Extinction
Overview
Extinction is the phenomenon where all individuals of a biological species or taxon cease to exist. Throughout Earth's history, many species have gone extinct due to natural factors and environmental changes, and claims that a rapid sixth mass extinction is currently underway due to human activity are gaining strength.
Main Content
Definition and Types of Extinction
Extinction goes beyond simply a decline in population; it means the complete loss of the species' genetic uniqueness. It is generally divided into background extinction and mass extinction. Background extinction refers to the low level of extinction occurring naturally over geological time, while mass extinction refers to events in which more than 75% of species on Earth disappear within a short period.
There are also concepts such as local extinction (extirpation) and ecological extinction. Local extinction occurs when a species disappears from a specific area but remains elsewhere, while ecological extinction refers to a state where the population is so small that it no longer affects ecosystem functions.
Causes of Extinction
The causes of extinction can be broadly divided into natural factors and anthropogenic factors.
- Natural factors: These include climate change, sea level fluctuations, volcanic eruptions, meteor impacts, disease, and the emergence of competing species. The mass extinctions at the end of the Paleozoic and Mesozoic eras are representative examples resulting from these natural factors.
- Anthropogenic factors: These include habitat destruction, overexploitation, environmental pollution, climate change, introduction of invasive species, agriculture, and urban development. In particular, since the Industrial Revolution, human activity has been reducing biodiversity at a rate hundreds to thousands of times faster than the natural background extinction rate.
The Five Mass Extinctions in Geologic History
Earth's history records a total of five mass extinctions.
1. Ordovician–Silurian extinction event (approximately 443 million years ago): About 85% of marine species disappeared due to an ice age and falling sea levels.
2. Late Devonian extinction event (approximately 359 million years ago): Marine invertebrates and coral reefs were severely affected, with the cause suspected to be oceanic anoxic events.
3. Permian–Triassic extinction event (approximately 252 million years ago): The largest in Earth's history; 96% of marine species and 70% of terrestrial vertebrates disappeared. Volcanic activity from the Siberian Traps is considered the main culprit.
4. Triassic–Jurassic extinction event (approximately 200 million years ago): Ocean acidification and volcanic activity caused the extinction of a significant number of reptiles and amphibians.
5. Cretaceous–Paleogene extinction event (approximately 66 million years ago): An asteroid impact wiped out 75% of species, including the dinosaurs. The Chicxulub crater, the impact crater, is located on the Yucatán Peninsula in Mexico.
Ecological Impacts of Extinction
Extinction does not simply end with the loss of one species. When food chains within an ecosystem collapse, or when specific plants lose their pollinators, other species are affected in a cascade. For example, the loss of large predators in a jungle can lead to an explosion in herbivore populations, resulting in trophic collapse that destroys vegetation.
Extinction also leads to a reduction in biodiversity and weakens ecosystem resilience. Because higher biodiversity provides greater adaptability to environmental changes, extinction poses a direct threat to human food security and pharmaceutical development.
Conservation Efforts and Reintroduction
Various international efforts are underway to prevent extinction crises. The International Union for Conservation of Nature (IUCN) publishes the Red List to assess the extinction risk levels of species worldwide. CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) regulates international trade in certain species. In addition, zoos and botanical gardens operate conservation breeding programs, and techniques such as natural habitat protection and restoration, anti-poaching enforcement, artificial insemination, and genetic preservation technologies are also used.
Latest Trends
As of 2024–2025, a United Nations (UN) report has warned that about one million species are at risk of extinction within decades due to human activity. As climate change accelerates, species that depend on specific habitats—such as polar bears, coral reefs, and alpine plants—face particularly elevated risks.
Moreover, in 2024, genetic preservation research such as the Espresso Diversity Project and restoration research on endangered species using CRISPR gene-editing technology are being conducted. Notably, de-extinction attempts such as the mammoth restoration project are sparking scientific debate. Some experts emphasize the importance of polar genetic banks such as the Svalbard Global Seed Vault in Norway and point to the potential of advances in DNA preservation technology.
However, entering 2025, the World Economic Forum (WEF) has projected that biodiversity loss will become one of the greatest threats to the global economy over the next decade, urging ecosystem protection policies at the corporate and governmental levels.
Related Topics
- [[Mass extinction]]
- [[Endangered species]]
- [[Biodiversity]]
- [[Evolution]]
- [[Natural selection]]