East African montane forests
East African montane forests are unique ecosystems located in the high-altitude regions of the Eastern Arc Mountains, spanning parts of Sudan, Kenya, Uganda, and Tanzania. These forests thrive at elevations of approximately 3,300 to 11,500 feet, where the climate is moderated, leading to higher rainfall than surrounding lowlands, typically ranging from 47 to 78 inches annually. Despite their rich biodiversity, these forests face significant threats from human activities, including agriculture, illegal harvesting, and the impacts of climate change. The region is home to an estimated 2,000 plant species, with around 800 being endemic, alongside numerous endemic bird and mammal species. Many notable locations within this biome, such as Mt. Kenya and Mt. Kilimanjaro, are protected as national parks and recognized as World Heritage sites. However, increasing local populations and development pressures have led to habitat loss outside protected areas, complicating conservation efforts. Some communities are exploring ecotourism as a sustainable solution to both economic challenges and environmental preservation, highlighting the importance of local engagement in protecting these vital ecosystems.
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Subject Terms
East African montane forests
- Category: Forest Biomes.
- Geographic Location: Africa.
- Summary: This group of mid- to high-altitude forests hosts species diversity in unique habitat niches—but growing human pressures are stressing their sustainability.
The East African Montane Forests biome is located in Sudan, Kenya, Uganda, and Tanzania. These woodlands exist only in moderate- to high-altitude regions of the volcanic mountain chain called the Eastern Arc Mountains. They thrive where altitude is roughly 3,300–11,500 feet (1,000–3,500 meters), which moderates the prevailing climate. Temperatures often fall below 50 degrees F (10 degrees C) here in July and August, when frost can occur. In the warm season, temperatures can exceed 86 degrees F (30 degrees C).
Typically, rainfall is in the range of 47–78 inches (1,200–2,000 millimeters) per year. Rainfall occurs mostly during the bimodal rainy seasons, which occur from March to June, and then October through December. Because of their elevation, these locations receive more rainfall than the surrounding lowlands, making them a good home for montane and submontane forests. Rain does not fall much above 9,840 feet (3,000 meters) on these mountains; the highest elevation areas are considered desert. The soil is typically very fertile and desirable for agriculture.
Geologic movement of the Africa tectonic plate has caused the Rift Valley to form, essentially as a large crack in the Earth's crust, which gave way to the formation of volcanoes and ultimately the current vegetation regime.
The East African Montane Forests biome today is spread over more than 25 forest patches, the northern extent of which is Mt. Kinyete of the Imatong Mountains in southern Sudan. The forest forms the headwaters of the White Nile; the southern range extends through southern Kenya into Tanzania. The biome includes Mt. Meru, Mt. Kilimanjaro, Ngorongoro Crater, and the Marang forests; parts of the ecosystem extend eastward into eastern Uganda. Many of these locations drain into Lake Victoria, and eventually flow into the Nile River.
Endemism
The East African Montane Forests biome has moderately high species richness, and some endemic species (those found nowhere else on Earth). Scientists believe that these environments have not existed long enough for speciation to create as rich a biodiversity level as seen in other zones in this part of Africa.
Still, there are an estimated 2,000 plant species growing in the East African Montane Forests biome; at least 800 of them are apparently endemic here. These forests are the centers of global endemism for various species of the African violet (Saintpaulia) and busy lizzy (Impatiens). Other notable endemic plants are Usambara violet (Saintpaulia ionantha), msambo tree (Allanblackia stuhlmanni), and a large wild nutmeg (Cephalosphaera usambarensis). There are many endemic bryophytes, or nonvascular plants, within the region. Many of the them are found within a single mountain range, such as the Usambara Mountains in Tanzania, which are home to 50 endemic tree species.
There are eight endemic bird species, some of which occur only within two or three montane locations, including Aberdare cisticola (Cisticola aberdare), Abbott's starling (Cinnyricinclus femoralis), Kenrick's starling (Poeoptera kenricki), Aita thrush (Turdus helleri), Usambara akalat (Sheppardia sharpie), Usambara eagle-owl (Bubo vosseleri), and the banded sunbird (Anthreptes rubritorques).
There are many endemic small mammals, including mostly shrews (Crocidura gracilipes, C. raineyi, C. ultima, Surdisorex norae, and S. polulus), and rodents (Grammomys gigas, Tachyoryctes annectens, T. audax). There are more small mammals that are close to endemic, including Jackson's mongoose (Bdeogale jacksoni), Abbot's duiker (Cephalophus spadix), the sun squirrel (Heliosciurus undulatus), and eastern tree hyrax (Dendrohyrax validus). Other notable, nonendemic mammals include the Angolan black-and-white colobus (Colobus angolensis), and forest-dwelling populations of the African buffalo (Syncerus caffer) and Harvey's duiker (Cephalophus harveyi).
As many as 19 endemic reptiles are known here, mostly chameleon species (Chamaeleo and Rhampholeon families), worm snakes (Typhlops family), and colubrid snakes including a montane viper (Vipera hindii). There are just two endemic amphibian species.
The distribution of species through the biome, or its biogeography, suggests that northern Kenyan forests were once linked with forests of west and central Africa. The fact that some of the mountains have endemic species not found anywhere else in the biome suggests that species evolved in that ecoregion independent of other areas. A classic example is a group of 45 species otherwise found only on the island of Madagascar. This suggests the East African Montane Forests biome has a very different biogeographical history than other East African mountain zones.
Protected Lands
Much of the East African Montane Forests biome exists today in forest reserves and national parks. The most prominent locations are Mt. Kenya, the Aberdare Range, the Mau Complex, Kakamega Forest, Mt. Kilimanjaro, Mt. Meru, Mt. Elgon, and Ngorongoro. Mt. Kenya and Mt. Kilimanjaro are listed by the United Nations as World Heritage sites. The previous forest biome outside of protected areas has been converted almost entirely to agriculture or other human uses. At lower elevations, such lands are now tea and coffee plantations, conifer plantations, and other types of agriculture. Much of the habitat loss occurred during the colonial period in the late nineteenth and early twentieth centuries.
Pressure on these lands has increased still more since then, due to rising local populations and their needs for more agricultural land. Another problem has been conflicts between humans and wildlife. Humans are developing agricultural land near the protected areas—and large mammals wandering outside the zone can do a lot of damage to the adjacent farm. Humans also enter the protected areas and illegally harvest bushmeat, timber, and other commodities.
Climate-change-driven temperature increases are exerting pressure on chronically underfed human populations here. Intensification of these circumstances in years ahead could cause social unrest, political upheaval, and continental hostilities—little of it good for habitat sustainability. Further, climate change and increased temperatures also threaten forests because the rising temperatures decrease the moisture in the area, hindering tree regeneration and plant growth.
Political issues have been rising over the illegal harvesting of wood for charcoal. Charcoal is created in kilns near the forests and sold to urban and rural communities that use it as a fuel source for cooking. Corrupt politicians and local townspeople can make a lot of money through charcoal production or through bribes. Poverty in villages can be a factor in the degradation or deforestation of these areas. Regions receiving little investment or development aid will tend to use the abundance of the forests to gather resources they need, such as food sources, fuel, and timber.
Some communities use ecotourism as a way to solve local poverty and protect the environment. To be successful, ecotourism must be supported by the local village; it is often villagers who lead the tours. The system invests the people in their community, keeps money out of the hands of large companies and corrupt officials, and lets money remain in local hands. Townspeople then have more incentive to preserve the forest and keep the revenue stream within the community, reducing their need for illegal gathering within the forest.
Bibliography
Abera, Temesgen Alemayehu, Janne Heiskanen, and Eduardo Eiji Maeda, et al. “Deforestation Amplifies Climate Change Effects on Warming and Cloud Level Rise in African Montane Forests.” Nat Commun, vol. 15 no. 6992, 2024, doi.org/10.1038/s41467-024-51324-7. Accessed 27 Nov. 2024.
"Africa's Montane Forests Are More Carbon-Dense than even the Amazon." Mongabay, 10 Sept. 2021, news.mongabay.com/2021/09/africas-montane-forests-are-more-carbon-dense-than-even-the-amazon/. Accessed 27 Nov. 2024.
Hamilton, A. C. and R. A. Perrott. “A Study of Altitudinal Zonation in the Montane Forest Belt of Mt. Elgon, Kenya/Uganda.” Plant Ecology 45, no. 2 (1981).
Lovett, J. C. and I. Friis. “Patterns of Endemism in the Woody Flora of Northeast and East Africa.” In L. J. G. van der Maesen, X. M. an der Burgt, and J. M. van Medenbach de Rooy, eds. The Biodiversity of African Plants. Wageningen, Netherlands: Kluwer Academic Publishers, 1996.
Lovett, J. C. and S. K. Wasser. Biogeography and Ecology of the Rainforests of Eastern Africa. Cambridge, UK: Cambridge University Press, 2008
Sayer, J. A., C. S. Harcourt, and N. M. Collins. The Conservation Atlas of Tropical Forests: Africa. Cambridge, UK: IUCN and Simon & Schuster, 1992.