The term invasive plant is synonymous with exotic and non-indigenous plant taxa, that quickly invade none native habitats through natural and man-made effects (Colautti et al., 2014; Crystal-Ornelas et al., 2021; Hartley et al., 2006). They are none-native plants, also called alien plants, which invade natural habitats causing environmental destruction, modification and immense socio-economic losses in the natural habitat (Crystal-Ornelas et al., 2021). Furthermore, invasive plant species have the potential of rapid expansion to new habitats and become a threat to native biodiversity (Early et al., 2016; Rohr et al., 2015). As an invasive alien species, the water hyacinth has a unique ability of producing a large number of offspring and easily spread over a considerable area (Bradley et al., 2022; Rejmánek, 2000). The origin of the water hyacinth is traced to the Amazon basin in South America, and north-eastern Brazil (Oliveira Junior et al., 2021; Simpson et al., 2022). The plant species later invaded Columbia, Guyana, Surinam, Venezuela and to other parts of the world (Karouach et al., 2020; Pagad et al., 2016). The worldwide distribution of water hyacinth was documented in more than fifty countries since the plant was first discovered in the early 1800s (Karouach et al., 2020). Subsequently, water hyacinth has been listed as one of the top worst weeds in the world (Sindhu et al., 2017; Weidlich et al., 2020; Zenni et al., 2021). Water hyacinth presently covers large areas of global water bodies and has become a challenge for developmental activities and the environment (Enyew et al., 2020; Hartley et al., 2006). Its rapid expansion depend on anthropogenic activities such as urbanization, agriculture, water transport and natural factors such as wind direction and wind-induced waves (Adhikari et al., 2019; E. Asmare, 2017).
In addition to natural and anthropogenic activities, accidental mechanical removal and animal movement increase water hyacinth expansion and invasion are (Amgoth et al., 2023; E. Asmare, 2017; Weidlich et al., 2020). In favorable reproductive environment, the water hyacinth grows and replicates itself two times in every five days (Firehun, 2017; Pérez et al., 2008). The plant’s life cycle shows that it is perennial, herbaceous, and free-floating over the water body (Subash, 2016; Kgabo H. Thamaga & Dube, 2019). However, its rapid infestations resulted in high competition with native species, as it prevents oxygen and sunlight from penetrating water bodies (Oliveira Junior et al., 2021; Subash, 2016). The plant has the ability to tolerate changes in environmental parameters such as water temperature, nutrients concentration and pH levels (Hartley et al., 2006; Van Kleunen et al., 2010). At newly covered wetland the plant can easily adapt the new habitat but causes oxygen blockages into the water body which diminishes biological diversity in the ecosystems (Eguavoen & Tesfai, 2012; Subash, 2016).
The invasion of water hyacinth has a negative impact on water quantity and quality through reducing the irrigation capability of the water; affecting the fishing and fish products industry; threatening human health, and damaging the environment (Mainali et al., 2015). Its expansion over the water bodies has negative impacts on socioeconomic and environmental health, and these impacts are detected through reduced fish breading and low fishing grounds, closing of the irrigation canals and restricting swimming and boat traffic (Adhikari et al., 2019; Harun et al., 2021; Mainka & Howard, 2010). In Africa, the spread of invasive plants is a well-known phenomenon affecting aquatic habitats in the Sub-Saharan region (Cordeiro et al., 2020; Early et al., 2016; Mukarugwiro et al., 2021; Yan et al., 2017). Ethiopia is a Sub-Saharan country, where the country's aquatic system, including freshwater bodies, marshes, and wetlands, has been severely impacted, and its native species' biodiversity richness and evenness have been dominated critically by the water hyacinth (Merga et al., 2020; Weidlich et al., 2020). This invasive plant has become a major problem in Ethiopia, as it has degraded the quality and quantity of wetlands, as some have dried up, becoming a breeding ground for hazardous vectors such as insects (Hartley et al., 2006; Tewabe et al., 2017).
The invasion of the water hyacinth has gravely threatened the livelihoods of rural communities that rely on the ecosystem services, as well as the reduction in the diversity and richness of native vegetation (Navarro & George, 2000; Peter, 2009). Its invasion was observed in several Ethiopian rivers, including Abay River, Baro-Akobo River, and other freshwater bodies (Firehun, 2017; Nega et al., 2021). Currently, the plant is being disseminated in Ethiopia in several water bodies (Churko et al., 2023; Type et al., 2023). It has shown a rapid spread in Awash River lakes (Churko et al., 2023; Shiferaw et al., 2018). Water hyacinth was initially purposely imported as an ornamental plant to Ethiopia's water bodies in the mid-19th century (Merga et al., 2020; Shift et al., 2021). The species quickly spread to numerous adjacent bodies of water, including Lake Ziway and Koka. Some findings suggested that the plant started to spread more than 60 years ago, in 1960 (Abhachire, 2014; Shift et al., 2021). Its spread in Lake Koka and Lake Ziway is alarming and detrimental to the environment and livelihood of nearby communities (T. Asmare et al., 2020; Enyew et al., 2020). The vast majority of these communities are small-scale farmers, particularly, those who reside near wetlands (Dersseh, Melesse, et al., 2019; Van Oijstaeijen et al., 2020). The wetland zone residents are mostly fishermen and smallholder farmers whose livelihoods are highly dependent on these natural systems (Shiferaw et al., 2018). Its invasion has caused the destruction of croplands, loss of pasture and indigenous grasses including some tree species (Ant et al., 2022; Peter, 2009). Remote sensing has been frequently employed in assessing the spread of the water hyacinth. In the categories of supervised classifications, the maximum likelihood algorithm was used to predict the expansion of water hyacinth (Alam, 2020; Buchari et al., 2017). Analysis of changes in land use and cover (LULC) is a methodical approach that supports environmental sustainability by helping to understand both the physical and non-physical interactions with the natural environment. An overview of current and potential future development paths is provided by research on the spatiotemporal shifting patterns of LULC and by simulating future scenarios. Using an integrated CA-ANN approach within the MOLUSCE plugin of QGIS, independent variables like distance from roads and DEM were employed. This approach can forecast, assess and appreciate the plant’s invasive patterns. The assessment of water hyacinth and other invasive plant species expansion using remote sensing is important for integrated water resource management (Ficetola et al., 2007). Hence, quantifying the past, present and future distribution of water hyacinth over Lake Koka and Ziway and identifying the relative impact on the livelihoods and the environment is critical. This study aimed at formulating policies and plans for long-term land and water resource management practices by assessing past, present, and future potential expansion of water hyacinths on Lake Koka and Ziway, using a multispectral remote sensing approach. The study provides important information on the invasive species and their effects on water resources for designing management plans and strategies.