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Key Facts About Earth’s Sixth Mass Extinction

Understanding the causes, significance, and urgent implications of the sixth mass extinction shaping Earth's biodiversity.

By Medha deb

Created on Sep 27, 2025

Understanding the causes, significance, and urgent implications of the sixth mass extinction shaping Earth's biodiversity.

The Earth is facing a critical crisis: scientists warn that we are currently amidst the planet’s sixth mass extinction. Unlike previous extinction events, the current crisis is overwhelmingly driven by human activity, with severe consequences for biodiversity and the stability of ecosystems worldwide.

What Is a Mass Extinction?

Mass extinction events are periods in Earth’s history where a significant, sudden, and widespread loss of biodiversity occurs. Typically, these are defined by the extinction of at least 75% of species in a geologically short time frame, often millions of years. These rare but catastrophic events have shaped life’s evolution and reset the trajectory of life on Earth numerous times.

Background extinction rate: The normal, continuous rate of species loss over time, balanced by the emergence of new species.
Mass extinction: An episode where the extinction rate far exceeds the background rate, evidenced by dramatic and abrupt species loss across multiple taxonomic groups.

The Five Preceding Mass Extinctions

Earth has experienced five major mass extinctions in the past 540 million years, each caused by large-scale environmental disruptions:

Event	Period (Million Years Ago)	Estimated % Species Lost	Likely Causes
Ordovician-Silurian	450–440	60–70%	Severe ice age, sea level fall
Late Devonian	375–360	70%	Global cooling, anoxic oceans
Permian-Triassic	252	90–96%	Volcanism, climate change, ocean anoxia
Triassic-Jurassic	201	70–75%	Volcanic activity, climate shifts
Cretaceous-Paleogene	66	75%	Asteroid impact, volcanism

Each event profoundly altered the composition of life, wiping out dominant species and paving the way for new evolutionary paths.

Defining the Sixth Mass Extinction

Today, scientists warn that a sixth mass extinction is underway, characterized by species disappearing at rates far above the natural background. Unlike historic events driven by volcanic eruptions, climate shifts, or asteroid impacts, the primary driver is human activity.

Current extinction rate is estimated at 100–1,000 times higher than the natural background.
Losses are occurring both on land and in the oceans, impacting a wide range of plant and animal groups.
If current trends persist, up to three-quarters of existing species could vanish within a few centuries.

How Are Extinction Rates Measured?

The standard unit for extinction rate is E/MSY (extinctions per million species per year). The background rate is about 0.1–1 E/MSY, but current estimates suggest extinction rates are at or above 100 E/MSY—a thousand times higher.

Past background rate: ~0.1 – 1 E/MSY
Current estimated rate: ~100 E/MSY

This spike, driven primarily by humanity, places the current rate well within the range considered to be a mass extinction event.

Main Causes of the Sixth Mass Extinction

While previous events were triggered by natural phenomena, the sixth mass extinction is overwhelmingly human-induced. The leading causes include:

Habitat destruction—through deforestation, urbanization, and agriculture, which displaces countless species and fragments ecosystems.
Climate change—warming temperatures, altered rainfall patterns, and ocean acidification stress many species beyond their adaptive limits.
Pollution—plastics, toxins, pesticides, and fertilizers poison environments and disrupt biological cycles.
Overexploitation—unsustainable hunting, fishing, and harvesting of plants and animals.
Invasive species—human introduction of non-native organisms upsets balanced ecosystems.

How the Sixth Differs from Past Mass Extinctions

Human Cause: Previous mass extinctions stemmed from natural disasters or climate shifts. Today’s crisis is dominantly anthropogenic.
Scope: Earlier events were mostly evaluated by marine fossil evidence. The current event affects both terrestrial and marine organisms.
Pace: Past events unfolded over thousands or millions of years. The current extinction surge is occurring over centuries or even decades—a geologically instantaneous rate.
Biodiversity Impact: The rapid erosion of biological diversity jeopardizes ecosystem services, food security, and global climate stability.

Why Biodiversity Matters

Biodiversity is the foundation of ecosystem health. Its decline threatens:

Food security: Loss of pollinators, wild crops and aquatic species can undermine agriculture and fisheries.
Medicines: Countless pharmaceuticals rely on plants, fungi, and animals.
Climate stability: Forests and oceans play a central role in regulating carbon cycles and climate, reliant on intact ecosystems.
Resilience: Diverse ecosystems are better able to withstand and recover from disturbances.

Warning Signs: The Current State of Threatened Species

Thousands of species are classified as critically endangered, endangered, or vulnerable, including many amphibians, reptiles, birds, mammals, and plants.

According to the International Union for Conservation of Nature (IUCN), over 28% of assessed species are threatened with extinction.
The loss of keystone species and ecosystem engineers can trigger cascading effects, potentially leading to ecological collapse.

Past Extinction Events: A Closer Look

Ordovician–Silurian Extinction

Occurred about 450–440 million years ago, eliminated 60–70% of species, mostly marine, due to rapid global cooling and sea level changes.

Late Devonian Extinction

Unfolded between 375–360 million years ago, erasing about 70% of species, likely caused by changing climate, ocean anoxia, and asteroid impacts.

Permian-Triassic Extinction

The largest such event, ~252 million years ago, removing 90–96% of species; volcanic eruptions, methane release, and oceanographic changes were probable triggers (sometimes called ‘the Great Dying’).

Triassic–Jurassic Extinction

Took place around 201 million years ago, resulting in 70–75% loss, thought to have been caused by volcanic activity and climate shifts, ending many early reptiles and paving the way for the dominance of dinosaurs.

Cretaceous–Paleogene Extinction

About 66 million years ago, famously wiped out the non-avian dinosaurs and many marine species, likely due to an asteroid impact causing global wildfires and rapid ocean acidification.

Evidence for the Sixth Mass Extinction

Accelerating extinction rates—species loss far exceeds background rates, particularly among vertebrates, invertebrates, and plants.
Habitat and population declines—over two-thirds of wild animal populations have vanished in recent decades.
Disappearance of unique evolutionary lineages—losses are not just in numbers, but in entire branches of the evolutionary tree, erasing millions of years of adaptation.

Can We Stop or Slow the Sixth Extinction?

While the scale of the challenge is immense, meaningful intervention is still possible. Actions must be coordinated globally and locally:

Protect and restore habitats, especially biodiversity-rich areas like rainforests, wetlands, and coral reefs.
Strengthen conservation laws and international agreements to ban illegal wildlife trade and habitat destruction.
Promote sustainable agriculture and seafood, reducing the impact on natural ecosystems.
Address climate change by rapidly reducing greenhouse gas emissions and transitioning to clean energy.
Reduce plastic and chemical pollution to minimize ecosystem contamination.
Support wildlife corridors and ecosystem connectivity to allow species to adapt and migrate.
Promote awareness and education about biodiversity’s value and the extinction crisis.

What Individuals Can Do

Support conservation organizations through donations or volunteer work.
Choose sustainably sourced products, such as certified wood and seafood.
Reduce personal carbon footprint by using public transport, conserving energy, and eating less meat.
Create wildlife-friendly gardens and avoid pesticides.
Stay informed and advocate for strong environmental protection laws.

Frequently Asked Questions (FAQs)

What is a mass extinction?

A mass extinction is a rapid and widespread loss of a large proportion of Earth’s species, typically more than 75%, over a short geological period.

How many mass extinctions have there been before?

There have been five universally recognized mass extinctions in the past 540 million years.

How do scientists know we are in a sixth mass extinction?

Extinction rates now dramatically exceed background levels, driven primarily by human activities, and many species are disappearing at unprecedented rates.

Can the sixth mass extinction be stopped?

It is possible to halt or slow current trends, but only with coordinated global action to address root causes, protect habitat, and transform human consumption patterns.

Why does this matter to humanity?

Biodiversity underpins food, water, health, climate stability, and economic wellbeing—its collapse directly threatens the future of human societies.

References

Based on synthesis of peer-reviewed sources including Mossy Earth, Skeptical Science, and published scientific reviews.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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