Imperiled in the Wild, Many Plants May Survive Only in Gardens

Researchers also began employing ex situ conservation, in which endangered plants are propagated outside of their natural habitats, under the assumption that the new plants will eventually be returned to the wild to bolster dwindling native populations. A backup collection of propagated Wollemi pines was created at Australian Botanic Garden Mount Annan, in a suburb southwest of Sydney, as an insurance policy against extinction. What’s more, because so few individuals remain in the wild and all of them are in a single area, newly propagated trees have been translocated to rainforest ravines outside the species’ current range. 

While the goal of plant conservation has long been to preserve imperiled species in the wild, there is a deepening realization that a growing number of them will lose their native habitats as climate change magnifies the destruction caused by land development, introduced pests and diseases, and other threats. In fact, Australia’s catastrophic Black Summer megafire of 2019 and 2020 made it clear that plant conservation procedures employed for decades are no longer sufficient. 

That firestorm, exacerbated by climate change, burned more than 42 million acres in eastern Australia — one of the largest wildfires ever recorded in the country. Crews raced to save the Wollemi pines, installing irrigation systems, deploying fire retardants, water-bombing with helicopters and other aircraft, and winching remote-area firefighters down the steep escarpments to extinguish flareups as soon as the main fire fronts had passed. Although they likely reduced the severity of the impact, even such heroic efforts could not prevent significant damage to both the native population and the translocated trees. 

“This tree survived 200 million years on this planet,” says Dan Luscombe, collections manager at Bedgebury National Pinetum and Forest in the U.K., which has a number of Wollemi pines in its care. In their heyday, dinosaurs brushed up against their branches. “And the biggest threat to them,” he adds, “is climate change we are causing now.”

“The number of species that are extinct in the wild is growing,” says Abby Meyer, a plant conservation and botanic garden consultant who until recently was the executive director of the U.S.-based Botanic Gardens Conservation International. Entire habitats are being lost, Meyer adds, pointing to cloud forests, alpine regions, and islands, which are already succumbing to sea level rise. “We’re literally right now deciding which species survive into the future and which do not.”

As the Black Summer fires demonstrated, the Wollemi pine may no longer be safe in its rainforest refuges — or in cultivated back-up collections, which are themselves at increasing risk of being wiped out by storms, floods, and fires. For these reasons, the creation of a genetically diverse and globally dispersed “metacollection” is now deemed essential. More than 200 young Wollemi pines that capture the full range of the species’ known genetic diversity have been distributed to additional botanic gardens in Australia, the U.K., Ireland, Europe, and the United States, which will collaborate on actions to ensure the conifer’s survival.

Protecting the surviving Wollemi pines in the wild remains the primary goal. Although the species’ genetic diversity can be captured in metacollections, it is impossible to replicate the majesty and structural complexity of the remaining wild trees and stands in cultivation, says Berin Mackenzie, an Australian ecologist who studies the Wollemi pine. Individual trunks on wild trees can reach 130 feet tall and may be over 500 years old, with some of the largest trees bearing over 40 trunks. “That unique set of environmental and ecological events that’s taken place over centuries or millennia to create those stands, that won’t ever be repeated,” he says.

But what happens when a native habitat disappears? As an increasing number of plants lose their wild habitats, will they survive only far from their ancient homes in scattered metacollections? And will it be feasible and affordable to protect even a fraction of the tens of thousands of threatened species in metacollections?

For years, Wes Knapp — the incoming chief executive officer of the Center for Plant Conservation, a California-based nonprofit — has studied species teetering on the brink of extinction in the wild. “The world is going to change rapidly over the next hundred years,” he says, “and if we don’t act right now, many plants will likely go extinct.” 

The 2020 State of the World’s Plants and Fungi report, published by Kew Gardens, revealed that two in five plant species are threatened with extinction. Some 50,000 of these imperiled plants are called “exceptional species” because they either produce seed that cannot be easily obtained or their seed cannot survive long term in seed banks. This makes them prime candidates for metacollections. They include not just rare conifers but other evolutionary relics such as cycads — palm-like plants with thick trunks, arching crowns of stiff, evergreen leaves, and a 300-million-year lineage. They also include a variety of ecologically and economically important species, such as oaks.

Other obvious candidates for metacollections are plants that have already lost their wild habitats and survive only in cultivation. In October 1765, for example, botanist John Bartram and his son William came across some small trees growing along a river in Georgia, then a British colony. By 1803, the species, Franklinia alatamaha, which produces snowy white, orange-scented, camellia-like blooms, could no longer be found in the wild. Fortunately, descendants of the seeds collected by William Bartram survive in the nursery trade today. Extinct-in-the-wild plants like Franklinia “aren’t just curiosities,” says Knapp. “They are our black rhinos.” They should be conservation priorities, he says, and yet many lack active recovery plans.

In addition, there is an entire group of plants called “one known occurrence” species, whose status is precarious because they exist only in one place on Earth. Knapp has identified 215 such plants in the U.S. and Canada alone. Also in need of metacollections are what Knapp calls “move them or lose them” species, which are already losing their habitats to climate change and need to be propagated and moved to suitable wild lands outside their current range. The endemic plants of the Florida Keys are a prime example. “We’re going to lose the Keys eventually to sea level rise,” Knapp says, or lose so much of their habitat to development that there is no place for them to retreat. But if researchers can find more hospitable habitat for them, “some of these plants may have new places,” he says. “Some are doomed just to be in gardens. But that’s better than being extinct, right?”

“Not to be doomsdayish,” says Emily Coffey, vice president for conservation and research at the Atlanta Botanical Garden, which is collaborating on the Wollemi pine metacollection, “but while we always want to focus on preserving species in the wild, when we are dealing with the falling apart of laws to protect biodiversity, and the acceleration of climate change,” preserving plants in cultivated metacollections “has to be a primary option.”

Meyer points out that collaborating on metacollections enables botanic gardens to share limited resources and collections in case of unexpected loss at a single site. She adds that this conservation tool is also beneficial because it allows scientists to spread an imperiled species’ genetic diversity around the globe, to more fully match the different microclimates in which the plant grows across its entire native range. “This brings the greatest amount of genetic, geographic, and ecological diversity to the table for conservationists to work with,” she says, “and will enable the species to better adapt to any climate change that lies ahead.” 

However, Kay Havens, chief scientist and vice president of science at the Chicago Botanic Garden, points out that whereas about 800 threatened animals are collaboratively managed by zoos around the world, tens of thousands of plants will require this kind of intensive care. “And we know that in the current resource environment we can’t do tens of thousands of species, so we are going to have to prioritize.” 

To complicate matters, a new study in Nature Ecology & Evolution finds botanic gardens around the world are running out of space for imperiled plants. Sam Brockington, a professor of plant sciences at Cambridge University and curator of the university’s botanic garden, who led the research, points out that endangered species must compete for room with famous ornamental but non-threatened plants that attract and inspire the visitors who help fund botanic garden programs. But he also notes that only about 5 to 10 percent of botanic garden capacity is devoted to plant conservation.

“Of course we need beautiful places where people can find respite,” says Coffey. But she believes that it is possible to do conservation, too. “We’ve got the space. We just need to figure out how to reallocate it. We don’t need another tulip bed.” She points out that botanic gardens work with partners, including parks, the U.S. Forest Service, and even golf courses, which can contribute living space for endangered plants. “I don’t think we panic,” Coffey says. “We just have to, as botanic gardens and as scientists, stop putting ourselves in boxes and open our minds to think creatively.”

The Wollemi pine is now safeguarded in the globally dispersed metacollection, and not a moment too soon. Two aggressive, non-native soil-borne pathogens have been detected in its rainforest habitat, thought to have been introduced by illegal visitors via contaminated clothing or equipment. According to scientists, this has caused extensive dieback in some of the adult trees. 

The frequency and severity of wildfires continue to threaten the remaining trees, along with heat waves and drought, which are also predicted to become more frequent and severe as the climate changes. Yet to recover from the Black Summer conflagration, researchers say, the wild Wollemi pines will need to be protected from fires for the next 50 to 100 years.

When asked how many plant species will likely survive only in metacollections over the next century, Wes Knapp replied, “That’s the scary part. We don’t really want to think about the future trend line. But I would say that the number is going to be very large.” To slow the pace of mass extinction, he says, “We need to act. We need urgent, coordinated action.”