Blog Extinction: a New and Tragic Phenomena

From animals.nationalgeographic.com

So this is my last post for a while, at least while I get through the last half of third year! Thanks to those of you have been reading along. But I wanted to end on a concluding point. While rewilding is an enticing idea the extinct megafauna are for now, gone. So can they help us save the wildness, particularly the megafauna, we have left?

The assessment of species vulnerability needs to be stepped up (Pearson et al., 2014), particularly in the face of climate change combined with increasing human populations and material wealth in the regions currently preserving much of the world's wildlife. These new &/ or increasing  (depending on how you see it) threats means that the IUCN Red List may need reviewing (Pearson et al., 2014). Looking at the megafauna we've lost, can future extinction be better predicted (and therefore mitigated)? The Ice Age megafauna were subject to increasing human populations and a shifting climate, with relative contributions of these factors in different regions (Stuart, 2014), much the same as today. Pearson et al. (2014) analysed the attributes that cause species to be at high risk of extinction specifically due to climate change. They found that occupied area and population size, actually already used in conservation assessments, were particularly important for predicting extinction risk. Other variables considered in this review included generation length, landscape connectivity and niche breadth (i.e., what ranges of temperatures and precipitation did their habitats include).

From Pearson et al. (2014). Variables were estimated for the year 2000. Y axes are scaled so that 0.0 is the mean value of the response

So essentially, it's pretty complicated even with modern species! And interactions between these variables can throw the whole thing off. For example, although extinction risk under climate change is highest when occupied area is small, the risk is lower when the species has a long generation time (i.e., a longer period between new generations) (Pearson et al., 2014). The papers that consider differential megafaunal extinction risk factors seem to do so as a side note, or as the last line of an otherwise largely incomprehensible (at least to me) sea of mathematical models (for example see Zuo et al., 2013). So this seems to be an area that warrants more research. Indeed, so is the topic of megafauna extinctions itself. A recent review of the current understanding of the extinctions concluded that assertions that we have resolved the debate are definitely premature (Stuart, 2014).

In the meantime, there are areas which have been sorely neglected in terms of data collection. For example Southern Asia, which has been studied much less than North America, Europe and Australia. However, Southern Asia contains an astonishing quantity and diversity of surviving megafauna, most of which is threatened to varying degrees.

The megafauna found here includes the Javan and Sumatran rhinos, Asian elephant, Malayan tapir, Indian water buffalo, banteng, gaur, Bornean orangutan, Sumatran orangutan, leopard, tiger, Asiatic lion, giant panda, sloth bear, saltwater crocodile and reticulated python. Both rhino species and the Sumatran orangutan are 'critically endangered' on the IUCN Red List. The Asian elephant, Indian water buffalo, banteng, Malayan tapir, Bornean orangutan, tiger and giant panda are 'endangered' (Stuart, 2014). That's the worst and second worst ratings. The Asiatic lion has been the focus of the Zoological Society of London's campaign Lions400 which is attempting to raise awareness of this little known species before the last 400 individuals disappear from the wild. A similar story can be told about the African continent, famous for it's megafauna.

In the face of so many megafaunal species predicted as likely to become extinct, it may be useful to look at the species that did not make it at the end of the Ice Age, and what set these survivors apart, if anything.

Overall, there is a need to focus on collecting reliable radiocarbon dates on megafaunal remains,
and lots of them (Stuart, 2014). In the case of Australia, the extinctions occurred beyond radiocarbon dating range. New dating methods will undoubtedly help to clear up uncertainties surrounding the mechanisms behind the megafauna extinctions here (Stuart, 2014).