Invasive Species in Australia and the United States

Introduction

Invasive species have significantly impacted the natural landscape and agriculture in both Australia and the United States. This lecture covers the various invasive species, their origins, impacts, and the control measures implemented by governments.

Invasive Species in Australia

Feral Goats

• Origin: Introduced in 1788 by British workers and miners as pets and for food.
• Population: Approximately 2.3 million; mainly in semi-arid and hilly areas (Western New South Wales, South Australia, Western Australia, Queensland).
• Impacts:
  • Environmental damage by competing with native wildlife for resources.
  • Agricultural damage through overgrazing, damaging crops, reducing farmers' profits.
  • Economic loss: around $25 million annually to agriculture.
  • Disease transmission: major cause of foot and mouth disease in cattle.
• Control Measures:
  • Commercial exploitation: industry worth $29 million. Farmers sell wild goats to meat processing plants.
  • Hunting and trapping: 39% of the population exterminated annually.
  • Without control, population would double every 1.6 years.

Wild Camels

• Origin: Introduced in the 1840s by the British for exploration purposes.
• Population: Around 1.3 million; present in 53% of Australia's grassland ecosystems.
• Impacts:
  • Destroy fences, vegetation, and deplete water reservoirs.
  • Aggressive behavior towards livestock, causing economic loss estimated at $17 million annually.
• Control Measures:
  • Aerial hunting, mustering, and butchering.
  • Unlimited hunting permitted in many states.
  • Annual culls of about 103,000 camels; additional deaths due to natural causes.
  • Control measures cost about $19 million annually.
  • Without control, population would double every 7-9 years.

Invasive Species in the United States

Canadian Geese

• Population: Approximately 7.3 million.
• Breeding: Nesting and laying eggs from March to May; each female lays about five eggs.
• Impacts:
  • Damage to grasslands, pollution from droppings, and noise pollution.
  • Flight hazards: about 1,200 plane crashes annually involve geese.
  • Crop damage during migration.
• Control Measures:
  • Hunting permitted; drones used to scare geese away from golf courses.
  • Catching and butchering during molting season when geese cannot fly.
  • Goose meat distributed to needy families by charities.

Swamp Rats (Nutria)

• Population: Widespread throughout southern United States.
• Impacts:
  • Destruction of swamp vegetation by eating plant roots.
  • Rapid reproduction: 40-60 young per year.
• Control Measures:
  • Trapping and hunting encouraged with a $6 reward per tail.
  • Promotion of swamp rat meat in culinary dishes.

Wild Horses

• Population Growth: 18-20% per year.
• Impacts:
  • Overgrazing native plants, contributing to invasive species establishment.
  • Competition with other ungulates, affecting cattle ranchers.
• Control Measures:
  • Bureau of Land Management gathers and removes feral horses from public lands.
  • Use of contraception to slow population growth in certain areas.

Conclusion

Invasive species management is crucial for protecting agriculture, native species, and the environment. Governments in both Australia and the United States employ various control measures to mitigate the negative impacts of invasive species.