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Life on Earth – The Good Times Won't Last Forever

Climate Change and Extinction Events

Life on Earth will not last forever. Several near life extinction events have happened on Earth in the past and will happen again. Here they are listed in the order in which they have, or will likely, occur.

To put everything in context, the Earth is about 4.5 billion years old. Single celled living organisms first appeared between 3.5 and 4 billion years ago. Complex life made of multicellular organisms first appeared as much as 1.6 billion years ago. Plants first colonized land 515 million years ago. The first member of the genus homo, to which modern humans belong, appeared about 2.8 million years ago.

Past Extinction Events

Ordovician Extinction
About 440 million years ago on Earth, over a nine million year period, three pulses of high volcanic activity produced very high CO2 levels and ocean acidification. These pulses alternated with snowball earth conditions followed by rapid thawing and floods. Loss of life is estimated to have been 85% of all species.

Devonian Extinction
About 359 million years ago, one or more supernova explosions directed enough radiation onto Earth to eliminate the ozone layer and cause prolonged exposure to ultraviolet radiation, causing an extinction event. This ended the Devonian period and ushering in the Carboniferous. The supernova are estimated to have been 65 million light-years away. A supernova within 25 million light-years of Earth can extinguish all life. Loss of life is estimated to have been 70% of all species.

Permian Extinction "The Great Dying"
About 252 million years ago, a large meteor hit what is now Antarctica nearest Australia. The crater, newly found under Antarctic ice, is twice as large as the one that landed 66 million years ago. Most life, which was then ocean dwelling, died. This was the end of the Permian period and the start of the Triassic. Loss of life is estimated at 90-96% of all species.

Triassic-Jurassic Extinction
About 200 million years ago, a series of large scale volcanic eruptions happened over an 18 million year period. This caused massive climate change and altered ocean acidity levels. Loss of life is estimated at 50% of all species.

Cretaceous Extinction
66 million years ago a large asteroid hit the Earth and famously wiped out the non-flying dinosaurs. The angle at which it hit the Earth, plus the location, a shallow seabed full of sulfur-containing gypsum, made it even more deadly. If the asteroid had been larger, it could have ended all multicellular life. If it had struck in the middle of the Pacific ocean, there would have been no lasting significance. This ended the Cretaceous period and started the Paleogene. Estimated loss of life: 75% of all species.

Future Extinction Events

Anthropocene Extinction: Human Population Growth
The growth of the human population has resulted in a massive impact on the Earth based on data from the past decades and past century. Scientists call our present period the Anthropocene because the Earth's climate is clearly more affected by human activity than anything else. Carbon dioxide has increased more rapidly, because of human activities, than at any time in the past 400,000 years. This carbon dioxide increase is producing ocean water warming and climate change at an alarming rate. The rate of species loss is also very high. What is especially alarming is that the rate of change is exponential, not linear. Things are going to get worse far more quickly in the near future, all due to the activities of a large human population.

Climate Change
Hotter global temperatures, vox.com
More forest fires carbonbrief.org
Slow-moving hurricanes containing more water sciencedaily.com
Sea level rises caused by melting glaciers and ice sheets climate.gov
Polar vortex shifts make winter colder in parts of the world sciencedaily.com

Increasing human population growth leads to town and city expansion and more contact with wild animals. Most communicable human diseases have come from animals, including smallpox, tuberculosis, measles, black plague, AIDS, Ebola, and Covid-19. The chance of a pandemic that will kill many people increases every year. The Covid-19 virus, originating in a species of bat, is just the latest in a series of diseases to come.
world economic forum

Solar Flare Destroys Electrical Grid and All Devices
A massive solar flare could knock out all electrical systems world-wide and destroy most electrical devices if one happened today. Society would suffer greatly and it would take one year to become partly normal and up to five years to fully recover.

Magnetic Field Reversal
A magnetic field reversal, such as the one that temporarily happened 42,000 years ago, could weaken Earth's protective magnetic field so much that cosmic radiation would get through and cause significant biological harm.

Future Asteroid Strikes
Asteroids will continue to hit the Earth. Detection and prevention must be improved.

Radiation Levels in Space Make Even a Trip to Mars Deadly
Astronauts have no way of escaping harmful radiation in space. Only a route taking minimal time is safe. There may be no way to move safely to another hospitable planet and carry on human civilization.

Earth Becomes Venus
In one billion years, the slowly increasing heat of the sun will cause Earth to overheat and become like Venus. Liquid water will boil off as steam and Earth will become a barren planet devoid of all life. Humans must have found a way to leave Earth and move to a younger, benign star system before this happens, or humans will become extinct.

Galactic Collision: Andromeda and the Milky Way
In about 4.5 billion years, the Andromeda galaxy will collide with our Milky Way galaxy which includes our solar system and Earth. The exact time of this event is difficult to pin down. While its scale will be huge, there are not expected to be many collisions between stars because of the vast distances between them. Some solar systems will be moved around, a few stars will be ejected. Unless they have found a way to move to a younger star system, humans will not be around to witness this slow-moving spectacle.

The Sun Becomes a Red Giant
The sun will swell up to a red giant at the end of its life in five billion years and swallow Earth. Humans will not have to worry. The Earth will have been lifeless for four billion years.

May 19, 2023

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