BIG POND — Across their kayaks, the three men passed the green shoot back and forth. Occasionally, one would cradle it in a palm and bring a hand lens to it with the other, inspecting the carnivorous plant that was their bounty.
By day’s end, the group — Seth Cunningham and Michael Tessler, biologists at the American Museum of Natural History; and John Thompson, coordinator of the Catskill Regional Invasive Species Partnership — filled eight vials with the plant, Aldrovanda vesiculosa, also known as the waterwheel.
The plant should not be here, and it presents an ecological conundrum.
Around the world, the waterwheel is going extinct. But from summer through late fall, the carnivorous, rootless, wetland-loving plant is plentiful in this swampy body of water near the Catskill Mountains.
Think of the waterwheel as an underwater Venus flytrap. Its whorled shoots are typically shorter than 8 inches and less than 1 inch thick. But for a plant, its diet is impressive: seed shrimp, shell-less crustaceans, insect larvae, and occasionally even tadpoles and small fish.
When tickled by prey, the waterwheel snaps shut in less than 10 milliseconds.
Until recently, the plant floated across fens, ponds and reservoirs in Australia, Asia, Africa and Europe. But today, human-driven habitat destruction has pushed the waterwheel into free fall.
Over the last 150 years, nearly 90% of its habitat has vanished worldwide, and the waterwheel’s survival status is extinct or unverified in at least 32 of the 43 countries where it naturally occurs. In 2012, the International Union for Conservation of Nature added Aldrovanda vesiculosa to its “red list” of globally threatened species.
“The species is completely imperiled,” said Adam Cross, an ecologist at Curtin University in Australia who studies the plant.
In 2013, Cross traveled to the Fort A.P. Hill army base in Northern Virginia to study a newly established population of more than 25 million waterwheels — at the time, more than the rest of the world’s populations combined.
But it’s doing more than just flourishing in the United States: In Virginia, the waterwheel is listed as a highly invasive species and a potential threat to native fish and plants. New Jersey includes the species on its invasive watch list, and it’s also considered invasive in New York.
But some botanists who don’t want the carnivorous plant to disappear see the Northeast’s waterwheels as a glimmer of hope for the species’ global survival.
Other experts are still grappling with the question of whether an imperiled species can also be a menace.
Because its arrival is so recent and research so scarce, biologists don’t know how, or how quickly, the waterwheel may spread. They also don’t know what exactly it’s eating in local waters, which could help quantify the threat it poses, if any.
So far, New York’s sole documented site is Big Pond, and environmental DNA sequencing by Tessler has not turned up the plant’s genetic fingerprint in other Catskills ponds.
Still, officials worry it could spread to nearby waterways and outcompete native carnivorous plant species, Young said, such as bladderworts.
“It’s pretty clear why this species is going extinct,” Cross said. “It’s experienced an almost perfect storm of what humans can do.”
Now, humans must decide what to do with these new populations.