They're turning their backs on traditional life among FSM's smallest atoll populations.

Nukuoro Atoll

Baseball cap tilted down to shield his eyes against the fierce western Pacific sunshine, Mayor Senard Leopold waits on Nukuoro Atoll's porcelain-white beach to greet our ship.

I'm aboard an expedition cruise vessel, Silver Discoverer, with 60 other passengers taking a 17-day voyage across FSM.

Few ships ever cross this watery nation of 607 islands.

Our traverse takes us from FSM's southernmost outpost north of Papua New Guinea to the westernmost tip of the Caroline Island chain to Palau.

Nukuoro is a necklace of tiny flat islets circling an emerald-green lagoon so clear the corals leap out in HD quality.

Islanders get their food from fishing and tending taro crops.

Coconut fiber is used to thatch wooden huts and for weaving clothes.

It's self-sufficiency learned across generations.

Population drain

Mayor Leopold explains Nukuoro is FSM's smallest distinctive language group.

Just 210 islanders remain and more than half their population now live away from the atoll.

"Those who remain are mainly middle-aged adults or schoolchildren," he says.

"We have elementary school on Nukuoro, but after that older children must move away to attend high school on Pohnpei."

Pohnpei is one of FSM's larger developed islands with a population nudging 35,000.

"Once the children experience the conveniences of Western life they don't want to return. They stay on Pohnpei or go to study and work in Guam, Hawaii or West coast USA."

Leopold says population drain is a more immediate threat to them than sea level rise.

Kapingamarangi Atoll

It's the same deal on Kapingamarangi Atoll, 250 nautical miles away.

Between 1994 and a last census in 2010, Kapingamarangi's population fell by a quarter, to 350 individuals.

Kapingamarangi's inhabitants had no idea our passenger vessel was calling by.

Perhaps they were disappointed.

They'd been waiting for a delayed supply vessel for several months and had run out of coffee and sugar.

Valentino Tumakirewe is a somewhat laconic islander in his late 40s.

"I do a bit of fishing, grow some crops and drink palm wine most days," he says. "But not much else."

"There's not enough for young people to do here. My children have left."

He highlights another issue threatening Kapingamarangi's long-term sustainability.

"Everybody on the island is related and as people leave it gets harder to find a wife or husband."

Lamotrek Atoll

Further along FSM's principal chain, the Caroline Islands, Lamotrek Atoll is known as the "summer lagoon."

Within the barrier reef encircling the turquoise-tinted lagoon, Lamotrek's islanders welcome us with melodic singing and flower leis.

Few ships ever call.

The welcome is authentic and heartfelt.

Not the sort of cliched "tiki" shows with sashaying grass-skirted beauties and "alohas" that many cruise passengers experience when traveling the South Pacific.

Micronesian culture shouldn't be confused with that of the better-known South Pacific Polynesians.

Our ship's resident ethnographical expert on Pacific cultures is Swiss-German Christian Walter.

He says the terms "Micronesian" and "Polynesian" were given to distinct groups of Pacific peoples in the 19th century by French seafarer Jules Dumont d'Urville.

He says Micronesia references "micro," reflecting many smaller islands with more distinct languages than the Polynesians.

"Physically, looking at Tongans and Samoans, I would consider Polynesians to be stronger and taller than Micronesians," declares Walter.

Money from abroad

Like other atolls, Lamotrek has seen its population slowly dwindle to around 329 islanders.

"Losing the young is one of the main threats to the atolls," Walter concurs. "It's difficult to imagine them wanting to continue to live under the same conditions as before.

"Even if they came back to these islands what would they do?"

But he argues that those leaving are a financial benefit to those remaining.

"The money generated abroad and sent home could never be obtained by those staying on their atoll," he says.

Stellar navigation

One skill under threat is the Micronesians' startling ability to negotiate the open Pacific by stellar navigation.

On a wooden outrigger canoe, islander Celestine takes me around Lamotrek Lagoon.

He holds Micronesia's most revered title: Master Pwo Navigator.

With pinpoint accuracy he can cross hundreds of miles of ocean without modern instrumentation, using only stars and ocean currents.

"Our children sail their first canoe around six years old," says Celestine. "Now they don't stay here long enough to learn proper navigation."

Celestine once made the 240-nautical-mile voyage west to our next port-of-call, Woleai Atoll.

Strict dress code

Woleai is conservatively traditional and strict dress code is required.

Both sexes wear palm-fiber woven lap-lap sarongs and are bare-chested.

Their undress reveals home-inked tattoos featuring nautical or Catholic motifs.

On the beach, young men haul tuna onto the sand and slice into its pink flesh with bamboo knives -- the freshest sashimi imaginable.

Frigate birds, the ocean's free-roving pirates, circle on high, eyeing a fishy meal.

Woleaian elder Martin Yangirelmar works for Yap State's education department.

His third-grade elementary schoolchildren are demonstrating traditional crafts.

The girls weave vivid lap-lap loincloths from banana and hibiscus thread; boys construct fish traps from bamboo.

Traditional skills

"We teach them traditional skills at an early age so at least they'll remember their heritage when they've left," says Yangirelmar.

"All these children will go to the larger Yap Island to study, staying with relatives and then eventually traveling further away in the future for work once they get a taste of Western culture.

"What you see here is dying out. I think in 20 to 50 years some atoll populations may no longer be here."

Some, however, are determinedly hanging on.

Ngulu Atoll

On Micronesia's westernmost frontier, most of Ngulu Atoll's population has long departed.

The eight remaining islanders are all members of the Mangthaw family.

A temporary ninth resident is cousin Henry.

He came to help rebuild after Typhoon Hagupit wrought havoc on Ngulu in December 2014.

He doesn't seem to mind the fact that he's been waiting two months for a cargo boat back home to Yap.

The typhoon has left the creamy beaches littered with fallen coconut palms, like matchsticks tipped from a box.

"When the cyclone struck big waves drove across the island," says George Mangthaw. "We were scared.

"We survived because of a brick shelter funded by the European Union."

TV, automobiles and convenience food

Mangthaw says a decade back Ngulu had 20 islanders.

Now, he's disdainful of their decision to leave for Yap.

"They went to drive cars, watch television and eat convenience food like chicken," he mocks.

He says he won't leave Ngulu because he's free to live exactly how he chooses.

"I think we will continue to find 'caretakers' for the families still residing on the atolls," says Christian Walter.

"But eventually the young population will look for brighter lights in other parts of the Pacific or the world."