The Eastern Arc Mountains are a band of solitary crystalline mountains that stretch in a crescent or arc shape from southern Kenya to Tanzania. The mountains were built around 100 million years ago when the earth’s crust faulted, and they are directly influenced by the Indian Ocean’s climate.

The Eastern Arc Mountains in Tanzania and Kenya are one of the world’s most significant locations for biological diversity protection. Tanzania’s Eastern Arc Mountains go over 15 districts.

North and South Pare, East and West Usambaras, Nguru, Ukaguru, Rubeho, Uluguru, Udzungwa, and Mahenge Mountains make up Tanzania’s Eastern Arc. Tanzania, as well as the rest of the world, values the mountains and forests that grow there. The forests provide a wide range of products and services to the Tanzanian people, as well as globally significant biological benefits.

Eastern Arc Mountain of Kenya & Tanzania

In Tanzania and Kenya, the Eastern Arc Mountains are a range of ancient mountains covered in rainforests and grasslands. Scientists think the woods atop the Eastern Arc Mountains have existed for over 30 million years and were originally connected to the Congo Basin and West Africa’s woodlands. Neighboring mountains are substantially younger, with Kilimanjaro Mountain being only 1-2 million years old.

The Eastern Arc Mountains are a series of independent mountain blocks that stretch in a crescent or arc form from southern Kenya to Tanzania.

They are East Africa’s oldest mountains.

Taita Hills (Kenya), North and South Pare, West and East Usambara, Nguru, Nguu, Ukaguru, Rubeho, Uluguru, to Udzungwa and Mahenge Mountains in the south make up the Eastern Arc Mountains (Tanzania). The Eastern Arc accounts for less than 2% of Tanzania’s overall geographical area. However, Tanzania’s mountains, particularly the forests they sustain, are crucial to the country and have worldwide conservation worth.


The Eastern Arc Mountains are significant on a global and national scale:


Biodiversity is the amount and variety of living things on the planet. The Eastern Arc Mountains are known for their high levels of endemism (species found nowhere else) and species diversity.

The Eastern Arc woods, for example, are home to 30-40% of Tanzania’s flora and fauna, have 16 unique plant families, and 20 of the 21 African violet Saintpaulia species are only found in the Arc. The Eastern Arc Mountains have 20-30% endemism among the 2,000 plants that grow there, and the Usambara Mountains have more endemic species than any other comparable-sized location in Africa. Because the Mountains are tiny and fragmented ‘islands’ (of the forest) inside a’sea’ of miombo woodland, they are frequently referred to as Africa’s Galapagos.


Tanzania’s government established the Udzungwa Mountains National Park (UMNP) in 1992, which encompasses 1,990 km2 and has elevations ranging from 250 to 2,500 meters.

It’s becoming more popular as a tourist destination. The rain forests of the Udzungwa Mountains in Iringa Region, but outside UMNP, have also been allocated for management. This zonation contains an amenity zone that aims to take advantage of the forests’ unique topography and other natural features for recreational reasons. The government also established the Amani Nature Forest Reserve in May 1997, with the goal of attracting ecotourists. Tropical forest tourism is a relatively recent business that has been effective in various places of the world, most notably Central America, and has the potential to be successful in Africa.


The woods of the Eastern Arc are crucial for large-scale agriculture.

They are able to trap humid air from the Indian Ocean because to their steep elevation on an otherwise flat coastal plain, resulting in rather steady heavy rainfall. The agricultural lands around the forests have rich soils as well, which, when paired with the favorable climate, explains their agricultural importance. Tea and coffee are the principal estate crops, with sections of additional revenue crops including cardamom and Cinchona spp. Sugar cane is farmed in Mtibwa and Kilombero in addition to these crops. These sugar plantations are located in the Nguru and Udzungwa Mountains’ foothills, respectively.

Evolutionary Research

The Eastern Arc Mountains serve as an essential “outdoor laboratory” for studying evolutionary processes.

This is due to their extensive forest cover (possibly 30 million years) and remoteness from Western Africa’s primary forest blocks (maybe 10 million years ago).

National Level importance

In addition to their worldwide significance, Tanzania’s Eastern Arc Mountains are significant on a national level:

Water Catchment Area

Tanzania’s water supply is dependent on the Eastern Arc. The woods in these highlands serve as the primary catchment area for most of Tanzania’s largest rivers. Rivers provide water to coastal towns, including several major cities. The Pang ani River is fed by the Usambara and Pare Mountains, while the Mligasi and Wami Rivers are fed by the Ngurus.

The Wami River is additionally fed by the Ukaguru, Rubeho, and Uluguru Mountains; River Ruvu is fed by the Uluguru Mountains, while Ruaha/Rufiji and Kihansi are mostly fed by the Udzungwa Mountains.
Dar es Salaam gets its water from the River Ruvu. The water supply for Tanga Municipality comes from the Sigi River, which originates in the Usambara Mountains. The Uluguru Mountains serve as a catchment region for the Morogoro River, which provides water to Morogoro Municipality and its environs. The Eastern Arc Mountains are thought to serve as a water catchment region for more than 4 million Tanzanians living in cities and much more in rural areas. Water from a catchment in the Ulugurus is also used by breweries and soft drink manufacturers in Dar es Salaam.


Kidatu and Mtera Dams (Ruaha/Rufiji), as well as Pangani Falls and Hale, produce the majority of Tanzania’s electricity (Pangani). It is possible to create a total of 382 megawatts of power. This accounts for 61.5 percent of the country’s total energy generating capacity of 621 megawatts. A hydroelectric project at Kihansi Falls is currently under construction, with a capacity of 180 megawatts. Tanzania’s growth requires hydropower. The rivers that produce this hydroelectricity all originate in the Eastern Arc Mountains, as previously stated.


Forest-adjacent settlements rely on the forests of the Eastern Arc Mountains for wood fuel. Cooking and heating are both done using fuel.

In the Iringa Region’s Udzungwa Mountain rain forests, residents frequently harvest deadwood for fuel. The woods of the Usambara Mountains are also an important supply of fuelwood for forest-adjacent villages, according to Hamilton (1989a), Ruffo (1989), and Mziray (1990).

Timber Harvesting

In the certain Eastern Arc Mountains, such as Udzungwa, timber is collected (selective harvesting).
In the ‘producing’ zone of the Udzungwa rain forests in Iringa District, selective timber harvesting is authorized. In this zone, mechanical logging is prohibited.
Previously, the Eastern Arc woods, particularly in the Usambaras, were removed for timber production, but this is no longer allowed.

The following timber species thrive in the Eastern Arc forests :

  • Milicia excelsa occurs in the foothills of West Usambaras, Uluguru, and the other Eastern Arc Mountains.
  • Ocotea usambarensis occurs in South Pare and West Usambaras.
  • Podocarpus usambarensis occurs in West Usambaras and Pare Mountains.
  • Khaya anthotheca occurs as a riverine forest in the foothills of Eastern and Western Usambaras, Ngurus, and Ulugurus.
  • Juniperus procera occurs in East Usambara.
  • Allanblackia stuhlmannii occurs in the East Usambaras, Uluguru and Nguru Mountains.
  • Cephalosphaera usambarensis occurs in the East Usambaras.

Herbal Medicine

People have relied on plants for medicine for hundreds of thousands of years all throughout the world. It is believed that around 80% of the world’s rural population relies on herbalists to solve their medical concerns. It was also discovered that trees from the local mountain forests were employed by 35 percent of the diverse plant species used by 14 herbalists (medicine men) in the Usambara.
Temu also mentions the importance of Usambara woodlands as a source of herbal remedies used to cure a variety of ailments. Forest-adjacent populations in the Udzungwa Mountains are authorized to pick medicinal herbs. The alkaloid quinine is found in the bark of the Cinchona tree and is used to cure malaria. The Usambara Mountains are home to Cinchona.

In the Udzungwas area of Iringa, there are 20 plant species that are used as medicine to cure a variety of illnesses, including cattle problems.

Fishing and hunting

Hunting is permitted as part of Joint Forest Management in the Udzungwa Mountain rain forests to provide game meat to forest-adjacent settlements. Fish may be found in most of the main rivers listed above. Fishing is a significant activity in many rivers, providing revenue to fishermen and adding to the community’s protein supply.

Natural Wildlife habitat

All of the forests in the Eastern Arc provide vital habitats for a diverse range of animals. Many vulnerable animal species, including two regionally unique primate taxa, the Iringa red colobus Colobus badius gordonorum and the undescribed new subspecies Cercocebus ‘SarDe crested mangabey,’ live in the Udzungwa woodlands.


These are East Africa’s oldest mountain ranges, and while being geographically separated, they have comparable geomorphology and ecology. They originated at least a hundred million years ago along a fault to the east of the East African Rift, a more modern formation. All of this land was covered in thick jungle thirty million years ago. The lowland woods were transformed to savanna around ten million years ago, when the temperature was cooler and drier, leaving the mountain ranges as “islands” where tropical forests thrived, supplied by moisture-laden breezes from the Indian Ocean.

Because of the isolation of each mountain range, the Eastern Arc has a high level of endemism and diversified flora and fauna, earning it recognition as one of the world’s top twenty biodiversity hotspots.

Plants and animals

Elephant shrews (Rhynchocyon elephanti) are a common animal found in the Eastern Arc Mountains. The three species are often restricted to tiny, fragmented forest areas inside the mountains, as seen by the distribution map.
The Eastern Arc is home to 75 unique vertebrate species and hundreds of endemic invertebrate species. These mountains are home to fifteen plant species, including the Streptocarpus sect. Saintpaulia, the African violet, is now grown as a houseplant all over the world.

Many of these endemics have recently emerged, while some are relics of once more widespread populations. The highest levels of biodiversity may be found in the Uluguru Mountains and the eastern Usambara Mountains. A single mountain range contains a large number of indigenous species. The Udzungwa forest partridge (Xenoperdix udzungwensis) is a remnant and example of this; it is exclusively found on the Rubeho and the Udzungwa Mountains, and its nearest relatives appear to be Asian hill partridges.

Mountain Blocks

Target Districts

North/South Pare Mwanga and Same
West/East Usambara Lushoto, Korogwe, Muheza, Mkinga
Nguu Kilindi
Nguru Mvomero
Uluguru Morogoro and Mvomero
Ukaguru Kilosa
Rubeho Mpwapwa and Kilosa
Malundwe Morogoro
Udzungwa Kilombero, Kilolo and Mufindi
Mahenge Ulanga