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.