Extinction is a natural process that has occurred throughout Earth’s history, but the current rate of species loss is accelerated. Scientists widely agree that the planet is currently experiencing its Sixth Mass Extinction event, a crisis driven almost entirely by human activity. For a species to be declared “recently extinct” means that a long, exhaustive process of scientific search has concluded that its last living individual has perished, leaving a void in the world’s biodiversity. The final declaration of loss often trails the actual disappearance of the species by years, or even decades, as researchers hold onto the hope of a rediscovery.
Identifying the Most Recent Losses
Recent years have seen the confirmation of several high-profile extinctions across various groups of animals. The Bramble Cay Melomys, a small rodent found only on a tiny coral cay in the Great Barrier Reef, was officially declared extinct by the Australian government in 2019, making it the first known mammal species lost directly due to human-caused climate change. Its low-lying habitat was repeatedly inundated by rising sea levels and storm surges. Another notable loss is the Chinese Paddlefish, one of the world’s largest freshwater fish, which was declared extinct in 2020 after no sightings since 2003.
Amphibians have been particularly hard-hit, with dozens of species confirmed or presumed extinct due to a fungal disease. The Mountain Mist Frog and the Sharp-snouted Day Frog, both native to Australia’s rainforests, were officially declared extinct in 2021. These species were victims of the chytrid fungus, a pathogen that has caused the decline of over 500 amphibian species globally. The Pinta Giant Tortoise became functionally extinct with the death of its last known member, “Lonesome George,” in 2012. The loss spurred conservation efforts to “back-breed” the species using hybrid tortoises carrying Pinta Island genes.
The Formal Process of Declaring Extinction
The formal declaration of extinction is a rigorous scientific and administrative process managed globally by the International Union for Conservation of Nature (IUCN). The IUCN Red List of Threatened Species assigns species one of nine categories, and moving a species from “Critically Endangered” to “Extinct” requires extensive documentation. Scientists must conduct exhaustive surveys across the species’ known or suspected range over a defined period to prove its absence. This methodical approach is necessary to guard against the “Lazarus effect,” the rare chance that a species thought to be extinct is rediscovered alive.
The standard for declaration is based on the lack of any confirmed record of the species for a period appropriate to its life span and life history, which can be decades for long-lived animals. Even after a species disappears, conservationists often classify it as “Possibly Extinct” or “Critically Endangered (Possibly Extinct)” before the final move to “Extinct.” This cautious system ensures that resources are not prematurely withdrawn from a species that might still be clinging to existence in a remote area.
Primary Drivers of Recent Species Loss
The disappearances of these species are overwhelmingly linked to four primary human-caused factors.
- Habitat loss and fragmentation: Clearing land for agriculture, logging, and development shrinks the range of species, often isolating populations and making them vulnerable to local disasters. This includes blocking migration routes, such as those caused by dam construction.
- Invasive species: Invasive predators and pathogens can wipe out native species that have no natural defenses against them. This is exemplified by the chytrid fungus, which has caused numerous amphibian extinctions after being spread globally by human activity.
- Overexploitation: Unsustainable resource use, such as intense fishing, pushes vulnerable populations past a tipping point.
- Climate change: The effects of climate change, such as sea-level rise, are becoming a rapidly accelerating driver of extinction.
Ecological Ramifications of Species Loss
The disappearance of a single species unleashes a cascade of detrimental effects that destabilize the entire ecosystem. This phenomenon, known as a trophic cascade, occurs when the loss of a key predator or herbivore allows populations at other levels of the food web to spiral out of control. For instance, losing an amphibian population can lead to a surge in insect numbers, including disease-carrying mosquitoes, and a reduction in the food source for riparian predators.
The loss of animals that perform vital ecosystem services also impacts the plant community. Many plants rely on animals for the dispersal of their fruits and seeds, a process essential for their reproduction and for their ability to colonize new areas, particularly as climates shift. When a species like a seed-dispersing mammal or bird is lost, the plants they supported may become geographically trapped, unable to recover from disturbances like fire or move to more suitable habitats. The net result is a simplification of the environment, making the entire system less resilient to future environmental shocks.