- A group of botanists has discovered a new species of rainforest tree in Tanzania’s Udzungwa Mountains.
- A total of around 100 mature trees were found growing in two village land forest reserves surrounded by abandoned croplands, and initial assessments suggest some of them could be up to 3,000 years old.
- The team behind the discovery says the trees are vulnerable to extinction because of their low numbers and tiny distribution.
- But the area in which they were found is the site of a forest restoration project, giving hope for their long-term survival.
Botanist Andrea Bianchi and local plant experts Aloyce Mwakisoma and his brother Ruben were exploring two tiny village forest reserves in the Udzungwa mountains in 2019, when they stumbled upon some imposing trees. Bianchi turned to the Mwakisoma brothers for advice, but even they had never seen this kind of tree before.
“This was already quite a shiver-down-your-back moment because if they didn’t know [the species], it could have been something interesting,” the botanist recalls.
The trees have now been identified as a new species, and named Tessmannia princeps. Some of them could be up to 3,000 years old. In total, Bianchi and his companions found around 100 mature T. princeps trees in the Boma la Mzinga and Uluti Village Land Forest Reserves. They say this small population and tiny distribution makes them vulnerable to extinction.
The trees’ specific name – princeps – comes from the Latin word for “most eminent”, a reference to their crowns that protrude through the forest canopy as they grow up to 40 meters above the ground supported by large buttress roots. Other similar trees from the Tessmannia genus are more commonly associated with the rainforests of West Africa.
The team found an individual tree that had fallen from natural causes and took samples to test the wood density. In a single centimeter of wood extracted from its core, Bianchi counted 12-15 rings. Trees normally deposit rings at a rate of one per year, suggesting the trees take up to 15 years to add a single centimeter to their girth.
“This would put the age of the bigger trees around 2,000-3,000 years,” says Bianchi, though he cautions that since these are rainforest trees that receive rainfall over Tanzania’s two main wet seasons, aging the trees from the number of rings they possess is not always a reliable guide.
The team plans to take a core sample from one of the living trees to obtain a more accurate idea of their age through radiocarbon dating.
The Udzungwa Mountains, the biggest massif within the Eastern Arc Mountain chain, host numerous species – including amphibians and plants – that are unique to specific areas, such as a single valley or forest patch. It’s possible the Tessmannia trees are scarce because they have specific needs found nowhere outside Udzungwa’s Mngeta Valley.
Fortunately, the two village land forest reserves are located within the Udzungwa Corridor, a 75 square-kilometer area of former farmland that the Udzungwa Corridor Limited, a private company, is working to restore and protect in collaboration with local landowners. The project will link the Uzungwa Scarp Nature Forest Reserve with the Kilombero Forest Nature Reserve and the Udzungwa Mountains National Park to the north-east.
Arafat Mtui, a conservationist based at the Udzungwa Ecological Monitoring Center (UEMC) in the national park, told Mongabay discoveries like the new Tessmannia species provide powerful incentives for conservation.
He cited the example of the rare and endemic Magombera chameleon (Kinyongia magomberae), a new species described in 2009 from the Magombera forest in Udzungwa, that helped to strengthen the case for upgrading the forest into a formal reserve in 2019.
“When new species are identified, conservationists like me at UEMC, prioritize studying their ecology, distribution, population size and threats, ensuring appropriate conservation measures are taken,” said Mtui.
Citation:
Bianchi, A., Tomasi, L., Mwakisoma, A., Barbieri, M., & Luke, Q. (2025). Tessmannia princeps (Fabaceae), a new rainforest tree from the Udzungwa mountains, Tanzania. Phytotaxa, 694(2), 109-118. doi:10.11646/phytotaxa.694.2.1
Banner image: Bole of a very large individual of Tessmannia princeps, showing the numerous buttresses. Image by Andrea Bianchi.
‘Extinct’ trees found in Tanzania spark hope for ecosystem recovery
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