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The Sixth Mass Extinction: One Million Species at Risk of Disappearing

World · January 26, 2025 · Liam Chen · 9 min

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Scientists warn we are in the early stages of Earth's sixth mass extinction, with species disappearing at 100-1,000 times the natural rate. One million species face extinction within decades unless urgent action is taken. Here's what's driving the crisis and what can still be saved.

The world is in the grip of a biodiversity crisis so severe that scientists describe it as Earth's sixth mass extinction. One million animal and plant species—around one in eight of all known species—are threatened with extinction, many within decades, according to the 2019 Global Assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). Species are disappearing at a rate 100 to 1,000 times faster than the natural background rate, driven by habitat destruction, overexploitation, pollution, invasive species, and climate change. Wildlife populations have declined by an average of 69% since 1970, with freshwater species down 83%, according to WWF's 2024 Living Planet Report. The UK is one of the most nature-depleted countries in the world, having lost 50% of its biodiversity since the Industrial Revolution, and ranking 189th out of 218 countries for biodiversity intactness. Unlike the five previous mass extinctions—caused by asteroids, volcanic eruptions, and ice ages—this one is driven by human activity and is happening at unprecedented speed. But unlike natural extinctions, this one is preventable. Here's the scale of the crisis, what's driving it, and what can still be done to halt and reverse biodiversity loss.

The numbers: one million species at risk

The IPBES 2019 Global Assessment, the most comprehensive review of the state of nature ever conducted, found that:

• One million species are threatened with extinction (out of an estimated 8 million total species)
• 25% of assessed species are threatened with extinction across all groups (mammals, birds, amphibians, plants, insects)
• 40% of amphibian species are threatened
• 33% of reef-forming corals are threatened
• 10% of insect species are threatened (though data is limited)
• More than 500,000 land species have insufficient habitat left for long-term survival

The rate of extinction is accelerating. Since 1900, the average abundance of native species in most major land-based habitats has fallen by at least 20%. More than 680 vertebrate species have been driven to extinction since the 16th century, and the rate is increasing—species that took millions of years to evolve are disappearing within human lifetimes.

The drivers: what's killing biodiversity

The IPBES assessment identified five direct drivers of biodiversity loss, in order of impact:

1. Land and sea use change (habitat loss): The biggest driver. Humans have converted 75% of ice-free land and 66% of ocean area for agriculture, cities, infrastructure, and industry. Forests, wetlands, grasslands, and coral reefs have been cleared, drained, or degraded, destroying the habitats species need to survive.

• Deforestation: 10 million hectares of forest are lost every year, mostly in the tropics (Amazon, Congo, Southeast Asia), driven by agriculture (soy, palm oil, cattle ranching) and logging.
• Agricultural expansion: Agriculture occupies 50% of habitable land, leaving little room for wildlife. Intensive farming (monocultures, pesticides, fertilisers) further reduces biodiversity within farmed areas.
• Urbanisation: Cities and infrastructure fragment habitats, isolating populations and reducing genetic diversity.

2. Overexploitation (overfishing, hunting, logging): Humans are harvesting species faster than they can reproduce.

• Overfishing: 34% of global fish stocks are overfished, and 60% are fished at maximum sustainable levels, leaving no buffer for recovery. Bycatch (unintended catch) kills millions of seabirds, turtles, and dolphins annually.
• Illegal wildlife trade: Worth $7-23 billion per year, driving species like elephants, rhinos, pangolins, and tigers towards extinction.
• Logging: Unsustainable logging degrades forests and removes old-growth trees that provide critical habitat.

3. Climate change: Rising temperatures, changing rainfall, and extreme weather are shifting habitats faster than species can adapt.

• Coral bleaching: 50% of coral reefs have died since the 1980s due to warming oceans. At 1.5°C of global warming, 70-90% of reefs will be lost; at 2°C, over 99% will be lost.
• Range shifts: Species are moving towards the poles or to higher altitudes to escape warming, but many can't move fast enough or have nowhere to go (e.g., mountain species).
• Phenological mismatches: Warming disrupts the timing of migration, breeding, and flowering, causing mismatches between species and their food sources (e.g., birds arriving too late for peak insect abundance).

4. Pollution: Pesticides, plastics, nitrogen, and other pollutants poison ecosystems and species.

• Pesticides: Neonicotinoid insecticides have been linked to bee declines and are banned in the EU but still used widely elsewhere.
• Plastic pollution: Kills marine life through ingestion and entanglement; microplastics are now found in every ecosystem.
• Nutrient pollution: Excess nitrogen and phosphorus from fertilisers cause algal blooms that deplete oxygen in rivers and coastal waters, creating "dead zones."

5. Invasive species: Non-native species introduced by humans (rats, cats, plants, diseases) outcompete, prey on, or infect native species.

• Island extinctions: Invasive rats, cats, and snakes have driven many island bird species to extinction.
• Diseases: Chytrid fungus, spread by the global wildlife trade, has driven 90+ amphibian species to extinction.

The UK: one of the world's most nature-depleted countries

The UK has lost more of its biodiversity than almost any other country. The 2023 State of Nature report, compiled by over 60 conservation organisations, found:

• 50% of UK biodiversity has been lost since the Industrial Revolution (1750s)
• 16% of species are threatened with extinction from Great Britain
• 41% of species have declined since 1970
• The UK ranks 189th out of 218 countries for biodiversity intactness (a measure of how much natural biodiversity remains)

What's been lost:

• 97% of wildflower meadows have disappeared since the 1930s, replaced by intensive agriculture
• 50% of ancient woodland has been lost since 1930
• 90% of wetlands have been drained for agriculture
• Farmland bird populations have fallen by 57% since 1970 (skylarks, lapwings, grey partridges)
• Insect populations have declined by 60% since 1970, including bees, butterflies, and moths
• Hedgehog numbers have fallen by 95% since the 1950s

What's driving UK biodiversity loss:

• Intensive agriculture: 70% of UK land is farmed, and most is intensively managed with pesticides, fertilisers, and monocultures that leave little room for wildlife.
• Habitat fragmentation: Roads, cities, and farmland have fragmented habitats, isolating wildlife populations.
• Pollution: Agricultural runoff, sewage, and air pollution degrade rivers, soils, and air quality.
• Climate change: Warming is shifting species ranges and disrupting ecosystems, particularly in upland and coastal areas.

The global picture: wildlife populations down 69%

WWF's 2024 Living Planet Report tracks population trends of over 30,000 vertebrate species (mammals, birds, fish, reptiles, amphibians) using the Living Planet Index. Key findings:

• Global wildlife populations have declined by an average of 69% since 1970
• Freshwater species have declined by 83% (the worst-affected group)
• Latin American populations have declined by 94% (driven by deforestation in the Amazon and habitat loss)
• Tropical populations have declined by 69%
• Temperate populations have declined by 18% (less than tropical, but starting from a lower baseline due to centuries of habitat loss)

The declines are not evenly distributed. Some species and regions are doing better (e.g., European bison, humpback whales), but these are exceptions. The overall trend is towards impoverishment—fewer species, smaller populations, less genetic diversity.

Why biodiversity loss matters: ecosystem services and intrinsic value

Biodiversity is not just about saving charismatic species like tigers and elephants (though that matters too). Biodiversity underpins the ecosystem services that humans depend on:

Food: 75% of global food crops rely on animal pollination (bees, butterflies, birds, bats). Pollinators contribute $235-577 billion per year to global agriculture. Insect declines threaten food security.

Clean water: Forests, wetlands, and soils filter and store water. Degraded ecosystems reduce water quality and increase flood risk.

Climate regulation: Forests and oceans absorb about half of human CO2 emissions. Deforestation and ecosystem degradation reduce this carbon sink, accelerating climate change.

Medicines: 50% of pharmaceuticals are derived from natural compounds (e.g., aspirin from willow bark, cancer drugs from Pacific yew trees). Biodiversity loss reduces the pool of potential medicines.

Disease regulation: Biodiverse ecosystems regulate disease by supporting predators and competitors that limit disease vectors (e.g., bats eat mosquitoes). Biodiversity loss increases pandemic risk—diseases like COVID-19, Ebola, and Zika emerge when humans encroach on wild habitats.

Beyond material benefits, biodiversity has intrinsic value—many people believe species have a right to exist regardless of their utility to humans, and that humans have a moral duty to protect the natural world.

What's being done: the Global Biodiversity Framework

In December 2022, 196 countries agreed to the Kunming-Montreal Global Biodiversity Framework at the UN Biodiversity Conference (COP15). The framework sets 23 targets to halt and reverse biodiversity loss by 2030, including:

30x30: Protect and conserve 30% of land and 30% of sea by 2030, focusing on areas of high biodiversity and ecosystem integrity. Currently, 17% of land and 8% of sea are protected.

Restore 30% of degraded ecosystems by 2030 (forests, wetlands, rivers, grasslands).

Reduce extinction risk: Ensure the extinction rate and risk of all species are reduced, with a focus on threatened species.

Reduce pollution: Cut nutrient pollution (nitrogen, phosphorus) by 50%, pesticide use by 50%, and plastic waste by 50%.