Wetland Ecosystem

Description

9.1 Description
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 (EFAP, 1989). According to Hillman (1993), there are 77 wetlands in Ethiopia and Eritrea with a total coverage of 13,699 km2 or 1.14% of the total landmasses of the country

The Ramsar Convention (Article 1.1) defined wetlands as: “areas of marsh, fen, peat land, or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide doesn’t exceed six meters”. In addition, the convention (Article 2.1) provides that wetlands: “may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six meters at low tide lying within the wetlands. In the Ethiopian context marshy areas, swamp lands, flood plains, natural and artificial ponds, volcanic crater lakes, high mountain lakes and upland bogs are treated collectively as wetland ecosystems. This booklet, therefore, deals on swamps, marshes, floodplains, ponds, micro dams, high mountains as well as crater lakes and upland bogs whose formation has been dominated by water and whose processes and characteristics are largely controlled by water. Wetland ecosystem has been considered as wasteland that have little or no value at all, and converted to agriculture and grazing through drainage. Often, they are considered as breeding sites and sources for several water borne diseases both to human and domestic animals.

Defining the various habitat types in wetland ecosystem
Flood plains can be defined as land adjacent to an active river channel which are occasionally flooded by those bodies of water and remain dry for varying portion of the growing season (Mitch & Gosselink, 1993). According to FAO (1984), swamps are defined as wetlands dominated by trees or shrubs, and marshes as wetlands dominated by emergent herbaceous vegetation. Swamp (marshy) ecosystem is an area, which is frequently or continually flooded, usually with emergent vegetation adapted to saturated soil condition. These areas are often with high water table and sub-surface water within the root zone. In most cases, flood plains are conspicuous features of the landscape in contrast with the surrounding vegetation. As a result, this habitat attracts wildlife, which seek the refuge of the diversified habitat types. Wetland ecosystem is considered to be more productive than the adjacent area because of the periodic inflow of nutrients.

There is a considerable diversity of swamp and marshy habitats in Ethiopia and for the purpose of this booklet we used both terms interchangeably. Floodplain differs from swamps in that it arises as a result of seasonal submergence by spill over from rivers, lakes or other water bodies. Swamp and flood plain generally occur where the water table is at or near the surface of the land or where the land is covered by shallow water depth. Strictly speaking, defining Wetland ecosystem in the Ethiopian context seems uneasy because of considerable change in hydrological properties (seasonal and long-term) and vegetation composition overtime and absence of clear boundaries between the wetlands and adjacent aquatic as well as terrestrial lands. The very transient nature they have with a great array of their types defied a clear distinction of what wetland ecosystem is.

Characteristics of wetland ecosystem
In wetland ecosystem water is the primary factor controlling both the plant and animal life. It favours particular type oftrees, shrubby species and associated herbs and grasses. Typical characteristic species of wetland ecosystem include those of aquatic macrophytes such as Cyperus, Eleocharis, Scirpus, Echinochloa, Panicum, Alisma plantago-aquatica, Nymphaea, Typha, Paspalidium, Potamogoton, Wolffia, Aeschynomene, Phragmites, Urochloa, Veronica, Hydrocotyle, Polygonium, kyllinga etc., and tree species include Ficus sychomorus, Tamarindus indica, Celtis africana, Mimusops kummel, Syzygium guineense, Terminalia brownii, Acacia polyacantha, Kigelia abyssinica, Phoenix sp., Trichilia sp., Diospyros sp. Although swamps, marshes, and flood plains are known to be a home to many different kinds of birds, mammals much more remains unsurveyed specific to the habitat types. Some birds, for example, Spot-breasted Plover, Blue-winged Goose, Rouget’s Rail, White-winged Flufftail, Wattled Crane, Corn Crake, Shoebill, Black-winged Pratincole, Great Snipe, and Lessr Flamingo in general favour, feed or breeds in wetlands (Mengistu Wondafrash, 2000).

The resource base
Swamp and Marsh are terms used to describe range of habitat types affected by water. These two habitat types hereafter refereed as swamp ecosystem, covering an estimate area of 1803 km2, which is about 0.16% landmasses of the country. In wetter part of the country, for example, in Illubabor swamplands are most common that accounts up to 5% of the area in the highlands. Similarly, other highlands of the Western, South, and Southwest of the country including Jimma, Wollega and Illubabaor Zones of Oromia Region, Keff-Sheka of South Region as well as the low-lying regions of Ethiopia have considerable area of wetlands (swamps and flood plains).

Distribution

9.2 Distribution
Wetlands are widely distributed in all climatic regions of Ethiopia. Wetland habitats such as swamps, marshes, flood plains, natural and man-made ponds, micro-dams, high mountains and volcanic crater lake, and upland bogs are distributed all over, occurring across all other ecosystems of Ethiopia. This ecosystem is governed by geomorphological, hydrological and climatic factors.

There are several important Swamp areas in the country. Among others the flood plains in Tekeze Vally (Tigray), Baro-Akobo (Gambella), Omo-Gibe (South), Awash Valley and swamps of Fogera, Dembia, Beles and Borkena in Amhara region; swamps of the Dabus River in Beni-Shangul Gumz; swamp area in highlands of Illubabor, Keffa and Wollega Zones (such as Fincha, Chomen and Amerti swamps), the central Shewa highlands such as Aba-Samuel, Legedade and Gefersa micro-dams, the Qumbi swamp and alpine lakes of Bale Mountains, Ziquala and those of Debre-Zeit volcanic crater lakes and the adjacent areas in Oromia Region; swamps of Dubti, Afambo, Gemari and Lake Abe in Afar Region are the few ones to be mentioned. This list is not complete and there are a lot of wetlands (swamps, marshes, seasonal flood plains) in different regions of the country, which are not mentioned above.

Diversity

9.3 Diversity
The wetlands of Ethiopia are formed from fresh, alkaline, small and large, permanent and seasonal water system that provide different ecological niche to various species of both plant and animals. The Floristic and Faunaistic composition of wetland ecosystem in Ethiopia remain un-surveyed until recently (Carr, 1998; Bayfers Tamene, 2000; Mitiku Tikssa, 2001). Nevertheless, Wetland ecosystem in Ethiopia supports a wealth of flora and fauna. Wetland ecosystem has been shown to be species rich and highly variable in species composition at lower, medium and higher elevations in the Tropics and outside the Tropics (Hughes, 1988). In general Wetland ecosystem show a considerable range of diversity in habitat types governed by altitude, rainfall, temperature, and geographic location. Therefore, the floral and faunal compositions in the Wetland ecosystem are highly variable and are specialized to a particular habitat types. They represent critical structural habitat that is distinct from their adjacent land and, in several places they are valued for their role in supporting regional biodiversity, rare and endemic bird species, game animals, as well as aquatic macrophytes, which are used in traditional house construction.

Key characteristics of floodplains are the formation of various structures of plant communities, which are distinct, both in terms of flora and fauna composition from the adjacent dry lands. Six plant community types were described in the swamps of Awash valley (Mitiku Tikssa, 2001) with a total record of 83 vascular plants from the area. Similarly, in his description of the vegetation in Cheffa Wetland Bayafers Tamene (2000) recognized ten plant community types and recorded about 208 plant species. On the other hand, study of the Avifauna by Tadesse Wolde Mariam (1999) showed that a total of 92 species of birds that belong to 40 families were recorded from wetlands of Illubabor, southwest Ethiopia. In the analysis it was found that of the total 48-afroalpine birds known in Ethiopia 17 (35.4%) species including three endemic and near endemic species were recorded from the study sites (Tadesse Wolde Mariam, 1999).

Uses,Values

9.4 Uses and Values
The biological interaction between the elements (water, soil, plants and animals) allow riparian and swamp ecosystems to perform certain functions and generate healthy wild life and forest resources. Their function as ecological and hydrological is several fold, for example, flood control, water purification, sediment and nutrient retention, dry season grazing, agriculture, microclimate, recreation and cultural values, water supply (domestic and livestock), construction (thatching reeds), flood, medicine, Important Bird Areas (IBA) as well as provision of flyways for migrant birds. Wetland ecosystem also provide shelter, among others, to the following bird species: Spot-breasted Plover, Blue-winged Goose, Rouget’s Rail, White-winged Flufftail, Wattled Crane, Corn Crake, Shoebill, Black-winged Pratincole, Great Snipe, and Lesser Flamingo.

The Awash valley corridor and Meteke swamp complex provide flyway to Palaearctic and African migrants (EWNHS, 1996). The Fincha and Chomen swamps in Wellega and the Koffe swamp in Jimma zone are some of the few examples of important bird areas in the country. These ecosystems are also crucial water source to the people and their livestock. Many pastoral people and livestock herds flock and graze over the dry season in Cheffa plain (Bayfers Tamene, 2000) Pastoralism and Tourism play their part in the local economy of the people. They have also cultural and aesthetic value including tourist attractions.

During famine and food insecurity people also rely heavily on wild plants from wetlands and the associated areas (Zemede Asfaw, 1995; Tesfaye Awas et al., 1997a). Among others, non-cultivated plants such as species of Discorea, erythrocarpus, Celtis tokka, Tamarindus indica, Echinochloa sp., Ficus sur, Carrisa edulis, Cordia africana, Gardenia ternifolia, Citrus auriantifolia, Ipomea aquatica, Nympha are used for human food in Baro-Akobo, Omo and Awash Valley (Tesfaye Awas et al., 1997a; Bayafers Tamene, 2000; Mitiku Tiksa, 2001). Species of plants used for human medicine include Achyranthus aspera, Asparagus africanus, Acokanthera schimperi, Celosia trigyna, etc. Of the 206 plant species recorded from Cheffa swamp 54 species were identified to be used for food by humans, 79 species as human medicine and 31 as veterinary medicine. The complex swamps that are found in the Afar depression are used mainly for Salt extraction.

Threats

9.5 Threats and rates of change
Wetland ecosystem is basically assumed to be less important than any other priorities irrespective of the many services they provide, and also regarded as free goods. Wetlands are lost or altered by conversion, over utilization and unregulated management. Deforestation and heavy decline in swamps of the Awash Valley were observed in connection with change in land use practices including heavy cattle grazing, clearing of the vegetation, construction of dams and irrigation channels and frequent fire are some of the major threats to the Wetland ecosystem. Environmental pollution due to application of agro-chemicals, salinization problem in irrigable lands, overflowing, siltation and soil erosion due to heavy devegetation are the consequences of human impact on this ecosystem. The conversion of swamps to agriculture with long-term drainage and cultivation reduce the diversity of wetland habitats and thereof, species and start to be invaded by meadow grasses of non-wetland species. Approximately, 20% of the swamps in Illubabor Zones were cultivated each year between 1986 and 1998 (Afework Hailu, 1998). Until recently, swamps and flood plains along major rivers are often seen as wasteland that have no values and are best converted by drainage (in the name of Waste Land Reclamation Programme) to allow agriculture (crop cultivation) or grazing (Wood, 2000).

The construction of dam on swamp areas, for example, in Fincha, Chomen and Amerti in Wellega zone has reduced the extent of the original marshy area thereby affecting the diversity of wetland flora and fauna, shortage of grazing land and higher infestation of livestock diseases to the surrounding area. Scarcity of reeds, vegetation change, lowered water table and reduced access to drinking water are some of the problems arise as a result of drainage and cultivation of swamps (Wood, 2000). Increased fluctuations in stream flow, reduced water quality and downstream hydrological impacts would also follow. In general, agricultural land expansion, urbanization dam construction, pollution, salinization and other forms of activities threat these ecosystems. In addition, failure of integrated planning and the desire of quick profit with out concern for social and ecological values of wetlands have already shown harmful impacts. For example, siltation problems in different water supply and hydropower generation projects impair the proper function of the dams and reservoir. The irrigation dam constructed on Borkena River was an exemplary failure registered as a wasteful attempt of pre-feasibility and integrated conservation activity plan.

Status

9.6 Conservation status
Ethiopia is not a signatory to Ramsar Convention on wetlands and, therefore, none of the numerous wetlands in the country is designated for protection accordingly. Wetland ecosystem in general and flood plains and swamp habitats in particular are facing pressure not only from unregulated access but also upstream effects, mismanaged watersheds, variation in water quality and quantity caused by siltation, inland water works and pollution. However, in few places where shortage of thatching reeds and other unique products become very serious, the community themselves developed by-laws to protect swamps for production of reed and other construction materials rather than allowing open access (Afework Hailu, 2000). Since the resource base in these ecosystems weren’t very well documented, their status of conservation is not known and needs future investigation. More importantly there is an urgent need to address the issue of wetland ecosystem conservation with emphasis on their extent, diversity, distribution, and sustainable utilization.

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