Ethiopia is endowed with diverse ecosystems in which diverse flora and fauna as well as microbial resources are found. The major ecosystems include: Afroalpine and subafroalpine, Montane dry forest and scrub, Montane moist forest, Acacia-Comiphora woodland, Combretum-Terminalia woodland, Lowland humid forest, Aquatic, wetland, Montane grassland, and Desert and semidesert ecosystems.
1. Afroalpine and Subafroalpine Ecosystem
The areas which on the average higher than 3200 meters above sea level (m.a.s.l) are generally referred to as the Afroalpine and Subafroalpine (Hedberg, 1957). The lower limit of the afroalpine belt falls at about 3500 m, while the upper limit of vascular plants lies around 5000 m (Hedberg, 1964), and subafroalpine areas ranges between 3200- 3500 m. These areas include chains of mountains, mountain slopes and tops of highest mountains in the country. The highest peak in Ethiopia is Ras Dashen (4533 m a.s.l), where an alpine climate near 0°C persists all year round, sometimes even with a snow cover lasting a couple of days (Hurni and Ludi, 1998). However, dry lowland savannas and deserts surround this moist highland area. Ethiopia has the largest extent of afroalpine habitats in Africa (Yalden, 1983).
2. Montane Grassland Ecosystem
The montane grassland ecosystem is distinguished from other types of ecosystems by its physiognomy, floristic composition and ecology. It consists of herbaceous stratum usually not higher than 30 – 80 cm, very rich in perennial grasses and species of Cyperaceae, but also with sub-shrubs and perennial herbs, among which bulbous and rhizomatous plants occur (Pichi-Sermolli, 1957). The original climax vegetation on the montane grassland of Ethiopia was supposed to be a dry evergreen montane forest intermingled with small areas of grassland (Zerihun Woldu, 1988). According to White (1983), the montane grassland of Ethiopia is a derived vegetation type, although small areas of the grassland may have existed before human settlement.
3. Dry Evergreen Montane Forest and Evergreen Scrub Ecosystem
The Ethiopian highlands contribute to more than 50 % of the land area with Afromontane vegetation, of which dry montane forests form the largest part (Yalden, 1983; Tamrat Bekele, 1994). The evergreen scrubland vegetation occurs in the highlands of Ethiopia either as an intact scrub, i.e. in association with the dry evergreen montane forest or usually as secondary growth after deforestation of the dry evergreen montane forest. The Dry Evergreen Montane Forest and Evergreen Scrubland vegetations are the chjarachteristic vegetation types of this ecostem.
4. Montane Moist Forest Ecosystem
The montane moist forest ecosystem comprises high forests of the country mainly the southwest forests, which are the wettest, and also the humid forest on the southeastern plateau known as the Harenna forest.The montane moist forest ecosystem is distiguished by supporting luxuriant growing epiphytes Canarina, Orchids, Scadoxus and fern plants such as Platycerium and Drynaria. Mosses also occur in the wettest porton of forests associated to major branches and barks of trees.
5. Acacia-Commiphora Woodland Ecosystem
The Acacia-Commiphora ecosystem is known for its varying soils, topography, and diverse biotic and ecological elements. These plant species are with either small deciduous leaves or leathery persistent ones. The density of trees varies from ‘high’, in which they form a closed canopy to scattered individuals to none at all forming open grasslands. The grasses do not exceed more than one meter, thus, no true savannah is formed.
6. Combretum-Terminalia Ecosystem
This ecosystem is characterized by Cmbretum spp., Terminalia spp., Oxytenanthera abyssinica, Boswellia papyrifera, Anogeissus lieocarpa, Sterospermem kuntianum, Pterocarpus lucens, Lonchocarpus laxiflorus, Lannea spp. Albizia malacophylla and Enatada africana. These are small trees with fairly large deciduous leaves, which often occur with the lowland bamboo- Oxytenanthera abyssinica. The understory is a combination of herbs and grasses. The herbs include Justecia spp., Barleria spp., Eulophia, chlorophytum, Hossolunda opposita and Ledeburia spp. The grasses include Cymbopogon, Hyparrhenia, Echinochla, Sorghum, Pennisetum, etc. Usually the herbs dominate the ground layer at the beginning of the rainy season while grasses dominate toward the end of the rainy season.
7. Lowland Tropical Forest Ecosystem
The characteristic species of this forest are Baphia abyssinica and Tapura fischeri (Chaffey 1979, Friis, 1992, Tesfaye Awas et al., 2001). The common species in the upper canopy include Celtis gomphophylla, Celtis toka, Lecaniodiscus fraxinifolius, Zanha golungensis, Trichilia prieureana, Alistonia boonei, Antiaris toxicaria, Malacantha alnifolia, Zanthoxylum lepreurii, Diospyros abyssinica, Milicia excelsa, Baphia abyssinica, Vepris dainellii and Celtis zenkeri.
8. Desert amd Semi-desert Ecosystem
It is a very dry zone vulnerable to wind and water erosion even with little or no pressure on the vegetation from grazing. The vegetation consists of deciduous shrubs, dominated by Acacia sp. interspersed with less frequent evergreen shrubs and succulents. It has very variable grass vegetation. The people of the area are pastoral and agro-pastoral. Large scale irrigated agriculture is gaining importance in some areas of the ecosystem. This ecosystem is the extreme lowland region of the country. The flora has developed an advanced xeromorphic adaptation. Shrubs and trees have developed dwarf growth and have small, sclerenchymatic or pubescent leaves.
9. Wetland Ecosystem
Ethiopia possesses a great diversity of wetland ecosystem (swamps, marshes, flood plains, natural or artificial ponds, high mountains lake and micro-dams) as a result of formation of diverse landscape subjected to various tectonic movements, a continuous process of erosion, and human activities. The different geological formation and climatic conditions have endowed Ethiopia with a vast water resources and wetland ecosystem including 12 river basins, 8 major lakes and many swamps, floodplains, and man made reservoirs with a total annual surface runoff about 110 billion cubic meter
10. Aquatic Ecosystem
Aquatic in literal meaning refers to water. As an ecosystem, widely taken, it includes freshwater (rivers, reservoirs and lakes), marine (oceans and seas) and estuarine (coastal, bays, tidal) ecosystems. The Ethiopian aquatic ecosystem has high diversity areas such as major rivers and lakes that are of great national and international importance. The country is well known for its richness in water potential. There are about 30 major lakes that are located in different ecological zones. These lakes are situated at altitudes ranging from about 150 m below sea level high up to 4000 m. The surface area of the lakes vary considerably from less than 1 km² to over 3600 km² and mean depths range from few meters to over 260 meters. However, the major lakes that are of economic importance are concentrated in the Rift Valley.