Alien Invasive Species

Elaine Blum 2009/Marine Photobank

Marine menace—an overview of the marine invasive species issue

More than 70% of the earth is covered by oceans and major seas and there are more than 1.6 million kilometres of coastline. Our marine habitats are biologically rich and extremely varied, from shallow coastal waters to deep sea trenches. People depend on the resources provided by oceans and coasts for survival and well-being in many ways. More than a billion people rely on fish as their main or only source of animal protein. Other marine resources such as shellfish and seaweed provide livelihoods through sustainable harvesting while coastal tourism provides employment and generates income. In the Florida Keys alone, reef-based tourism generates more than US$ 1.2 billion every year.

Yet our marine world is under threat: over-exploitation of its resources, habitat destruction, pollution and climate change are all driving biodiversity loss. Arguably the most insidious threat however, is the one posed by marine invasive species.

Marine habitats are populated by different species of animals, plants and microorganisms that have evolved in isolation, separated by natural barriers. But humans have overcome these barriers with shipping, air travel and other transport means. As a result, species are now moving far beyond their natural ranges into new areas.

Species that have been moved, intentionally or unintentionally, as a result of human activity, into areas where they do not occur naturally are called ‘introduced species’ or ‘alien species.’ Many of them perish in their new environment but some thrive and start to take over native biodiversity and affect human livelihoods—these are known as invasive species. When a species establishes in a new environment, it is unlikely to be subjected to the natural controls that kept its population numbers in balance within its natural range. Without such control by predators, parasites or disease, such species tend to increase rapidly, to the point where they can take over their new environment. Marine invasive species have had an enormous impact on biodiversity, ecosystems, fisheries and mariculture (breeding and farming marine organisms for human consumption), human health, industrial development and infrastructure. Alien species can be transported by various means: in ship ballast water or by attaching to hulls, as ‘hitch-hikers’ clinging to scuba gear or packaging, as consignments of live organisms traded to provide live bait or gourmet food and as pathogens, carried by other organisms (text from the IUCN booklet: Marine Menace - Alien invasive species in the marine environment )

For more information about the IndoPacific lionfish invasion of the U.S. south Atlantic sea coast and Caribbean Sea, click here.