africawaterandenvironmentchallenges

BAD TIMES FOR FISHES

Hi everyone, here's my second blogpost on my Water and environmental challenges in Africa blog !

In the last post, I tried to expose a brief content about the water resources on the african continent. I exposed three kinds of water supply in Africa : Rainfall, Groundwater, and rivers. This short introduction didn't mention environmental changes.

I think we can understand water and environment changes in Africa from two points of view. First, how does the environmental changes can influe the human activites and needs. Second, how do human activities affect the environment ? The topic I chose today can be understood from the both points of view.

I use to follow satellites remote sensing accounts on Instagram (like ISS, European Space Agency, NasaEarth, ESA Earth) and a few months ago, one of these agencies published an post about the deterioration of the Victoria lake throught two satellite pictures. Thus today I decided to treat the case of an african lake. Generaly, lakes are threatened by human pressures and climate change as well. For this post, I would like to focus on how the human activities influence on african lake environment, espacially on the biodiversity issues.

As we don't first suspect, there are many lakes among the continent. I chose one freshwater transboundary lake : Lake Victoria. It is located in the middle-east of the continent, in the region of great lakes of Africa, on borders of three countries : Uganda, Tanzania, and Kenya.

Great lakes region

Lake Victoria Basin source : IUCN (International Union for Conservation of Nature)

Lake Victoria is the world's second largest freshwater lake by syrface area also the destination of many tourists. This region knows a huge demorgraphic increase all around the lake.

Travel to Lake Victoria, and get Natural

IUCN elaborated, with 200 scientifics, a survey that explores 5167 freshwater species in Africa to establish the Red list of threaten species. That includes fishes, mollusks, crabs, dragonflies and some aquatic plants.

According to this report, the Victoria Lake Basin is famous for its high range of freshwater biodiversity and endemism species. But, under the analysis, twenty percent of all freshwater considered in this survey are threaten with extinction and this rate rises up to 76% for the endemic species to the area. (2)

204 out of 5167 species are identified as endemic in this project. For exemple, the report estimates 78,2% of fishes of the sutdied area as endemic specimens to the basin. As they are endemic, these species are more vulnerable to changes. Indeed, while some common sepcimens can eventually leave the environment where they live to another, endemic species are more limited to move to other areas (2).

But why having to pack its suitcases?!!

In the report, it is exposed that overfishing is the primary threat to freshwater species of Victoria Lake. But other causes are identified. Pollution ( industrial, agriculture) is huge issue for lacustrine biodiversity. Today, Lake Victoria receives industrial releases and sewages. These mass of discharges are non-treated waters. I also found that freshwater biodiversity (espacially endemic species) is highly threaten by biological ressources uses : it includes organism (fishing for food for exemple) but also genetic ressources uses. (5) Invasive species are also highly responsible for decline of biodiversity in lake environments.

Invasive species case study : Nile Perch (Late Niloticus)

The most famous case, which also got noted with media attention, is the Nile Perch (Late Niloticus). This large freshwater fish (sometimes with 2 metres in lengh), also known as « captain » in some regions, is native of Ethiopia and has been inserted into the Victoria lake in 1954. This allochthonous species is a dreadful predator for other victoria Lake's species (6). The predator entered into competition and bring disorder between species and ecosystem balance. The Nile Perch adapted itself to the Victoria Lake habitat, and began to colonise the environment at the cost of other living beings (6).

This species is highly fished by local populations, and in this case, the human activity have positive consequences onto the environment, hopefuly, the decline of the Nile Perch population have been noticed because of overfishing.

That also can engage the question of the ecological process, that balances the biodiversity of the ecosystem with the return of species threaten by Nile perch before, or the depletion of biodiversity record.

Unfortunately, Lake Victoria is not an isolate case.

According to the UNEP (Africa's lakes : Atlas for our changing environment), the environmental situation of lakes in Africa is critical because of the diversity of its multiple uses by human populations (over-extraction of water, diversions from rivers feeding lakes (agriculture irrigation, domestic needs), pollution, extensive fisherie and invasive species. Anyway, not useful to repeat what I have said before : Victoria Lake issues are definitely illustrating what african lakes ecology are surffering from african society development (1). Ironically, this phenomenon is a cycle. Many people depend on fishing activities, fish protein ressources and biodiversity of the lake provides livelihoods to a large population, which is, moreover, growing again. Soon, ressources will disappear, and this decline will probably be responsible of social and political issues like ressources distribution (water, protein, irrigation...) and a lot of people won't have any livelihood anymore.

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