The threat of invasive species has been an ongoing and increasing challenge globally. It is anticipated that climate change will exacerbate this challenge. Being particularly vulnerable to invasion by alien species, Small Island Developing States (SIDS) will be further threatened under conditions of climate change. Therefore, in addressing these issues, in this chapter we seek to:
Definition and Examples of Invasive Species
Invasive species threaten the ecosystems they occupy. If they become established and expand, they pose a risk of degradation to the invaded habitats and/or suppression or extinction of other species (Kairo, Bibi, Cheesman, Haysom, & Murphy, 2003; IUCN, 2011). These invasives may also affect processes such as the nutrient and water cycles as well as fire regimes. Invasive species are alien, i.e. introduced from the geographic range where they have existed historically into territories which are ecologically/environmentally different and more conducive to their spread (e.g. in the absence of natural enemies and other species that would compete with them for resources). Some indigenous species can also become invasive if abiotic or biotic changes in their habitats, such as extinction of a major competitor or natural enemy, lead to greater availability of space, light or other resources. Species exhibit varying levels of invasiveness which are mainly influenced by environmental factors (CBD, 2013).
Crop related invasive species (IS) include, insects, viruses, microbes, protists, fungi, plants and animals. Through its association with human activity insects have become frequent invaders. Several invasive alien species (IAS) are associated with host organisms as predators or parasites; the hosts or vectors may be non-invasive but can carry pests or diseases that become invasive in new environments (Moutou & Pastoret, 2010). Most invasive species recorded in SIDS are not pests of agricultural crops, however many invasive pests have been introduced and established in islands, resulting in high economic cost to the agriculture sector.
Some examples include:
(Kairo et al., 2003; Lowe, Browne, Boudjelas, & De Poorter, 2000.)