African walnut  (Lovoa trichilioides)

Classified as Vulnerable (VU) on the IUCN Red List 2007 (1).

This tall African forest tree is an important source of timber. The straight trunk is covered with smooth dark bark that becomes rougher with age (3), and the first branches appear at a height of 15 to 20 metres (2). A cut into the trunk reveals red wood with white streaks and releases a sweet scent and sticky sap (2) (3). The leaves of the African walnut are slightly folded and comprise four to six smaller parts, or ‘leaflets’ (2) (3), and, depending on the time of year, the tree is also adorned with numerous, small greenish-white to white flowers that grow in large, loose clusters. Bunches of black woody, cigar-shaped fruit open to release four to eight winged-seeds (2).

Occurs in western Africa; from Sierra Leone, through Liberia, Côte d’Ivoire, Ghana, Nigeria, Cameroon, Gabon, Congo, Democratic Republic of Congo, Uganda and Tanzania, to Angola (4).

The African walnut grows in evergreen and deciduous forests, generally in moist areas (4), preferring deep, humid soils (2).

Almost all year round, clusters of small, greenish-white flowers hang from the African walnut tree, with each tree bearing both male and female flowers (5). The seeds of the African walnut, contained within the woody, pod-like fruit, are dispersed by the wind, carried by the long wing at the base (3) (6). The length of time for which the seeds can successfully develop once dispersed is short, and the seedlings will only develop when there is a gap in the forest canopy to allow sufficient light to the new plant. The chance of a seed successfully germinating is also hindered by the high probability of it being eaten by a forest-dwelling animal (4) (6). If conditions are favourable and the seedling develops into a mature tree, it is predicted to take an incredible 106 years to reach a trunk diameter of around 2.7 metres (6).

The African walnut is classified as Vulnerable to extinction due to population declines caused by clearance of forests for agriculture, and harvesting of this species for its timber (1). The African walnut is exploited at high levels (4), and has many uses including fuelwood, ship building and in furniture and piano making (5). It is one of the two principal timber species in Congo (4), an area that is home to an astonishing number of animal and plant species dependent on the continued existence of the magnificent Congo Basin rainforests. Unfortunately, large areas of these forests have been allocated to commercial logging operations and illegal logging is also rampant in certain regions (7).

Several actions may aid the conservation of the African walnut, including the promotion of this species in afforestation programs in Uganda (5), and its inclusion in a list of 18 species in Ghana for which the export of logs is banned. While this is primarily to encourage national wood processing industries, it is also seen as a conservation measure (8). The African walnut also occurs in protected areas throughout its range, such as Dja Faunal Reserve, Cameroon (9). Whether these measures are sufficient to ensure the future of the great African walnut and the many species which depend on the ancient forests of Africa is not yet clear.

For further information on which timber products to buy and which to avoid see:

• Greenpeace Good Wood Guide:
  www.greenpeace.org.uk/media/reports/good-wood-guide