The effect of insecticides on the environment
p. 88
Résumé
From 1973, in order to make riparian areas suitable for agriculture, large quantities of anti-simulium insecticides were discharged into the rivers of West Africa as part of the OCP programme.
Texte intégral
1The 1970s saw the launch of a large-scale campaign in West Africa to control the populations of black flies, the vector for human onchocerciasis. Large amounts of insecticide were discharged into the rivers of the region week after week, with a potential environmental impact that researchers endeavoured to study. First of all, they had to understand the initial ecological functioning of ecosystems and the local aquatic invertebrates and fish. This presented a challenge as, at the time, they only had a rather incomplete list of species to work with.
2Then they had to define the acceptable limit of the impact of pesticides on the environment. If the slightest effect was observed on fish populations, or when black fly larvae developed resistance, it was imperative to change insecticide, for example by switching from temephos to chlorphoxime, to a bacillus capable of eliminating larvae. This extremely effective strategy involved monitoring the ecosystems treated in real time, to maximise the effect of treatment while minimising costs and the environmental impact.
3For the entire duration of the 20-year programme, many African researchers were trained to ensure the ecological monitoring of the environment. Studies ultimately showed that the treatments, on balance, had little influence on the fish populations which provide the inhabitants of landlocked countries with essential protein intake. While initially unforeseen effects were observed subsequently, these are not linked to insecticides: land recolonisation by local peasant communities, combined with the setting up of water-intensive agri-food industries (cotton, sugar cane, etc.), contributed to deforestation and environmental damage, resulting in overall ecological degradation.
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