Extinction is a natural process where species disappear from Earth. While it has occurred throughout geological history, current extinction rates are significantly higher than historical levels. This accelerated biodiversity loss raises concerns about global ecosystem health and highlights environmental challenges.
The Most Recent Officially Declared Extinction
The most recent animal widely recognized as officially extinct is the Bramble Cay melomys (Melomys rubicola), a small rodent native to Bramble Cay, a tiny island at the northern tip of Australia’s Great Barrier Reef. The International Union for Conservation of Nature (IUCN) formally declared this species extinct in 2015, with the Australian government officially recognizing its extinction in February 2019. The Bramble Cay melomys holds the distinction of being the first mammal extinction attributed primarily to human-caused climate change.
The last known sighting of a Bramble Cay melomys was in 2009. Researchers believe the population, which once numbered in the hundreds in 1978, rapidly declined due to repeated ocean inundation of their low-lying island habitat. Rising sea levels and more frequent, intense storm surges led to significant loss of vegetation, which served as food and shelter. The island’s highest point was only three meters (ten feet) above sea level, making it exceptionally vulnerable.
How Extinction is Confirmed
Confirming a species’ extinction involves a rigorous scientific process, often overseen by organizations like the IUCN, which maintains the Red List. A species is declared “Extinct” (EX) when there is no reasonable doubt that the last individual has died. This determination follows exhaustive surveys in known or expected habitats over a timeframe appropriate to the species’ life cycle.
Proving a species’ complete absence is challenging. Scientists consider population decline, geographic range reduction, and the severity of threats. Another classification is “Extinct in the Wild” (EW), meaning the species survives only in captivity or outside its natural historical range. The IUCN Red List uses specific criteria, including population size, distribution, and quantitative analysis, to categorize species and assess extinction risk.
Key Drivers of Recent Extinctions
Human activities largely drive the accelerated rate of recent extinctions. Primary drivers include habitat loss, climate change, invasive species, pollution, and overexploitation. These often interact, creating complex pressures.
Habitat loss and fragmentation are the leading cause of biodiversity decline. This results from converting natural landscapes for agriculture, urbanization, and resource extraction, leaving species without necessary space and resources. Climate change, exemplified by the Bramble Cay melomys, directly alters habitats through rising temperatures, sea-level rise, and extreme weather events. It also indirectly affects species by disrupting ecosystems and increasing disease spread.
Invasive species, non-native organisms, can outcompete native species, prey upon them, or introduce new diseases. They are a significant factor in many extinctions, particularly on islands where native species lack defenses. Pollution, from chemicals and waste to light and noise, degrades ecosystems and harms wildlife, causing health and reproductive problems. Finally, overexploitation, the unsustainable harvesting of wild populations, depletes species numbers faster than they can reproduce. This includes overhunting, overfishing, and excessive logging.