For some plant species, fewer than ten mature wild plants remain in nature—sometimes even just a single individual. Such species show how far a decline can go: habitats shrink, populations break apart, and in the end only isolated plants remain, their survival often depending on chance.
15 plant species with fewer than ten individuals
This evergreen shrub in the coffee family occurs only on Rodrigues. Its name means “brown coffee” and refers to its former use as a medicinal plant, for example against liver complaints and hangovers. Because of invasive species and the extensive transformation of the island’s original vegetation, the species was already considered extinct until one last wild remnant specimen was rediscovered in 1980. Descendants were raised at the Royal Botanic Gardens, Kew, near London, and some plants were returned to Rodrigues; however, the known natural wild population still traces back to this one remaining plant.
Image: Tamanou at English Wikipedia, CC BY 2.5, via Wikimedia Commons
This hibiscus species is endemic to Rodrigues and now occurs there at only a very few sites in the island’s more mountainous areas. In 2019, only two individuals were known in the wild from the Cascade Mourouk/Batatran area. It grows on steep, rocky slopes over basalt. The mandrinette is threatened by soil erosion, hybridization with the ornamental hibiscus Hibiscus rosa-sinensis, old weakened remnant trees, termite attack, and probably also climate-related changes that may affect flowering time and pollination. Although hundreds of clones have been planted in protected areas and plantings, mortality remains high.
Image: Hibiscus liliiflorus Cav. Observed in Mauritius by Pierre-Louis Stenger, CC BY-NC 4.0, via GBIF
This small tree or shrub species is restricted to Glen Catacol on Scotland’s Isle of Arran. It probably arose through hybridization between rowan and endemic whitebeam relatives on the island. For a long time, only a single mature wild tree was known; an earlier documented seedling and another specimen were not found again. In 2020, a second tree was confirmed. The Catacol Whitebeam is therefore among Europe’s rarest trees. Its range covers less than one square kilometer, with a few additional plants in ex situ collections. In the wild, the species remains highly threatened by browsing, flooding, rockfall, and its tiny population.
Image: Sam Thomas, CC BY-SA 2.0, via Wikimedia Commons
This species, found only on St. Helena, was already considered extinct until a supposedly last tree was discovered in 1982. It was destroyed by a storm in 1986, but seedlings had previously been raised from its seeds. When the last surviving descendant was also severely damaged in 2008, the species’ survival again became uncertain. Only in 2009 did gardener Lourens Malan discover another wild specimen on an inaccessible cliff. The decline is attributed mainly to introduced goats, which have destroyed large parts of the island’s original vegetation since the early 16th century. Today, only one wild specimen is known; a small cultivated population is intended to preserve the species.
Image: Commidendrum rotundifolium (Roxb.) DC. Observed in Saint Helena, Ascension and Tristan da Cunha by Annalena Becker, CC BY-NC 4.0, via GBIF
This evening primrose species, first scientifically described in 2019, is endemic to Isla Clarión in Mexico’s Revillagigedo Archipelago. It was the first record of the evening primrose family from the entire island group. It was discovered in 2018; its natural habitat appears to be limited to a single rocky outcrop above the coastal cliffs. This site covers less than 50 m² and has special soil and rock properties not found elsewhere on the island. Fewer than ten mature individuals were recorded there. Coastal erosion and unstable cliffs have probably already destroyed large parts of its habitat; without rapid ex situ conservation measures, the species is at risk of becoming extinct in the wild.
Image: Oenothera resicum Benavides, Kuethe, Ortiz-Alcar Áz & León de la Luz Observed in Mexico by Norma Castillo, CC BY-NC-ND 4.0, via GBIF
This tree species, up to 15 meters tall, is endemic to Putuo Island in China’s Zhoushan Archipelago. In the wild, only a single mature specimen exists, fenced off at the edge of a small mixed forest on Mount Foding. The tree was discovered in the early 1930s; no other wild individuals have been found. Although the species can theoretically reproduce by itself, natural regeneration is almost absent: strong winds during flowering and seed formation, as well as typhoons when seeds ripen, lead to very low seed production, and seedlings are rarely found. The Putuo hornbeam is therefore threatened not only by habitat loss, but also by its extremely low genetic diversity.
Image: Siyuwj, CC BY-SA 4.0, via Wikimedia Commons
This tree, up to 13 meters tall and in the rue family, was historically reported from Kauai and Maui (Hawaii). As late as the 1970s, about a dozen trees were known; in the 2020 IUCN assessment, only a single mature wild individual was documented on Kauai. In addition to this natural remnant population, cultivated and outplanted specimens exist as part of conservation projects; however, they do not yet replace a stable, self-sustaining wild population. The last known wild tree grows in a moderately wet montane forest at an elevation of 891 meters. The species is threatened by habitat loss, invasive plants and introduced animals such as deer and pigs, droughts, landslides, hurricanes, and climate change.
Image: Forest & Kim Starr, CC BY 3.0, via Wikimedia Commons
This small tree in the mallow family occurs only on Kauai, Hawaii. It was discovered only in 1991 on the steep cliffs of Kalalau Valley; at that time, only four individuals were known. Three were later destroyed by falling rock, and the last known specimen was found dead in 2011. The species was then considered extinct until three plants were discovered on a cliff face in 2019. The current population remains extremely threatened: invasive plants, pigs, goats, and rats alter the habitat, rockfalls can destroy individual plants, and flower damage by introduced Japanese white-eyes probably hampers reproduction. Attempts to propagate the species have so far been unsuccessful.
Image: Hibiscadelphus woodii Lorence & W.L.Wagner Observed in United States of America by Kenneth R. Wood (NTBG), CC BY-NC 4.0, via GBIF
This flowering plant in the bellflower family is endemic to Maui; it was scientifically described only in 2020. Botanist Hank Oppenheimer discovered it in 2010 in the highlands of the West Maui Mountains, initially from a distance with binoculars. Only one wild individual was known on the slopes of Helu, after which the species was named. The plant grows as a shrub and produces white flowers and orange berries, which are probably dispersed by birds. Its habitat is affected by invasive plants and introduced animals such as pigs, goats, rats, and snails; landslides, fire, and drought add further pressure. Clones from the single wild individual have already been raised in cultivation and planted in the discovery area.
Image: H. Oppenheimer, from: Oppenheimer (2020), PhytoKeys, CC0 1.0.
This species in the protea family occurs only in the Palmiet River Mountains in South Africa’s Western Cape. It is closely adapted to fynbos: adult plants die in fires, but their seeds can persist in the soil for a long time and apparently germinate only after especially hot summer fires. As a result, the species can seem to have disappeared for decades. Between 1967 and 2001, M. stokoei was considered lost until young plants reappeared after a severe fire. According to the SANBI Red List, seven mature individuals of the species were still known in 2020. The plant remains threatened by its tiny population size, unfavorable fire regimes, and Phytophthora pathogens, which can damage plant roots.
Image: Tony Rebelo, CC BY-SA 4.0, via Wikimedia Commons
This flowering shrub in the protea family belongs to the fynbos vegetation of South Africa and is endemic to the Cape Flats area of Cape Town. Historically, the species was known only from an area of about 6×8 km between Brackenfell, Bottelary, and Kraaifontein. Urban and industrial development destroyed 86% of its habitat; the remaining areas are heavily degraded. Today, only a single mature individual remains from the original wild population. Reintroductions are underway, but they are not yet considered established wild populations. Because the species is very long-lived, resprouts from underground structures after fire, and apparently rarely regenerates successfully from seed, its future remains uncertain.
Image: Andrew massyn, CC BY-SA 3.0, via Wikimedia Commons
This palm in the family Arecaceae is endemic to east-central Madagascar and is known from only one site near Andasibe, just outside the boundary of the Analamazaotra Reserve. Fewer than ten mature trees grow there. Earlier estimates still assumed about 25 individuals, suggesting a decline. Although access to the site is restricted, the species remains threatened: the possible removal of seeds for the international horticultural trade could be especially problematic, because it weakens natural regeneration and, in extreme cases, may even involve cutting down trees.
Image: Ravenea louvelii Beentje Observed in Madagascar by Louis Aureglia, CC BY 4.0, via GBIF
This small tree is endemic to Manawatāwhi / Great Island in New Zealand’s Three Kings Islands. Since its discovery in 1945, only a single specimen has been known in the wild: a female tree on an inaccessible scree slope that was formerly protected from goat browsing. For a long time, the species was therefore considered functionally extinct. Later, it emerged that the tree can occasionally produce viable pollen and seeds. In addition, the kaikōmako has been propagated from cuttings and hand-pollinated cultivated plants; propagated plants have now also been planted out. But as long as only one original wild tree exists, P. baylisiana remains acutely threatened with extinction by storms, drought, aging, and chance events.
Image: Beeveria, CC BY-SA 4.0, via Wikimedia Commons
This magnolia species is endemic to Colombia and is known only from Santa Rosa in the department of Risaralda. There it grows in a tiny remnant of montane forest about two hectares in size, completely surrounded by coffee plantations. In a 2006 survey, only three mature trees were recorded; although they produced flowers and fruits, little or no natural regeneration was observed. Because of severe habitat fragmentation, ongoing pressure from coffee cultivation, and the extremely small population, M. wolfii is considered threatened with extinction. Whether the last known trees still exist today is unclear; the species may already have disappeared from the wild.
Image: Magnolia wolfii (Lozano) Govaerts Observed in Colombia by Miguel Ángel Gómez-Riaño, CC BY-NC 4.0, via GBIF
This flowering plant occurs only on Mauritius and grows in humid tropical forest. It owes its name “Bois dentelle”—French for “lace wood”—to its delicately fringed white flowers. In the 1990s, only two known wild trees were known at Piton Grand Bassin; later, a few additional individual plants were found. According to IUCN data, probably fewer than ten small trees now grow near an Indian temple in the Grand Bassin area. The species is threatened by the loss and alteration of its habitat: invasive plants overgrow the site and displace native vegetation. Although protection and propagation measures are underway, the wild population remains extremely small.
Image: Elaeocarpus bojeri R.E.Vaughan Observed in Mauritius by jeanjacquesgodon, CC BY-NC 4.0, via GBIF
These examples are only a small selection, because the true scale of plant extinction is difficult to grasp. The IUCN has so far assessed only part of the plant species that exist worldwide. Even so, more than 150 plant taxa are already considered extinct, 47 extinct in the wild, and almost 650 others possibly extinct because they have not been recorded for a long time. Many losses probably go unnoticed, especially among inconspicuous species, inaccessible sites, or regions that have barely been studied botanically.
Why the survival of individual plants is not enough
Many plant species known from only a few mature wild individuals now also have additional cuttings, clones, seeds in seed banks, or young plants in botanical gardens. But that does not automatically mean that a species is secure in the long term.
The decisive factor is not simply the number of plants that exist. Whether a species can survive depends above all on whether it can reproduce successfully, has enough genetic diversity, and still has suitable habitats available.
Reproduction as a prerequisite for survival
Image: Purves, M., CC BY-SA 3.0, via Wikimedia Commons
Only if a plant can reproduce is it able to build a stable population over the long term. Many conditions must be met for that to happen: reproductive individuals, successful pollination, viable seeds, and suitable conditions for germination and new growth.
In some species, these conditions are barely met anymore. There are plants in which some individuals produce only male flowers and others only female flowers. Female plants can produce fruit and seeds only if a male plant is nearby and pollination succeeds. The South African Wood’s cycad (Encephalartos woodii) is a well-known example: all specimens alive today trace back to a single male wild plant; no female has ever been found. Natural reproduction is therefore impossible.
Even when several plants remain, reproduction can fail. Some species depend on specific insects, birds, or bats as pollinators. If these animals disappear, flowers remain unpollinated and no seeds are produced. Other plants need animals to disperse their seeds. Without these seed dispersers, offspring no longer reach suitable sites. In addition, many species produce only a few viable seeds, or young plants rarely survive in the wild. A species can therefore stand on the brink of extinction despite the presence of living individuals if successful reproduction no longer occurs.
Why genetic diversity is crucial
Genetic diversity matters too. If all surviving plants are clones of the same individual or descend from only a few closely related plants, they have almost the same genetic makeup. That can help keep a species alive in the short term, but in the long term it creates problems: diseases, pests, or environmental changes then affect practically all individuals in the same way. As in animals, inbreeding can also occur when closely related plants reproduce with one another. This often reduces germination, vigor, and resilience in the offspring. For the long-term conservation of a species, it is therefore not enough to have as many plants as possible—enough genetic diversity must also be preserved so that the population can adapt to changing environmental conditions.
The role of botanical gardens and reintroductions
Image: Forest & Kim Starr, CC BY 3.0 US, via Wikimedia Commons
Botanical gardens, seed banks, and research institutions play a central role. They can grow cuttings, secure seeds, hand-pollinate plants, or prepare propagated plants. But maintaining a species in cultivation is not the same as maintaining a stable wild population. In the long term, a plant species can survive only if its natural habitat is also preserved or restored. Successful reintroduction requires suitable site conditions such as the right soil, enough space, a suitable microclimate, functioning ecological interactions, and protection from invasive species. Pollinators, genetically diverse plants, and long-term management of the populations are just as important. Many plantings fail because young plants dry out, are eaten, cannot cope with competing species, or do not produce offspring of their own.
It is no coincidence that so many of these extremely rare plants come from islands. In Hawaii, St. Helena, Rodrigues, Mauritius, Madagascar, and also in South Africa’s Cape region, many species evolved in small, isolated habitats. Their close adaptation to particular sites makes them unique, but also especially vulnerable. When these habitats are lost or heavily altered, plants often lose the conditions they need to survive. If forests are cleared, invasive plants are introduced, goats, pigs, rats, or snails are brought in, or the climate changes, entire species can shrink to a few remnant plants within a few decades—or disappear altogether.
For the conservation of rare plant species, early protective measures, habitat protection, control of invasive species, and the preservation of genetic diversity are essential. The smaller a population becomes, the more difficult and costly it is to rescue. Species extinction is not a sudden event, but a gradual process; timely action determines whether a species dies out or has a future.
Sources
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About the author: Doreen Fräßdorf
Doreen Fräßdorf is the author and publisher of artensterben.de. She researches and writes about extinct and endangered species in the modern era, with a focus on red lists, scientific studies, historical sources, and current conservation efforts. The goal is a clear, evidence-based overview of biodiversity loss and species protection.
She is also the author of a non-fiction book about extinct modern-era mammals.
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