According to a
BBC News Online report by
Alex Kirby the
IUCN has estimated that worldwide
invasive species cause $400 billion of damage a year!!!
Speaking at the
annual meeting of the governing council of the
United Nations Environment Programme,
Dr Klaus Toepfer, executive director of UNEP, said
invasive species were one of the greatest threats to Africa's wildlife.
A report also published at this meeting entitled "
Alien Invasive Species in Africa's Wetlands" gives a number of examples of the damaging effects individual invasive species have already had. These include;
*
Nile perch, an alien fish introduced to
Lake Victoria in East Africa, which constituted
1% of the annual catch soon after its introduction in the 1960s but which now makes up
80% of the catch, and is thought to have
helped to drive more than 200 native fish species to extinction.
* The ornamental
water hyacinth which now forms very dense floating mats on many of East Africa's freshwater lakes. These fast-growing mats can be extremely difficult to destroy and cause serious problems when they
block water supplies, harbours + hydro-electric dams...
* The
Red fern (
azolla) which also smothers lakes, but in this case provides the perfect
breeding grounds for mosquito larvae + for
snails carrying bilharzia, a debilitating disease which infects about
300 million people...
For further details see the
Global Invasive Species Programme +
Ramsar Convention of Wetlands websites...