Scholars say eradication efforts on the water hyacinth, “Emboch”, which has seriously rocked the ecosystem of Lake Tana, may not bring sustainable and desirable outcome unless the root causes for the infestation are addressed as soon as possible.
Tadese Fetahi Associate Professor of Aquatic Ecology at Addis Ababa University says even though it is appreciable that the problem gained due attention nationwide with the relentless efforts of different stakeholders, the root causes for the expansion of the invasive Emboch has been unnoticed.
According to him nutrient and the scarce resource are major factors that have kept the weed spreading and created bottlenecks on the eradication efforts.
As a result, the situation has been spreading on other lakes in the country even if the volume and rate of damage are different, he adds.
Tadesse notes excess availability of phosphorus and nitrogen, which are essential nutrients for photosynthesis or primary production in aquatic system, allows invasive weeds, such as water hyacinth to aggressively use the available resources and easily establish in the system. Such anthropogenic enrichment of nutrients is called eutrophication or nutrient pollution.
In the case of Ethiopia, Tadesse says the principal sources of Eutrophication are industrial, municipal wastes, agricultural and urban runoffs. Speaking of agricultural
effects, he indicates that not only low forest coverage but also sloppy farmland and cultivation system, conversion of wetlands, lake shore degradation aggravate soil erosion and nutrient runoff. “Runoff from agricultural land is one of the major sources of non point nutrient pollution,” he adds.
Urbanization on the other hand is the other major source of nutrient pollution according to him. With the rapid growing of urban population and urbanization as well as manufacturing and industrial growth in Ethiopia poor sanitation service liquid waste could result water quality degradation and eutrophication.
Therefore, Tadesse notes that eutrophication due to agriculture expansion and intensification, urbanization, industrial growth, promote prolific growth of algae and aquatic vegetation such as invasive water hyacinth. Thus, he stresses that if nutrient influx to aquatic ecosystem continues the current water hyacinth controlling endeavor is futile exercise.
Birhanu Wubneh an expert in fishery resources and fisher Man around Lake Tana says he has conducted several researches on the ecosystem and surrounding effects. He tells The Ethiopian Herald that the issue of the water hyacinth, Emboch, has not been understood in detail, which is why the eradication efforts did not go on expected level and speed.
The efforts to control the weed using manual removal and machine-based harvesting have been applied, though the magnitude and intensity of control activities have not slowed down the expansion of the weed.
“Most of the efforts are undertaken in a way that did not understand the ecosystem of the Lake. For instance the harvesting machines that have been used on the wetland areas of the North-East shores of the Lake are not successful due to the volatile behavior of the areas in different seasons.
They have a behavior of reducing during summer times and increasing volume of water on winter he notes.
According to, Brihanu, there are local methodologies that could rescue the lake from this invasive hyacinth if they are implemented with integrated disciplines.
As to Assefa, controlling of point and non point nutrient pollution should be seriously considered in the weed controlling strategies. He says soil and water conservation and afforestation programs, including fruit trees, fodder grass, need to be reactivated.
According to him, it could also be better if there are buffer zones that could limit the extent where farmers should do their farming and cover the buffer zone with value added fruit plants and fodders. He also stresses this is not an issue that only concerns Tana.
Based on the research conducted by Ethiopian Environment and Forest Institute, there are three possible ways to reduce the expansion rate of the weed, which are biological, chemical and physical. Meanwhile, the study suggests that biological method based on the use of natural enemies of the invasive hyacinth is the best option.
However, Assefa argues that if the root causes are not given due attention and the eutrophication is not controlled, the weed may heavily affect many other lakes throughout the country. Scientists, governmental and nongovernmental actors both in Federal and State levels have to work closely, both Assefa and Brihanu agree.
The Ethiopian Herald February 23/2019
BY HENOK TIBEBU
