#oxmegafauna
Megafauna and methane emissions through their burps
It doesn’t take much to drive a big animal to extinction. All you do is need to add a little extra mortality and the species is heading to extinction (Zuo et al (2013) The American Naturalist)
Who went extinct? In North America, 78 species went extinct, In South America 71 species. Most of these were large-bodied herbivores
There were a 100 million animals that were lost from North America and similar or more from South America. That’s a lot of microbial vats!
Questions:
1. Did the arrival of humans into the Americas 13.4 kyr and the subsequent extinction coincide with a decrease in atmospheric methane
2. Could the megafaunal extinction have caused the is
3. Is there a detectable climate effect
Answer 1. There was a large drop in methane around the time of Clovis arrival in the Americas. This drop is much more rapid and distinct compared to the previous 700,000 years
The isotopic signature of methane was also different from previous blips
Answer 2. Estimate emissions from megfauna related to body size. Animal population density well predicted by body size. Geographic range was harder to estimate. Maximum and median range can be reasonably well-predicted from body size.
To estimate methane emissions per animal use IPCC approaches
Significant influence of methane emissions on body size but also on strategy: hind gut (horses and elephants) or ruminants (cattle etc. higher emissions).
Calculate that megafauna loss of methane source 9.6 Tg/year. This can explain anything from the entire drop to 13% of the drop (the assumption of residence time is critical)
Could human extinction of megafauna have contributed to the onset of the Younger Dryas cold event. The Anthropocene could be said to have started at 13.4 kyr BP
Rinderpest epidemics in Africa in 1880s. Aroind 90% of cattle and grazing wild animals died. This would have caused a decline of 6.5 Tg year-1 in methane emissions
Conclusions: Wild animals influence climate. Herbivores are “walking microbial vats” and we lost 100s of millions of them in the American megafaunal extinctions.
Megafauna and methane emissions through their burps
It doesn’t take much to drive a big animal to extinction. All you do is need to add a little extra mortality and the species is heading to extinction (Zuo et al (2013) The American Naturalist)
Who went extinct? In North America, 78 species went extinct, In South America 71 species. Most of these were large-bodied herbivores
There were a 100 million animals that were lost from North America and similar or more from South America. That’s a lot of microbial vats!
Questions:
1. Did the arrival of humans into the Americas 13.4 kyr and the subsequent extinction coincide with a decrease in atmospheric methane
2. Could the megafaunal extinction have caused the is
3. Is there a detectable climate effect
Answer 1. There was a large drop in methane around the time of Clovis arrival in the Americas. This drop is much more rapid and distinct compared to the previous 700,000 years
The isotopic signature of methane was also different from previous blips
Answer 2. Estimate emissions from megfauna related to body size. Animal population density well predicted by body size. Geographic range was harder to estimate. Maximum and median range can be reasonably well-predicted from body size.
To estimate methane emissions per animal use IPCC approaches
Significant influence of methane emissions on body size but also on strategy: hind gut (horses and elephants) or ruminants (cattle etc. higher emissions).
Calculate that megafauna loss of methane source 9.6 Tg/year. This can explain anything from the entire drop to 13% of the drop (the assumption of residence time is critical)
Could human extinction of megafauna have contributed to the onset of the Younger Dryas cold event. The Anthropocene could be said to have started at 13.4 kyr BP
Rinderpest epidemics in Africa in 1880s. Aroind 90% of cattle and grazing wild animals died. This would have caused a decline of 6.5 Tg year-1 in methane emissions
Conclusions: Wild animals influence climate. Herbivores are “walking microbial vats” and we lost 100s of millions of them in the American megafaunal extinctions.
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