The past century has not been kind to the natural world. As the human population has continued to boom, our voracious appetite for resources and land has seen the natural world pushed further and further back.

Unfortunately, this trend seems to show no signs of stopping as in the last forty years alone it is estimated the planet has lost over half of its wildlife. This has led many to conclude that humans have ushered in the sixth mass extinction, as species continue to disappear at a rate thought to be between 100 and 1,000 times greater than the natural background rate.

From insects and fish to mammals and birds, no species, no matter how remote, seem to be able to escape these downward trends. The classification of whether or not a species is endangered is not a precise science, but one based on a variety of factors including the number of individuals left, the rate of decline, threats they are facing, and how fragmented their populations are.

Bearing all that in mind, meet some of the world’s most endangered animals, and let’s hope this won’t be the last we see of them.

Spix’s macaw (Cyanopsitta spixii)

In 2000 it was thought that this beautiful blue-grey parrot – made famous by the animated film Rio – only survived in private collections. It is currently thought that there are around 110 of the birds held in captivity, all of which are descended from just seven chicks taken from only two nests. Hopes were raised, however, when one individual was potted in the wild in Brazil in 2016.

Javan rhino (Rhinoceros sondaicus sondaicus)

Once found ranging across Southeast Asia, from Bangladesh to East Java, the species has been reduced to just a single population of perhaps 50 living in Ujung Kulon National Park on the western tip of Java, Indonesia. Though once found in zoos, there are now none left in captivity, making the poor Javan rhino perhaps the rarest large mammal in the world.

Vaquita (Phocoena sinus)

The smallest, but also the most endangered, cetacean is not faring well. It is thought that only around 30 of these tiny porpoises survive in the Gulf of California, pushed to the brink of extinction as bycatch for poachers targeting the totoaba fish. Efforts to capture and save the few remaining porpoises were abandoned last year. 

Wood’s cycad (Encephalartos woodii)

In 1895 a single cluster of an unknown cycad was discovered growing in South Africa, all of which was recovered and brought into captivity. Since then, a second plant has never been found, meaning that not only is it extinct in the wild and that all examples of this plant in botanical collections are clones of this original individual, but all of them are male.

New Caledonian owlet-nightjar (Aegotheles savesi)

Not seen in the wild since 1998, this bird is only known from two collected specimens. Only found on the island of New Caledonia, it is unusual among the owlet-nightjars for being bigger and having longer legs, hinting at a more terrestrial lifestyle. The best estimate to date suggests that there are probably no more than 50 of the birds surviving.

Devils Hole pupfish (Cyprinodon diabolis)

In a single pool found in the hottest place on Earth lives one of the world’s rarest fish. Restricted to Devils Hole in Death Valley in the US, the entire wild population of pupfish exists in a collapsed cavern filled with water that measures just 22 meters (72 feet) long and 3.5 meters (11.5 feet) wide. The number of fish surviving in the pool thought to be around 115 at last count, although there is now a captive population as a backup.

Lord Howe Island stick insect (Dryococelus australis)

Often considered one of the rarest insects in the world, the tree lobster once thrived on the remote Lorde Howe Island, until it was likely driven to extinction there due to the introduction of rats. Some 80 years later, and a tiny population of the massive stick insects was rediscovered on a sheer lump of rock jutting from the ocean. Since then, Melbourne zoo has managed to captive breed thousands more, and hopes to reintroduce them back to the main island.  

Black softshell turtle (Nilssonia nigricans)

Long thought to be inbred individuals from other species of softshell turtles, genetics finally revealed that the turtles found in the manmade ponds at the Bayazid Bastami shrine in Chittagong, Bangladesh, were actually their own species and existed solely within the temple pond. In recent years, two tiny wild populations have been found, while another temple in Assam might be supporting the species, too.

Barbary lion (Panthera leo leo)

While it is generally accepted by most that the Barbary lion went extinct sometime in the 1960s, others reckon that lions descended from those kept by the Sultan of Morocco could be keeping the North African subspecies alive. It is thought that only a handful of these lions survive in captivity, but there are questions about the degree of hybridization that has occurred and the authenticity of their heritage.