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Quaternary climate-driven megafaunal extinctions

It has been claimed that the Quaternary ice ages impacted species diversity, evolution and extinction (Lister, 2004; Davis and Shaw, 2001). Today, and throughout the past, it has been repeatedly proven that species respond to changes in climate. Both changes in the altitude of species, as well as latitudinal shifts in their range, are common responses to the warming and cooling of climate (Davis and Shaw, 2001). If an animal cannot adapt to these changes, it may become extinct. In the next 100 years there is predicted to be a major loss of species diversity (Cahill et al., 2012), therefore understanding how animals adjusted to climate change over past glacial cycles is particularly important in predicting how they will respond to anthropogenic climate change in the next century.

We can view this as:

 Climate Shift à Environmental Change (vegetation shift) à Species response (adaptive shift) à Survival/Extinction 

A Contemporary Context 

Today we can see all manner of animals adapting to climate change, even some of the smallest. For example, Argynnis paphia (Silver-washed fritillary) is a species of butterfly residing in Northern areas of Europe and Scandinavia. This is an insect adapted to cooler climates. Since 1970 there has been a poleward shift in the distribution of this butterfly, due to an increase in cold zone temperatures (fig.1) (Parmesan et al., 1999). After a certain length of time, this species may be pushed so far north, it will lose suitable habitat, and face becoming extinct. This could have been the case with many of the animals which have lived during the Quaternary period, which is why it is so important to understand past implications of climate  on ice age fauna.

Figure. 1: Argynnis paphia (Silver-washed fritillary) range in 1970 (blue) and shift in range by 1997 (green). 

(Parmesan et al., 1999  p. 582; UK Butterflies, 2016)

Quaternary Climate Change: Megafaunal Response

It has been suggested that many species underwent dramatic changes in their range in response to vegetation shifts brought about by  late-Quaternary climate (Stuart and Lister, 2007). Many of these may have caused extinction. Below is a compilation of selected late-Quaternary megafauna, including their estimated date of disappearance. 

Extinction Chronology 

Figure.2: A chronology of selected species affected by Quaternary climate change.

Compiled from: (Stuart and Lister, 2007)

Links to species and term definitions:

Stephanorhinus hemitoechus, Hippopotamus amphibious, Palaeoloxodon antiquus, Late Glacial, Eemian, Holocene, Last Glacial Maximum, Ursus spelaeus, Crocutacrocuta, Mammuthus primigenius, Coelodonta antiquitatis, herbivorous.

Top left: Crocuta crocuta. Top right: Ursus spelaeus. Bottom: Stephanorhinus hemitoechus.

Extinction Complexity

Prior to 21^st century research it was generally considered that most late-Quaternary extinctions occurred prior to the end of the Pleistocene epoch. It is now clear that this extinction was much more staggered than previously assumed, with many animals surviving into the Holocene (Stuart and Lister, 2007). Though, as we have discussed in previous posts, climate was by no means the only mechanism responsible for species extinction. Many of these animals were affected by changes in vegetation brought about by climatic deterioration or warming. This means that in a warming world there may be significant changes to current species distributions, including extinctions. 

Thanks for the read!