Lava cactus  (Brachycereus nesioticus)

Classified as Vulnerable (VU) on the IUCN Red List 2007 (1) and listed on Appendix II of CITES (3).

The smallest of the cacti species that inhabit the Galápagos (2), the lava cactus consists of a number of short, cylindrical stems that grow in dense clusters, covering up to two metres (4). Suitably, the scientific name of this cactus, Brachycereus, arises from the Greek word for short and the Latin word for candle, referring to its unmistakable appearance (5). Each stem is covered with numerous sharp spines, which are yellow on the young parts of the plant, turning dark grey or black with age (6). Due to the colour of the spines, the age of the stems are easily identified, with the new parts of the plant appearing paler and more yellow than the older parts (6). The flowers of the lava cactus are creamy white and measure up to 5.5 centimetres across (2) (5), while the fruits are small, fleshy, red to reddish-brown berries covered with yellow spines, each containing numerous blackish-brown seeds (5).

Found only in the volcanic archipelago of the Galápagos, on the islands of Bartolomé, Fernandina, Genovesa, Isabela, Pinta and San Salvador (4).

As its name suggest, the lava cactus occurs exclusively on barren lava fields (2), lying at sea level (4). Not only is it one of the few plants that survive in this extremely dry, challenging habitat (4), it is often one of the first plants to colonise a fresh lava flow (2).

Despite the scientific interest that the Galápagos Islands have received ever since Darwin visited in 1835, and the numerous observations of the lava cactus, the biology of this plant remains poorly known (4).

Like all cacti, this succulent plant is capable of storing moisture in its stems when water is available, enabling it to survive periods of drought (6), and the spines, which are actually the leaves of the cactus, provide defense against any plant-eating animals (2). The lava cactus flowers very briefly (2), with its cream-coloured blooms opening just before dawn, and usually shrivelling by seven or eight o’clock in the morning (6).

While the Galápagos are a protected area, and are considered one of the most unspoiled areas remaining on the planet (7), the fauna and flora of these islands still face major threats, such as introduced species, pressure from increasing tourist numbers, and a decline in the maintenance of protective laws (7). However, the lava cactus is not currently known to be facing any specific threats, and is considered to be Vulnerable based primarily on its restricted distribution (1).

The unique biodiversity of the Galápagos has been recognized and these islands are well protected as a result, being classified as a National Park and a Natural World Heritage Site (7). More specifically for the lava cactus, the government of Ecuador prohibits the collection of any plant in the Galápagos (4).

For further information on conservation in the Galápagos see:

• Galapagos Conservation Trust:
  www.gct.org