Two invasive species cost the world $16 billion: study

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LONDON — Scientists tallying up the economic damage caused by invasive pests around the world have found that two species are responsible for more damage than any other.

The American bullfrog and brown tree snake have collectively caused $16.3bn (£13.4bn) in global damage since 1986.

In addition to ecological damage, the invasive pair has ruined agricultural crops and triggered costly power outages.

The researchers hope their findings will encourage more investment to help block invasive species in the future.

Writing in Scientific Reports, scientists held the brown tree snake alone responsible for $10.3 billion in total damage – in part by spreading out of control across several Pacific islands.

In Guam, where the reptile was accidentally introduced by US marines last century, the snake’s mere current population is causing massive power outages as they slither on power lines and cause costly damage.

More than two million brown tree snakes inhabit the tiny Pacific island, with one estimate calculating up to 20 inhabitants per acre of Guam jungle.

Island ecosystems are thought to be more vulnerable to invasive species – where they pose a greater threat of extinction to native animals and wildlife.

In Europe, the explosion in the number of American bullfrogs required ambitious and expensive management programs.

To prevent the spread of the amphibian – which can grow up to 30cm (12in) long and half a kilo (17.6oz) in weight – authorities have been forced to install expensive fencing around the ordeal of frogs around known breeding sites.

Fencing just five ponds to prevent amphibians from escaping cost German authorities €270,000 (£226,300), according to an older European study cited by the authors.

The amphibian is said to eat almost anything, including other bullfrogs.

Another species, the common cockle frog, has been blamed for causing economic damage in a different way: their extremely loud mating song is said to have triggered a drop in property values ​​in areas where they have infested.

The study authors hope their findings will encourage officials to invest more in pest control and other biosecurity measures in the future. —BBC

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