1. 1 Background
Wetlands are the ecosystems or units of the landscape that are found within the interface between land and water which are either fen, peatland, or water, whether natural or artificial, permanent or temporary, with water that’s static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low water doesn’t exceed six meters (Ramsar Convention Secretariat, 2013). They’ve distributed everywhere around the globe and are estimated to cover approximately 6% of the worldwide land surface (Schuyt and Brander, 2004), 4% of Africa (Lehner and Doll, 2004; Zedler and Kercher, 2005), and 2% of the total land mass of Ethiopia (Wondie, 2010). The biggest areas of wetlands are in Asia (32% of the worldwide area), North America (27%) and Latin America, and also the Caribbean (16%). Wetland areas in Europe (13%), Africa (10%), and Oceania (3%) are smaller (Davidson et al. 2018).
So far no comprehensive documentation and studies of wetland characterizations are made in Ethiopia. However, it’s estimated that there are 58 major lakes and marshes and a total of 77 wetlands in Ethiopia including lakes that cover a vicinity of 18,587 km2, which is about 1.14% of the country’s landmass (Karlsson, 2015). Ethiopia is usually referred to as the water tower of Africa with the whole annual volume of runoff water being about 110 billion cubic meters (USAID, 2008). The wetlands of Ethiopia vary in attributes like size, type, and location, and that they represent a substantial microenvironment in many parts of the country (Endalew, 2015). Various varieties of wetlands are found to exist in Ethiopia including alpine formations, riverine, lacustrine, palustrine, and floodplain wetlands (Abebe and Geheb, 2003) except the coastal and marine-related wetlands, and extensive swamp-forest complexes (Dixon and Wood, 2001). Ethiopian wetlands will be broadly grouped into four major categories supported by ecological zones, hydrological functions, geomorphologic formations, and atmospheric conditions. These categories intersperse to create four key biomes, which also designate the climate in Ethiopia. These biomes are the Afro-tropical highlands, the Somali Masai, the Sudan, Guinea, and also the Sahelian Transition Zone groups (Tilahun et al. 1996; Wonderfrash 2003; Bezabih and Mosissa, 2017).
Ethiopia having variable topography and altitudinal range, from 126m below sea level to 4,620m above water level may be a country endowed with rich wetland resources (Yimer and Mengistou, 2009). In Ethiopia, the wetland ecosystem covers quite 58 differing types of wetlands, which offer enormous socio-economic and environmental values despite these being under severe pressure and degradation. Due to improper extraction of uses and misconceptions forwarded to wetlands, the health of the wetlands is uninterruptedly declining from time to time and that is suspected their existence within the near future (Gebresllassie et al. 2014).
1.2 Importance of Wetland Ecosystem
Ecologically, wetlands play critical ecosystem roles in biodiversity conservation, hydrological balance, and human welfare both through economic and sociocultural benefits (Ramsar, 2007; Zeleke et al. 2015). The world’s surface freshwater wetland is rich in species composition and is a habitat for over 40% of plant and animal species (Zedler and Kercher, 2005). They’re particularly important in Sub-Saharan African countries like Ethiopia through sustaining the agricultural livelihoods, mainly in areas with low or unpredictable rainfall, and land scarcity where uplands have poor soil (Bezabih and Mosissa, 2017, Menbere and Menbere, 2018).
Wetlands offer natural resources and services to humankind. According to Hailu (2003), wetlands are used virtually by all households within the Western Wellaga and Illubabor zones in Ethiopia directly or indirectly. The most uses are social/ceremonial reeds, medicinal plants, thatching reeds used for housing construction and granary roofing, domestic water supplies, dry season grazing land, water for livestock, and temporary crop-guarding huts of reeds, cultivation, and craft materials. The indirect uses of wetlands are because of their hydrological and ecological functions, which support various economic activities, life support systems, and human welfare. This includes groundwater recharge, flood control, nutrient cycling, erosion control, sediment traps, climate regulation, stream flow moderation, water filtration, and purification, plant and fish products, biodiversity, wildlife habitat for nomadic wildlife, and pest control (Dugan, 1990; McHugh et al. 2007).
Thus, understanding the standard of a wetland by measuring its biota is one of the direct tactics to preserve the biological diversity for extreme ecosystem services delivery (Fennessy et al. 2007). Information on plant species of a specific wetland is incredibly helpful for understanding wetland conditions and diagnosing the impacts of human interference on wetlands (Bijos et al. 2017; Woldemariam et al. 2018). It further helps in understanding appropriate ecological processes and developing suitable and sustainable conservation policies (Junk et al. 2013; Rosolen et al. 2015). Da Ponte et al. (2017) and Rahman et al. (2005) further stated that the community’s perceptions of the importance of ecosystem services can play a valuable contribution toward successfully conserving natural resources like wetlands protection and management.
1.3 Composition and Diversity of Wetland Plant
Wetland disturbance reduces plant species composition and relative abundances and facilitates opportunistic plant species establishment (Zedler and Kercher 2005; Handa et al. 2012; Battisti et al. 2016). EWNRA (2008) identified 36 plant species belonging to 18 families; Cyperaceae, Combretaceae, and Asteraceae families were the widespread families. This showed that the wetlands of the study area were rich in plant diversity; however, further management intervention was required to scale back disturbance and ensure sustainable biodiversity conservation.
Wetland vegetation varies from wetland to wetland in numerous ways. Consistent with Mulatu et al. (2014) among wetland plant species of uncultivated sites of south Bench district 7 plant species dominant plants within the plant community with the relative abundance of over two percent. These plant species were Leersia hexandra (46.35%), Cyperus latifolius (23.79%), Thelypteris confluens (3.96%), Phyllanthus boehmii (3.73%), Persicaria glabra (2.71%), Dissotis canescens (2.58%) and Achyranthes aspera (2.09%). These 7 plant species accounted for 85.21% of the community while the remainder 22 species had a relative abundance of but 2% which accounted for 14.79%. The result revealed that important species such as Leersia hexandra and cyperus latifolius decreased significantly due to cultivation.
The dominant plant species of the Tana wetland of the Amhara region of Ethiopia were reported by Wondie (2018), in addition, it specifies that the collective plant community similarity index in the midst of wetlands was mostly low (20%). The explanations for the low average percentage similarity are due to low plant diversity in some urban and agriculture-impacted wetlands.
1.4 Drivers of Wetland Degradation
Though, the wetlands faced a substantial threat due to human interaction that indicated about 50% of the world's wetlands are lost since 1900 (Bezabih and Mosissa, 2017; Hirpo, 2018; Moges et al. 2018). Unregulated utilization of wetlands including diversion of water for agricultural intensification, urbanization, dam construction, population pressures, food shortages, increased drainage and cultivation, and collection of sedges and reeds for roofing and housing were identified as major drivers of wetland degradation in Ethiopia (Bezabih and Mosissa, 2017, Menbere and Menbere, 2018). Such drivers have resulted in wetland disturbances, degradation, and loss, which ultimately can cause the elimination of native plant species, encroachment of exotic species, and reduction of ecological and socioeconomic values of wetlands in Ethiopia (Collins, 2005; Mulatu et al. 2014). Little awareness of the prominence of wetlands, or maybe the prerequisite for their conservation and sustainable utilization could be a delinquent in Ethiopia (Wondarfrash, 2003).
The most common threats to wetlands are the results of a mixture of social, economic, and climatic factors, which have increased pressure on the natural resources in Ethiopian wetlands. Another constraint to the judicious use of African wetlands is the lack of knowledge by planners and natural resource managers of the advantages that they supply and also the techniques by which they’ll be utilized in an exceedingly sustainable manner (Jogo and Hassan, 2010). A large number of wetlands in Ethiopia are considered vulnerable zones; some are most exploited, mismanaged, and lost their regenerating capacity (Alemayehu, 2006).
In 1999, the government increased its pressure on farmers to cultivate wetlands so as to make amends for more drought-induced food shortages (Dixon et al. 2008). Nowadays, wetland cultivation provides between 10 and 20% of the annual food needs of the region but will be as high as 100% during the summer months in some areas. Eucalyptus, banana, sugarcane, and Khat cultivation on the perimeters of wetlands, and Teff cropping in wetlands, has been identified as a threat to the survival of those areas.
1.5 Consequences of Wetland Degradation
Consequences of wetland loss and degradation in Ethiopia's alterations of the hydrological regime of wetlands have significant Physico-chemical and biological, ecological, and socio-economic implications at a wider scale (Roggeri, 1995; OECD, 1996). In Ethiopia, the implications of wetland loss and degradation are enormous as well as directly affecting the livelihood base of rural communities, decrease and extinction of wild flora and fauna, loss of natural soil nutrients, and water reservoirs, and their subsequent benefits (Bezabih and Mosissa, 2017; Menbere and Menbere, 2018). They have affected various traditional occupations, socioeconomic conditions, and cultural activities (Kumsa, 2015). The entire drainage of wetlands in Illubabor Zones, southwest Ethiopia has led to a variety of ecological and economic problems (Wood, 2003).
In Ethiopia, wetland management isn’t efficiently harmonized and lacks acceptable policy support. Due to the absence of workable institutional arrangements and wetland management policy, sustainable management of wetlands and capacity building don’t seem to be strengthened. As a result, the sector suffers from a shortage of skilled manpower which is capable of disseminating the concept of wise use of wetlands (Birhan et al. 2015, Seid, 2017).
Wetlands in southeastern Ethiopia, particularly in Sinana district are ecologically, socially, and environmentally crucial for the realm. The enormous direct and indirect consequences of wetland loss and degradation are observed at the Kedar wetland. However, empirical evidence on the plant species diversity, ecosystem services of the wetland, and therefore the drivers for wetland degradation within the region and Sinana district isn’t available. Thus, the target of the study was to investigate plant species diversity and assess the perception of people on ecosystem services, and drivers of wetland degradation within the Sinana District of Bale Zone, Southeast Ethiopia. As a result, the study tries to fill this gap by providing scientific information useful to style an efficient management plan vital for sustainable management of the wetland.