A native grass destroys Water hyacinth in Lake Victoria East Africa

By John W. Gichuki (PhD)

Water hyacinth locally known as “FORD” (the weed appeared in the lake at the same time as the dawn of multiparty democracy and also when Forum for the Restoration of Democracy was born in the early 1990s), is a perennial water herb and a native of tropical America. It has been classified as one of the worst aquatic weeds in the world. The weed has spread into many parts of the world due to its beautiful large purple and violet (lavender) flowers similar to orchids that make it a popular ornamental plant for ponds. In the areas bordering Lake Victoria, the weed was first recorded in Lake Kyoga (Uganda) in May 1988. Within Lake Victoria, it was observed in the Ugandan sector in 1989 Tanzania, in 1989 and Kenya in 1990.

Water hyacinth showing a beautiful flower

The weed forms thick mats over the infested water-bodies causing obstruction to economic development activities and impacting negatively on the indigenous aquatic biodiversity. Furthermore the weed affects the conditions of the water-body and life of the plants and animals in them. Floating mats of water hyacinth for example drastically curtail the penetration of light into the aquatic ecosystem thus inhabiting the growth of phytoplankton.

Early effort to remove water hyacinth

Initially efforts to control water hyacinth in Lake Victoria during the early 1990s were of limited success and were primarily directed at manually removing and conducting public awareness exercises. In the mid-late 1990s, management to combat water hyacinth increased with efforts such as the Lake Victoria Environmental Management Program (LVEMP-1) and U.S. Agency for International through development funding for coordination efforts by Clean Lakes, Inc. (Martinez, CA, USA). Control actions included bio-control using weevils, mechanical control using large harvesting and chopping boats known as the swamp devils

Biological success using water plant – hippo grass

A new approach to remove the water hyacinth effectively was devised with the use of water plant biological succession which culminated in the disappearance of water hyacinth in the Nyanza Gulf of Lake Victoria in 2008. The water hyacinth is destroyed through several stages

Stage of pure water hyacinth population

During this stage the plant community is entirely a population of water hyacinth.

Water hyacinth in a stage pure population

Early stages of succession,

Early stages of succession occur when the pure water hyacinth mats are invaded by opportunistic (usually surfacing/emergent plants) native invaders. The first common invaders were observed to be creeping water plants of the water potato family on the water hyacinth plants. In some areas, it is at this stage that scanty shoots of hippo-grass (which is the main food for hippopotamus) started to appear among the other plants.

Water hyacinth showing early stage of mat

Mid stages of succession

During the mid stages of succession, the invader native aquatic plants are found to coexist within water hyacinth. With the increase of the opportunistic emergent invaders, there is an observed decrease in the proportion of the water hyacinth in the mat.

Late stages of succession

During this stage, hippo grass has established itself within the community. Although the hippo grass is an emergent plant, its survival on water is by use of the water hyacinth as a substrate while proliferation within the community is because of the nutrients and detritus of the decaying water hyacinth. The buoyancy of the hippo grass is provided by the water hyacinth biomass. The results of this succession are that the proportion of the water hyacinth decreases further in the mat.

Water Hyacinth Colonized by hippo grass

Lack of sunlight

At this stage the water hyacinth is fully covered by the hippo grass owing to the fact that the hippo grass grows to height of 1.5 meters while the water hyacinth grows to a height of 0.5 m. The taller hippo grass shades the water hyacinth and other creeping plants from sunlight. The water potato however, evades the shading effects of the hippo grass by climbing/twinning itself around the hippo grass. The shaded water hyacinth and some creeping plants die off due lack of sunlight contributing significantly to the organic matter (rich in nutrients) which fuels more proliferation of the hippo grass. During heavy storms and wind activity, the population of the hippo grass is sloughed of the sheltered bays into the lake resulting into floating islands. The sloughing is aided by the compact mass of the hippo grass and its height.

Late stage showing being replaced with hippo grass

Exhausted water hyacinth

After the nutrient rich mat of the dying water hyacinth is exhausted, the hippo grass floating islands starts to die off since it cannot extract its food from the water as it normally lives on the shoreline of the lake. The few mats of water hyacinth existing under the mat do not sink with the mat but float out into the open water to start the new colonies of the water hyacinth mats.

This study observed large fragments of fleshly sunk hippo grass at the bottom of the lake indicating that indeed large amounts of hippo grass had sunk into the bottom of the lake. It is estimates that more than 3,000 hectares of hippo grass could have sunk to the bottom of the lake.

The climax stage of plant succession

Utilization of water hyacinth for poverty alleviation and Empowerment of local communities in Western Kenya

Water hyacinth was brought to Africa from Latin America by the virtue of its aesthetic beauty. It has flowers similar to orchids that make it a popular ornamental plant for ponds

The weed forms thick mats over the infested water bodies causing obstruction to economic development activities and impacting negatively on the indigenous aquatic biodiversity. Furthermore the weed affects the conditions of the water body and life of the flora and fauna in them. Floating mats of water hyacinth for example drastically curtail the penetration of light into the aquatic ecosystem thus inhabiting the growth of phytoplankton. It has therefore been christened the world’s worst aquatic weed.

Sinking mat of hippograss

In view of these facts most inhabitants in water hyacinth infested areas conceive the weed a serious environmental problem and as a pest to be eradicated.

Various studies on the water hyacinth have recognized that during the management of the water hyacinth, the utilization aspect is very important. For the developing countries the control of water hyacinth and other aquatic plants using the conventional methods is rather very expensive. Thus to be able to convert the biomass of water hyacinth to useful purposes instead of accepting the costs of its destruction is important for the economy of developing countries. Water hyacinth may also be used as part of a water purification process, since the plant has a high uptake of many substances dissolved in the water it floats on. Moreover harvesting of water hyacinth itself reduces infestation. It may also significantly reduce the underlying water nutrient levels and thereby slow down water hyacinth growth.

Supplemental source to improve the nutritional quality of grain protein and making of quality products

Finished water hyacinth product

Surprisingly the water hyacinth has some very crucial positive attributes. The leaves of water hyacinth are rich in protein, comparable to that of potato or clover. The plant has also a fibrous root system. The ash from the roots is rich in Potassium (K2O), Sodium (Na2O) Calcium (CaO), Phosphorous (P2O5) and Chlorine. In addition it has also high levels of amino acids that could serve as supplemental source to improve the nutritional quality of grain protein.

Local women making products from water hyacinth

Further, the plant is plant is abundantly available; grows readily without any need for sowing, weeding or fertilizing, does not require land space, costs nothing and to harvest it is to do an environmental favor.

Women groups have been assisting local population especially AIDS widows and orphans to get into handcraft making.

The women groups and local CBOs who have used the plant before indicated that they required empowerment and capacity building to utilize the water hyacinth. The training should focus on training in water hyacinth rope making and weaving, paper making and conversion and marketing. The training should have the theoretical and practical components. Training in product design and development is quite essential to be able to come up with quality products.

(The writer is a Research/Ecology Consultant based in Kisumu)