PerspectivePlant Science

Exploring Terra Incognita

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Science  24 Apr 2009:
Vol. 324, Issue 5926, pp. 472
DOI: 10.1126/science.1173323

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During visits in May 2006 and February 2007 to Ogaden (or the Somali National Regional State of Ethiopia, as it is formally called), the botanist Mats Thulin and his team encountered a tree previously unknown to science on limestone hills southeast of the town Kebri Dehar. The researchers soon found that it dominates the vegetation over large areas in southeastern Ogaden, covering an area of at least 8000 km2 (see the figure, panel A). For comparison, the Greek island of Crete has an area of 8379 km2. Hundreds of the trees were inspected on the ground, and tens or probably hundreds of thousands were seen with binoculars; the total number must be in the millions. The tree, a species of Senegalia (Leguminosae), is about 6 m tall, with a canopy 8 to 10 m in diameter. It flowers when leafless during the dry season (see the figure, panel C). Thulin has recently formally described it as Acacia fumosa (1). It differs from its relatives by having, among other things, a gray, smooth bark and pink flowers (see the figure, panels B and C).