- Botanists surveying a remote forest reserve on Pemba Island in Tanzania’s Zanzibar archipelago have discovered a forest of rare trees — the only place in Africa where they’re known to occur in the wild.
- The botanical survey, the first of its kind in 35 years, has shed light on Ngezi Forest Reserve’s rich plant biodiversity.
- But the section of intact coastal forest where the Intsia bijuga trees grow is earmarked for a new “eco-resort.”
- The forest’s status as a reserve has not been withdrawn, meaning any developments within its boundaries could be illegal.
MICHEWENI, Tanzania — Botanists have found a stand of rare trees in Tanzania’s Zanzibar archipelago not known to grow wild anywhere else in Africa. The intsia trees (Intsia bijuga) were found growing within moist coastal forest in the north of Ngezi Forest Reserve on the island of Pemba. Worryingly, the area is earmarked for the first phase of a new “eco-resort.”
Earthmoving equipment and tipper trucks are already stationed near the forest, Mongabay witnessed.
“It is the only place in Africa where Intsia dominates a forest formation,” says Andrea Bianchi, a consultant tropical botanist. He, fellow botanist Simone Orsenigo and plant taxonomist Giacomo Baldesi from the University of Pavia, Italy, conducted plant surveys throughout Ngezi in early December.
The trio found 80 plants never before recorded in Pemba. “This coastal forest is really interesting, it’s super-rich [in plant species],” Bianchi says.
Some of the plants are potentially new to science, including a tiny white ground orchid found by Orsenigo that stands a few centimeters above the forest floor. The orchids are thought to be a species of Disporis, a genus also known from the Eastern Arc Mountains on the Tanzanian mainland.
“It may be a montane species that evolved into something unique,” Bianchi says. “It’s very much restricted to this little patch of forest.”
The botanical survey was done as part of the conservation and sustainable development work that the Oikos Institute, a Milan-based nonprofit, began in Ngezi and surrounding communities in September 2024 with funding from the EU and a private foundation.
Pemba’s 89,000 hectares (220,000 acres) were originally covered by moist evergreen and coastal forests, mangroves, swamps and heathlands. From 1840, most of these were cleared to make way for crops and pastures, and to grow mango, banana and coconut trees.
The relatively intact Ngezi reserve protects less than 5% of the island’s former landscapes — a vital “storehouse” of species, scientists say.
“It’s a plant paradise,” says Oikos project adviser and veteran Tanzania-based conservationist Silvia Ceppi. “You still find 100 year-old trees in the forest. Somehow they made it.”
These tree centenarians include the intsias, whose flat, buoyant seeds are adapted to float and disperse in ocean currents. That’s how they ended up here from Southeast Asia and Madagascar, where the species is also found. The trees, near-threatened with extinction globally due to overharvesting of their valuable timber that polishes to a deep shade of maroon, develop broad buttress roots and reach heights of up to 40 meters (130 feet). Their vivid white-and-pink flowers were what caught the eyes of the team of botanists on their first night in Ngezi.
It’s uncertain what impact the construction of a new hotel will have on the intsia forest, which is also a stronghold of the Pemba scops owl (Otus pembaensis), a vulnerable species unique to the island whose calls drift across the forest at night.
A public noticeboard outside where the earth-moving equipment is currently corralled behind galvanized iron sheets says the initial construction project is for a fence for the “Mantuli Eco-Resort.” Reports in local media in early 2024 suggested Mantuli will be East Africa’s first seven-star hotel, built at a cost of $8 million.
The map of the project site on top of the noticeboard appears to cover the entire 300 hectares (740 acres) of coastal forest where Bianchi and his colleagues found the intsias and ground orchids growing.
If it goes ahead, the new development will likely boost tourism in Pemba, which currently only gets around 25,000 visitors per year compared to the 700,000 or so who visit Zanzibar’s main island, Unguja, a 30-minute flight to the south.
But Ceppi says she worries about the impact the new development will have on one of the least-disturbed parts of the forest reserve. The targeted section doesn’t appear to have been stripped of its forest reserve status, making any privately owned tourism development within its boundaries illegal.
“That patch of coastal forest hosts exceptional and world-important biodiversity, including possibly species of plants unknown to science, and it must be kept intact and protected,” she says. “Any plan for tourism development must account for the needs of this unique ecosystem and contribute to protect it rather than entirely remove it.”
It’s not the first time a planned resort has set off conservation alarm bells in Pemba.
Thirty-five years ago, a much smaller area measuring just 900 by 300 m (about 3,000 by 1,000 ft) of coastal thicket was cleared to make way for a fishing resort on the Tondooni Peninsula that sits in the southwest section of Ngezi.
Trees and shrubs here range from massive baobabs (Adansonia digitata), to screw palms known locally as mkadi (Pandanus kirkii), whose stiff, sword-shaped leaves are edged with teeth as sharp as hacksaw blades. They’ve all found their niche on the coral rag, a thin layer of alkaline soil sitting on top of fossilized coral.
The sport-fishing resort was never built, but despite recommendations made in 1989 for the peninsula to become one of two core areas for conservation, this was never done. Today, it’s crisscrossed with paths that give access to wood poachers and motorbikes ferrying passengers to and from the sea. According to the last plant survey done in 1989, the forest canopy cover on one spot along the peninsula was 80%; Bianchi and his colleagues note that it now has less than 30%.
The botanists lament the scarcity of plants in a place that was once as diverse as Ngezi’s moist evergreen forest. An area on the digital map that appears to show a small hill on the peninsula rising to a height of 60 m (200 ft) turns out to be nonexistent, and the team speculates that the “raised ground” detected via old airplane images was in fact once the towering crowns of mvule trees (Milicia excelsa) that have since been felled.
“It’s completely changed,” Bianchi says. “I don’t see a good future for the Tondooni Peninsula.”
Clearly, the forest needs more people to protect it, and Oikos has recruited four new forest guards to complement the four currently employed by the government.
One evening near a roosting site where dozens of one of the island’s most iconic animals — Pemba flying foxes (Pteropus voeltzkowi) — squeak and chirp and stretch their chestnut bodies and broad black wings, Ngezi acting chief-in-charge Khamis Ali Khamis spots a couple of men herding cattle along the road that skirts the edge of the forest.
He immediately suspects they’re carrying axes and a large saw hidden inside a sack.
Khamis summons the help of one of the newly recruited forest guards, 20-year old Abubakar Faki Shoka. Before they can apprehend the men, however, the suspects stash their tools in the undergrowth and slip away. But Khamis finds the sack and confiscates it.
“I’m happy because we have been successful,” he says as he lays out two saws, an axe and a machete on the roadside. Overhead, the flying foxes wing their way through the gathering darkness.
In Pemba, where the average wage is around $72 per month, conservationists and locals point out that a large mvule tree (Milicia excelsa), also known as African teak, is worth around $800 once it’s felled, sawn into planks and carried by boat across the sea to buyers on the mainland.
Shoka, who’s well aware of how much the trees he’s employed to protect are worth, tells Mongabay their value wouldn’t tempt him.
“I will never cut a tree,” he says. “We live on an island. If we cut down trees, a tsunami could come and overwhelm us.”
Ceppi, who has worked to protect wildlife on the mainland, says that like elephant poaching syndicates, it’s likely only a handful of individuals poaching precious timber from Ngezi for commercial gain.
But 35,000 people in Micheweni district live in 10 villages that border the forest reserve. They depend on it for subsistence — from food to cattle forage and medicine. Even removing dead wood for firewood can be harmful to the forest’s ecology. Frogs and skinks, for instance, live beneath fallen logs and leaves.
To ease pressure on the forest, Oikos is providing equipment to promote the value chain for local seaweed farmers, who are mostly women; training youths in nature guiding; and helping to promote skills among the hundreds of farmers living along the forest’s border to improve agricultural productivity through basic interventions like composting.
Ngezi now stands at a crossroads, Ceppi says.
“Under good management, there’s a good chance the forest can totally restore its functions. But if that doesn’t happen, if the trend keeps at the level that it is now, in five years we will have lost [the battle to protect Ngezi],” she says.
“There are still areas that are very well preserved,” she adds. “We’re going to promote it, at least put it on the map as an exceptionally biodiverse spot — that’s our job.”
Banner image: Andrea Bianchi examines a species of Anthocleista in Ngezi Forest Reserve on Pemba Island. Unlike the species that grows in Tanzania’s Eastern Arc Mountains, the ones he and colleagues found in Ngezi are armed with spines, more akin to a species that grows in West Africa. Image by Ryan Truscott for Mongabay.
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