Management of Invasive Aquatic Plans
Increasing trade, travel, and transport of goods across borders, has facilitated the spread of plants into ecosystems where they do not occur naturally. These plants are causing enormous damage to biodiversity and the valuable ecosystems upon which we depend. Direct and indirect health effects are increasingly serious and the damage to nature is often irreversible.
 Nuisance aquatic plants – or aquatic weeds - come in both macroscopic and microscopic forms. Macroscopic forms include such common plants as water hyacinth and macroalgae. Microscopic forms include algae and cyanobacteria, commonly called algal blooms when their concentrations are great enough to be visible and discolor the water.  Key challenges Invasive alien species can transform natural ecosystems and reduce biodiversity. Aquatic weeds can also impose high costs on agriculture, forestry, fisheries, water supplies, as well as on human health. For instance, mats of water weeds blocking the intake of the Owen Falls power station in Uganda cost the Ugandan Electricity Board $1 million per day. Weeds that choked Kisumu harbor during the 1996-8 outbreak of water hyacinth in Lake Victoria are estimated to have cost the Kenyan economy at least $1 million in lost catches from artisinal fishing.  Water managers typically underestimate the economic loss from invasions of aquatic weeds. Aquatic plants can seriously interfere with many water uses, including drinking water quality, accessibility, navigability, irrigation and hydropower production, water withdrawals, and ecological functioning. The potential health consequences of aquatic weeds can also be very significant. Often, aquatic weeds harbor vectors of disease. Weeds provide habitat for snakes and other dangerous animals. Some species of algae can produce potent toxins that can enter drinking water supplies.  Management of aquatic weeds starts with prevention and early detection. Once established, aquatic weeds are very difficult to control and usually impossible to eliminate. Control measures range from physical, chemical, biological, and environmental methods. Often different methods have to be combined for longer-lasting control of weeds or algae at reasonable costs and with fewer undesired side effects. Harvesting aquatic weeds can sometimes provide a product for sale.  World Bank Response Since the late 1990s, the World Bank has supported a number of aquatic weed management programs. World Bank projects address problems arising from aquatic plants in a wide variety of contexts. Projects funded by the Global Environment Facility play an important role. For instance, GEF supports the control water hyacinth and algal blooms in Lake Victoria and the control of a range of aquatic weeds in Southern Africa. The Bank has also been active in helping set up a secretariat for the Global Invasive Species Programme (GISP).  |
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