The St Helena Olive (Nesiota elliptica) symbolizes extinction and the fragility of unique island ecosystems. This rare plant was found only on the remote South Atlantic island of St Helena. Its journey from native flora to extinction highlights the profound impact of human activity on isolated environments. The species’ story serves as a reminder of nature’s delicate balance and the irreversible consequences of biodiversity loss.
Unique Characteristics
The St Helena Olive was a small, low-spreading tree, typically reaching 5 meters tall with a trunk diameter of 0.4 meters. Its bark was dark brown to black. The leaves were thick, rounded, and oblong, measuring 50-70 millimeters, with a dark green upper surface and a hairy, paler underside.
It produced small, pink flowers, about 10 millimeters in diameter, arranged in clusters, primarily from June to July but often throughout the year. Pollination, often by the endemic hoverfly Sphaerophoria beattiei, led to hard, woody seed capsules. These capsules matured slowly, taking about a year, and contained three shiny, black seeds. Despite its common name, the St Helena Olive was not a true olive, belonging instead to the Rhamnaceae family. It was the sole member of its genus, Nesiota, making its extinction a double loss for botanical diversity.
History and Decline
Historically, the St Helena Olive thrived in the cloud forests of St Helena’s upland regions, at elevations above 750 meters, particularly around areas like Diana’s Peak. Records from the 1850s indicate that between 12 and 15 trees were present, suggesting it was already rare by the 19th century. Its decline began rapidly after the island’s discovery by Portuguese explorers in the early 16th century and the establishment of permanent settlements by the East India Company in the mid-17th century.
Human activities significantly contributed to its demise through deforestation. Forests were cleared for timber, agricultural expansion, and plantations, including coffee and New Zealand flax. Non-native species further exacerbated the problem; introduced goats devastated young tree shoots, preventing regeneration, while invasive plants, insects, and microbial pests disrupted the native ecosystem. The tree’s inherent biological vulnerability also played a role; it was highly self-incompatible, meaning self-pollination or pollination with closely related trees rarely produced viable seeds, making natural reproduction challenging even under undisturbed conditions.
Conservation Journey
Despite being presumed extinct for a period, a remarkable rediscovery occurred in 1977 when naturalist George Benjamin located a single surviving plant in the wild. This finding spurred intensive conservation efforts. Cuttings were taken from this last wild specimen, but initial propagation attempts yielded limited success, with only two cuttings surviving.
The last wild St Helena Olive tree perished in October 1994. Self-incompatibility made seed production and germination difficult. Despite hundreds of attempts to cultivate new plants from seeds and cuttings, only a handful of seedlings were successfully raised. The final known cultivated specimen, a seedling from a cutting of the original wild tree, succumbed to fungal infections and termite infestation in December 2003, marking the species’ official extinction. Although no living St Helena Olive trees exist today, genetic material, including DNA samples, is preserved in institutions like the Kew Gardens DNA bank.
Ecological Role and Significance
The St Helena Olive was an integral component of St Helena’s tree fern thicket and cabbage tree woodland, thriving in high-altitude cloud forests. Its flowers provided a food source for the endemic hoverfly, Sphaerophoria beattiei, its primary pollinator. Its extinction disrupts intricate ecological relationships, demonstrating the interconnectedness of island biodiversity.
Beyond its ecological function, the St Helena Olive holds symbolic significance as a flagship species for conservation. Its disappearance underscores the fragility of island ecosystems, which often harbor unique species vulnerable to external disturbances. The St Helena Olive’s story provides valuable lessons on the impact of habitat destruction and invasive species. Efforts to preserve its genetic material serve as a testament to ongoing global initiatives aimed at preventing further extinctions and understanding biodiversity loss.