The negative economic impacts of
water hyacinth infestations have long been appreciated. In the United States,
the problem was so serious that the
American Congress in 1897 made an appropriation to study the problems posed by
the weeds.
Texas now spend $1 I million yearly trying to control water hyacinth in
infested waterways. In the Sudan,
the control of water hyacinth is estimated at $10 million annually.
The ECOWAS Report (1995) examined
the socio-economic impacts of floating weeds in the ECOWAS region. In the
fisheries sector, the potential losses as a result of water hyacinth
infestation in the sub-region was put at $20 million. Estimate of other experts indicated
that at current infestation, the losses could even be of the order of $68
million for the affected countries. Their calculation was based on 20%
infestation and 40% fish catch reduction in infested waters.
Irrigated agriculture is of crucial
importance in the ECO WAS region.
Aquatic
weed infestation causes marked losses in agricultural production. The order of
magnitude of the losses in the region when the production of irrigated
agriculture would drop by 1% was estimated at $36.8 million.
The
estimated losses in hydro-energy production in the sub-region' was put at
between 7 and 14 million US dollars. It noted that the losses could be
substantially higher.
In
several countries in the sub region, energy production is regularly interrupted
for a number of days, as the inflow to the turbines had to be cleared of weeds.
Water
hyacinth also reduces the volume of water in the reservoirs through (a)
Mechanical Control harvesting evaportranspiration. A summary of
losses caused by floating weeds is given in Table
1. Using a defensive expenditure
approach, the World Bank report, "Towards the Development of an
Environmental Action Plan for Nigeria"
estimated that water hyacinth control in Nigeria would cost $50 million
annually and that the species negatively affects about five million people
(Western African Department, 1990; West Central Africa Department, 1995).