The central Pacific nation of Kiribati has a few claims to fame. Its flag-bearer at the past two summer Olympics won international attention and became a meme because of his memorable dancing. The country — known under British colonial rule as the Gilbert Islands (the name Kiribati, pronounced KI-ri-bahss, is a local transliteration of “Gilberts”) — has 33 islands spread over more than 1.3 million square miles, making it one of the world’s largest nations in terms of sea area, though one of the smallest in terms of land. But what it gets the most attention for these days is impending doom: The nation may be one of the first in line to be wiped out by the effects of climate change.

In the century to come, we’re likely to see dramatic changes to the physical shape of the world as we know it, thanks to rising sea levels and other environmental changes. But the immediate challenges faced by most countries pale in comparison to those of Kiribati, which has an average elevation of less than six feet. The atoll of Tarawa, where nearly half the country’s 110,000 residents live, could soon be substantially underwater. “By 2050, 18-80% of the land in Buariki, North Tarawa, and up to 50% of the land in Bikenibeu, South Tarawa could become inundated,” the government told the United Nations in 2015. Kiribati’s smaller outlying islands could be wiped out even sooner. “The results of sea level rise and increasing storm surge threaten the very existence and livelihoods of large segments of the population,” officials wrote.

Small island states like Kiribati have become symbols of the potential impacts of global warming. At the 2015 Paris climate summit, they pressured larger countries to accept the goal of limiting global warming to 1.5 degrees Celsius, rather than two degrees, over preindustrial levels. (It was mostly a symbolic victory: Barring unforeseen circumstances, particularly since the Trump administration pulled the United States out of the accord, both targets will be exceeded.) They are also working to develop first-line defenses against the effects of sea-level rise, including planting mangroves to prevent coastal erosion and improving rainwater-collection systems to protect water quality.

But if none of that works, they may have to consider more drastic options. And so, in 2014, Kiribati purchased about eight square miles on the Fijian island of Vanua Levu for a little less than $9 million, potentially for the purpose of moving its population there one day. “We would hope not to put everyone on one piece of land,” the country’s then-president, Anote Tong, said. “But if it became absolutely necessary, yes, we could do it.” Fiji would become the new home of the nation’s inhabitants, known as the I-Kiribati.

The relocation of people due to climate change isn’t unprecedented. Papua New Guinea has already begun moving the population of the Carteret Islands, a group of low-lying atolls, to the mainland. But this would be the first time an entire country had to relocate because the land on which it was built no longer existed. This raises a new and frightening question: If a country no longer exists in physical form, can it still exist as a political entity? Can a nation just up and move?

I knew Tong by reputation from the impassioned speeches he delivered at U.N. General Assemblies and climate change conferences during his time as president, from 2003 to 2016. So when I visited Kiribati in 2016 to research a book about border changes and the future of the world map, I called him. When we met one afternoon in Tarawa, he had just come in from fishing and was relaxing in shorts and a sleeveless T-shirt in the maneaba, or meeting house, outside his family’s home in a crowded residential neighborhood. John Denver played softly from a Bluetooth speaker. But the former president was troubled. “One of the most difficult things I’ve had to expect is planning for the demise of my country,” Tong told me.

He wants the I-Kiribati to stay if it’s even remotely possible. But, he rued, relocation is probably unavoidable. “The science is pretty clear: zero emissions, we’ll still go underwater. Unless some drastic work is undertaken, there will be no option. That’s the reality. It’s not a hope. It’s not a desire. It’s the brutal reality.”

Yet no one’s quite sure what that reality will look like. When I visited Secretary of Foreign Affairs Akka Rimon, she cracked the joke I’d been afraid to: “Climate change really put us back on the world map. The irony is that we’re being erased from the world map.” Rimon had tried to think through what relocation could entail, though she didn’t really know how Kiribati’s nationhood could be preserved. “We don’t have the answer. There doesn’t seem to be any entity that looks after that. Sovereignty exists within the borders of your nation, but what happens when that changes? Nobody has the answer,” she said.

Historically, countries are not physically destroyed; they simply become other countries, the land they occupy controlled by someone else. But at a minimum, to exist, a country needs a government, a population and a piece of real estate within a defined territory — the boot of Italy, the hanging triangle of India, the narrow strip of Chile. The shape of a nation has long been defined by two kinds of lines: the borders that separate it from other countries and the coasts that separate it from the sea. We may understand why political borders are subject to change, but in an era of rising seas and increasingly extreme weather and natural disasters, we have to get used to the fact that coastal boundaries can’t be taken for granted, either. Indeed, our land-water borders are changing quickly and significantly, and in ways that will probably never be reversed.

Environmental-law scholars have begun to discuss the notion of “ex-situ nationhood,” under which governments, with some financial support from the international community, would continue to represent their populations on an international level at bodies like the United Nations, without any connection to a physical territory. Under one model, the I-Kiribati would retain some rights as citizens, even as they dispersed around the globe. As Maxine Burkett of the University of Hawaii, who has written extensively on the political dilemmas facing small island states, told me in 2014: “A number of us understand the modern notion of citizenship, where people have ties to more than one country. But the notion of that happening without a physical territory is quite novel.”

In a 2013 essay, Jenny Grote Stoutenburg, a law professor at the University of Colorado at Boulder, recommended that, to maintain international recognition, island states facing destruction should reinforce their territory to maintain at least some physical structure above water and keep a small group of inhabitants behind, even if the bulk of the population has relocated. The Kiribati of the future, in other words, may be little more than a skeleton crew, a reinforced platform with a flag perched in the open ocean after the rest of the population has moved to another piece of land or to several of them. This is a very different notion of national sovereignty than anything the world has seen before.

There are understandable motivations behind plans like these: The people of small island states want to continue to have political representation in the international community, and they have economic interests to protect — rights to fisheries and natural resources in their territory, for instance. But these plans also offer a version of cartographical stasis taken to the point of parody: the erection of a fig-leaf physical presence in the middle of the ocean just so that maps showing a country in a particular place will be technically correct.

Still, a nation ending entirely, with no successor, might be a wholly new event in human history. In grappling with the possibility, some scholars have dusted off models and concepts that predate the modern nation-state.

One is the Sovereign Order of Malta — a Catholic order that controls no physical territory but has existed in multiple locations, including Jerusalem, Cyprus, Malta and Rome, throughout its nearly 1,000-year history. In an odd geopolitical quirk, despite controlling no territory today, the order has diplomatic relations, including embassies, with dozens of countries and observer status at the United Nations.

The order’s sovereign status makes it a throwback to an earlier, more fluid era of international politics, when sovereignty was tied more closely to ruling families or dynasties than to territories with fixed locations. Today, for instance, the historical kingdom of Burgundy is associated with the central French region of that name. But in his book “Vanished Kingdoms,” British historian Norman Davies identifies 15 kingdoms of Burgundy dating back to 410 and occupying locations from the west bank of the Rhine to what is now Switzerland to the Netherlands. Describing the disintegration of Burgundy in the 13th century, Davies writes: “The typical Burgundian count was no longer the ruler of one straightforward fief dependent on one overlord. More often he was head of a complex clutch of lands, titles and claims, assembled over the generations by the combined efforts of his family’s knights, wives, children and lawyers.”

If the vanishing countries of the future are to survive in any form, they’re likely to look less like contemporary nation-states and more like the Knights of Malta or medieval Burgundy, political creations set up to represent a group of people, and their political interests, who will be increasingly dispersed geographically and culturally.

These are not scenarios you’re likely to hear much about in Kiribati. For all that countries like Kiribati have done to bring urgency to the fight against climate change, many locals seem no more troubled about the issue than people in the United States are. When I visited on my reporting trip, people for the most part agreed that the climate was changing, pointing to shifting rainy seasons and irregular fishing patterns. But they usually didn’t believe that the islands would come to an end.

I heard several odd pseudoscientific arguments from Kiribati people during my time there, including that hotter weather would evaporate all the water released by the melting polar ice caps and that the coral in the Kiribati atolls would help the islands float as the water rose. Many people pointed out, correctly, that the shape of the islands regularly shifted before sea-level rise — and that the impacts of climate change so far had been difficult to disentangle from other factors. Most people I met weren’t making plans to relocate anytime soon. In contrast to Tong, the new government has not made the evacuation of Kiribati a priority, even a theoretical one.

Instead, I heard a lot of frustration that the rest of the world seems to take notice of the I-Kiribati only to tell them they’re doomed. Several people I spoke with had already given interviews about climate change to foreign reporters. “In my case, you are the fifth person,” remarked Teewata Aromata, the director of Te Toa Matoa, an organization for people with disabilities. “People come and ask us the same questions. They see pictures of us and think we are drowning in the ocean.”

Yet the stubborn facts remain. Countries like the Maldives and Kiribati are probably disappearing — and not that long from now. I came to Kiribati expecting to find a place planning for its own destruction, but instead I found something more dispiriting: a place that, with a few exceptions, wasn’t even contemplating that destruction. “Who wants to believe that their home won’t be here?” said Tong. It was an understandable sentiment. “People here don’t even like to plan for next week. But we’ve got to be hardheaded about it.”

The mental block that prohibits thinking about what will happen when the islands are no longer inhabitable seems to be a major impediment to planning for that eventuality. In this regard, too, Kiribati is a microcosm of the world’s unwillingness to face the reality of the future. A nation disappearing off the map is something that’s never happened before and, so far, is something people seem unable to imagine.