A single plant has become the first species in the United States to be wiped out of the wild by the combined effects of rising seas, scientists say. It’s a sad first, but not the last, as scientists fear the plant’s disappearance could be a “bellwether” for other species as the climate crisis tightens.
The combined effects of rising sea levels, rising tides and intense storms have driven the wild population of Key Largo tree cacti to extinction at its only known locality in the United States, in the Florida Keys, according to the paper published this week in the Journal of the Botanical Research Institute of Texas.
“This is just one example of what is happening to dozens of species, and people need to understand that if we do nothing, this loss will only accelerate,” said George Gann, study co-author and executive director and president of the Institute for Regional Conservation.
The Key Largo tree cactus still exists in parts of the Caribbean, including Cuba, Puerto Rico and the Bahamas, but the chances of it reestablishing itself naturally in the Florida Keys are virtually “zero,” Gann said.
In 2011, there were about 150 of them growing on a barren rock atop a small limestone outcrop amid a plethora of mangroves at John Pennekamp Coral Reef State Park. But in 2015, researchers noticed the cactus was dying at an alarming rate, a result of both an occasional animal attack and its location in the Florida Keys, much of which sits just 5 feet above sea level.
The plant’s habitat was overwhelmed by salt water from storms and high tides, compounded by rising sea levels. As pollution from fossil fuels warms the planet, it also warms and expands the oceans and melts ice caps and glaciers, raising sea levels.
Sea levels around the Florida Keys have risen an average of about 0.16 inches per year, or just over 8 inches, since 1971, the researchers reported.
“Too much salt is a stressful environment for most plants,” James Lange, study co-author and research botanist at Fairchild Tropical Botanic Garden in Miami, told CNN.
Plants can tolerate salty seawater for a few days, but when that period extends to weeks or more, “their structures are simply not prepared to deal with it because they’re not getting any fresh water anymore – they can’t feed their bodies.”
By 2021, after years of exposure, only a few cacti remained. The researchers chose to remove them from the wild rather than let them die. The last wild cactus was removed in 2023 “because it was clear that the area would only continue to succumb to sea level rise,” the researchers said.
The species’ disappearance in the United States is “an indicator of a larger problem,” Gann told CNN.
Sea levels are expected to rise by up to 2 metres by the end of the century around the Florida Keys, leading to even more intense tides and seawater intrusion – an existential threat to many more species, scientists say.
“Unfortunately, the Key Largo cactus may well be an indicator of how other low-lying coastal plants will respond to climate change,” said Jennifer Possley, lead author of the study and regional conservation director at Fairchild.
Possley said more than one in four native plant species are critically endangered in South Florida. These include the rare Garber’s spurge, small lily thorn, small varnish leaf and Grisebach’s dwarf morning glory.
And it’s not just plants. Saltwater intrusion deprives local wildlife of drinking water and forces them to consume moisture-retaining plants, like cacti, which only makes the problem worse for endangered plants. To solve this problem, biologists have had to create small pools of fresh water to help sustain the animals and plants.
But these solutions are only temporary. Pollution already in the atmosphere has caused sea levels to rise for decades, making protecting biodiversity particularly difficult, researchers say.
Researchers rescued the last remaining cacti from the wild, wrapped them in towels to protect them, and took them to an off-site greenhouse to ensure the plants’ survival.
Although there are plans to reintroduce the species to the Keys, researchers say it is “difficult” to find suitable habitat that can cope with rapid climate changes.
Ultimately, the Key Largo tree cactus may have no future in a wilderness made too wild by the climate crisis.
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