Conclusions, and Looking to the Future.

Sixth Mass Extinction?

This blog has investigated the claim that the Earth is undergoing a 'sixth mass extinction', and has attempted to determine whether this is a natural fluctuation or a human induced tragedy. This has been done by comparing the present rates of extinction with those from the five previous 'mass extinction events' and discussing what the future could hold, as well as considering the perspective of skeptics. I have also tried to include a number of interesting articles to highlight the importance of this topic, as well as the wide-ranging effects that this loss of biodiversity is having. Throughout this blog I have come to the personal conclusion that despite the inaccuracies known in absolute numbers, the Earth is experiencing an extremely elevated level of species loss, primarily due to the impact of humans. Whether this can be described as the 'sixth mass extinction event' is a matter of opinion. All previous events have resulted in more than 75% of species being lost from Earth (Jablonski 1994). The timescale of species loss is currently not long enough for this to have occurred, however predictions believe that we could exceed this figure by 2100 if we continue as we have, hopefully we can prevent this from occurring.

Evidence

Actual species rates are very difficult to quantify with different scientists expressing different opinions. Most conservative estimates place the current rate at 1000 times the background rate, whereas some place it as high as 10,000 times greater (Call of Life 2009). Wilson estimates that 27,000 species are lost per year, whereas, Ehrlich believes that this may be as high as 130,000 species per year. It must be noted that these estimates rely on a number of assumptions decreasing their accuracy.

Clear links have been identified between human dispersal and the extinction of a number of species, including examples such as the loss of 135 mammal species (representing 70% of North Americas large mammals), when humans migrated from Asia to North America 12,500-10.000 ya, and the loss of 17 of 50 species of lemur in Madagascar after the arrival of humans 2000 ya (CBD 2010). This correlation undoubtedly shows that humans have had a drastic influence in the global loss of species. Human activities that are believed to impact extinctions include: over-hunting, introduction of infectious diseases, increased inter specific competition, habitat destruction, and the introduction of exotic species.

I looked at the previous five 'mass extinction' events to try and determine any similarities between these and the current postulated event. All of these five events had natural causes, unlike the 'sixth mass extinction' and also occurred over a much longer timescale (in the order of millions of years), highlighting how severe the problem is; that the high current extinction rates could be severe enough to carry extinction magnitudes to the 'big five' benchmark in as little as 300 years (Barnosky et al. 2011).

The future appears bleak for global biodiversity. The IUCN considers 11,046 species of plants and animals 'threatened' considering them vulnerable, endangered or critically endangered. There is a significant chance that these species may go extinct in the near future, almost all resulting from human activities. To put this into perspective this accounts for 24% of mammals and 12% of birds. (IUCN 2000). The figures are likely to be much higher due to the large amount of unidentified species, and every update of the IUCN Red List has resulted in an increase in the number of species considered 'threatened'.

Prominent scientist Georgina Mace believes that if nothing changes 14-22% of all species and sub-species could be lost over the next 100 years (www.whole-systems.org/extinctions.html). However, nature film Call of Life (directed by Monte Thompson, 2010) believes that this will be much higher, and if current trends continue within a few decades at least 50% of plant and animals species will disappear forever.

Prominent advocates of the mass extinction include Niles Eldredge, Edward Wilson, and Richard Leakey. The two quotes that really drew my attention to this cause were those of Eldredge and Wilson. 

• Niles Eldredge (1999): "It is well established that the Earth is undergoing yet another mass extinction event, and is clear that the major agent for this current event is homo sapiens".
• Edward Wilson (2002): "At current rates of human destruction of the biosphere, half of all species will be extinct in 100 years"

These two quotes, in a few simple words identify the significance and extent of this problem as well as identifying what they believe is the cause. However, as discussed above this topic is far from simple, and what is even more complex is how we should go about attempting to prevent this disaster.

What should be done?

The natural world could be devastated beyond recognition, with the loss of human life in the billions if we do not act not to prevent further biodiversity loss. However, scientists believe that we still have time to avert the worst of the crisis and save much of the biosphere, but only if we act now. 

Firstly we need to create broad public awareness of this issue, including magnitude and implications. Only then can the whole of society begin to recognise the systematic changes that will be required. The solution is clear, in order to save Earth and secure a future for the human race we need a new worldview. We must accept that technology alone cannot solve this issue, instead we need to create fundamental change, in culture, our minds, and most importantly our hearts. 

References


Barnosky, A. D., et al. (2011). Has the Earth's sixth mass extinction already arrived? Nature. 471: 51-57.
Call of Life: Facing the mass extinction. Monte Thompson (2009)
Centre for Biodiversity and Conservation Conference. Humans and other catastrophes: perspectives on extinction. New York. American Museum of Natural History. Available at:http://www.amnh.org/science/biodiversity/extinction/IntroSymposiumFS.html
Eldedge, N. (1999). Cretaceous meteor showers, the human ecological niche and the sixth extinction. Centre for Biodiversity and Conservation Conference. Humans and other catastrophes: perspectives on extinction. New York. American Museum of Natural History. 
IUCN. (2000). Compiled by C. Hilton-Taylor. 2000 IUCN Red List of threatened species. Thanet Press Ltd.: Margate.
IUCN. (2009). The IUCN Red List of threatened species 2009 update.
Jablonski, D., (1994). Extinctions in the fossil record. Philosophical Transactions of the Royal Society London. B. 344: 11-17.
Wilson, E. O. (2002). The future of life. Vintage.
www.whole-systems.org/extinctions.html