At first glance, the findings, published in the journal Nature Communications, appear to challenge the conventional wisdom that low-lying nations might one day disappear into the sea. But the lead author, Paul S. Kench, a coastal geomorphologist (the study of how the earth’s surface is formed and changed) at the University of Auckland in New Zealand, said simply that the effects of climate change on islands can be complicated.

“Our work isn’t suggesting they have nothing to worry about,” said Dr. Kench, who has been studying climate and islands for about 20 years. “But there is more to this than the simple, linear doomsday scenario.”

His team’s research found that Tuvalu’s land area, spread out among nine low-lying coral atolls and 101 reef islands, grew by 182 acres since 1971. That’s about twice the size of Vatican City.

The reason? Islands are dynamic ecosystems, he said, which means that changing wave patterns and sediment dumped by storms might be offsetting the erosion caused by rising seas. Some of Tuvalu’s islands grew, and some shrank, but averaged together they gained overall.

Similar things could happen with other island nations, Dr. Kench said, depending on the nature of the sand and other ecosystem dynamics.

Island leaders have not embraced the findings. “It is poor science, and irresponsible, to average out these changes and conclude that sea level rise is not a problem for Tuvalu,” said Dr. Ian Fry, Tuvalu’s chief climate change negotiator at the United Nations, in an email.

He also criticized the study for not mentioning the implications of ocean acidification or coral bleaching on island health. Tuvaluans, he said: “Are suffering a whole gamut of problems associated with climate change. The paper is very shortsighted.”