Holocene extinction

The Holocene extinction, often described as the “sixth mass extinction,” refers to the ongoing, human-induced decline and disappearance of species during the current Holocene epoch. Unlike earlier mass extinctions driven by volcanic activity, asteroid impacts, or major climatic shifts, the Holocene extinction is distinguished by its exclusive origins in human activity. It has resulted in species loss across virtually all major taxonomic groups, including mammals, birds, reptiles, amphibians, fish, invertebrates, and numerous plant families, and has affected ecosystems on both land and sea. Although many species have disappeared without ever being documented, the scale of biodiversity loss has become a central concern of modern conservation biology.

Causes and Drivers of Extinction

Human actions, beginning with the expansion of Homo sapiens during the Late Pleistocene and accelerating during the Holocene, have fundamentally reshaped global biodiversity. Early human migration contributed to the extinction of numerous megafaunal species between 50,000 and 10,000 years ago. More recent losses reflect an intensification of pressures associated with agriculture, industrialisation, and a rapidly expanding global population.
The modern phase of the extinction crisis is commonly linked to the “Great Acceleration”, a period in the twentieth century marked by a fourfold increase in human population and a dramatic expansion of economic activity. During this era humanity emerged as an unprecedented “superpredator”, contributing to widespread habitat transformation, resource exploitation, and the disruption of global ecological networks.
The principal drivers of the Holocene extinction include:

• Habitat destruction, particularly through deforestation, agricultural expansion, and urbanisation
• Overexploitation of wildlife and natural resources, including overhunting and overfishing
• Climate change, which alters ecosystems and shifts species’ ranges
• Pollution, from plastics to chemical contaminants
• Introduction of invasive species, often leading to predation or competition
• Environmental degradation associated with high-consumption lifestyles, especially in affluent societies

These drivers interact synergistically, compounding the vulnerability of species. Fragile island ecosystems have been especially affected, as seen in the historical extinctions of animals in New Zealand, Madagascar, the Indian Ocean islands, and the Hawaiian archipelago.

Historical Background and Early Extinctions

Prior to the Holocene extinctions, the Late Pleistocene saw substantial declines in large mammals, with around 81 per cent of megaherbivores disappearing. Debate continues over the respective roles of climate change and human activity during this period, though recent analyses suggest that human hunting and landscape modification were the dominant drivers. Even modest pressures were sufficient to eliminate populations of large, slow-breeding animals, particularly in geographically isolated environments.
As human societies expanded across continents and islands, patterns of species loss followed. Overhunting, land clearance, and the arrival of domesticated animals and commensal species contributed to dramatic declines. In many cases extinctions occurred rapidly following human settlement, reflecting the vulnerability of native fauna to unfamiliar predators and habitat changes.

Extinction Rates and Scientific Assessment

Contemporary extinction rates far exceed natural background levels. Estimates suggest rates between 100 and 1,000 times higher than the long-term geological norm, with some analyses proposing figures as high as 10,000 times the background rate. Extinction rates vary across taxa, but plants, amphibians, and island species are among the most severely affected groups.
A number of studies highlight the scale of the crisis:

• Evidence indicates that only around 3 per cent of Earth’s terrestrial surface remains ecologically intact, retaining full native faunal assemblages with minimal human disturbance.
• Research on specific groups, such as Hawaiian land snails, suggests that as many as 7 per cent of global species may already be extinct.
• Projections for the coming century estimate that 13 to 27 per cent of terrestrial vertebrates may face extinction under continued global warming and land-use change.

The 2019 Global Assessment Report on Biodiversity and Ecosystem Services estimated that one million species are currently at risk of extinction within decades, underscoring the magnitude of the ongoing decline.

Ecological and Environmental Implications

The Holocene extinction affects ecosystems at multiple scales. The disappearance of species destabilises food webs, reduces genetic diversity, and limits ecosystem resilience. Amphibians, often regarded as early indicators of environmental disruption, have experienced severe population declines linked to pollution, disease, habitat loss, and climate change.
Marine ecosystems have also suffered from overfishing, ocean acidification, and pollution. Coral reefs, which support a vast array of marine species, have declined sharply due to warming oceans and destructive practices, reducing biodiversity in tropical waters.
Terrestrial environments face parallel pressures. Tropical rainforests and other biodiversity hotspots have experienced extensive clearing, while grasslands, wetlands, and temperate forests have undergone fragmentation and degradation. These processes reduce habitat connectivity and amplify extinction risk.

Attempts at Conservation and Mitigation

Global concern about biodiversity loss has led to numerous conservation initiatives, including protected areas, species recovery programmes, ecological restoration, and international agreements such as the Convention on Biological Diversity. Sustainable development frameworks aim to balance human needs with ecological protection.
However, the rate of habitat transformation and resource consumption continues to outpace conservation efforts. Scientists warn that without systemic changes—such as reducing environmental impact, shifting to sustainable food systems, protecting remaining wilderness, and mitigating climate change—biodiversity loss could continue at extreme rates, with long-term consequences for ecological stability and human wellbeing.

Context within Geological History

Mass extinctions are defined as events in which at least 75 per cent of species disappear within a relatively short geological interval. The Holocene extinction is often called the “sixth mass extinction,” following five major ancient crises: the Ordovician–Silurian, Late Devonian, Permian–Triassic, Triassic–Jurassic, and Cretaceous–Palaeogene extinctions. If the Capitanian extinction is considered a distinct event, the Holocene loss of species may be identified as the “seventh”.
There is ongoing debate about whether the Holocene extinction constitutes a separate phenomenon from the broader Quaternary extinction event that began in the Late Pleistocene. While the exact boundary remains unclear, the dominant scientific view is that human actions are the principal force behind recent biodiversity loss.
The consideration of an Anthropocene epoch reflects the extent to which human activity has altered the planet, though the proposal to recognise it formally was rejected in 2024. Nonetheless, the Anthropocene concept remains influential as a framework for understanding human domination of Earth systems and its role in shaping extinction patterns.

Continuing Trajectory

The Holocene extinction remains ongoing and is expected to intensify without significant changes in human behaviour. Numerous species on every continent have been lost, with near-continuous discoveries of both extinct and threatened species. The crisis highlights the fragility of ecosystems and the far-reaching consequences of human activity, raising profound questions about the sustainability of current economic and cultural practices.
Despite extensive conservation work, the future trajectory of biodiversity will depend on global efforts to reduce environmental pressures, protect habitat, and address climate change. The Holocene extinction underscores the interconnectedness of life on Earth and the urgent need to safeguard the planet’s remaining species and ecosystems.