Water hyacinth in Lake Victoria
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Water hyacinth is a major invasive plant species in Lake Victoria. While native to the continent of South America, human activity introduced the plant to Lake Victoria around the 1980s.[1] It negatively affects the local ecosystem and people. The presence of water hyacinth in Lake Victoria is associated with lower amounts of dissolved oxygen in water and increased water acidity.[2] It is also correlated to a higher risk of malaria, schistosomiasis, and cholera.[3] Economically, the weed has damaged the fishing industry through reducing catchability of fish, and of boat transportation.[4] Biological control agents have been used to control the growth of water hyacinth, and satellite monitoring is used to track its spread.
The exact time and place of introduction of water hyacinth into Africa has been a topic of debate. As its flowers are reputed for their beauty, it may have been brought over as an ornamental for garden ponds by Belgian colonists in Rwanda and Burundi.[5] Water hyacinth is currently theorised to have physically entered Lake Victoria from Rwanda via the Kagera River,[6] most likely in the 1980s[7]. The hyacinth has since spread prolifically, due to a lack of natural predators, an abundance of space, and agreeable temperature conditions. Abundant nutrients are also present in the lake, exacerbated by increasing levels of heavy metal pollution.[8][9]
The population of water hyacinths increased rapidly between 1992 and 1998.[10] Their population was greatly reduced by 2001, but has since resurged to a lesser degree.[11][may be outdated as of February 2025] Management techniques include insect controls and manual beach cleanup efforts.[12] Water hyacinth infestations are rarely exterminated in full; instead, they must be continually managed to prevent excessive regrowth.[5][13]
Development
Water hyacinth negatively affects the people living around Lake Victoria. Its proliferation has halted fishing by reducing catchability [14]. While this has impeded overfishing, it has also resulted in economic losses. The presence of water hyacinth has increased disease presence, as it creates breeding areas for mosquitoes and other insects. This has led to a higher risk of skin rash, cough, malaria, encephalitis, gastro-intestinal disorders, and bilharzia/schistosomiasis. Water hyacinth also interferes with water treatment, irrigation, and water supply.[8] It can smother aquatic life by deoxygenating the water, and it reduces nutrients for young fish in sheltered bays. It has blocked supply intakes for the hydroelectric plant, interrupting electrical power for entire cities. The weed also interrupts local subsistence fishing, blocking access to the beaches.[13]
There are also indications that water hyacinths can provide benefits to the Lake Victoria Region.[15] Water hyacinths have been planted in an attempt to purify eutrophicated water.[16] Once established, the plants can be harvested and used for biogas production,[17] fertilizer, and other things.[18] In 2018, two biogas digesters were installed in the village of Dunga in Kenya, with many more slated to be installed in Kenya.[19] Water hyacinth can also be tested for other uses, like sea cucumber that is being used to make some medicine from its chitin and chitosan.[citation needed]
