Nobel Prize winning Dutch chemist, Paul Crutzen popularised the term ‘Anthropocene’ (The Age of Humans) that represent this human dominated geological epoch. His argument was based on the facts, 18 years ago, that human activity has transformed between a third and a half of the land surface area of the planet; that most of the world’s major rivers have been dammed or diverted; that fertiliser plants produce more Nitrogen than is fixed naturally by the Earth’s land ecosystems; that overfishing removes more than a third of marine life born in the oceans’ coastal waters and finally that humans use more than half of the world’s readily accessible fresh water runoff.
The 5th Cretaceous-Tertiary mass extinction, also known as the K-T extinction, occurred 66 million years ago and it annihilated 76% of all plant and animal species on Earth. This is the mass extinction that also killed off all the dinosaurs. It was caused by an asteroid hitting the planet at the Yucatan Peninsula that separates the Gulf of Mexico from the Caribbean Sea. The bolide was travelling at seventy thousand kilometres per hour and coming in at a low trajectory from the southeast. It hit the ground as a plane landing and blasted into the air more than fifty times its own size in pulverized rock. A vast cloud of searing vapour and debris raced over North America, vapourising everything in its path. All this sulphur laden ejected debris had two major catastrophic effects. Firstly as it fell back to Earth through the atmosphere it incandesced scorching the surface of the Earth and secondly the sulphur blocked the rays of the sun depressing global temperatures and catapulted the earth into a perennial winter.
Forests were decimated and marine ecosystems collapsed. On land every animal larger than a cat was wiped out. Three quarter of all bird species became virtually instantly extinct. 75% of all mammals, 80% of all snakes and lizards and 90% of all marine micro-organisms disappeared. The equivalent of today’s molluscs, crustaceans and corals were devastated. Following the K-T extinction it took millions of years for life on Earth to recover its former level of biodiversity.
Paul Wignall and Anthony Hallam, British palaeontologists define mass extinction as “events that eliminate significant proportions of the world’s biota in a geologically insignificant amount of time”. Extinction expert David Jablonski calls it “substantial biodiversity losses” that occur rapidly and are ”global in extent”. Palaeontologist Michael Benton uses the metaphor of the tree of life “During a mass extinction, vast swathes of the tree are cut short, as if attacked by a crazed axe wielding madman“.
Mass extinctions are caused by diverse causes. It is not the case that there is a pattern of events that repeats itself and that has caused all past mass extinctions. Life on Earth is in a constant state of flux. Situations across space and time may be similar but they are never identical. Nature is never really out of balance. It is what survives in that balance that changes. So when we talk of disrupting the balance of ecosystems what we mean is that we are throwing out of sync that particular balance and flow that sustains life as we know it. Remember Nature does not need people – we still have much to learn.
365 billion metric tons (mt) of carbon have been added to the atmosphere up to 2013 by the burning of fossil fuels. Deforestation has contributed another 180 billion mt. Each year we add another 9 billion mt that increases by 6% a year. The concentration of carbon dioxide in the air in 2014 was 400 parts per million. This is the highest it has been in the last several million years. If this continues uncontrolled the concentration on average of carbon dioxide in the air globally will increase to 500 ppm by 2050. This will cause temperatures to rise by two to four degrees Celsius. These are global averages so in some places in may not be so bad and in others much worse. The rise in temperatures across the globe will cause a domino effect of world-altering events. This would trigger the loss of most of the world’s remaining glaciers, the melting of the arctic ice and low lying islands and coastal cities will disappear under water.
Animals, insects and plants survive and reproduce within a range of temperatures and depend on very specific climatic conditions. Climate is an integral part of the function of life supporting ecosystems that species have evolved with and within. If that changes then everything changes. The symbiotic relationship between prey and predator changes as does the ability of the species to reproduce. Whole populations of species are lost rapidly as that on which they depended is no longer there and they are not equipped to adapt or do not have enough time.
The oceans and seas are absorbing two and a half billion tons of carbon annually and are today 30% more acidic than they were in the 1800. Things remaining as they are this will be 150% by 2100. Ocean acidification will do to marine life what temperature fluctuations will do to terrestrial life.
Over the past 300 million years, ocean pH has been about 8.2. Today, it is around 8.1, a drop of 0.1 pH units, representing a 25-percent increase in acidity over the past two centuries. pH stands for potential hydrogen and measures how much hydrogen is present in water. A measure of below 7pH is said to be acidic and above 7pH is said to be alkaline or basic. For example the pH of blood is 7.35 to 7.45.
Elizabeth Kolbert quotes the following very relevant research in her book “The Sixth Extinction” – Castello Aragonese is a tiny island thirty km west of Naples. This is a volcanic region and there are vents on the sea floor around the island that send a stream of gas bubbling out. This gas stream is 100% Carbon Dioxide. Carbon Dioxide dissolves in water to form acid and acid reduces the pH balance. This environment at the bottom of the sea replicates faithfully the carbon dioxide absorption at the top of the sea from human pollution of the atmosphere. Ongoing experiments are carried out here to ascertain the effect of acidification on marine species. One third of the species on the sea floor that thrived in the vent free zones had disappeared from the sea floor around the vents where the pH had gone down to 7.8. The Oceans and seas are expected to reach a pH of 7.8 at some point in the second half of this century. Most living organisms can only survive within a narrow pH range. If the pH of their body or of their environment fluctuates too much the organisms die.
Marine biologist Jason Hall Spencer ominously warned “Unfortunately the biggest tipping point, the one at which the ecosystem starts to crash, is pH7.8 which is what is expected to happen by 2100”. Acidification of the seas and oceans kills marine life – this is not a theory but a fact.
The burning of coal and oil deposits is releasing carbon back in the air that had been captured in solid mass underground hundreds of thousands to hundreds of millions of years ago. We are running geological time in reverse many hundreds of thousands times faster than would normally have happened if we did not exist. Geologist Lee Kump and climate modeller Andy Ridgwell noted in an issue of journal Oceanography dedicated to acidification that if humanity continues along this path it “is likely to leave a legacy of the Anthropocene as one of the most cataclysmic events in the history of our planet.”
Main source: Book ‘The Sixth Extinction – An Unnatural History’ by Elizabeth Kolbert