Home Sixth Mass Extinction of Species : Implications

Sixth Mass Extinction of Species : Implications



Global warming and climate change, and its implications for Earth and humans, is a much talked about issue. However, another threat, that had started to manifest after the Industrial Age began, is now raising concern, i.e. the accelerated decline in populations of a huge number of plant and animal species, and the extinction of large numbers of such species on account of human overpopulation, industrialization and overconsumption, especially by the rich[i]. Many scientists are opining that Planet Earth is now in the midst of the ‘Sixth Mass Extinction’[ii] (Holocene extinction) of non-human species. The loss of biodiversity is one of the most critical environmental problems, and will therefore have consequences for humans too.


Previous Five Mass Extinctions


Extinction is inevitable in evolution and is a natural, on-going phenomenon. Consequently, extinction of species has been occurring at a natural “background” rate of about one to five species per year. However, there also have been ‘mass extinctions’, which paleontologists define as the loss of 75 per cent of Earth’s species in a geologically short interval. Such mass extinctions have happened five times in the past half-billion years and are often referred to as the ‘Big 5’ [iii]:-



Approximate Period

What Happened

Cretaceous–Paleogene extinction event

65 million years ago

Perhaps the most well-known and recent of the ‘Big 5’. A combination of volcanic activity, asteroid impact, and climate change effectively ended 76% of life on Earth. It however paved the way for the evolution of mammals on land and sharks in the sea.

Triassic–Jurassic extinction event

199 million to 214 million years ago

This phased loss of species is attributed to asteroid impact, climate change, and flood basalt eruptions. The end of this era laid the foundation for the evolution of dinosaurs, which later existed for around 135 million years.

Permian–Triassic extinction event

251 million years ago

This mass extinction, in which around 96% of the species were lost, is considered the worst in all history. “The Great Dying” was caused by an enormous volcanic eruption that filled the air with carbon dioxide, which fed different bacteria that began emitting large amounts of methane. The Earth warmed, and the oceans became acidic. Life as we know today has descended from the 04% of the surviving species.

Late Devonian extinction

364 million years ago

Although it is not clear whether this extinction happened in one event or was spread over thousands of years, it led to a loss of about 75% of species. It is thought that giant land plants with deep roots released nutrients into the oceans. The nutrient rich waters spawned massive algal blooms which depleted the seas of oxygen; this killed animal life. Volcanic ash is also presumed to have cooled the Earth’s surface, killing off many species. Importantly, if the late Devonian extinction had not occurred, humans might not exist today.

Ordovician–Silurian extinction events

439 million years ago

This had wiped out around 86% of life on Earth. Scientists believe two major events resulted in this extinction: glaciation and falling sea levels.




Sixth Mass Extinction


There is an important difference between what caused the ‘Big 5” and the ongoing cataclysmic, sixth ‘mass extinction’ event[iv]. The previous five extinctions were caused by climatic or planetary or galactic physical processes (e.g. climate change, an intense ice age, severe volcanic eruptions, or an asteroid crashing into the Earth). The ongoing wave however, is exclusively being driven by a single species - mankind – with the current extinction rate of animals and plants being up to 100 times higher than the normal ‘background’ rate. As per the 2016 Living Planet Index, in just 42 years (1970 to 2012), the global populations of fish, birds, mammals, amphibians and reptiles have declined by 58 per cent.  Since population reductions are a prelude to species extinctions, at the current rate of decline, 30 to 50 percent of all species may be extinct within the next few decades[v] - and that’s taking into account only the kinds of animals and plants that we know about. A recent report by the US’ National Academy of Sciences[vi] states that “in the last few decades, habitat loss, over-exploitation, invasive organisms, pollution, toxification, and more recently climate disruption, as well as the interactions among these factors, have led to the catastrophic declines in both the numbers and sizes of populations of both common and rare vertebrate species ….... the loss of biological diversity is one of the most severe human caused global environmental problems.


Sadly, there is little realization that all species on Earth – including humans – need to exist within the physical limits of the geosphere. Instead, we continue to treat the Earth as merely a source of resources as well as a huge garbage dump for our pollution. The ‘Ecological Footprint’ – which measures our use of goods and services generated by nature – indicates that we are consuming as if we had 1.6 Earths at our disposal and have already crossed four of the nine “Planetary Boundaries” (i.e. safe thresholds for critical Earth system processes that maintain life on this planet)[vii].


Human Population and the Increasing Pressure on Earth’s Resources


5.      Humans evolved on Earth by chance, and not by design, after about 4.5 billion years of Earth history[viii]. Modern humans evolved about 200,000 years ago and had started migrating about 100,000 years back. Around that time, the total human population was less than one (01) million. Humanity has expanded exponentially since then. Population growth picked up with the advent of farming and by 1 A.D, the world population had reached 170 million. By 1800 A.D, it increased to about one (01) billion; in 1930 it touched two (02) billion and in 1960, three (03) billion. In mid-2017, it reached 7.6 billion[ix].  In sum: it took about 200,000 years for our population to reach one billion - and just over 200 years to reach 7.6 billion. As our population grew, our exploitation of Earth’s resources increased exponentially. It is assessed that overall:-


  • Humans are consuming over 50% of the total net biological productivity on land and 50% of the available supply of freshwater[x].
  • 37-40% of the planet’s land is devoted to human food production or pastures, up from 06-07 percent in 1700 AD[xi].
  • 50% of the planet’s land mass has been transformed for human use.
  • More atmospheric nitrogen is now fixed by humans than all other natural processes combined[xii].


The growing population and the increasing scale of the human enterprise, particularly industrialization and the quest for greater Gross Domestic Product, is thus putting immense pressure on Earth, which in turn is having a number of direct as well as second-order effects. These effects include climate change, a reduction in the populations of species as well as their extinction.  The report by the US’s National Academy of Sciences assesses that "the ultimate drivers of these immediate causes of biotic destruction … trace to the fiction that perpetual growth can occur on a finite planet .. [and these drivers] are increasing rapidly.




There are both direct and indirect effects of such population declines and extinctions. For example: in the USA, 25% of bumblebees are at risk of extinction; bees help pollinate 35% of the world’s food; at the ongoing rate of pollution, by 2050, the oceans may contain more plastic than fish by weight, which will impinge on food availability. Indirectly, species diversity helps ensure that our ecosystem remains resilient and is able to withstand stress. This is because most species are linked to each other in a complex ecological web. Some species even serve as buffers between humans and some dangerous pathogens[xiii].  Therefore, whether it’s pollinating crops, purifying water, harvesting fish for food, fibres to weave or sourcing medicines, humans are deeply dependent on biodiversity - and if we want ecosystems to continue to provide things for us, then they must be allowed to function in approximately the same way as hitherto fore. But with human populations increasing; dietary requirements and preferences improving; with lifestyles seeking more “style and entertainment’; humans wanting greater luxury, comfort, and using more and more resources; and with humans polluting resources at a rate faster than they can be replenished, our existence is in jeopardy unless we re-think our consumption patterns and implement widespread sustainable initiatives.


The ‘Science Advances’ (June 2015) assesses that thwarting the ongoing sixth mass extinction will require rapid, vastly intensified and widespread efforts to conserve already threatened species and to alleviate pressures on their populations from habitat loss, overexploitation for economic gain and climate change[xiv]. The US’s National Academy of Sciences has a similar but stark message - that "the window for effective action is very short, probably two or three decades at most. All signs point to ever more powerful assaults on biodiversity in the next two decades, painting a dismal picture of the future of life, including human life. The resulting biological annihilation obviously will have serious ecological, economic and social consequences. Humanity will eventually pay a very high price for the decimation of the only assemblage of life that we know of in the universe.” While “two or three decades” may seem like a long time, the fact is that conservation efforts have a very long gestation period and 20-30 years are not even a blip in the evolutionary timescale.   


India and Its Biosphere


In geopolitical terms, India is oft thought of as an “island” - it has seas on its southeast, south and southwest; to the North and East are mountains; it also has hostile neighbours to its West and East. In other words, it has to accommodate all the needs of an increasing population within this finite landmass. The rising aspirations of the population include development and improvements in infrastructure (of all types), industrialization to increase per capita GDP, as well as food security. The problem is that industrialization, infrastructure-building and agriculture are all land-use intensive.


The mid-20th century Green Revolution had improved food security in India by expanding farming areas, double-cropping farmlands, and improving land yields. However, with our population growing, the demand for food is increasing – and India is expected to have 144 crore people by 2024 and 150 crore by 2030. With land yields having peaked, more food production can therefore be achieved through two main routes, i.e. by bringing more land under the till and/or through radically new farming and seed technologies. Data from various sources[xv] indicates that India presently holds the second largest agricultural land globally (after the USA) and that 60.3% of India's land area is taken by agriculture[xvi]. There are however, competing demands for land for living, infrastructure, industrialization, etc.


Hence, there is a body of opinion which suggests that environmental sustainability could become the next major challenge as India surges along its projected growth trajectory, with the competition between land for agriculture use and  that required for building infrastructure as well as for industrialization leading to severe encroachments on existing biospheres. Thus, although the government is doing a fair amount in terms of inducting “green” and renewable technologies, the biosphere challenge in India only appears to be starting. This is perhaps what should occupy thinkers and planners in the coming days and months.




[i] 23 May 2017 Report by the USA’s National Academy of Sciences  entitled “Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and decline”.

[ii] The Earth has already witnessed five mass extinction events. The last, during the Cretaceous–Paleogene period, ended the dinosaurs.

[iii] http://www.worldatlas.com/articles/the-timeline-of-the-mass-extinction-events-on-earth.html

[iv] International Union for the Conservation of Nature (2009): Worldwide, 12 percent of mammals, 12 percent of birds, 31 percent of reptiles, 30 percent of amphibians, and 37 percent of fish are threatened with extinction [6].

[v] Ibid. and Thomas, C. D., A. Cameron, R. E. Green, M. Bakkenes, L. J. Beaumont, Y. C. Collingham, B. F. N. Erasmus, M. Ferreira de Siqueira, A. Grainger, Lee Hannah, L. Hughes, Brian Huntley, A. S. van Jaarsveld, G. F. Midgley, L. Miles, M. A. Ortega-Huerta, A. Townsend Peterson, O. L. Phillips, and S. E. Williams. 2004. Extinction risk from climate change. Nature 427: 145–148.

[vi] Entitled “Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines”.

[vii] “Faced with decline in global biodiversity, the world needs to re-think production systems and consumption patterns”, Oct 2016; http://www.wwfindia.org/news_facts/wwf_publications/living_planet_report/living_planet_report_2016/

[viii] US Geological Survey, “Human Impact on the Planet: An Earth System Science Perspective and Ethical Considerations”, By Richard S. Williams, Jr.

[ix] United Nations – “World Population Prospects The 2017 Revision Key Findings and Advance Tables”.

[x] US Geological Survey, “Human Impact on the Planet: An Earth System Science Perspective and Ethical Considerations”, By Richard S. Williams, Jr.

[xi]  Vitousek, P. M., H. A. Mooney, J. Lubchenco, and J. M. Melillo. 1997. Human Domination of Earth's Ecosystems. Science 277 (5325): 494–499; Pimm, S. L. 2001. The World According to Pimm: a Scientist Audits the Earth. McGraw-Hill, NY; The Guardian. 2005. Earth is All Out of New Farmland. December 7, 2005. 

McKee, J. K., P. W. Sciulli, C. D. Fooce, and T. A. Waite. 2004. Forecasting Biodiversity Threats Due to Human Population Growth.Biological Conservation 115(1): 161–164. 

[xii]  Ibid (Footnote 11) 

[xiii] http://sciencing.com/extinctions-other-creatures-affect-humans-directly-20692.html

[xiv] “Accelerated modern human–induced species losses: Entering the sixth mass extinction:, June 2015;  http://advances.sciencemag.org/content/1/5/e1400253.full

[xv] World Bank;  India Brand Equity Foundation, a trust established by the Ministry of Commerce and Industry

[xvi] World Bank data

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