Increasingly over the past years, exotic invasive species have become recognized
as a significant cause of species declines and habitat degradation. Although
exotic species may increase species richness temporarily, over the long-term
they contribute to species extinction, reduce biological diversity and induce
changes unpredictable change to ecosystem dynamics and function. This threat
is most significant when introduced species persist as predators, disease vectors
or competitors in an ecosystem. Ultimately, exotic species alter ecosystem processes
and threaten sustainable populations of native species, leaving behind the difficult
and costly human task of restoring ecosystem structure and function.
In marine and coastal habitats, species introductions have historically occurred and continue to occur largely through the inadvertent translocation of sessile adults attached to ship hulls and as larvae carried in ballast water. Increasing evidence of this human induced threat has lead the International Maritime Organization (IMO) to develop guidelines, best practices and technologies to address this threat.
Additionally, a number of national, regional and international legal instruments have evolved in recent year to prevent unwanted introductions. However, there remain a number of gaps and inconsistencies with these existing instruments, and few go beyond prevention, to address the very important social and economic considerations of eradication and control of existing exotic invasive species.
As for the future, some researchers now predict that exotic invasive species will soon become the leading cause of ecological degradation in human-disturbed habitats. But, despite increasing attention from the scientific community, the current ability to predict the biological, social and economic impacts of exotic species introductions remains limited.