Deep in the rain forest on the southern edge of Australia’s Nightcap Range, around 200 unassuming gray trees are among the last survivors of a fallen world. These are Eidothea hardeniana, trees that trace their roots to the bygone supercontinent of Gondwana, where long-necked sauropods grazed on towering conifers and flowers were an evolutionary novelty.
The Eidothea lineage has survived the fracturing of its continent and the cosmic catastrophe that ended the age of the dinosaurs. But it might not survive the disaster now facing it, living in a biosphere that’s been vandalized by humanity.
Tens of millions of years of tectonic transfiguration and the slow desiccation of Australia have steadily eroded Eidothea’s territory, constricting its two living species to patches of forest along the continent’s eastern coastline. One of those species, Eidothea hardeniana, or the Nightcap Oak, occupies just a few acres of land in a rain-forest preserve. The grove’s adult trees resprout over and over by cloning, and some of them are likely to be many thousands of years old.
This past bushfire season killed at least 10 percent of the population. It was the worst in living memory—a disaster brought on by a multiyear drought, months of extreme heat, and the warming, drying effects of humanity’s fossil carbon emissions—and up to 30 percent of Eidothea hardeniana’s grove was harmed by fire. For a species that numbers so few, Robert Kooyman, a botanist at Macquarie University, told me, “losing any individuals is a disaster.”
“Elements of what you lose … are irreplaceable,” he said. “If we’ve lost some of its genetic diversity, in evolutionary terms that’s lost forever.”
While the Nightcap grove is ancient, the scientific community was unaware of its existence until a few decades ago. In 1988, Kooyman was walking along a creek in a remote part of Nightcap National Park when he discovered a juvenile tree with elliptical, sawtooth-edged leaves he couldn’t identify. The tree seemed to have some affinity to Proteaceae, an early family of flowering plants with a lineage going back more than 120 million years. But its identity would remain a mystery until Kooyman returned to the same patch of forest 12 years later and came upon specimens of the same type of tree in different stages of growth: a seedling, a sapling, and an adult tree with fleshy golden fruits underneath it. When he returned a few months after that, he discovered its tubular, cream-colored flowers.
With the entire life cycle of the plant now evident, Kooyman and fellow botanist Peter Weston of the Royal Botanic Garden in Sydney soon confirmed that the tree was, in fact, a member of Proteaceae. They set about formally describing the species, and in 2002, they gave it a name: Eidothea hardeniana.
Eidothea was a goddess from Homer’s The Odyssey, a daughter of Proteus, with extraordinary powers. Hardeniana, meanwhile, paid homage to Gwen Harden, a prolific botanist at the Royal Botanic Garden who was on the brink of retirement.
“We regarded Gwen as something of our goddess of the rain forest, but she’d never had a species named for her,” Kooyman said. “To support women in science and acknowledge her incredible contributions, we named our newly discovered goddess for Gwen.”
The mythological epithet is appropriate in more ways than one. Based on DNA evidence, researchers have estimated that the Eidothea genus evolved more than 70 million years ago, deep in the history of flowering plants. At that time, Antarctica, Australia, and South America’s Patagonia region were stitched together into an evolved form of Gondwana blanketed in temperate rain forest. Many of the plant lineages found growing in the Nightcap area today, including araucaria and eucalyptus trees and evergreen tree ferns, are present in Gondwanan fossil beds from Argentina to Antarctica, suggesting Eidothea is part of a primitive botanical community that spanned the supercontinent.
“It represents an ancient lineage from an ancient family,” Peter Wilf, a paleobotanist at Penn State University who studies remnant Gondwanan forests, told me. “It also represents an ancient type of forest.” In fact, ecological surveys suggest that in addition to sheltering dozens of threatened endemic animals, the Nightcap area is more “Gondwanan,” floristically speaking, than any other place in Australia.
“It’s a true refugia,” Kooyman said—an area that serves as a sort of biotic bomb shelter where species can survive geologic upheaval.
Now, it’s a shelter in crisis. In early November, a lightning-sparked blaze flared up near Nightcap National Park’s border, and before long, the grove’s understory had started to burn. With firefighters’ resources stretched thin and the weather working against them, not every leafy resident could be saved.
When Kooyman traveled to the Nightcap area in late November to start assessing the damage, he found a grim sight. All of the ground-level shrubs and ferns had been burned away; piles of smoldering wood lay everywhere. Charred rain-forest trees were split and dying. Adding to the surreal quality of the scene, the forest canopy remained largely intact: an umbrella of green over a blackened forest floor.
“It was pretty distressing,” he said.
Working with members of the National Parks and Wildlife Service’s Saving our Species conservation program, Kooyman quickly set up a series of forest-monitoring plots, which have become the site of a morbid science experiment. As researchers assess the fire’s impacts on dozens of rain-forest species in the Nightcap area, they’re monitoring these plots over time to see how many trees succumb to the knock-on effects of fire damage. As Kooyman explained, if heat or fire penetrates the thin bark of rain-forest trees, they can develop fatal vascular embolisms or fungal infections long after the flames have passed.
Kooyman’s biggest concern is that the loss of even a few individuals could deal a crippling blow to Eidothea hardeniana’s gene pool. Early genetic work spearheaded by Maurizio Rossetto at the Royal Botanic Garden Sydney revealed that the species is remarkably diverse given its small population size. If the recent mortalities included some of the most genetically distinct individuals, the species’s ability to adapt to long-term changes might be severely diminished.
“Losing 10 percent of stems doesn’t necessarily mean you’re losing 10 percent of evolutionary potential,” Rossetto told me. “It will depend on what has been lost and the distribution of individuals.” Once Kooyman’s ongoing surveys have painted a clearer picture of which trees have been killed by the fires, Rossetto and his team plan to revisit their genetic data to quantify the evolutionary impact.
Because the fires occurred before the fruiting season, new Eidothea hardeniana seedlings could take root this year. Even adult trees that were severely affected might yet be able to put out new suckers, or sprouts. But Eidothea hardeniana grows slowly, and in a fragmented habitat, where local fauna doesn’t seem to find its fruit particularly palatable, its ability to spread is limited. Humans could help by actively propagating the tree into other suitable habitat areas, Rossetto said; Kooyman, by contrast, emphasized the need to redouble conservation efforts within the Nightcap area by clearing out encroaching weedy vegetation and felled timber left behind after historical logging.
However, centuries could pass before any new seedlings reach reproductive maturity, Kooyman said. And with Australia’s fire season rapidly worsening, as humans pump heat-trapping carbon into the atmosphere at a rate not seen in the last 66 million years, the next pyrotechnic assault could arrive long before that.
The Gondwanan glory days are over, and in geologic terms, time capsules such as the Nightcap area were on their way out. But humanity has “really kicked things forward,” Wilf, the paleobotanist at Penn State, said, pushing species such as Eidothea hardeniana that much closer to extinction and threatening to sever our connection to an ancient world far sooner than nature intended.
“It is tragic to think about,” he added. “These are plants that have survived an enormous amount of global change—immense global cooling, continent splitting.” But with Eidothea hardeniana’s lone life raft now breaking apart in a geologic eyeblink, the survivors might not be able to chart an evolutionary escape route fast enough.
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