The lowest point is just above sea level, a spot from which you can be tricked into thinking that you are somehow standing below the vast Pacific, looking up rather than out into it.

Data from the National Research Council in the United States predict that global sea levels could rise by as much as 55 inches by 2100 as a result of climate change, which, when combined with damage to the coral roots of Tuvalu by rising acidity in seawater, could threaten the country’s very existence. Then there is coastal erosion, a result of rising water and harsh weather but also human activities like excavation for construction and other development projects.

During World War II, as fighting between the United States and Japan raged across the Pacific, the British government granted the United States military the use of its colony on what is now Tuvalu but was then known as the Ellice Islands. Massive antiaircraft guns, the concrete base of at least one of which still stands a lonely vigil in the surf, were quickly erected. But for the islands to reach their full wartime potential, they needed an airstrip. Large quantities of coral were dug up and carted off to be crushed and mixed for the tarmac. The gaping pits that were left behind across Funafuti, called “borrow pits,” were never filled and eventually began to be used for refuse. Add to this the doubling of Tuvalu’s population since 1980, and it is easy to understand why, as usable land dwindled, homes like Ms. Uilese’s started to stretch across the pits.

For Betty Vuva, 49, the head teacher at Nauri Primary School, the borrow pits and their attendant health problems are a constant source of anxiety. As the changing tides have steadily encroached on the island from without, she says, the land around the pits has become more crowded.

“Well, so far no houses have collapsed,” she said with a wry laugh.

The government of Tuvalu, which survives on a combination of foreign aid and dividends from the sale in 1998 of the .tv Internet domain name, has repeatedly asked the United States government for assistance in refilling the borrow pits. In 2003, the United States Army Corps of Engineers carried out a site assessment and cost study at the behest of the State Department. The 152-page report acknowledged the provenance of the pits and starkly identified their cost to the island.