Wetlands are among the planet most biologically productive ecosystems and rich in diversity of species. Human activities pose threats on the well-being of wetlands, leading to either their loss or degradation (Bjerstedt, 2011). Wetlands, constituting only 1.5 % of the area of earth, renders about two-fifth (40 %) of the ecosystem services globally (Zedler and Kercher, 2005). A wetland (inland) ecosystem provides services with an estimated value of US$ 44,000 per/ha/year (TEEB, 2013; Clarkson et al., 2014); these services include provisions (fish, fodder, timber, medicines and oil, etc.,), support farming, carbon sink, maintaining air and water quality and supply, and the hydrological and biogeochemical cycles, regulating climate, stabilizing shorelines, curbing flood hazard, sustaining flora and fauna, treating liquid waste, cultural and recreational uses, etc., (Dise, 2009; Egoh et al., 2012; Clarkson et al., 2014).
Wetlands undergone loss or degradation despite the multiple services they provide to people. ‘Wetland loss’ is defined as the transformation of wetlands to non-wetlands due to the impact of natural and anthropogenic factors; whereas ‘wetland degradation’ is human actions-induced “impairment of wetland functions” which delivers goods and services (Moser et al., 1996). Wetland loss or degradation occurs due to natural and human factors. These factors lead to depletion of ecological values of services derived from wetlands, and the loss of livelihood sources of people nearby wetlands. Livelihood is described as the combination of social, human, physical, economic, and natural capitals (Scoones, 2009). The use of wetlands for crop farming has increased in recent decades (Dixon and Wood, 2003), which is underlain by population growth, climate change, globalization (Van-Asselen et al., 2013), and changes in policy and governance structures (Davidson, 2014).
Several studies stress on the role of ecosystems (natural capital) to extend access to the other capitals, resulting in poverty reduction and resilience to global climate change impact (Akwetaireho and Getzner, 2010; Fisher et al., 2014). Recent global ecological crises, such as climate change and ecosystem degradation, severely affect the livelihoods of ecosystem dependent communities in sequential order, such as reduced agricultural production, squeezed livelihood options, increased poverty, and eroded adaptive capacities across various scales (Reed et al., 2013b). Even if livelihood diversification is commonly suggested as a viable option to those crises and uncertainties, it is also essential to assess the livelihood vulnerability within the broader perspective of ecosystem-based adaptation and sustainable livelihood planning (Gautam and Andersen, 2016). One important pre-requisite in ecosystem-based livelihood development is to have a qualitative and quantitative understanding of the relationship of the livelihood system and ecosystem in a given social-ecological system (Gautam and Andersen, 2016).
Wetland loss/degradation has been associated with rapid population growth, overexploitation and unsustainable management practices, which adversely affect the livelihoods of local communities (Trinh et. al., 2003). Wetlands are often perceived to have little or no value compared to other potential uses of land that enable to produce immediate economic benefits. But wetland ecosystems have been severely degraded since some recent decades-past due to its overwhelming exploitation (Davidson, 2014). The protection of the wetlands reserves numerous valuable goods and services to the local communities and also, to the people outside the wetland areas (Egoh et al., 2012).
The deteriorating state of wetlands and consequent threats on sustainability of livelihoods remains a key concern to many governments, especially in developing countries. Increasing population and rural poverty have already damaged wetland ecosystems (Rahman and Islam, 2005). Wetland ecosystems are important from conservation and sustainable management viewpoints as they are rich in diversity of flora and fauna (CBD, 2015). Tangible and intangible diverse services and products of wetland functions such as fodder, fishes, fuel-wood, non-timber forest products, ecotourism and flood control have been sources of income and livelihood means for humans. However, population growth and associated factors have depleted these resources and reduced the flow rates of the ecosystem services. The loss of wetland ecosystem services damages the health and well-being of individuals and communities and diminishes their development prospects (MEA, 2005; Clarkson et al., 2014).
The sustainable use of wetlands and associated ecosystems is influenced by diverse interactive factors such as rapid population growth, expansion of farming, use of chemical farm inputs, irrigation, invasive or alien species, changes in the way of life of people, infrastructure expansion, urbanization, overgrazing, open access and overuse of resources, drought, climate change, policy change, lack of sound policy, etc., (Egoh et al., 2012; Heathwaite et al., 2012; Van-Asselen et al., 2013; Davidson, 2014; CBD, 2015). Diverting water flow from tributaries, runoff from croplands and urban areas, withdrawal of water from lakes, high evaporation, frequent siltation, pollution, etc., are the specific factors which threatens the biodiversity and services of wetlands (Ayenew, 2004). But all these factors could not be equally significant in degrading the functions and services of wetlands, and the lives of people whose livelihoods are linked to the wetlands everywhere (MEA, 2005b).
The interlinkage between wetland ecosystems and livelihoods is hardly appreciated by policy makers despite the paramount importance of the diverse services wetland ecosystems render to people and nature (MEA, 2005a; CBD, 2015). The formulation of sound policy and management strategies on wetlands requires holistic understanding on how wetland ecosystem functions are affected by natural and anthropogenic factors, and how degradation of wetland resources influence livelihoods (Boyd, 2012; CBD, 2015). It is also vital to understand how people make decisions on resource exploitation and how sociocultural and policy factors affect those decisions (MEA, 2005b; Boyd, 2012).
Wetland ecosystems of Ethiopia have experienced severe degradation due to anthropological factors. The wetland ecosystems have been threatened due to shortage and expansion of cropland, overgrazing and shrinkage of grazing-land, open access and overuse of ecosystem services, etc., underlain by rapid population growth. As a consequence of changes in land use land cover, sloping areas faced raising erosion and depletion of nutrients required for vegetative growth. Increased erosion and the resulting sedimentation elsewhere can have a major impact on the lake hydrology (Feoli and Zerihun, 2000). Soil degradation, dwindling landholding-size plus its fragmentation, and increasing rainfall variability-induced decline agricultural productivity in the highlands of Ethiopia has resulted in the shift of farmers from upland to wetland-based crop production (Symeonakis and Drake, 2010; Sakané et al., 2011). Increasing food production from wetlands needs to be reconciled with protection of environmental resources. Striking the balance between maximizing benefits of wetland agriculture while minimizing adverse impacts on other ecosystem services has been described as the main dilemma of current policies on and management of wetlands (McCartney et al., 2010).
Wetlands of Abaya-Chamo basin, being within the Ethiopian Rift-valley, have been providing diverse goods and services to the people locally and away from the wetlands. However, the wetland resources have been severely threatened by the impact of largely anthropogenic factors. In fact, studies about land use/cover dynamics, ecosystem services-values, food security conditions, biophysical-geological changes of the lake-water, etc., have been conducted within and around Abaya-Chamo wetlands, Southern Ethiopia (Gelaw, 2007; Kebede, 2012; Uncha, 2014; Assefa and Bork, 2016; Teffera et al., 2017; Gelaw, 2019). But none of these studies has attempted to assess the current conditions and benefits of Abaya-Chamo lake-wetland, and the extent and driving forces of degradation of the wetland ecosystem. Assessing the services derived from the lake-wetland, the sphere of its degradation, and the direct and root causes of degradation is useful to formulate sound policy and sustainable management options about the lake-wetland resources (Boyd, 2012; CBD, 2015). This study was targeted to (1) asses the goods and services derived from lake Abaya-Chamo lake-wetland by the local people; (2) analyze the impacts of selected household and livelihood-related variables on the wetland ecosystem (degradation); and, (3) examine the driving forces of degradation of the lake-wetland resources.