In low-lying island nations like Tuvalu and the Maldives , the term climate migrant is all too familiar. Rising sea levels have already forced some Pacific Ocean communities to flee from their homes and there are fears that several whole islands will be underwater in just a few decades.

But its not just island dwellers who need to worry about climate-related migration. As coastal areas are deluged over this century, millions of mainland Americans could be forced to flee inland, where they may overwhelm already crowded cities, according to new research from the University of Georgia.

We typically think about sea-level rise as a coastal issue, but if people are forced to move because their houses become inundated, the migration could affect many landlocked communities as well, said Mathew Hauer, the University of Georgia demographer who wrote the paper.

Using migration data from the Internal Revenue Service and climate migration models, Hauer concluded that a 6-foot increase in sea levels would cause every U.S. state to experience climate-related migration by 2100. Scientists are predicting a 6-foot global sea-level rise by the end of the century if greenhouse gas emissions are left unchecked .

In a study last year, Hauer had estimated that a 6-foot rise in regional sea levels would put 13 million people in more than 300 U.S. coastal counties at risk.

The new report, published in the journal Nature, finds that nine states could see population declines as rising waters force people to flee. Florida would be worst off with millions of people leaving the state.

Other states would be taking in climate migrants. Texas could absorb as many as 2.5 million internal migrants.

Several metropolitan centers, in particular, could see significant population boosts. Houston; Austin, Texas; Orlando, Florida; and Atlanta could receive more than 250,000 net migrants each, the report said. Other popular cities for climate migrants would likely include Phoenix and Las Vegas.

The incoming human flood might spell trouble for already packed cities, said Hauer. Some of the anticipated landlocked destinations, such as Las Vegas, Atlanta and Riverside, California, already struggle with water management or growth management challenges, he said.