Emily Chan
For decades, a rare tree cactus has grown on Florida’s Key Largo, hidden from view by a tangle of mangrove trees. It was first discovered in 1992 and has been monitored on and off since then.
The tree cactus still grows on a few islands in the Caribbean, including parts of the Bahamas and northern Cuba.
However, it is now considered extinct in the United States. The demise of the cactus is what researchers believe to be the first local extinction of a species as a result of rising sea levels in the country.
When it was discovered on a low limestone outcrop in Key Largo, there had been a stand of about 150 cactus stems. Its stems can reach more than 20 feet and produce fragrant, cream-colored blossoms, as well as bright red and purple fruit. Bats are attracted to the flowers, while birds and mammals are drawn to the fruit.
It was confirmed in 2019 that the trees were the first and only known occurrence of the species in the U.S. By 2021, the cactus cluster had been reduced to just six. Researchers salvaged them in the hopes that they would survive.
Salt water flooding from rising seas, soil erosion from high tides and hurricanes, and the consumption of the plants by animals all worked together to dwindle its numbers to zero.
“Unfortunately, the Key Largo tree cactus may be a bellwether for how other low-lying coastal plants will respond to climate change,” Jennifer Possley, the lead author of the study and director of regional conservation at Fairchild Tropical Botanic Garden, said.
Originally, the site that the Key Largo tree cactus grew on had a distinct layer of soil and organic matter that allowed it to thrive. But passing hurricanes and high tides depleted the material.
A 2012 study led by Fairchild also showed increased salinity in the soil beneath dead versus living cacti, leading to the conclusion that salt levels play a part in the survival of the species.
Sign up for Chip Chick’s newsletter and get stories like this delivered to your inbox.
