(Washington) A species of cactus is now extinct in the wild in the United States, a loss that represents the first local extinction linked to rising sea levels in the country, according to a study released Tuesday.
This cactus (Pilosocereus millspaughii) which can grow up to six meters, with white flowers and red fruits surrounded by thick woolly hairs, still exists in the Caribbean, but was only present in the United States in Florida, on the island of Key Largo.
Saltwater intrusion and soil erosion from hurricanes and tides have taken their toll on this population, which has been monitored annually since 2007.
Their fate “could be an indicator of how other low-elevation coastal plants will respond to climate change,” Jennifer Possley, co-author of the study, warned in a statement.
These cacti grew on limestone soils surrounded by mangroves, near the shore, but their habitat has been eroded.
Previous work has shown that soils under dead cacti contain more salt than under living cacti, establishing a connection between this increased salinity and their mortality.
In 2015, researchers also noticed that many of these cacti, which contain water reserves to withstand periods without rain, had been eaten by animals.
Scientists have speculated that these animals turned to cacti in the face of increasingly limited fresh water resources due to repeated intrusion of seawater.
In 2017, the very powerful hurricane Irma swept across Florida, then high tides in 2019 caused flooding for several months.
By 2021, there were only six living cacti left out of 150 previously. The researchers decided to save them by replanting them in a greenhouse or a protected outdoor location. More than a thousand seeds were also preserved.
Attempts to replant them in the wild are being considered, but suitable environments are becoming increasingly rare.
“We are on the front lines of biodiversity loss,” said George Gann, a co-author of the study. “Our research in South Florida over the last 25 years shows that more than one in four native plant species is critically endangered or already extirpated,” meaning locally extinct.
With global warming, glaciers and ice caps in Antarctica and Greenland are melting and their water is flowing into the oceans, causing sea levels to rise. The expansion of the oceans, due to the absorption of heat, is also contributing.