Leslie Massey
Australia has lost about 100 native plants and animals to extinction since colonisation, with 27 of those extinctions occurring since the 1960s. The leading cause of these extinctions has been invasive species, followed by habitat loss, hunting, and livestock grazing. There is also evidence that humans played a role in the extinction of Australia's megafauna, which included 1,000-pound kangaroos, 2-ton wombats, and 25-foot-long lizards. Some researchers argue that the arrival of early Aboriginal Australians and their use of fire and hunting practices contributed to the extinction of these giant creatures. Others attribute the extinction to climate change, with major climatic upheaval beginning around 280,000 years ago causing the disappearance of diverse rainforest fauna.
| Characteristics | Values |
|---|---|
| Date of human arrival in Australia | Between 65,000 and 44,000 years ago |
| Date of megafauna extinction | Between 45,000 and 43,100 years ago |
| Megafauna species | 1,000-pound kangaroos, 2-ton wombats, 25-foot-long lizards, 400-pound flightless birds, 300-pound marsupial lions, Volkswagen-sized tortoises |
| Number of megafauna extinctions | 82% of megafauna species |
| Primary cause of megafauna extinction | Human activity (hunting, use of fire) |
| Other causes of megafauna extinction | Climate change, environmental deterioration, invasive species |
| Impact of human activity on megafauna | Overhunting, modification of the landscape through fire |
| Impact of climate change on megafauna | Changes in vegetation, water availability, and fire frequency |
| Impact of invasive species on megafauna | Competition for resources, predation, transmission of diseases |
| Vulnerable groups | Large mammals, native species |
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What You'll Learn
Hunting by early humans
The extinction of megafauna in Australia is a topic that has been debated for many years. While some sources argue that climate change was the primary cause, new evidence suggests that humans played a significant role in driving these creatures to extinction.
Early humans in Australia are known to have hunted and preyed on large animals such as the 400-pound flightless bird, Genyornis newtoni. The use of fire to manage their environment and for cooking may have also contributed to the extinction of these large animals. Burned eggshells of Genyornis, for instance, provide evidence of human contribution to the extinction of this particular species of megafauna.
The impact of early human hunting on the decline of megafauna populations is further supported by studies. A 2006 study by Australian researchers indicated that even low-intensity hunting of Australian megafauna could have had significant consequences. For example, the killing of one juvenile mammal per person per decade could have resulted in the extinction of a species within a few hundred years. This phenomenon has been described as "imperceptible overkill," where anthropogenic pressures gradually lead to the extinction of species.
Additionally, the arrival of early humans in Australia is estimated to have occurred around 50,000 years ago, coinciding with the decline and disappearance of megafauna. This temporal correlation further implicates human activity as a contributing factor to the extinction of these giant animals.
While the role of early humans in the extinction of megafauna is significant, it is important to acknowledge that other factors, such as environmental changes and the use of fire, also played a part. The megafauna of Australia were already facing pressures from climatic stress and changes in vegetation, water availability, and fire frequency. The combination of these factors, along with human hunting and land management practices, likely contributed to the ultimate extinction of these unique and astonishing creatures.
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Fire usage by early humans
Fire was a critical tool for early humans, enabling their evolution and geographic dispersal. It provided warmth, lighting, protection from predators, and cooking. The earliest evidence of controlled fire usage by early humans dates back to around 1.7 to 2 million years ago, with microscopic traces of wood ash discovered. Sites in Morocco and Israel provide evidence of fire usage by early Homo sapiens and Homo erectus, respectively, around 790,000 to 300,000 years ago.
In the context of Australia, the use of fire by early humans is particularly relevant to the debate surrounding the extinction of megafauna. While some researchers attribute the extinction primarily to human hunting, others argue for a combination of factors, including fire usage by early Aboriginal Australians.
Evidence suggests that early Aboriginal Tasmanians used fire to shape their environment around 41,600 years ago. This early use of fire, 2,000 years earlier than previously estimated, showcases a long-standing human impact on the Tasmanian landscape. Researchers analyzed ancient mud containing charcoal and pollen, indicating that these early inhabitants cleared forests by burning them to create open spaces. This practice of using fire to manage their environment may have contributed to the extinction of megafauna in Tasmania.
In mainland Australia, the use of fire by early humans may have had similar effects. Sediment cores from Queensland suggest that fire increased in the local ecosystem after the disappearance of megafauna, leading to a transition to fire-tolerant vegetation. While the direct link between human fire usage and megafauna extinction is debated, it is clear that fire played a significant role in shaping Australia's ecosystems.
Additionally, early humans in Australia may have used fire for hunting and toolmaking. The use of fire allowed for the heat treatment of silcrete stones, increasing their workability for creating tools. This technology, along with the benefits of fire for hunting, may have contributed to the imperceptible overkill of megafauna species.
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Invasive species
Introduced vertebrates have driven several bird species on Norfolk Island to extinction. Australia's stringent biosecurity measures have slowed the number of new invasive species, but those already present continue to spread and their cumulative effect is growing. Research shows that 1,257 of Australia's threatened and endangered species are directly affected by 207 invasive plants, 57 animals, and 3 pathogens. These invasive species affect Australia's unique biodiversity, as well as clean water and oxygen.
Some of the invasive species in Australia include the honey bee, European wasp, yellow crazy ant, common myna, common starling, spotted dove, rock pigeon, feral horses, feral cats, feral dogs, feral pigs, goats, deer, and camels. These species threaten the existence of native animals through competition for resources, predation, and habitat degradation. For example, feral horses are known to trample and trash sensitive alpine ecosystems and streams, leading to the decline and extinction of native animals. Similarly, the honey bee invades potential nesting hollows meant for native animals and is difficult to remove once established. The yellow crazy ant has caused significant environmental damage by killing and displacing crabs on the forest floor.
The Australian government has implemented various programs to control invasive species. For instance, a cane toad control program aims to prevent the species' spread towards Darwin and Western Australia through trapping. Additionally, red foxes, feral cats, feral dogs, and feral pigs are often baited or poisoned. However, the use of poison can also inadvertently affect native animals.
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Habitat loss
Australia has lost about 100 native plants and animals to extinction since colonisation, with 27 of those extinctions occurring since the 1960s. The country has the highest mammal extinction rate in the world. Habitat loss is a significant contributor to this crisis.
Invasive species are the main driver of extinctions in Australia, but habitat loss is a close second, accounting for 36 of 100 extinctions. Feral animals, such as horses, deer, pigs, goats, camels, and others, are degrading vast areas of threatened species' habitats. Feral horses, for example, are trashing and trampling sensitive alpine ecosystems and streams, causing the decline and extinction of native animals. Foxes and cats also threaten the existence of many Australian mammals, with cats alone killing an estimated 2 billion animals in the country every year.
The Orange-bellied Parrot, a migratory ground-dwelling parrot, is one of Australia's most threatened species. Its decline is influenced most strongly by habitat loss and degradation in its non-breeding range. The bird usually stays within 3km of the coastline to forage on coastal saltmarsh vegetation and adjacent weedy pastures.
In addition to the destruction of habitats by invasive species, human activity has also caused habitat loss through hunting and the use of fire to manage the environment. Early Aboriginal Australians may have contributed to the extinction of megafauna in this way.
Today, all native animals are protected species, and organisations like WIRES are dedicated to the rescue, rehabilitation, recovery, protection, and preservation of Australian wildlife.
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Human impact on ecosystems
Humans have had a profound impact on Australia's natural environment, with some scientists arguing that we are currently witnessing the sixth mass extinction, the only mass extinction caused by a single species—humans. The arrival of humans in Australia, both Indigenous and non-Indigenous, has had significant effects on the country's ecosystems, with the extinction of megafauna being a notable consequence.
Indigenous Impact on Ecosystems
Indigenous Australians, including Aboriginal and Torres Strait Islander peoples, have a long history of interacting with Australia's natural environment, dating back to at least 65,000 years ago. During this extended period, they undoubtedly influenced the course of evolution and shaped the environment through their land-use practices and cultural traditions.
The use of fire as a land management tool by Indigenous people is well-documented and is believed to have influenced vegetation patterns. Their hunting practices, including the hunting of megafauna, may have impacted animal population levels. Additionally, the construction of fish traps in coastal and inland rivers could have had further environmental consequences.
Indigenous knowledge and management of the land and sea are based on an extensive system of ecological understanding accumulated over millennia. This knowledge has similarities to modern-day "adaptive management," emphasizing feedback learning and adapting to the unpredictability of ecosystems.
Non-Indigenous Impact on Ecosystems
The arrival of non-Indigenous humans, specifically Europeans, marked a significant turning point in the human impact on Australia's ecosystems. The introduction of new species and human activities such as agriculture, overgrazing, and industrial development have all contributed to habitat change and loss of biodiversity.
Overgrazing, for example, promotes desertification, erosion, and the spread of invasive plant species. Agriculture clearing has resulted in the removal of around 13% of Australia's original vegetation since European settlement. The introduction of exotic species, such as cane toads, rabbits, feral cats, foxes, and invasive plants, has led to local extinctions and significant reductions in the range of native species through habitat modification and predation.
Additionally, human activities contribute to climate change through the release of carbon dioxide and other gases, further altering ecosystems. Overfishing has also decreased Australia's fish stocks to dangerously low levels, threatening the biodiversity of marine ecosystems.
The Case of Megafauna Extinction
The extinction of megafauna in Australia provides a significant insight into human impact on ecosystems. While there is ongoing debate, growing evidence suggests that early humans played a pivotal role in the extinction of these giant creatures around 45,000 years ago.
Analyses of sediment cores, oxygen and carbon isotopes from megafauna teeth, and the decline of the fungus Sporormiella (found in herbivorous animal dung) all point towards human hunting and landscape burning as primary drivers of megafauna extinction. The arrival of humans coincided with a rapid population collapse of megafauna, and the absence of significant climate change during this period weakens the argument for climate change as the primary cause.
Conservation Efforts
Indigenous communities are actively involved in 21st-century conservation, managing vast areas of Australia, including traditional lands, National Parks, Marine Parks, and Indigenous Protected Areas. Their millennia-old knowledge and practices are invaluable in protecting and restoring Australia's unique ecosystems.
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Frequently asked questions
Humans are believed to be the primary cause of the extinction of Australia's megafauna around 45,000 years ago. Hunting, the use of fire, and environmental changes caused by humans are all factors that contributed to the extinction of these giant creatures.
The megafauna that went extinct in Australia included 1,000-pound kangaroos, 2-ton wombats, 25-foot-long lizards, 400-pound flightless birds, 300-pound marsupial lions, and Volkswagen-sized tortoises.
Humans reached Australia somewhere between 65,000 and 44,000 years ago. The extinctions of megafauna occurred between 52,000 and 9,000 BCE, with most of the large mammals disappearing soon after human arrival.
The evidence includes sediment cores, oxygen and carbon isotopes from megafauna teeth, and fossil records. The sudden decline in the fungus Sporormiella, found in herbivorous animal dung, coincides with megafaunal population collapse and the increase in fire frequency.
Yes, human activities continue to threaten Australia's native wildlife. Invasive species, habitat loss, hunting, and climate change are all factors contributing to Australia's ongoing extinction crisis. Introduced cats and foxes, in particular, have had a significant impact, with cats alone killing an estimated 2 billion animals in Australia annually.
