Invasive alien species (IAS) are either plants, animals or microorganisms that have been introduced outside their natural distribution area, and which exhibit rapid growth, reproduction and dispersal to such an extent that they are highly competitive to native species, destructive and difficult to control, particularly if the new ecosystem lacks the predators or pathogens of their own native range.

Their introduction to a new ecosystem threatens biodiversity, food security, human health, trade, transport and economic development. The cost of damage caused by IAS globally is estimated at USD1.4 trillion per annum1. The invasiveness of alien species lies in their adaptive behaviors, such as rapid growth, great dispersal characteristics, large reproductive capacity, broad environmental tolerance, and effective competition with local species.

The globalization of trade and industry has facilitated the mobility of people and goods over the past decades. Its effect is the increased associated transport of animals, plants and micro-organisms2. Shipping, for one, is a major pathway for the unintentional introduction of aquatic invaders when, for instance, some species get carried either in the ballast water or other parts of a vessel. Species introduction can be both intentional and unintentional. People export or import species for trade to support agriculture, aquaculture, horticulture, forestry, fisheries, food and others.

Some species introduction, employed for the biological control of certain pests, ironically turn out into major nuisances themselves. International aid organizations with altruistic intentions of introducing new sources of food to impoverished nations have brought in plants and animals that eventually grew to be invasive. Instances when exotic pets, such as snakes, monkeys and ornamental fish, are released into the environment by its owners also account for some of the intentional introduction of invasive species.