045 - SMALL BOATS CAUGHT IN WATER HYACINTHS ON THE NILE, EGYPT (29°43' N, 31°15' E).
The water hyacinth (Eichhornia crassipes) was first reported at the beginning of the 20th century in the Nile delta in Egypt and in the province of Natal, South Africa. It is an invasive aquatic plant that originated in Brazil, where it grows at a moderate rate in its natural habitat. Introduced to Africa as an ornamental plant, in less than a century it spread to more than 50 countries around the world. An obstruction to navigation, this species can block agricultural irrigation canals and turbines in hydroelectric dams. It forms a thick vegetal carpet, which can double in area in twelve days and causes eutrophication—this is a fall in the oxygen content of deep waters, which leads to the asphyxiation of underwater life. No effective means of destroying this invader has been found to date, but organic defence methods could serve to limit its proliferation. Only 1 percent of introduced species cause major ecological and economic losses, but their presence remains the second cause, after the destruction of natural habitats, of the disappearance of species in the world.