I’m moved to blog today because of the State of the World. Unfortunately – we live in very interesting times – as in the Chinese curse: “May you live in interesting times!“ Despite the facts, I do not want to be alarmist. Human nature is such that alarmist warnings tend to be discounted or – if considered – they tend to become watered down to a significant degree. The problem is things are worse now – for life on the planet – than they have been for 65 million years.
But what does that really mean? Our planet has had a very interesting history – which has only become well understood recently. In the mid 19th century – when Charles Darwin and Alfred Russell Wallace developed their “Dangerous Idea” – evolution by natural selection – genetics and related science was unknown. Since Darwin’s time science has powerfully confirmed the reality of evolution – and identified an interesting planetary history. It turns out that life has had a long history on Earth.
The Sun and planets formed 4.54 billion years ago (Ga). Shortly thereafter a Mars-sized body – Theia – collided with the early Earth at very high speed. The material ejected by that collision coalesced and formed the moon. It turns out that the moon has had very beneficial effects on the Earth – by stabilizing its spin axis and angle of inclination relative to the plane of the solar system. Scientists argue that the moon has allowed life to develop as it has – by greatly stabilizing Earth’s climate.
The early earth – after formation of the moon – may have remained a hellish place. Some scientists believe that the process that initially formed all of the planets, i.e. collisions of small bodies made of gravitationally accumulated interplanetary dust – accreting into larger and larger bodies – may have included what has been termed the Late Heavy Bombardment (LHB). In this scenario a large number of asteroids and comets collided with Earth (and with all of the other inner solar system bodies) from 4.1 Ga til 3.8 Ga. Only once this LHB was over – could the surface of the planet cool enough to allow life to develop. And it’s now thought that the LHB may have provided much of Earth’s water. But by 3.5 Ga – life had appeared – but conditions on Earth were still not pleasant.
The early atmosphere was mostly nitrogen and carbon dioxide – with perhaps remnants of the solar nebula contents – ammonia and methane – but no oxygen. And the moon was very close to earth – perhaps only 32,000 km away. The moon would have been really huge in the sky – and earth days were only a few hours long – so the tides would have been much, much higher – and very frequent.
Early life on Earth was photosynthetic – and therefore it released oxygen. But all of this oxygen was captured by reaction with iron dissolved in the ocean, with minerals in the ocean and on the ocean floor, and later with minerals on the surface of the continents. This process was long – taking from 3.5 Ga until 850 Mya. Only at this point could free oxygen begin to accumulate in the atmosphere. Since then – free oxygen has varied from 12% – 31% – currently at 21%. At its peak free oxygen allowed for a dragonfly with a 29 inch wingspan to terrorize Permian skies.
A more speculative feature of the Precambrian Earth (before 541 Mya) are the suspected Snowball Earth episodes. The available evidence suggests that at several points the Earth has experienced near complete global glaciation – including frozen oceans. The first such event is called the Huronian glaciation (approximately 2.4 to 2.1 Ga) perhaps triggered by the Great Oxygenation Event (GOE, 2.45 Ga). There were also apparently several more snowball episodes – between about 760 Mya and 635 Mya – after free oxygen began to accumulate in the atmosphere – but before multicellular life exploded in diversity. Multicellular life first really bloomed in the Precambrian – about 600 Mya.
Which brings us back to the present. Biologists consider that Earth is experiencing a Mass Extinction episode – caused by human activity. If it continues – this episode will be the sixth such extinction – the most recent previous episode was 65 Mya – when an approximately 10 Km diameter extraterrestrial body slammed into Earth on the coast of the Yucatan Peninsula in Mexico at 14 mi/sec – ending the reign of the dinosaurs. And why are humans having such a disastrous effect now? There are two main reasons, more negative impact per average human, and many, many more humans.
The most significant increase in negative impact per average human is increased carbon dioxide release – primarily from fossil fuel use – although other very negative patterns are also involved. These include pesticide and herbicide use, industrial pollution (particularly mercury release through coal burning) and wildlife habitat and population destruction (especially oceanic over-fishing and rain forest destruction). And the wealthy are responsible for much negative environmental impact. They use a lot of fossil fuel – per individual – especially in the form of frequent travel by air.
But all of these problems are made much worse by human population growth. In the time of Jesus estimated world population was about 100 million. Human population was about 1 billion on February 12, 1809 – the day both Charles Darwin and Abraham Lincoln were born. The 1929 stock market crash was witnessed by a population of 2 billion. When I was born it was 2.5 billion. World population is now about 7.3 billion. If I live a few more years world population will have tripled in my lifetime. Between 1999 & 2012 one billion souls were added to our crowded world. This means a rate of increase during this period of – 77 million/year – 6.4 million/month – 1.5 million/week – 212,000/day & 8800/hour.
But like many other important facts – world population is a verboten topic. It’s never, ever discussed in the main stream news. People who do discuss it in public are then treated as pariahs – like conspiracy theorists are. This is truly crazy. Global warming – the current mass extinction episode – and the human population crisis – constitute the greatest challenge ever faced by our species ***.
*** Perhaps the Mount Toba eruption 74,000 years ago was equally catastrophic. It is thought to have resulted in a human population bottleneck – with only a small number of humans surviving that event.