Are invasive species harmful?
Introduced species enter the country either intentionally or accidentally. Some of them were brought here to help with transportation or farming, while others were brought in as pets or as spoils for hunting. Those that arrive by accident enter together with shipping cargo or are unknowingly brought by travellers.
Only those that have negative impacts on the environment or human health are considered invasive. Others, like honey bees, are known to be beneficial.
Invasive species can cause loss or alteration of habitat for native species. They can also kill endemic creatures. According to Science.org, a study published in 2016 found that the estimated cost of invasive species was $AUD13.6 billion in the 2011-12 financial year.
9 examples of introduced species in Australia
Some introduced species in Australia are so established that it’s become impossible to eradicate them. Here are a few examples, as well as an overview of their effects on their new habitat.
9. Red foxes
European red foxes were brought to Australia in the 1850s for recreational hunting. Most of them were released in Melbourne, though established populations now exist all over the continent. They’re categorised as a pest species, hunting native rodents and marsupials. They’re also a threat to poultry and small children.
To control the fox population, people set baits with 1080 poison. Building fences to keep them at bay is also quite effective.
8. Wild dogs
Wild dogs refer to pure-bred dingoes, feral dogs and hybrids. Dingoes are semi-domesticated canines that were brought to the continent about 3,000 to 4,000 years ago from South Asia. While they’re an introduced species, they’ve become so common that they’re synonymous with the term “Australian wild dog.”
Feral dogs are domesticated dogs that were released or escaped from the home. As such, they have not had any interaction with humans for the majority of their lives. To survive, they scavenge for food in garbage or hunt for wild animals. Dingoes can interbreed with feral dogs and produce hybrids.
Local authorities hold management programs for wild dogs to prevent them from attacking livestock. Wild dogs cause livestock producers to lose about $AUD25 million per annum in Western Australia alone. They’re legally classified as pests.
Feral rabbits are fluffy, cuddly, and surprisingly destructive. Introduced in the 1800s by European settlers, their population multiplied due to the lack of predators in their new environment. They were initially introduced for food and sport but ended up disrupting their habitat.
Without proper control, rabbits can damage vegetation and clear lands. They may have also caused the extinction of small mammals and lowered the numbers of native plants and animals.
Camels were brought into the country by European settlers to assist in the exploration of the outback. From 1840 to 1907, somewhere between 10,000 to 20,000 camels were transported to the continent from India.
According to the BBC, people riding camels “opened lines of supply, transport and communication between isolated settlements… they also enriched the cultural landscape.” But after motorised transport became widespread in the 1930s, the need for camels dropped significantly. Thousands of them were then released into the wild.
Feral camels cause several problems for desert communities. They destroy fences, break pipes and drink waterholes dry. They can also graze lands bare, affecting the native wildlife.
To manage feral populations of camels, they’re usually trapped and shot at waterholes. About 1 to 1.2 million of them live in Australia.
Black rats likely hitched a ride with the First Fleet, making them one of the first introduced species in Australia. Compared to native rodents, like bush rats, black rats often prefer to live in cities. And despite their name, black rats can have grey, black, cream white or light brown fur.
The black rat is a known source of various diseases affecting humans and wildlife. Still, their overall impact on our continent is relatively low compared to the rest of the world.
4. Feral pigs
Hogs came to the country with The First Fleet, making them one of the first invasive species in Australia. They were initially brought in as livestock but later escaped and established wild populations in the continent.
Feral pigs in Australia spread weeds and degrade soil and water. They hunt native species like small mammals, birds, reptiles and frogs. Additionally, they can carry diseases that affect other animal and plant species. For these reasons, they’re considered pests.
Despite being descendants of the domestic swine, feral pigs resemble the wild boar. They can either be black, rust-coloured or black with white spots.
3. European honey bees
European honey bees are an introduced species that are considered vital to Australian farmers. They were brought to the continent 190 years ago by early settlers to pollinate plants grown for food. To this day, managed hives are kept for food and honey production.
Feral European honey bees may disrupt natural pollination processes and force endemic wildlife out of tree hollows. But there’s not enough research to conclusively tell how they negatively affect the environment.
2. Cane toads
No list of invasive species in Australia is complete without the infamous cane toad. They were intentionally brought into the content in 1935 to control cane beetles, which fed on sugar cane crops.
While the toads have a healthy appetite, they hunted other native insects instead of the local beetle population. This made them compete with native insectivores and ended up disrupting the natural ecosystem.
To control the cane toad population, people remove adult toads or toad eggs from creeks or ponds.
1. Feral cats
Domestic cats were brought by European explorers in the late 18th century to hunt rodents in sailing vessels and to live as pets. They were later released into the wild and established a feral population. As strong hunters and prolific breeders, they now cover about 99.8% of the continent.
Feral cats prey on birds and mammals, including endangered animals like the bilby, bandicoot and numbat. According to the Australian government, feral cats “threaten the survival of more than 100 native species.” They’re also responsible for driving about 20 mammal species to extinction.
To mitigate the feral cats’ impact on the native ecosystem, the Australian government has pledged to lower the feral cat population by two million in 2020.
Protect Australia's native species
Controlling or managing invasive species is costly. To prevent them from spreading, organisations like the Invasive Species Council advocate for the prohibition and control of particular species. As an individual, you can help by keeping yourself informed about the latest research involving the impacts of introduced species on the environment and spreading awareness.