Theoretically, every one of Guyana’s 800,000 or so residents could claim for themselves about 66 acres of real estate inland, safe from the sea. Much of that land is forested, some of it full of rare wonders, like endangered polychromatic tree frogs and waterfalls spilling from green plateaus. In reality, roughly 90% of the population is crammed into the narrow floodplain hugging the Caribbean. Almost half of them live in Georgetown, the waterlogged capital, most of which sprawls across a coastal basin that’s about 7 feet below sea level and depends on a network of drainage canals to remain habitable.

They live on the coast because that’s where the economic opportunities, such as they are, can be found. Guyana historically has been one of the poorest countries in the Western Hemisphere; from 2000 to 2015 the gross domestic product of the entire country was much smaller than that of most midsize US cities.

Such modest fortunes could be swept away in an instant. That 2005 tidal surge wiped out 59% of the annual GDP. Putting in adequate countermeasures—expanding and reinforcing the 280-mile long seawall, upgrading drainage canals, building housing infrastructure on higher ground—will cost billions.

Guyana will almost certainly experience another devastating surge. Warming Caribbean waters are projected to rise 8 to 10 inches in the next 30 years, according to the U.S. National Ocean Service. And if the world continues to burn fossil fuels at the going rate, the same report says the sea will rise 6 feet by century’s end. If nothing else changes, Georgetown’s seawall will be under water, and its residents will have scattered.

In the face of this, Guyana’s government is betting on a paradox: The very thing that threatens the country will be its salvation. The country’s leaders, praised in the past for their environmental stewardship, now believe the most effective way to rescue Guyana from fossil-fuel-induced climate change is—crazy as it sounds—to fully embrace the business of fossil fuels.

At the bottom of Guyana’s share of the Caribbean Sea sits a massive cache of oil. In 2015 exploration crews from Exxon Mobil Corp. found what would prove to be billions of barrels of crude about 120 miles from the shore—a once-in-a-generation jackpot that accounts for about one-third of the total oil discoveries worldwide since then. Some industry analysts estimate that the reserves in Guyanese waters could equal China’s.