Scientists say the combined effects of rising sea levels have made this unique plant the first species to go extinct in the wild in the United States. It’s a tragic first, but it won’t be the last. As the climate crisis worsens, scientists worry that the plant’s extinction could be a “harbinger” for other species.
The combined effects of rising sea levels, storm surges and severe storms have wiped out wild populations of the Key Largo tree cactus in the only known U.S. archipelago, the Florida Keys, according to a paper published this week in the Journal of the Texas Botanical Institute.
“People need to understand that this is just one example of what’s happening to dozens of species, and that if we don’t do anything, this loss will only accelerate,” said study co-author George Gunn, executive director and president of the Regional Conservation Institute.
The Key Largo tree cactus still lives in parts of the Caribbean, including Cuba, Puerto Rico and the Bahamas, but the chances of it naturally re-establishing itself in the Florida Keys are essentially “zero,” Gunn said.
In 2011, about 150 specimens were found on tidal rocks atop a small limestone outcrop amid the myriad mangroves of John Pennekamp Coral Reef State Park, but by 2015, researchers noticed that the cacti were dying at an alarming rate, not just as a result of a one-off animal attack, but also because of their location in the lowlands of the Florida Keys, much of which is just five feet above sea level.
Plant habitats were inundated with saltwater from storms and storm surges exacerbated by rising sea levels. As fossil fuel pollution warms the planet, oceans also warm and expand, causing ice sheets and glaciers to melt and gradually raise water levels.
Sea levels around the Florida Keys have risen by an average of about 0.16 inches per year since 1971, or just over 8 inches, the researchers report.
“Too much salt creates a stressful environment for most plants,” study co-author James Lange, a research botanist at Miami’s Fairchild Tropical Botanical Garden, told CNN.
Plants can tolerate salty seawater for a few days, but if that period lasts for more than a few weeks, “their structure can no longer accommodate the lack of fresh water to nourish their bodies.”
Officials from Fairchild Tropical Botanical Gardens and the Florida Department of Environmental Protection removed all remaining green plants in 2021 after it became clear the plant population would not survive. – Courtesy Jennifer Posley
By 2021, after years of exposure to saltwater, only a few cacti remained, and the researchers chose to remove them from the wild rather than let them die. The last wild cacti were removed in 2023, “as it was clear that this area will continue to be affected by sea-level rise,” the researchers said.
Gunn told CNN that the species’ decline in the US is “a symptom of a larger problem.”
Scientists say sea levels around the Florida Keys are expected to rise by up to seven feet by the end of the century, resulting in even more severe tidal surges and saltwater intrusion, threatening the survival of many other species.
“Unfortunately, Key Largo’s arboreal cacti may be a bellwether for how other lowland coastal plants will respond to climate change,” said Jennifer Posley, lead author of the study and Fairchild’s regional conservation director.
Posley said more than a quarter of native plant species in South Florida are at risk of regional extinction, including rare-flowering Gerber’s spurge, small-flowered lilythorn, small-fruited varnished leaf and Grisebach’s dwarf morning glory.
And it’s not just plants that are a problem: Invading saltwater deprives local wildlife of fresh drinking water, forcing them to eat water-retaining plants like cacti, only making the problem worse for endangered plants. To combat this, biologists have had to create small freshwater pools to help animals and plants survive.
But these measures are only temporary: researchers say the amount of planet-destroying pollutants already building up in the atmosphere is set to cause sea levels to rise for decades, making protecting biodiversity especially difficult.
For the safety of the cactus and those handling it, the cuttings were carefully wrapped in towels. – Courtesy Jennifer Posley
Researchers rescued the last remaining cactus in the wild, wrapped it in towels for protection, and transported it to an off-site greenhouse to ensure the plant’s survival.
There are plans to reintroduce the species to the Keys, but finding suitable habitat that can withstand rapid climate change will be “challenging,” researchers say.
Ultimately, Key Largo’s overgrown cacti, caused by the climate crisis, may not have a future.
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