Researchers say that a type of tropical plant that lived in the Florida Keys is now extinct. It is the first species in U.S. history to go extinct because of rising sea levels.
A big group of Key Largo tree cactus, the only one left in the U.S., was wiped out by rising ocean levels because the Earth’s ice sheets are still melting, according to a paper released earlier this month by the Botanical Research Institute of Texas.
According to James Lange, a research botanist at the Fairchild Tropical Botanic Garden in Miami and co-author of the study, the cacti died because of the saltwater from the extra ocean water flooding into the mangrove where they lived. This could happen to other plants in the future.
Extreme storms and high waves from rising seas have washed away soil and let the salt water into a mangrove that was home to Pilosocereus millspaughii. Lange said that this species has wooden trunks and tall columns that “flower prolifically” and smell like garlic.
The cactus grew on a low limestone outcrop near the water. It was surrounded by mangroves, which used to have a clear layer of dirt and organic matter that other plants and the cactus could grow in. The material was worn down to almost nothing by storm surges from hurricanes and “exceptionally” high tides, the experts said.
Lange said that experts started to see saltwater flooding in the area in 2011 because of king tides, which are very high tides that happen when the moon is new or full. It stresses the plants by osmosis, which means that they lose water through their cells, and by throwing off the balance of ions, he said.
Researchers said that salt-tolerant plants that used to only grow in muddy soils under the mangroves started slowly making their way up, which was a sign that the salt levels were rising. The paper says that by 2012, half of the people had died.
It was in 2015 when animals ate trees so much that they were chewed down to the vascular cambium. This put stress on the population and eventually killed off the species in the U.S. Lange said that all of the trees’ meaty parts were gone.
L. Lange said that scientists still don’t know what kind of animals did the damage.
A Category 5 storm called Hurricane Irma destroyed Southwest Florida in 2017. It also caused a five-foot storm surge that flooded the area for days. When the water went away, the mangrove was in such bad shape that scientists brought baby pools to the area to fill them with fresh water.
The paper says that in 2019, king tides flooded parts of the island for more than three months, especially the low-lying crops. There were only six Key Largo tree cactus stems left by 2021, and it was clear that the people would not make it.
Lange said that scientists decided in 2023 that the species was extinct for good.
The Key Largo tree cactus may be a sign of how other low-lying coastal plants will react to climate change, which is not good, said Jennifer Possley, who is the lead author of a study and the head of regional conservation at Fairchild Tropical Botanic Garden.
Lange said that not much is known about the rare plants that live in Florida. Pilosocereus millspaughii was found in 1992, but not much is known about the find because the cacti were found in a dense area of mangroves that was mostly made up of tough, thorny plants, he said.
A different species of Key tree cactus, Pilosocereus robinii, is also nationally endangered and can be found in other parts of the Florida Keys. It is also dying because of some of the same environmental problems, the researchers said. In 1984, the federal government said that cactus was threatened, but between 1994 and 2007, the number of those plants dropped by 84%.
Researchers have seen what could happen to other native species in the area by looking at how quickly the Key Largo tree cactus has died off.
In a statement, George Gann, executive director of the Institute for Regional Conservation and co-author of the study, said that over the past 25 years, more than one in four native plant species in Florida have been listed as critically threatened with regional extinction or have already gone extinct. This is because of habitat loss, over-collecting, invasive species, and other things that cause degradation.
Lange said, “We’re in a biodiversity crisis on a global scale.” “We have thousands of species, probably millions, that are, threatened with extinction.”
“People don’t always fully understand how important a species is until it’s gone,” Lange said. Bats, bugs, and moths pollinate the Key Largo tree cactus, and birds and other small mammals eat its fruit.
The species still has hope. The plant Pilosocereus millspaughii is no longer found in the United States, but it still grows on islands in the Caribbean, such as northern Cuba and parts of the Bahamas. Two Florida institutions and the National Seed Bank in Fort Collins, Colorado, have hundreds of live endemic plants and seeds that they could use to start a new grove in the future, once a good spot is found, Lange said.
Possley said that Fairchild botanists are working on plans with the Florida Department of Environmental Protection to plant some of them again in the wild.
