False gumwood  (Commidendrum spurium)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

With only eight individuals left in the wild, the false gumwood is one of the rarest trees in the world (1). This flowering tree is densely branched (2), with light green, diamond-shaped leaves with rough toothed edges, which cluster around the tips of the branches (3). It produces clusters of white, daisy-like flowers that (2), unlike those of the closely related and also highly threatened, St. Helena gumwood (Commidendrum robustum) (1), point towards the sky rather than drooping downwards (3).

The false gumwood (and indeed, all Commidendrum species) occurs only on the island of St. Helena in the South Pacific (1). As of 2004, the false gumwood was restricted to just two locations on the island, with seven individuals occurring near Mount Vesey and one individual situated at Coles Rock (2).

The false gumwood was previously a major species of the moist gumwood woodland and cabbage tree woodland of the island, found at altitudes from 500 to 750 metres (2) (4). However, due to habitat destruction, the few remaining false gumwoods reside on cliff edges (1).

The false gumwood requires a habitat with high moisture levels compared to other members of its genus (4). It reacts badly to dry conditions and this is one of the reasons it is so rare compared to its close relative, the St. Helena gumwood, which persists in a number of other habitats (4).

Information on the biology of the false gumwood is scant. The pretty, delicate flowers of this species emerge from November through to March (1).

With just eight plants remaining, the false gumwood is in an extremely perilous position. Its demise began with the discovery of St Helena Island in 1502; ever since, the false gumwood has been used as timber for fires (2), and huge areas of its habitat have been cleared for pastures and the grazing of goats (2). Forests once inhabited by the false gumwood have been all but destroyed, and native flora now covers less than one percent of the island’s area (5).

As well as the introduction of the goat, other invasive species have caused significant population declines in the false gumwood, including introduced flora, with which it competes, and, most significantly, the accidentally introduced jacaranda bug (Orthezia insignis). The bug can infest all members of the Commidendrum genus and, although never found naturally on false gumwood, is known to be responsible for nearly causing the extinction of the St. Helena gumwood (Commidendrum robustum) during the 1990s. The bug infests trees, sucking the sap from the leaves, allowing secondary infestation by black sooty moulds which rapidly kill the plant (5).

There has been a significant amount of conservation action aimed at preserving all endemic flora of St. Helena. The earliest action, during the 1970s, was the control of the goat population on the island (4), after it was recognised that goats were causing major damage to almost all of St. Helena’s wooded habitats (4). There are currently only a few wild goats left and all domestic goats must be kept penned by law (4). Then, during 1985, conservation areas were created and, under the Endangered Plants Propagation Programme,habitats where the false gumwood occurred were designated as endemic forest reserves (6).

In 1993, the South American coccinellid beetle, Hyperaspis pantherina, was introduced to the island as a predator to the jacaranda bug with great success (5). Surveys were stopped in 1995, as so few jacaranda bugs were found and there have been no new reports of large population findings since (5).

In March and February 1996, seeds were taken from the false gumwood near Mount Vesey and germinated at the Endemic Nursery (2), and the ongoing removal of invasive flora should hopefully allow the planting of seeds near existing false gumwood trees (2). During 2009, seeds were collected from false gumwood trees by members of Kew’s Millennium Seed Bank project, to prevent extinction of the species should it be lost from the wild (7).

For further information on Kew’s Millenium Seed Bank project see:

• Kew:
  http://www.kew.org/science-conservation/conservation-climate-change/millennium-seed-bank/index.htm

 To learn more about conservation work on the island of St. Helena see:

• St. Helena National Trust:
  http://www.nationaltrust.org.sh

 To find out about efforts to conserve the world’s most threatened trees see:

• Global Trees Campaign:
  http://www.globaltrees.org