Earth’s ‘Big Five’ Mass Extinctions
Global Warming: Is it something NEW to our planet?
Extinctions are a normal part of evolution: they occur naturally and periodically over time.
Evolution occurs through the balance of extinction – the end of species – and speciation – the creation of new ones.
In a mass extinction, at least 75% of species go extinct within a relatively (by geological standard) short period of time, typically less than two million years.
The first known mass extinction – End Ordovician (444 million years ago) – with intense glacial and interglacial periods - resulted in 86% of species lost - with significant changes in Ocean Chemistry. Resulted in Climate Change.
The 2nd known mass extinction – Late Devonian (366 million years ago) resulted in 75% of species lost. Resulted in severe Global Cooling.
The 3rd known mass extinction – End Permian (250 million years ago) resulted in 96% of species lost - with elevated CO2 and Sulfur levels from volcanoes caused ocean-acidification/acid-rain. Resulted in Global Warming.
The 4th known mass extinction – End Triassic (200 million years ago) resulted in 80% of species lost - with drastic changes in the chemical composition of Oceans. Resulted in Global Warming.
The 5th known mass extinction – End Cretaceous (65 million years ago) resulted in 76% of species lost - with an asteroid impact in Yucatan, Mexico. Resulted in rapid Global Cooling.
Are we already going through 'Sixth Mass Extinction'? If so, 'Anthropocene' to be blamed?
Не названы еще как минимум 2 вымирания: 1. При смене анаэробных организмов аэробными; 2. Вымирание вендской (эдикарской) фауны
Suresh Kumar Govindarajan Dmitry Ivanov
There is growing evidence to suggest that the Earth is currently experiencing a "Sixth Mass Extinction" event, characterized by a rapid and widespread loss of biodiversity. While mass extinctions have occurred in the Earth's history before, the current rate of species loss far exceeds the natural background extinction rate. Human activities, particularly those associated with the Anthropocene era, are widely implicated in driving this biodiversity crisis.
The Anthropocene, often referred to as the "Age of Humans," is marked by significant human impacts on the Earth's geology and ecosystems. Human activities such as deforestation, habitat destruction, pollution, overexploitation of natural resources, climate change, and the introduction of invasive species have all contributed to the current biodiversity crisis. These factors disrupt ecosystems, degrade habitats, and directly threaten species survival, leading to population declines and extinctions.
While natural factors such as volcanic eruptions, asteroid impacts, and climate fluctuations have historically driven mass extinctions, the primary drivers of the current biodiversity crisis are anthropogenic. The profound changes brought about by human activities highlight the need for urgent and concerted action to mitigate further biodiversity loss and preserve ecosystems for future generations. Efforts to address climate change, conserve habitats, protect endangered species, and promote sustainable practices are essential in combating the Sixth Mass Extinction and safeguarding the planet's biodiversity.
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