Bencomia sphaerocarpa is a critically endangered species in the rose family. According to the IUCN Red List of Threatened Species, only 24 known individuals remain in the wild as of 2011.
The island of El Hierro, in the Canary Islands, Spain, is home to the last wild Bencomia sphaerocarpa individuals. There are three subpopulations on the northern part of the island: six individuals grow near Tinco, fifteen near Tábano, and three near Hoya de Fileba. All together, the distribution of Bencomia sphaerocarpa (PDF) covers an estimated 0.75 to 3 square kilometres. There are also historical reports of individuals growing on the nearby island of La Palma.
In Spain, Bencomia sphaerocarpa is commonly known as bencomia herreña or rosalito de riso, the latter of which translates roughly to “cliff rosebush”. Bencomia sphaerocarpa shrubs are found at altitudes of 400 to 1200 metres (~1300-4000 ft.) above sea level on El Hierro. From the IUCN report, the habitat of the species:
It grows preferably in very humid valley floors and basaltic shady crags, on deep well developed substrates, within the potential distribution of evergreen laurel-leaved tree forest (monteverde), always under the influence of low clouds.
El Hierro also has high humidity, mild temperatures throughout the year, an annual rainfall of 700mm (27 in.), and trade winds.
Bencomia sphaerocarpa is a woody evergreen plant that has both dioecious and monoecious forms (i.e., individual plants may male, female, or both). The 10-25cm (up to 10 inch) long amentiform or catkin-shaped inflorescences bloom from March to May. The mainly unisexual flowers lack petals, are surrounded by linear bracts, and are largely wind-pollinated. The leaves are compound, with 13-15 opposite leaflets. Each lanceolate-elliptic leaflet is smooth and glossy on the upper surface, but covered in fine hairs on the lower surface. The tightly-packed, fleshy, globular fruits contain seeds that are either dispersed by birds or drop to the ground near the parent plant. Bencomia sphaerocarpa has a branching form and is 2-4 m (~6-13 ft.)in height when mature.
The rarity of Bencomia sphaerocarpa corresponds to a number of factors. Domestic sheep and goats eat the seedlings and graze on mature plants. Natural reproduction within the species is low, partly because Bencomia sphaerocarpa individuals take three years to reach reproductive maturity. Bencomia sphaerocarpa subpopulations are also endangered by landslides, fires, drought, road maintenance, and storms.
Measures taken to protect Bencomia sphaerocarpa include a) fencing to protect the plants from predation by livestock; b) seed collection and storage; and c) propagation in nurseries. A comprehensive recovery plan (PDF) was published by the Consejero de Medio Ambiente y Ordenación Territorial in 2009 with the aim of seeing the Bencomia sphaerocarpa population increase to at least 1000 individuals, including 500 mature plants.