Florida scientists document first local extinction due to sea-level rise
Scientists in Florida have reported the first local extinction of a species caused by sea-level rise. The Key Largo tree cactus, native to the US, has been eradicated due to saltwater inundation and soil depletion from hurricanes, according to researchers from the Florida Museum of Natural History and Miami’s Fairchild Tropical Botanic Garden.
Species decline and relocation efforts
The cactus, which now only exists on a few remote Caribbean islands, northern Cuba, and parts of the Bahamas, was already critically endangered with just one population of six stems remaining in the Florida Keys. These were moved to a greenhouse in 2021 to ensure the species’ survival. Subsequent searches have failed to find any naturally growing Key Largo cactuses, and despite tentative plans for replanting with the Florida Department of Environmental Protection (DEP), there is little hope for its re-establishment.
Vulnerable Florida Keys
Approximately 90% of the Florida Keys are at an elevation of 5 feet or less. NASA predicts ocean levels could rise by up to 7 feet by 2100, exacerbating the challenges for coastal plants. “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, lead author of the study published in the Journal of the Botanical Research Institute of Texas.
Long-term decline
Scientists first noticed the decline of Pilosocereus millspaughii in 1992, when it was identified as a distinct species. A storm surge in 2005 linked water salinity to cactus mortality. Subsequent hurricanes and high tides further eroded the soil where the cactuses grew. Additionally, mammals deprived of fresh water began eating the moisture-retaining plants, causing further harm.
“In 2011, we started seeing saltwater flooding from king tides in the area,” said James Lange, a research botanist at Fairchild and co-author of the study. “We’d never seen cactus herbivory like this anywhere in the lower Keys, where flooding has tended to be less extensive.”
Irreversible damage
Salt-tolerant plants began to encroach on the cactus habitat, indicating rising salt levels. By 2017, Hurricane Irma devastated the area, and successive king tides in 2019 led to the decision to remove the remaining stems.
The study, which included contributions from the DEP and the University of Florida, highlights the challenges of preserving rare species in the face of climate change. “Understanding and predicting the fate of rare organisms and their habitats in the face of climate change will likely be complicated by similar ecological interactions, and will require a multi-disciplinary approach to conservation,” Lange said.