Alien invasion hits native wildlife hard

·3-min read

* Australia has 73 species of introduced vertebrates, including 25 mammals, 20 birds, four reptiles, one amphibian and at least 23 freshwater fish.

* But just three - rabbits, pigs, cats - along with the introduced plant pathogen Phytophthora cinnamomi, threaten more than 800 threatened species.

* European rabbits are the single biggest menace to threatened native species and cover two thirds of Australia. They are responsible for $216 million in lost farm productivity every year.

* Feral cats kill more than 456 million native mammals, 272 million birds, 92 million frogs and 446 million reptiles every year. They have contributed to the extinction of 27 native species and threaten the survival of 124 more.

* Feral pigs inhabit 45 per cent of the country and cause crop damage of about $106 million a year. In some areas they destroy up to 90 per cent of turtle nests.

* Cane toads have invaded more than one million square kilometres of Australia. They are deadly to many native predators, including northern quolls and goannas.

* European carp are found everywhere except the Northern Territory and are a major threat in the Murray-Darling Basin. They number about 200 million in an average season, compete for food with native fish and damage aquatic habitats.

* Australia has more than 2700 weeds, making up about 12 per cent of the nation's flora. About 20 new weed species set up home in Australia each year. That's one new weed every 18 days.

* 66 per cent of weed species were deliberately imported as garden plants

SOME UNWELCOME RECENT ARRIVALS:

* MYRTLE RUST

Myrtle rust is a disease caused by an exotic fungus that threatens trees and shrubs in the Myrtaceae family of plants, which includes Australian natives such as bottle brush, tea tree, and eucalypts. It can cause deformed leaves, heavy defoliation, reduced fertility, dieback, stunted growth, and plant death.

It is not known how myrtle rust entered Australia but it was first detected in Australia in 2010 on the NSW central coast and is now established in native ecosystems along the east coast.

* WHITE SPOT DISEASE IN PRAWNS

In 2016 an outbreak of whitespot disease forced the closure of four prawn farms in southeast Queensland.

It's a highly contagious viral infection that can kill crustaceans such as prawns, yabbies and crabs.

It's feared the disease is here to stay after also being detected in wild prawns and some crabs in the southeast.

* EHRLICHIOSIS DISEASE IN DOGS

This disease is caused by a bacteria called Ehrlichia canis, carried by the brown dog tick. Ehrlichiosis was first detected in May 2020 in the north of Western Australia.

It has since been detected in the Northern Territory and South Australia.

Dogs with the disease can suffer from fever, decreased appetite, lethargy, nose bleeds, severe and rapid weight loss, swollen limbs, difficulty in breathing and blindness. Some die due to effects on their bone marrow.

* THE FALL ARMYWORM

This worm reached the Australian mainland in early 2020. It has since spread across much of northern and eastern Australia.

It's reported to feed on more than 350 plant species including sweet corn, maize and sorghum. High levels of infestation can destroy entire crops.

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