The Anthropocene: Are we living in the sixth mass extinction?

Extinction refers to the irreversible loss of a species – when the last individual dies and no living members remain anywhere on Earth. Biologically, extinction marks the end of a unique evolutionary lineage, including the loss of that species’ genetic information, ecological functions, and interactions with other organisms. Unlike species population decline, which may be reversible, extinction is final. Once a species is extinct, it cannot be recovered, except in speculative and ethically contested forms such as ‘de-extinction’ through genetic technologies. Extinction is often perceived as a distant or dramatic event, confined to prehistoric epochs or remote ecosystems. However, as humanity reshapes the planet’s systems, extinction has become a defining feature of the Anthropocene, with some scientists arguing that we are experiencing a sixth mass extinction – the aptly named Anthropocene Extinction. This article unpacks how extinction has unfolded in the past, how it is manifesting today, and what actions are being taken to mitigate species extinction.

Historical extinctions and their causes

Earth’s history is punctuated by episodes of mass extinction, defined as periods during which 75% of species disappear in a relatively short geological timeframe (typically taken as 200 million years). Five such events are widely recognised, including the end-Permian extinction approximately 252 million years ago, which eliminated an estimated 90% of marine species, and the end-Cretaceous extinction 66 million years ago, which famously led to the disappearance of non-avian dinosaurs. These mass extinctions are thought to have been driven by globally impactful environmental disturbances, including volcanic activity, asteroid impacts, rapid climate change, ocean acidification, and anoxia (loss of oxygen). Beyond these dramatic episodes, extinction has also occurred continuously at lower levels through processes such as climate oscillations, continental drift, ecological competition, and evolutionary replacement. Species with narrow ecological niches, limited geographic ranges, or specialised life histories have historically been more vulnerable to extinction. 

Importantly, pre-human extinctions were driven by natural Earth system processes, unfolding over timescales that allowed surviving species to diversify and fill vacated ecological roles. The arrival of humans added a new and increasingly dominant extinction driver. Archaeological and palaeoecological evidence suggests that the global expansion of Homo sapiens was closely associated with the extinction of large mammals (‘megafauna’) in Australia, the Americas, and parts of Eurasia during the late Pleistocene. These extinctions were likely driven by a combination of overhunting, habitat modification, and climate stress, foreshadowing patterns that would intensify in later eras.

The Anthropocene and the sixth mass extinction

The contemporary period is increasingly described as the Anthropocene, a proposed geological epoch in which human activity constitutes the dominant force shaping Earth’s systems. Within this context, many scientists argue that the planet is undergoing a sixth mass extinction, driven by the cumulative effects of human behaviour. Current extinction rates are estimated to be tens to hundreds of times higher than natural levels, with some projections suggesting even greater acceleration in the coming decades. An estimated 200 million species are at risk.

The primary drivers of Anthropocene extinction are well established. Habitat destruction and fragmentation, driven by agriculture, urbanisation, mining, and infrastructure development, remain the leading cause of species loss. Climate change is increasingly acting as a threat multiplier, altering temperatures, precipitation patterns, ocean chemistry, species food security, and the timing of ecological interactions. Overexploitation of ecosystems through hunting, fishing, and wildlife trade continues to push many species beyond recovery thresholds, while invasive species and pathogens disrupt ecosystems ill-equipped to respond.

Species at greatest risk tend to share common vulnerabilities. Amphibians experience particularly high extinction rates due to habitat loss, climate sensitivity, and emerging diseases such as chytridiomycosis. Large mammals and apex predators face pressures from habitat contraction and human-animal conflict, while coral reefs are undergoing widespread bleaching as ocean temperatures rise. Freshwater species, including fish and invertebrates, are declining due to overfishing, pollution, water extraction, and river modification.

Some extinctions have already occurred within living memory – the dodo, the quagga, the woolly mammoth. The passenger pigeon, once amongst the most abundant birds on Earth, was driven to extinction in the early twentieth century by industrial-scale hunting and habitat loss. The last thylacine, or Tasmanian tiger, died in 1936, the species driven to extinction following persecution and ecological disruption. More recently, species such as the Bramble Cay melomys have been declared extinct as a direct result of climate-driven habitat loss. Various existing species are projected to become extinct in the near future such as species of the rhinoceros (there are only about 3000 black rhino’s left), pangolins, and some primates, and the number of species assessed as threatened with extinction on the IUCN (International Union for Conservation of Nature) Red List has continued to grow as assessment coverage expands.  

What happens when a species goes extinct?

Species are embedded within and contribute to complex ecological systems. Some species play functionally disproportionate roles, such as apex predators, pollinators, scavengers, or habitat-forming organisms, such that their loss triggers cascading effects throughout the system. The extinction of such species, therefore, represents a potential loss of ecosystem function, with effects beyond the loss of a unique species. For example, insects such as bees, butterflies, beetles, and flies are vital for pollination and the reproduction of a large proportion of flowering plants, including many crops central to human food systems. Indeed, pollinators are necessary for approximately 75% of food crops. Over the past 25 years, there has been a decline of about 75% of insect populations, at a rate of 1-2% every year, and 40% of insect species face extinction. As pollinator populations decline, plants experience reduced reproductive success, leading to effects on species that depend on those plants for food and shelter. Insects also contribute to soil formation, decomposition, and nutrient cycling, and their loss can impair ecosystem functions that are fundamental to supporting life. The extinction of species, therefore, is a process that erodes the integrity of ecological systems, diminishing the capacity of both natural and human systems to adapt and survive.

What can be done?

Extinction does not have to be inevitable for all threatened species. Throughout history, there are examples of deliberate efforts that have halted species decline and enabled recovery. For example, the recovery of the bald eagle in the United States following the banning of DDT (a pesticide) was achieved through regulatory reform. Conservation programmes (e.g., captive breeding and habitat management) for species such as the black-footed ferret, the giant panda, and several whale populations have reversed trajectories of decline. Community-led conservation initiatives, particularly those involving Indigenous stewardship, have also proven effective in sustaining species. Other measures include establishing protected areas, reconnecting fragmented landscapes (e.g., wildlife corridors), and creating legal frameworks that protect terrestrial and marine areas, regulate land use, wildlife exploitation, and pollution. Additionally, addressing climate change and other environmental crises is inseparable from species conservation.

Conclusion

While extinction has always been part of Earth’s history, the Anthropocene presents a uniquely moral, political, social, and economic challenge. For the first time, a single species exerts disproportionate power over the fate of millions of others. Extinction, moreover, does not affect only non-human species; it has consequences for human societies and the systems on which we depend. In 2018, extinction was described as a “silent killer” by the United Nations’ then biodiversity chief, Cristiana Paşca Palmer, capturing the crisis’s complex, protracted, and often invisible nature, as well as its potentially catastrophic implications for human wellbeing. Unlike acute environmental disasters, extinction unfolds gradually, attracting limited political attention even as species collapse around us. Encouragingly, global conservation efforts have coalesced around ambitious targets, including proposals to protect 30% of the planet by 2030 and up to 50% by 2050. While such commitments are necessary, they need to be backed by widespread systems change. Preventing mass extinction will require rethinking humanity’s relationship with the living world, extending beyond protected areas to encompass how societies organise economies, consume resources, produce food, and navigate population pressures.