The International Union for Conservation of Nature (IUCN) defines Invasive alien species (IAS) as species of plants or animals that are introduced by man, accidentally or intentionally, outside of their natural geographic range into an area where they are not naturally present. They are often introduced as a result of the globalization of economies, for instance by trade via ships, shipment of wood products infested with insects, or the transport of ornamental plants that then establish themselves into the wild and spread.
Invasive alien species, introduced and/or spread outside their natural habitats, have affected native biodiversity in almost every ecosystem type on earth and are one of the greatest threats to biodiversity. Since the 17th century, invasive alien species have contributed to nearly 40% of all animal extinctions for which the cause is known (CBD, 2006). IAS exacerbate poverty and threaten development through their impact on agriculture, forestry, fisheries and natural systems, which are an important basis of peoples’ livelihoods in developing countries.
The Convention on Biological Diversity has identified the following common characteristics of Invasive Aline Species:
- rapid reproduction and growth
- high dispersal ability
- phenotypic plasticity (ability to adapt physiologically to new conditions)
- and ability to survive on various food types and in a wide range of environmental conditions.
The introduction of IAS has the following adverse impact on biodiversity:
- decline or elimination of native species – through competition, predation, or transmission of pathogens;
- disruption of local ecosystems and ecosystem functions.
In the Philippines, invasive alien species like the water hyacinth are slowly creeping, menacing one ecosystem at a time, including otherwise healthy water bodies like Pasig River and Laguna de Bay and Agusan marsh, undermining their biodiversity and productivity.
A good predictor of invasiveness is whether a species has successfully or unsuccessfully invaded elsewhere.What are Invasive Alien Species? CBD 2010 https://www.cbd.int/invasive/WhatareIAS.shtml
National List of Invasive Alien Species of the Philippines