Written by Henry Neondo
A local community in Ethiopia is at risk of losing out on its livelihood following infestation of the country’s largest water body, Lake Tana by water hyacinth, Eichhornia crassipes.
This noxious weed is now abundant along 40 km of the northern and north-eastern shoreline of the lake, posing a significant threat to livelihoods, biodiversity and tourism.
“In the last year the fishing industry totally collapsed affecting thousands of fishing communities who are dependent on this natural resource,” says Ayalew Wondie, Assistant Professor in Aquatic Ecology at Bahir Dar University.
First reported in Lake Koka in 1965 and the Awash River, water hyacinth has since then been found in Lake Ellen and other rivers.
But it is infestation of the upper basin of the Blue Nile near the mouth of the Megeche River on the northern shores of Lake Tana, in September 2011 that is causing concerns.
Lake Tana is the largest lake in Ethiopia and provides livelihoods to over 3 million people living around it and is important as a source hydro-electric power generated at the Blue Nile Falls further downstream.
Other than being a significant water resource for crop and livestock production up to 1,454 tons of fish are caught each year at Bahir Dar, which the Ethiopian Department of Fisheries and Aquaculture estimates is only 15% of the sustainable catch.
The lake is also an important biodiversity hotspot - about 70% of the fish species in the lake are endemic.
In addition, many ancient churches and monasteries, some dating back to the 13th century, can be found on some of the lakes 37 islands attracting thousands of tourists to Lake Tana every year.
“Unless water hyacinth on Lake Tana is managed it will spread throughout the lake with serious impacts on local livelihoods and economic development in Ethiopia,” says Arne Witt, Regional Coordinator for Invasive Species, CABI.
Rezene Fessehaie, a weed scientist at the Ethiopian Institute of Agricultural Research (EIAR) is of the opinion that unless action is taken soon the impacts will be similar to those that were experienced on Lake Victoria. “It took years before an effective management strategy was implemented on Lake Victoria and by that time most of the damage had already been done – we cannot make the same mistake on Lake Tana”.
Infestations of this South American plant on Lake Victoria had significant impacts before the introduction of host-specific and damaging biological control agents reduced the extent of the infestation.
Water hyacinth on Lake Victoria reduced water quality, increased the incidence of vector borne diseases, contributed to the migration of communities, fuelled social conflict and made it more difficult for communities to access water points.
The infestations also resulted in a reduction in fish catches, increase in transportation costs, fewer tourists, blockage of irrigation canals, increased water loss through evapo-transpiration, siltation, increased potential for flooding and a decline in aquatic life.
For example, mmaintaining a clear passage for ships to dock at Port Bell in Uganda cost US$3-5 million per annum while cleaning of the intake screens at the Owen Falls hydroelectric power plant at Jinja in Uganda cost US$1 million per annum.
“Increased cooperation between the Bahir Dar University, the Environmental Protection Agency, EIAR, CABI and other stakeholders will go a long way to managing water hyacinth on Lake Tana,” says Fessehaie.
However, says Witt, “We will have to accrue considerable financial and human resources before we can initiate any effective management strategies.”
He is hopeful, as are others that resources will be made available in the very near future to protect Lake Tana and the millions of people who depend on it. “It is the source of all life in the region,” says Wondie.