Tuesday, 8 January 2013

Concluding Comments

The mystery of the vanished giants is no easy one to solve. This is still very much a dynamic field where new research reveals more dimensions of the puzzle and throws up more questions than answers. After gaining a better understanding of the topic through keeping this blog, I am ever more aware that the answer is not a simplistic, uni-dimensional one.

I found the arguments where human impacts are the ‘last straw’ for already stressed populations struggling to adapt to climate change the most convincing. Critics have argued that megafauna  survived the previous glacial-interglacial transitions, citing anatomically advanced humans with sophisticated hunting technologies as the only differentiating factor. This is a simplistic view of past climates which assumes that all transitions are the same. There is evidence that the late Pleistocene was unusually, warmer rather than cooler than the Holocene and supported a rich mosaic of vegetation types which was in turn able to support a huge variety of megafauna. This disappeared during the Holocene.  Besides, ‘megafauna’ is not a static concept; Graham and Lundelius (1985) concept of ‘co-evolutionary disequilibrium’ suggests that species often co-evolve in unique and individualistic ways, meaning that the species composition of ecosystems change all the time. The late Pleistocene was a biotically unique period, limiting comparability with other glacial-interglacial transitions.

Besides, extinctions did not happen in the rapid ‘Blitzkrieg’ manner that some researchers have argued. Especially in Eurasia, where humans were not necessarily present in all areas, extinctions occurred gradually and even happened in areas where there were no humans, e.g. the Irish Elk. The African Anomaly also adds another piece to the puzzle – African hunters were also sophisticated but it is the continent which experienced the fewest extinctions, and there is evidence that climate change was less pronounced in Africa.

Whispers from Ghosts Past: Lessons for the Future
So where does this all leave us? I do not think it is possible to provide a conclusive answer to the mystery of the vanished giants, but I hope I have left room for more thought. I also hope that a better understanding of past climates and extinct species would lead us to be more aware of the importance of modern conservation – once species are lost, they are irrevocably gone.

I can see 3 major takeaways from this blog:

Our current level of biodiversity is already a depauperate version of what it once was, yet human impacts are resulting in ever more extinctions than before.

Today, our actions are themselves causing climate change. In the late Pleistocene, climate change was essentially separable from human impacts such as hunting. Today, we have entered what Nobel Prize winner Paul Crutzen (2002) calls  ‘The Anthropocene’ – human impacts have reached such unprecendented levels that they have become significant geological forces. 

The late Pleistocene megafauna extinction event has shown that the adverse impacts of humans and climate change are a lethal combination for species biodiversity, and the effects are further amplified today.    

      Crutzen, P. J. (2002) The ‘anthropocene’, Journal de Physique IV, 12, 10, pp. 1-5

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