Over the last few centuries, human activities have spread a large number of animal and plant species from one region of the world to another. One of these species is the water hyacinth, a floating aquatic plant that is native to South America but is currently found in more than 50 tropical and subtropical countries around the world. Outside South America these water hyacinths lack natural enemies, and this has allowed them to grow and spread uncontrollably, which is disrupting the local ecosystems and affecting the people that depend on these ecosystems.
Water hyacinths have been a problem in at least two lakes I’ve visited on two continents – Inle Lake in Myanmar and Lake Victoria in Kenya, Uganda and Tanzania. In both locations water hyacinth growth is negatively affecting the fish population and consequently also the fishermen and the local communities. But in both cases the local people have also found a way to use the invasive plant to their advantage. While the people of Inle Lake are using water hyacinths to build floating gardens, in Kenya the locals are instead using crafts and design to turn the invasive plant into a source of income.
Water hyacinths as a problem
Water hyacinths started appearing on Lake Victoria around 1990 and since then they have become a major ecological problem. It is believed that the plant spread to the lake naturally through rivers from Rwanda, where it was originally introduced by Belgian colonists for decorative purposes. Water hyacinths grow at a very fast rate and without control they can completely cover parts of the lake, especially bays. The scale of the problem varies seasonally as the water hyacinths migrate from one part of the lake to another guided by wind.
The main problem associated with water hyacinths is how they affect the fishermen of the lake and subsequently the local economy. Water hyacinths reduce the amount of oxygen in the water, and because of this the fish population has been dropping. At the same time they block sunlight from entering the lake which affects native plants and subsequently also the fish. The plants also block harbors and make it difficult for fishermen to move in their boats. Water hyacinths shouldn’t take all the blame however, since overfishing and pollution are also significantly contributing to the dropping fish population.
Water hyacinths also induce a number of other problems, including heath risks. The plant can cover the lake so densely that it looks like solid ground, which can be dangerous for people who don’t know the area. The covered lake also provides excellent breeding grounds for mosquitoes which has increased cases of mosquito-borne diseases such a malaria. Water hyacinths also clog water intakes and they affect the quality of the water, which causes problems with water distribution and treatment.
Since the water hyacinths first appeared over 25 years ago, different measures have been taken to reduce their growth. One of the more successful measures has been biological control with South American insects. This has reduced the amount of water hyacinths from the peak years, but complete eradication is very difficult.
Water hyacinths as a solution
Despite being an invasive plant that disrupts the local ecosystem, water hyacinths don’t only have negative impacts. Lake Victoria is severely polluted by human activities, and according to some studies water hyacinths can clean polluted water and they are particularly good at absorbing heavy metals. And ironically, by blocking the fisherman from entering the lake the invasive plant could actually help protect the fish from overfishing, giving the fish population time to recover.
Even though water hyacinths alone can’t be blamed for the dropping fish population, the fishermen are surely being affected, and this is affecting a large number of people around Lake Victoria where people have depended on fishing for a long time. But while the fishermen are suffering, the water hyacinths have become are source of livelihood for a different group of people, especially women, who have formed a number of small crafts groups. These groups are turning the water hyacinths into useful products, and this not only helps remove the invasive plant from the lake but also generates income through sales.
The first stage of water hyacinth crafts is harvesting the plant from the lake. The roots and the leaves are cut off and only the stem is used. The stem is cut into thinner vertical strips and left to dry in the sun. Once the strips are dry, they are then woven together into ropes. Before weaving, the dried water hyacinths are first soaked in water with a chemical mixed in to make the weaving process easier. The resulting ropes can then be turned into different products such as baskets, bags or even furniture. The thickness of the woven rope is varied depending on the desired end-use, and the ropes can also be dyed.
Water hyacinths also have other potential uses. They are already used for making charcoal, animal feed and manure, and they could even be turned into biofuel. Even though this type of utilization can help remove some of the invasive plant from the lake, there are also risks associated with becoming too dependent on the water hyacinths. Too much dependence on water hyacinths as a resource might result in people trying to keep the invasive plant around, even if it harms the local ecosystem. Using the plant while it is around is a great way to benefit from a bad situation, but it is important to remember that the ultimate goal should be eradication. Thus it is important to plan for the future and to consider what local resources could be used to replace the water hyacinth when it is gone.