The Ecological and Economic Threats of Invasive Alien Species

Invasive alien species are species that do not naturally occur in Namibia but which have been introduced either directly or indirectly and have the potential to cause harm to the environment and economy.

• Loss of biodiversity, through competition and displacement of indigenous species
• Reduced stability and productivity of natural ecosystems
• Increase in human and animal diseases and allergies
• Reduction in soil and ground water and other natural resources
• Choked drainage lines and waterways
• Threat of extinction to indigenous species
• Hybridization and loss of genetic diversity

• Lower yields of agricultural crops, fish and other wild species
• Threats to agricultural exports
• Reduced cultural and tourism potential
• Creation of conflicts about resource use-selection of indigenous vs. alien species
• Control and rehabilitation costs

Imported food, plant material and animal products have introduced some of the world's most serious pests and diseases into Namibia. Failing to declare quarantine items could devastate our fragile environment, agriculture and tourism.

(Text of poster compiled by Joyce Katjirua and Pierre Smit on behalf of SADC Biodiversity Support Programme. More information.)

A relevant quotation:
"Given that the impact from invasive alien species can be direct, indirect, cumulative and/or complex, unexpected, surprising and counter-intuitive and that they often only show after considerable lag times, any alien species must be considered 'guilty' until proven 'innocent', where the risk of becoming invasive is concerned." (McNeely et al, 2001).