First local extinction in the US due to sea level rise

The United States has lost its only stand of the massive Key Largo tree cactus in what researchers believe is the first local extinction of a species caused by sea level rise in the country.

The Key Largo tree cactus (Pilosocereus millspaughii) still grows on a few scattered islands in the Caribbean, including northern Cuba and parts of the Bahamas. In the United States, it was restricted to a single population in the Florida Keys, first discovered in 1992 and monitored intermittently since.

Salt water intrusion from rising seas, soil depletion from hurricanes and high tides, and herbivory by mammals had put significant pressure on the population. By 2021, what had been a thriving stand of about 150 stems was reduced to six ailing fragments, which researchers salvaged for off-site cultivation to ensure their survival.

“Unfortunately, the Key Largo tree cactus may be a bellwether for how other low-lying coastal plants will respond to climate change,” said Jennifer Possley, director of regional conservation at Fairchild Tropical Botanic Garden and lead author on a study published Tuesday, July 9 that documents the population’s decline.