioning into our homes.

Out here, there are no factories, no air pollution, no cars or roads. Lydia says she's only been in a car once in her life, and it was to take her son to another family member's funeral. Her son cried, she says, because he didn't understand what was happening. Only one or two cell phones (solar powered) exist on the island, and there's a single dusty television set. Its owner uses it mostly to play Kung Fu movies from a USB stick for the island's kids.

Yet, this is an existential crisis.

To be Vezo, according to some, you have to work on the water.

This place -- and its culture -- could vanish with the reef.

I ask James Paul, a diver who surveys reefs in this area for Blue Ventures, and is Vezo himself, how he handles local conversations about climate change.

It's difficult, he says.

"I tell them just be careful, it's sick. Don't touch it. If you touch it, it's dead quick."

Of course, there are solutions.

But if you're on an island with essentially no carbon footprint there isn't much you can do to prevent global warming -- aside from sharing your story.

Their only real hope is for us to listen.

'We're as good as dead'

I invite Lydia to sit down on a sand dune to talk about all this.

I feel like the prophet of doom.

I tell her that people like me on the other side of the world -- people who are addicted to dirty energy sources, like coal and oil, and who drive around in cars and make things in factories that billow black smoke -- have a hand in turning the coral here white.

Lydia is a master at finding and identifying ocean creatures.

Yes, there are local problems contributing to problems with the coral. The cyclone that almost killed her son destroyed some coral, and overfishing plays a role. But scientists say people like me must change or coral reefs all over the world -- not just here -- will disappear.

She stares at me -- more in disbelief than anger.

Then she laughs, seemingly to cover the discomfort.

"We're as good as dead," she says.

"There'll be no more ocean livelihoods when the coral turns white."

"It scares me, people far away are causing this," she adds, rightly. "It's like they're the ones sending us this heat, which is destroying the coral. So what happens if there's something else they do or make that causes death here?"

She worries about her children. Before Hary's mother died two years ago, some of her kids lived with their grandmother on the mainland so they could attend classes. But after she died the family couldn't afford it, she tells me, so they had to come back to the island. ( School, by the way, costs only $3 per month per child , but the family earns too little.) She wants her children to grow up Vezo -- to know the ocean -- but she also wants them to have options.

Without an education, what other career options will they have?

What happens to them if all the coral turns white?

She turns to our translator and asks a question about me and a CNN videographer.

"So when they go back home, they'll teach people what they've learned here? They'll tell people about what they've seen? They'll tell people this is what life is like in Madagascar?"

She trails off.

"Maybe there are just too many cars where they're from."

I tell her the reason I've come is to tell her story. And that yes, I hope that when people turn on their lights or start their cars or get on airplanes (or, most importantly, vote for public officials who care about this) that they will think about a tiny island in Madagascar.

About people whose lives are threatened by the curse of the white coral.

But, secretly, I worry about those of us causing the curse.

Will we actually care enough to stop?

Side to side

The night after that conversation I wake up with a piercing headache.

I'd been dreaming about swimming down a pristine canal that suddenly turns into an industrial wasteland.

Blue water turns brown and smells of gasoline.

Smoke fills the air.

Nosy Andragnambala is located off the coast of Madagascar, a large island nation in eastern Africa.

When I awake, I realize the smell of gas is real. I unzip the tent and walk into a stiff wind, toward the beach. The horizon glimmers the color of peach, the first sign of dawn.

Where is that smell coming from? I can almost taste the tang of gasoline in my mouth. But how can that be? There are no motors on the island.

Then I see it.

Our boat, with its 25-horsepower Yamaha engine.

We used the motor to cut across the Mozambique Channel to this island in an hour, as opposed to the three or four or five needed to cross by sail. The irony didn't hit me at the time. I figured we would need the motorboat to maximize the reporting we'd do.

We're as good as dead. There'll be no more ocean livelihoods when the coral turns white. Lydia, Nosy Andragnambala

We make these choices by default. Too often, we don't see them or smell them -- don't actually feel the results of our actions. That's particularly true of climate change, since the effects are both diffuse and long term. Our actions now determine the type of world Lydia's great-great-great-great-great grandchildren will inherit. Climate change is sinister that way.

There are signs of progress.

We're moving into the clean-energy era. Technology is helping.

But all this is happening at a glacial pace.

And it doesn't help that US President-elect Donald Trump has threatened to scrap the Paris Agreement, which aims to get the world to ditch fossil fuels and limit warming to 2 degrees Celsius.

Will we do enough to save the coral -- and so many other species?

We depend on them more than we know.

I walk around the boat to get some fresh air, blowing in straight from the sea.

I sit down to watch the sunrise. A flock of birds hold formation in the wind. Crabs with little telescoping eyes skitter side to side in the sand. A hunk of dead coral is at my feet.

We are scheduled to leave Nosy Andragnombala in a day.

The scent of gasoline will evaporate then.

But our mark remains.