Rising Seas Wipe Out Key Largo Tree Cactus, First U.S. Plant Extinction Linked To Climate Change

Researchers have confirmed that the Key Largo tree cactus, a distinctive tropical species native to the Florida Keys, has gone extinct in the United States due to the impacts of rising sea levels. This marks the first time in U.S. history that a plant species has been lost solely to climate change.

The cactus, scientifically known as Pilosocereus millspaughii, was once a prominent fixture in an isolated mangrove near Key Largo. However, the relentless rise of ocean waters, exacerbated by melting polar ice sheets, proved fatal to its survival. According to a recent study published by the Botanical Research Institute of Texas, the cactus population was devastated as saltwater infiltrated its habitat, causing irreversible damage to the mangrove ecosystem.

James Lange, a botanist from the Fairchild Tropical Botanic Garden and co-author of the study, explained that the mangrove, which sheltered the cacti, experienced increased saltwater intrusion due to extreme storm systems and high tides linked to rising sea levels. These environmental stresses compromised the cactus' ability to thrive, leading to a significant decline in its population.

The situation worsened notably after 2015, when an herbivory event caused substantial damage to the cacti, leaving them vulnerable. Subsequent hurricanes, including the destructive Hurricane Irma in 2017, further inundated the mangrove with storm surges, accelerating the decline of the already diminished cactus population.

"Unfortunately, the Key Largo tree cactus may be a harbinger of what other coastal plants could face as climate change progresses," remarked Jennifer Possley, director of regional conservation at Fairchild Tropical Botanic Garden and lead author of the study. She highlighted that the loss of this species underscores the broader biodiversity crisis affecting Florida and beyond, with many native plants under threat from habitat loss and other environmental pressures.

Despite its extinction in the U.S., hope remains for the Key Largo tree cactus. Small populations still exist in the Caribbean, offering a potential source for future conservation efforts. Institutions in Florida and the National Seed Bank in Colorado are poised to support these efforts by preserving seeds and plants for potential reintroduction into suitable habitats.

As efforts continue to mitigate the impacts of climate change, scientists emphasise the urgent need for conservation actions to protect vulnerable species like the Key Largo tree cactus from disappearing entirely.