The Holocene Extinction refers to the ongoing widespread disappearance of species across Earth. This event represents a significant biological change in the planet’s history, distinct from past natural extinction cycles. It is characterized by an unprecedented rate of species loss, primarily driven by human activities.
Defining the Holocene Extinction
The Holocene Extinction is recognized as the sixth major mass extinction event in Earth’s geological history. Unlike previous mass extinctions caused by natural phenomena, this ongoing event is predominantly attributed to the actions of a single species: Homo sapiens. It began approximately 11,700 years ago, coinciding with the start of the Holocene epoch and the advent of agriculture, which marked a period of increasing human impact on the planet.
Drivers of Species Loss
Human activities are primary drivers of species loss. Habitat destruction and fragmentation, where natural environments are converted for agriculture, urbanization, and infrastructure, reduce living space and resources, leading to population declines and extinctions. Pollution also plays a substantial role, with forms like chemical runoff, plastic accumulation, and nutrient overload harming ecosystems and wildlife. These pollutants degrade habitats, poison organisms, or disrupt reproductive patterns, impacting entire food chains.
Climate change is another significant factor, altering habitats and disrupting species’ life cycles as global temperatures rise. Changes in temperature and precipitation patterns can push species beyond their physiological tolerances, making environments uninhabitable or affecting food sources. Overexploitation, including unsustainable hunting, fishing, and harvesting of natural resources, depletes populations faster than they can reproduce.
This practice can lead to population collapse and cascading effects on ecosystems. Finally, the introduction of invasive species by humans can severely impact native populations. These non-native species outcompete native organisms for resources, prey on them, or introduce new diseases.
Magnitude and Rate of Extinction
The current rate of species loss during the Holocene Extinction is significantly higher than the natural background extinction rate observed throughout geological history. Estimates suggest present-day extinction rates are between 100 to 1,000 times greater than the background rate, which is estimated at one to five species per year across all organisms. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) reported in 2019 that approximately one million plant and animal species are at risk of extinction within decades due to human activities.
Vertebrate populations have experienced substantial declines, with an average plummet of nearly 70% since 1970. While all taxonomic groups are affected, large vertebrates, amphibians, and insects are particularly vulnerable. The concept of “extinction debt” describes species committed to future extinction due to past environmental changes, such as habitat destruction. This time lag means many species are on an irreversible path to disappearance, even if current impacts cease, highlighting long-term consequences.
Ecological Consequences
The loss of species extends beyond individual disappearances, profoundly impacting entire ecosystems and the services they provide. As biodiversity declines, ecosystems can experience simplification and even collapse. The removal of certain species, especially those with foundational roles, can destabilize intricate food webs and disrupt essential ecological processes. This reduction in complexity makes ecosystems less resilient and more vulnerable to disturbances like disease outbreaks or climate extremes.
Ecosystem services, natural processes that benefit human well-being, are also severely affected. These services include functions such as pollination for crops, natural water purification, soil formation and nutrient cycling, and climate regulation. The degradation or loss of these services can have significant economic and social costs, impacting food security and overall environmental quality. As ecosystems become less diverse, their capacity to adapt to changing conditions diminishes, creating a cycle of decline that affects both natural systems and human societies.