Invasive alien species refers to those species that occur outside their natural range and are known for their intensive colonizing capacity and potential to change the structural and functional composition of an ecosystem. Species invasions are considered to be the second largest threat to biodiversity on Earth. Species invasion is a common problem of both developing and developed nations; however, due to lack of knowledge and resources, they carry a prominent impact in developing countries like Nepal. The impact of the invasive species needs to be identified and addressed timely. 

Eichornia crassipes, commonly known as water hyacinth or “Jalkumbhi” in Nepali is considered to be one of the most notorious aquatic weeds. Eichhornia crassipes is an aquatic plant that grows to a height of three feet and has thick, round, wide leaf and blue-purple flowers. Due to its capacity for both sexual reproduction via seed propagation and asexual reproduction through vegetative propagation, water hyacinth possesses reproductive traits that are well-suited for achieving invasive success. The plant is known for its fast growth rate, wide distribution, and excellent tolerance for temperature, pH, and nutritional changes. Therefore, it is listed among the 100 of the world’s worst invasive alien plant species.

Native to South America, water hyacinth is speculated to be introduced to different countries because of its beautiful flower. The invasion of water hyacinth has been reported from different parts of the world including Asia, South America, Central America, Australia, New Zealand, etc. Water hyacinth incursions mostly impact warm equatorial locations, where rivers and wetlands are more frequently and severely affected. Water hyacinth was first reported in Nepal during the 1960s and since then it has colonized different water bodies across the country. Water hyacinth is mostly distributed via floating rosettes that separate off the developing mat. During the past decade, water hyacinth has emerged as a persistent issue in several lakes of Nepal, including Phewa Lake, Begnas Lake, Khaste Lake, Ghodaghodi Lake, and Bishazari Lake. 

The highly invasive plant has an ability to cover the entire water body that reduces the light penetration which ultimately reduces the primary productivity and can also deplete the oxygen level that disturbs the overall ecosystem of the water bodies. Different studies have shown that the presence of water hyacinth has a negative impact on water birds and aquatic lives. The invasion of water hyacinth can result in a depletion of water quality and a decrease in the availability of open water regions for endangered bird species, leading to a fall in their populations. Water hyacinth invasions benefit exotic and invasive fish species that compete with the native fish which threatens their existence. The thick layer of water hyacinth can alter the natural runoff which in turn can result in flooding. Water hyacinth also carries a socio-economic impact by limiting fisheries and recreational activities. While commonly regarded for its detrimental effects, water hyacinth exhibits some positive attributes as well. Water hyacinth can remove toxic pollutants from the water and its dense root provides habitat to different macrophytes. In addition, water hyacinth has been used as livestock fodder and in the production of paper, rope, etc. 

The proper management of water hyacinth is very crucial due to its highly invasive nature. If left unchecked, water hyacinth can disrupt native ecosystems by outcompeting local vegetation, decreasing biodiversity, and clogging waterways. Therefore, it is imperative to control and manage its population. Different physical, chemical and biological methods have been adopted worldwide to control the invasion of water hyacinth. Physical method involves the removal of water hyacinth manually or mechanically. However, the removal by physical method is not feasible for a larger area since it is quite tedious and expensive. Despite being a cheaper and effective alternative, the use of chemicals to remove the weed has proven to be highly toxic for the aquatic ecosystem. Therefore, the biological control of water hyacinth by the use of their natural enemy is seen to be the most effective and sustainable removal method.  

Different efforts have been taken in Nepal at the local level to mitigate the invasion of water hyacinth. Pokhara Metropolitan City has employed a traditional fisher group to remove water hyacinth. However, the effort has not been sustainable as they have to remove the water hyacinth on a regular basis. The Rupa Lake Restoration and Fish Farming Cooperative (RLRFFC) has been playing a significant role in the removal of water hyacinth from Rupa Lake. They have introduced the grass cutter fish for removing the vegetation. The introduced fish not only removed the water hyacinth, it also removed other native vegetation reducing the food availability for many other species. Furthermore, the introduced fish later on damaged the paddy of the nearby field as well for which RLRFFC was forced to pay compensation. Biogas plant was constructed in nearby two houses with the motive of using the water hyacinth for fuel production. The project became irrelevant after the grass cutter fish was introduced in the park. Similarly, water hyacinth from Jakhor lake had been managed with the help of Nepal police and Nepal army. However, the management of water hyacinth has been primarily based on physical removal and not in identifying and utilizing its potential role.

Water hyacinth has been found to be effective in the removal of pollutants from the waste water. The use of water hyacinth in the sewage system can be a potential way for its proper utilization. Water hyacinth can be used in production of bio-gas and bio-fertilizers. Additionally, water hyacinth also possesses significant medical properties. It carries anti-cancer, anti-fungal, anti-inflammatory and antibacterial properties which can be utilized in curing different health alignments. Therefore, by identifying the potential ways in which water hyacinth can be utilized, we can develop comprehensive management approaches. These approaches can focus on utilizing the plant resources efficiently while controlling its spread in aquatic ecosystems. Through proper management, we can mitigate the negative impacts of water hyacinth and promote its sustainable utilization for various beneficial purposes thereby striking a balance between environmental conservation and socio-economic development.