About Invasive Species
Managing their spread
The best point at which to control a potentially invasive species is prior to introduction. Once an invasive species is established in an area it becomes more difficult and costly to manage it. Quick action may be essential to eradicating an invasive species before it becomes established. To illustrate the point, an invasive strain of the tropical seaweed Caulerpa_taxifolia now carpets 120 square kilometers of the Mediterranean. Missed opportunities to eradicate it by authorities meant the chance to eradicate the weed in the early stages was missed. Since then a successful four million dollar eradication of the weed has since been undertaken in San Diego, USA.
The Global Invasive Species Database (GISD) categorizes management of invasive species into the following headings: preventative, physical, chemical, biological, educational, legal, research and Integrated Pest Management (IPM).
Risk management plans are used in assessing the potential impacts of invasive species before allowing introductions to occur and fall under preventative management. Risk assessments need to consider the likelihood of a species establishing and spreading beyond its entry point and its potential impact on human interests and native biota. The incorporation of more biosecurity measures, such as quarantines, once a species is introduced may be necessary.
IPM involves a combination of different management strategies and is widely considered by experts to be the most effective form of control. Common obstacles to invasive species management include insufficient policy, inadequate research and management funding, scarce resources and gaps in scientific knowledge.
Legal control at different levels exist for preventing or controlling invasive species or mitigating their impacts. Screening of imported species is one of the most effective approaches to reduce major pathways of invasive species introductions. Timber imports from Siberia and solid wood packing material have been evaluated using risk assessments for high-risk entry routes. Australia and New Zealand have an effective and efficient “clean” list of pre-approved species; if a species is not on this list it is denied entry. New Zealand, the USA, Norway and a few other countries are adopting regulations that require ships to exchange their ballast water while out at sea, reducing the risk of translocating marine invasive species into new locations.
Lessening the impacts of invasive species requires substantial investments into basic and applied science. “Invasion biology” can go a long way to understanding the processes of invasion and raising important questions. What makes ecosystems vulnerable to invasion? In what circumstances is eradication feasible? Is the propagule pressure hypothesis (which states that the greater the propagule number the higher the chance of invasion) appropriate or does chance play a larger part in colonisation than previously assumed? What makes a species invasive or likely to be invasive? Thus far, studies have supported the hypothesis that the best predictor of invasiveness is whether or not a species has proven to be invasive elsewhere under similar conditions.
The list of '100 of the World's Worst Invasive Alien Species' illustrates the incredible variety of species that have the ability, not just to travel in ingenious ways, but also to establish, thrive and dominate in new places. Today, alien invasion is second only to habitat loss as a cause of species endangerment and extinction.
Click here to view images and follow links to species profiles of '100 of the World's Worst Invasive Alien Species' on the Global Invasive Species Database.