WATCH | Earth is losing animal species at 1,000 to 10,000 times the natural rate.
In 2018, scientists announced that three bird species vanished from the Earth for good, and more species on the brink could disappear forever in 2019.
Dissimilar to mass extinctions in the past, our current extinction crisis is almost solely caused by humans — specifically activities that cause loss of habitat, introduce alien species and contribute to the changing climate.
The Earth is losing animal species at 1,000 to 10,000 times the natural rate, and as many as 30 to 50 percent of the planet's species may be extinct by 2050, the @CenterForBioDiv describes. The natural rate is around one to five species lost each year.
"Our planet is now amidst its sixth mass extinction of plants and animals—the sixth wave of extinctions in the past half-billion years," @CenterForBioDiv stated. "We're currently experiencing the worst spate of species die-offs since the loss of dinosaurs 65 million years ago."
A small songbird native to Hawaii, the Po'ouli was discovered over 45 years ago. In 1981, its population topped some 150 birds, but saw a decline driven by invasive alien species, according to the U.S. Fish and Wildlife Service.
Habitat destruction by feral pigs, being hunted by mongooses, cats and rats, mosquito-spread diseases and competition with birds introduced in the area all were factors in the Po'ouli's extinction. The last wild sighting of Hawaii's Po'ouli was in 2004.
2⃣Alagoas Foliage-gleaner and Cryptic Treehunter
The Alagoas Foliage-gleaner was discovered in 1975, Neotropical Birds lists, and it wasn't until 2002 that researchers discovered the Cryptic Treehunter was a new species of its own, according to BirdLife International.
When the treehunter was discovered, it was immediately placed into the "Critically Endangered" category, like other unique birds in the region.
The last sighting of the Cryptic Treehunter was in 2007, while the Alagoas Foliage-gleaner was last seen in 2011.
A 2016 sighting brought hope that the then-critically endangered species was still alive in the wild, but it was later believed to be one that escaped captivity.
4⃣On the brink - Vaquita
Discovered in 1958, the vaquita is the world's rarest marine mammal and could go extinct any day, according to the World Wildlife Foundation. A small porpoise, the vaquita is the smallest cetacean species and calls the northern Gulf of California home.
The vaquita's decline in population largely stems from being caught and drowned in illegal gillnet fishing equipment. Less than 30 vaquita remain in the wild.
5⃣On the brink - Northern White Rhino
In March 2018, Sudan, the last remaining male northern white rhino, died at the age of 45. With Sudan's passing, the total number remaining northern white rhinos dropped to two—both of which are female and incapable of natural reproduction.
The population's decline was caused by extensive poaching for their horns, the World Wildlife Foundation says.
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