Invasive Species Statistics

Invasive species cost the USA over $120 billion annually, considering both management expenses and losses due to lack of management. The USA has experienced invasions by over 4000 plant species and 2300 animal species. About half of all pest species in the USA are exotic species, with nurseries, mail order, and the aquarium trade leading the way in new introductions. Just recently a shipment of an invasive snail not yet known in the USA was intercepted on its way to Hartford, CT. These are not trivial numbers.

We know about the impacts to agriculture and lake recreation, but often we get resistance to management from regulatory or private groups concerned over non-target impacts. This may be a valid concern in some cases, but doing nothing also has impacts on non-target species. About 30% of endangered species in the USA got on that list, at least in part, due to invasive species impacts. About 27 of 40 fish that have become extinct over the last century were eliminated by invasive species. After development, invasive species is the largest cause of loss of biodiversity. Doing anything represents risk to some component of an aquatic ecosystem, but so does doing nothing, and this needs to be recognized to get balanced decisions when considering possible management options.

Invasive species experts encourage managers to treat invasions like we do communicable diseases in medicine. Key steps include quarantine, assessment of damage, consideration of treatment options, and implementation of rapid response, rehabilitation, or maintenance. Prevention is important to avoid invasion in the first place or prevent re-infestation, but won’t reverse an invasion in progress.

Variable water milfoil

Zebra mussels

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