week 9 Flashcards
What were megafauna?
large animals that occupied many ecosystems prior the
last glacial period. Now only left in large numbers in Africa
When did the megafaunal extinction occur in Australia?
around 42,000 years ago,
although extinctions had been occurring earlier, and some species persisted for longer.
What are the hypotheses on what caused the megafaunal extinction?
Humans
Climate
A combination of humans and climate
What are the different variations of the human cause of extinction?
Overkill
Innovation
• Environmental modification
• Attrition
What is the Overkill hypothesis?
– humans arriving in a new landscape targeted the vulnerable prey
What is the Innovation hypothesis?
– humans adopting new technology to better hunt megafauna
What is the Environmental modification hypothesis?
- Humans modified the landscape to put megafauna at a disadvantage.
- The use of fire changed vegetation communities
- Particularly important for herbivore species
What were Australia’s climate changes similar to?
Changes generally more similar to Antarctica than
Greenland
where were Glaciers in Australia?
Glaciers were confined to small areas in the
Tasmanian highlands and the Snowy Mountains
What happened in Australia during the deglaciation?
• Increase in woody taxa and Eucalyptus across
eastern Australia
• Changes generally more inline with Antarctica than
Greenland
What where the features of the Antarctic Cold Reversal in Tasmania?
- Enhanced westerly winds and northward migration
- Increased windspeed across Tasmania
- Western Tasmania: Enhanced rainfall and reduced biomass burning
- Eastern Tasmania: Enhanced evaporative conditions
- No evidence for readvance of glaciers
What is Kati Thanda (Lake Eyre) levels an example of?
Example of insolation forcing on Australian climate through the Australia Summer Monsoon
When had ice in australia melted by?
~16,000 years ago
What is the definition of megafauna?
big animals > 45 kg
How many genera of megafauna before and after extinction?
Prior to 50,000 year ago there were 150 genera of mammals larger than 45 kg. By 10,000 years there were 50 or fewer genera
What is the Attrition hypothesis for megafaunal extinction?
Humans slowly drive megafauna to extinction, through
hunting, habitat modification and competition for
resources
Which theories on megafaunal extinction would be favoured by humans and megafauna coexisting for a long time?
climate change
Innovation
Attrition
Which theories on megafaunal extinction would be favoured by humans and megafauna not coexisting for a long time?Why?
Overkill hypothesis
requires humans to be a novel predator
What is the theory that Climate change drove the megafauna to extinction?
• Extinctions occurred following climate changes that
the megafauna were not able to survive
• In Australia, an increase in arid conditions over the
last 430,000 years meant that conditions eventually
became too extreme for the megafauna.
What is the theory that Both climate change and humans drove the megafauna to extinction?
• Pressure from both humans, through hunting and
landscape modification
• With reduced freshwater, people and megafauna
would have congregated around areas of freshwater, increasing the chance of encounters and hunting
Did humans a megafauna likely coe exist what was the likely cause? What is this evidence against?
• Humans and megafauna co-existed for ~17,000
years, at least in some regions
Evidence against the overkill hypothesis
Can climate change explain the megafauna extinction in australia?
No Most evidence suggests that the Australian climate
was relatively stable during periods of extinctions
Is there evidence that climate change did cause the megafauna extinction in australia?
Yes, Extinctions were already in place well before humans arrived in Australia
When was the last glacial maximum in australia?
• Earlier date than in Northern
Hemisphere, including Greenland
• ~28 ka
