The livelihoods of thousands of people who depend on Lake Victoria are at risk as pollution and over-harvesting drive hundreds of species to extinction.
According to a report by the International Union for Conservation of Nature (IUCN), which assessed the global extinction risk of 651 freshwater species native to Lake Victoria, 20 per cent of these species and 76 per cent of the 204 fresh water species which are only found in the lake, are at risk of extinction.
The report, Freshwater biodiversity in the Lake Victoria Basin, says climate change, pollution from industrial and agricultural sources, over-harvesting and land clearance for agriculture has led to the decline of some species, including the African Lungfish, putting millions of livelihoods at risk.
“The Lake Victoria Basin is incredibly rich in unique species found nowhere else on earth, yet its biodiversity is being decimated. The effects on communities that depend on the lake for their livelihoods could be disastrous,” said Will Darwall, the head of IUCN’s Freshwater Biodiversity Unit and a co-author of the report.
Major threats to the lake’s ecosystem include pollution from agricultural effluent including nutrient loads, herbicides and pesticides, industrial effluent and domestic sewage (including solid waste) and pharmaceuticals from urban areas discharged into the lake. They are affecting 57 per cent of all species and 88.3 per cent of threatened species native to the Basin.
A recent study by Tanzania’s University of Dar es Salaam on lakeshore sediments revealed high concentrations of zinc, copper and lead metals while a separate study by Uganda’s Makerere University identified alarming levels of lead in yams cultivated in Nakivubo wetland through which Kampala city’s effluent flows before discharging into Lake Victoria.
According to the report, the sharp rise in overharvesting of the lake’s resources is due to more and more people opting for advanced modes of harvesting fish using outboard motors and trawlers in place of the less efficient paddle canoes.
The number of fishermen has also increased from 50,000 fishermen using about 12,000 fishing boats in the 1970s to over 200,000 people and 60,000 boats in 2015.
There are more than 2,000 new vessels appearing on the lake every year, according to the Lake Victoria Fisheries Organisation (LVFO), the body charged by the East African Community with safeguarding the lake’s future.
In addition, clearance of land for agriculture, which supports more than 70 per cent of livelihoods in the Basin, has also been cited as a major threat to the lake, negatively affecting 44 per cent of the fresh water species and 17 per cent of threatened species.
“Invasive species also present an important threat to native biodiversity in the Basin, affecting 31 per cent of all species and 73 per cent of threatened species. The purple-flowered water hyacinth was accidentally introduced into the lake from South America in the 1980s, and at its peak, covered close to 10 per cent of the lake surface,” the study said.
Among the most threatened fish is the Nile Perch, one of the main commercial fish species in Lake Victoria, which was introduced from lakes Turkana and Albert between the 1950s and 1960s.
Last month, Tanzania, Uganda and Kenya launched a $1.8 million initiative dubbed Operation Save the Nile Perch to increase the fish stocks in the lake and save it from extinction.
Tanzania’s Ministry of Livestock and Fisheries data shows that Tanzania harvested an estimated 300,000 tonnes of Nile Perch, Kenya about 50,000 tonnes and Uganda 350,000 tonnes in 2017.
However, out of the 101,573 tonnes of Nile Perch harvested in 2015, only 8,337 tonnes were mature fish.
“The risk of extinction for freshwater biodiversity in the region is increasing. The Lake Victoria Basin is home to hundreds of species which have not yet been described,” said Catherine Sayer, IUCN programme officer and co-author of the report.
Lake Victoria is the largest freshwater fishery in Africa producing 800,000 to 1,000,000 tonnes of fish annually, worth around $600 million.