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. 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. 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. 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. As a result, species are now moving far beyond their natural ranges into new areas. But humans have overcome these barriers with shipping, air travel and other transport means. Marine habitats are populated by different species of animals, plants and microorganisms that have evolved in isolation, separated by natural barriers. Arguably the most insidious threat however, is the one posed by marine invasive species. Yet our marine world is under threat: over-exploitation of its resources, habitat destruction, pollution and climate change are all driving biodiversity loss.

In the Florida Keys alone, reef-based tourism generates more than US$ 1.2 billion every year. Other marine resources such as shellfish and seaweed provide livelihoods through sustainable harvesting while coastal tourism provides employment and generates income. More than a billion people rely on fish as their main or only source of animal protein.

People depend on the resources provided by oceans and coasts for survival and well-being in many ways.

Our marine habitats are biologically rich and extremely varied, from shallow coastal waters to deep sea trenches. More than 70% of the earth is covered by oceans and major seas and there are more than 1.6 million kilometres of coastline.

Marine menace-an overview of the marine invasive species issue

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