Extinction, a natural part of Earth’s history, has seen species disappear through evolutionary changes or environmental shifts. However, the current rate of species loss is significantly higher than natural background rates. This accelerated pace of extinctions is largely attributed to human activities, making understanding recent extinctions increasingly important.
Defining Recent Extinction
Biological extinction refers to the complete and permanent disappearance of a species or taxonomic unit from Earth. While extinction is a continuous process, “recent extinction” typically refers to species lost since the mid-20th century, coinciding with intensified human impact on the planet, often termed the Anthropocene extinction event. Determining a species’ extinction status usually involves a lack of verified sightings for a considerable period, often decades, and thorough surveys of its known habitats. The International Union for Conservation of Nature (IUCN) plays a significant role in assessing and declaring species extinct through its Red List.
Notable Recent Extinctions
Many species have vanished recently, serving as examples of this accelerated loss.
Tasmanian Tiger
The Tasmanian Tiger (Thylacine), a carnivorous marsupial native to Australia, Tasmania, and New Guinea, was characterized by its dog-like appearance and distinctive striped lower back. It was hunted to extinction, with the last known individual dying in captivity in 1936.
Steller’s Sea Cow
The Steller’s Sea Cow (Hydrodamalis gigas), a massive marine mammal reaching up to 10 meters and weighing 11 tonnes, inhabited the sub-Arctic waters of the North Pacific. Discovered by Europeans in 1741, it was relentlessly hunted for its meat, fat, and hide, leading to its extinction by 1768, less than three decades after its discovery. Its slow movement, gregarious nature, and habit of feeding on kelp in shallow waters made it an easy target.
Passenger Pigeon
The Passenger Pigeon (Ectopistes migratorius) was once the most abundant bird in North America, with flocks numbering in the billions that could darken the sky. This pigeon, with males featuring bright orange throats and bluish-grey heads, primarily lived in eastern North America. Despite its vast numbers, overhunting for food and habitat loss due to deforestation led to its rapid decline, with the last known individual, Martha, dying in the Cincinnati Zoo in 1914.
Yangtze River Dolphin
The Yangtze River Dolphin (Baiji, Lipotes vexillifer), a freshwater dolphin native to China’s Yangtze River, was a slender, greyish-white mammal with a long, narrow beak. Its population drastically declined due to intense human activity on the river, including fishing, boat traffic, and pollution. The last confirmed sighting was in 2002, and it was declared functionally extinct in 2007.
West African Black Rhinoceros
The West African Black Rhinoceros (Diceros bicornis longipes) was a subspecies of black rhinoceros that once roamed the savannas of sub-Saharan Africa. Its numbers plummeted due to widespread poaching for its horn, used in traditional medicine and for making dagger handles. Despite conservation efforts, the last known individuals were seen in 2006, and the subspecies was declared extinct by the IUCN in 2011.
Golden Toad
The Golden Toad (Incilius periglenes) was a small, brightly colored amphibian, with males exhibiting a striking golden-orange hue, found only in a small cloud forest region in Costa Rica. Its rapid disappearance was well-documented, with the last sighting occurring in 1989. Climate change leading to drier conditions and the spread of chytridiomycosis, a fungal disease, are considered primary factors in its extinction, officially declared in 2004.
Pinta Island Tortoise
The Pinta Island Tortoise (Chelonoidis abingdonii), a subspecies of Galápagos giant tortoise, was native to Pinta Island. These large terrestrial turtles faced severe threats from harvesting by whalers and fishermen, and competition for food from introduced goats. Lonesome George, the last known individual of this subspecies, died in 2012, marking its extinction.
Primary Drivers of Recent Extinctions
Human activities primarily drive accelerated species extinctions.
Habitat loss and fragmentation converts natural environments for agriculture, urbanization, and infrastructure. This destruction reduces available living space and resources, often isolating populations and making them more vulnerable.
Overexploitation, including excessive hunting, fishing, and unsustainable harvesting, has driven many species to extinction. Demand for products like rhino horns or passenger pigeon meat exemplifies how overexploitation decimates populations.
Climate change alters habitats through rising temperatures, changing precipitation, and extreme weather events. These shifts can push species beyond their adaptive capacities, as seen with the Golden Toad.
Invasive species introduced to new environments pose a serious risk. These non-native organisms can outcompete native species for resources, prey upon them, or introduce new diseases, leading to declines and extinctions.
Pollution contaminates air, water, and soil, directly harming wildlife and degrading habitats. Pollutants disrupt food chains, cause reproductive problems, and lead to population crashes.
Ecological and Global Consequences
Species loss has far-reaching implications, contributing to biodiversity loss that weakens ecosystem resilience and stability. Fewer species make ecosystems less adaptable to challenges like climate change or new diseases. Disrupted food webs and ecological relationships can lead to cascading effects. For instance, pollinator loss can negatively impact crop production and global food security. Ecosystems provide essential services like clean water, air, soil formation, and climate regulation. As biodiversity erodes, these services are compromised, diminishing the planet’s capacity to support life, including human populations.