Titus Mula, a Kenyan fisherman, anxiously watched Lake Victoria from his home port of Kisumu. His apprehension was well founded as he observed the wind and waves carry a green mass across the surface of the water towards him. It was 2007, and Mula was keenly aware of the threat the weed posed to his livelihood as it had decimated the local fish population over the previous ten years. Lake Victoria has the second largest surface area of any lake in the world, but in the past two decades large portions of the lake have been covered in a particular type of vegetation—the hyacinth weed.
The water hyacinth—commonly referred to as hyacinth weed in Kenya—is an invasive aquatic plant species that has spread rapidly across Lake Victoria and can be readily found in ports like Kisumu. Although the weed is indigenous to South America, it is currently present on every continent except Europe and Antarctica. Its large blue flower and big green leaves makes it aesthetically pleasing in full bloom and a favorite aquatic species in water gardens. Man’s introduction of the plant to new environments, its ability to adapt to a variety of habitats, and its ability to reproduce asexually at a rapid rate have all contributed to the plant’s sudden emergence across the globe. Large colonies of water hyacinth, or mats, double in surface area every four to seven days—or an average increase of 8% every day. Vegetative propagation, the process through which the hyacinth reproduces asexually, means that it only takes one plant in ideal growing conditions to enact an invasion.
These factors have contributed to the proliferation of the weed into Lake Victoria through the White Nile since the 1990s, attaining a critical level of volume in 1997. Although only 6% of Lake Victoria—the Winam Gulf—is part of Kenya, Kisumu, Ndere, Homa Bay, and Mfangano are home to a disproportionate hyacinth weed population compared to Ugandan and Tanzanian waters. Indeed, the presence of water hyacinth in Kisumu (and elsewhere) has altered the aquatic environment, affected the local economy, and created serious health hazards. Controlling, eradicating, and reusing the weed are among the most pressing environmental issues in Kenya today.
The rapid emergence of the hyacinth weed has had devastating consequences for Lake Victoria and those Kenyans who lived around it. Hyacinth mats block rivers, clog irrigation canals and electric turbine intakes, hinder fishing, and create breading grounds for diseases like bilharzia, malaria, and river blindness.
It affects transportation and navigation on Lake Victoria for oar- and engine-propelled boats alike as the thick mats are virtually impenetrable. Dangerous predators like snakes and crocodiles can also ambush unsuspecting fisherman as they wade through the weeds towing their boats to open waters. Docking, particularly in ports like Kisumu, is quite difficult, inhibiting the loading and unloading of ships. Floating weeds make netting fish impossible, and have a negative impact on local fish populations as well.
According to biologist Brijj Gopal, “it has been estimated that the oxygen depleting load of one hectare of waterhyacinth (sic) mat equals the sewage created by 80 people. This action lowers the natural ability of the waterbody (sic) to absorb organic pollution, and creates [a] septic and odorous condition.” The ability of the hyacinth weed to dissolve oxygen content can render whole sections of freshwater bodies “dead zones”—often visible to humans in large-scale “fish kills”—while also providing a suitable habitat for new, non-native species which live on the mats, or predators like the invasive Nile perch in Lake Victoria that use the mats as temporary cover to stalk their prey. (Hyacinth mats may also provide cover for other fish species which the Nile perch prey on.)
These lifeless zones have been devastating for the fishing industry in Kisumu and other places affected by the hyacinth infestation. Titus Mula is just one of many fishermen whose livelihoods have been impinged upon by the invasion. Many people in affected areas like Kisumu have begun to use the weed in new industries as a result.
After initially dithering to control the spread of the hyacinth weed allegedly due to political factors, the Kenyan government has finally woken up to the devastating impact of the hyacinth weed. It tried out several methods to control the weed. One of the first control methods implemented by the Kenyan government in the 1990s was a manual picking program in which local Kenyans would physically extract the weed from the lake. The government hired fishermen who would pull the weed out of the lake by hand from their boats, drying them and later burning them in large piles. Mechanical control methods that have also been implemented include the building of floating barriers and using floating cutting and harvesting machines. Progress is slow, however, and the cost of labor is expensive. The danger posed to fisherman by disease and wild animals is exacerbated by the process of hand-picking the weed from the water too.
The chemical control method was another eradication process at the disposal of the Kenyan government. These chemicals (like 2, 4-D) can be sprayed by hand, boat, or aircraft to kill whole mats. The phytotoxicity of chemicals to natural vegetation and agriculture, however, can have serious consequences on human health and the surrounding environment. Indeed, the spraying of 2,4-D in the early 1970s caused a massive public outcry due to an increase in deformed babies and abortions in areas surrounding other chemical treatment sites in East Africa.
A third approach to controlling the hyacinth population is the biological method. Neochetina bruchi and eichhorniae, two weevil subspecies, have been part of the eradication effort in Winam Gulf because of their preference for hyacinth leaves and petioles. The introduction of weevils in Lake Victoria has had some success, but biological methods have limitations as well. The release of weevils on Lake Victoria in the late 1990s, for instance, hurt crop yields as the insects fed on maize grown around the lake in addition to their intended food source.
While “aggressive removal efforts…cut the plant back to manageable levels … in December 2006 … the water hyacinth was back.” In 2006 and 2007, “heavy rains and nutrient-rich runoff fueled an even more extreme outbreak. The plant-covered area increased from about 40 square kilometers in March 2007 to more than 400 square kilometers just a month later—about one-third of Winam Gulf.” As the National Aeronautic and Space Administration’s (NASA) satellite imagery indicates, farm run-off in November and December of 2006 during the wet season directly correlated with the explosion in the water hyacinth population on the lake because of the nitrogen content in fertilizer and pesticides.
In the meantime, as the government struggles to control the spread and impact hyacinth weed, local entrepreneurs have taken the initiative to turn the weed into profitable ventures. Behind every cloud there Isa silver lining. Indeed, small businesses in Kisumu have begun to turn dried water hyacinth stalks into ornamental objects, buckets, furniture including tables and chairs, and even coffins. (For example the weed was used to make a coffin for one of the most important Kenyan minister of the environment, Professor Wangari Maathai.).
Dried water hyacinth also has many applications in household gardening and industrial agriculture and livestock rearing. The plant is high in protein—comparable to milk protein—and is useful in plant and animal nutrition, as well as fertilization. One of the most efficient uses of dried water hyacinth, however, occurs when it is converted into fuel. Biogas is a combination of different gases which can be harnessed for energy use, particularly cooking. Chopped and ground and manually placed in fermentation plants and digesters, harvested hyacinth weed is a potential fuel source for many households throughout Africa and the Middle East, and has proven particularly useful in Kisumu.
Nevertheless, the growth and spread of water hyacinth colonies continues to pose a constant problem for Kisumu, and Lake Victoria as a whole. There is a need to control the weed. If eradication and control methods are imperfect then new strategies must be implemented to, if nothing else, sustain the economies which have been negatively affected by the plant. Indeed, physical, chemical, and biological approaches to controlling the plant can and have been integrated to diminish the weed’s population on Lake Victoria, but are not a permanent solution to the many problems the weed poses.
Many of these methods themselves have a detrimental effect on the environment as well, though they are still practiced with ambivalence by the government. A diminished fishing industry and potential health risks posed by the spread of the plant in Winam Gulf means that local economies in places like Kisumu will need to continue to reinvent themselves in order to utilize the abundant weed for their own benefit. Though the hyacinth weed has myriad advantages—as in the fashioning of ornamental wears and other craft goods, fertilizer, animal feed, and, most significantly, biogas—it is in the best interest of every Kenyan affected by the weed to participate in its manual harvesting if possible. If a sustained, comprehensive program—one that takes into account every influential factor in water hyacinth growth, from farming practices and pollution to biological control and economic use—Kisumu could be an example before the world in adapting to the weed.