Good while it lasted – III: Why this is a mass extinction

Subject: Environment

Context:

Of the 4 billion species that have evolved over the last 3.5 billion years, some 99 per cent have disappeared in a series of extinctions

Mass extinction:

The Earth has experienced five mass extinctions so far; one every 100 million years on average. Each extinction period has lasted from 50,000 to 2.76 million years.
we are currently experiencing the sixth mass extinction.
Fossil records of earlier species and extinction studies suggest a species exists for around 1 million years before it goes extinct.
This is called the background extinction rate, and is expressed as “one species extinction per million species-years”.
It is used to establish whether an extinction rate is unusual or faster.

Sixth mass extinction:

Today’s extinctions per million species-years are between 10 and 10,000 times higher than the background rate.
The ongoing sixth mass extinction is different from the previous events.
While the earlier extinction periods were triggered by the planet’s warming, the ice age or even volcanic eruptions, the current one is being driven by just one species—Homo sapiens.

Anthropocene:

The “age of humans” or the Anthropocene (Anthropos is Greek for human and -cene is a substantial geological time period within the current 66-million-year-old Cenozoic era) is the third and fundamentally new stage of evolution for the planet.
Simple single-cell microbial organisms were at the core of the first stage of evolution, spanning over 3.5 billion to 650 million years ago.
The second stage started some 540 million years ago with multi-cellular life springing widespread biodiversity.
The third stage is all about the Homo sapiens.

Census of the biomass on Earth:

The one-of-its-kind exercise was conducted in 2018 by scientists Ron Milo and Yinon M Bar-On of Israel’s Weizmann Institute of Science, and Rob Phillips of the California Institute of Technology, US.
The census involved deciphering the composition of the 550 gigatonnes of biomass distributed across all kingdoms of life on Earth.
According to the census, the 7.6 billion humans account for just 0.01 per cent of all biomass on Earth.
In contrast, bacteria account for 13 per cent of the total biomass; plants 82 per cent and all other forms of life just around 5 per cent.
The census also attributes humans to the annihilation of 83 per cent of all wild mammals and half of all plants.
Of the birds left in the world, 70 per cent are poultry chickens and other farmed birds. And of all the mammals, 60 per cent are livestock (cattle and pigs), 36 per cent are humans, and a mere 4 per cent is wild.