Bob Brockie: Stopping exotic invaders may be impossible

New Zealand's biosecurity laws are the most stringent in the world. Yet there is probably little chance of slowing down ...
Bob Brockie

New Zealand's biosecurity laws are the most stringent in the world. Yet there is probably little chance of slowing down the invasion rate. |

OPINION: Back in the 1800s, settlers brought shiploads of plants and animals from Europe to New Zealand. Every province set up acclimatisation societies to bring in more invaders.

How different from today.

Today, thousands of border and biosecurity staff check passengers and their luggage, used cars, imported goods, the mail, and over 6000 containers a year trying to stop foreign microbes, plants and animals from entering our country.

About 6000 incoming foreign plants and animals are intercepted annually.

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Over recent years, 50 kinds of hitchhiking beetles have been intercepted, 12 kinds of mosquito, 12 different ants, the painted apple moth, the asian gypsy moth, mud wasps, stink bugs, a new white butterfly, fruit flies and, rarely, live snakes, lizards, scorpions, crabs, fish, turtles and birds eggs.

Foreign wasps and bees have been found on recreational vessels being refitted here. Plenty of insects and spiders are blown here from Australia. Others, such as pelicans, and a handsome dragonfly from the Pacific have flown here under their own steam.

Thirteen kinds of foreign seaweeds have found their way into Wellington Harbour, and 20 species into Lyttelton Harbour.

In a broader context, European biologists Hanno Seebens​ and Tim Blackburn recently surveyed 21,000 plants and animals that have invaded countries of the world over the last 500 years.

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They write that from the 1500s to 1800s, European settlers took boatloads of mammals, birds, and plants to their new colonies. In the 19th century they took plenty of foreign plants and animals back to Europe as ornamentals and pets. Today, birds are still traded on a massive scale between Southeast Asian countries.

The number of invasive species has increased since the 1600s, when there were only eight introductions between countries a year. Because of increased trade and more travel between countries, the invasion rate has increased dramatically over the last 50 years. Today over 500 plants and animals invade other countries every year.

Small creatures and seaweed spread as contaminants and as stowaways or in ship ballast. Large numbers of Indian Ocean fish have invaded the Mediterranean through the Suez Canal, and the new Arctic shipping line and new railway between Beijing and London will give invading plants and animals more travelling options.

Seebens and Blackburn say invasive species homogenise faunas and floras, and have far-reaching implications for native biodiversity, evolution, ecosystem functioning, human health and the world economy.

Over the last century many attempts have been made to impede invasive species but these have not been effective enough to keep up with accelerated globalisation and the exponential increase in the number of invaders over the last 50 years.

New Zealand's biosecurity laws against invasive species are the most stringent in the world. Yet there is little chance of slowing down the invasion rate as accidental introductions will grow as more people travel and we trade with more countries.

NZ Biosecurity Services cost $190 million this year. Its assistant director says, "We could spend 10 times that amount and could still not guarantee 100 per cent security".

 - Stuff

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