Turtles are one of the oldest extant reptile groups on earth, with the earliest known members dating from the Middle Jurassic Epoch over 160 million years ago. Unfortunately, many turtle species are now threatened with extinction, with the greatest threats to their survival stemming from habitat destruction and overexploitation in the pet trade. Of the 356 known species of turtles, 161 of them are listed as threatened by the International Union for Conservation of Nature (IUCN). Of the 161 threatened species, 51 of them are considered Critically Endangered, the designation from the IUCN indicating the highest risk of extinction. Thus, over one-seventh of all turtle species may soon be extinct if greater conservation efforts are not implemented.

1 of 11 Radiated Tortoise Kyle Bedell / Wikimedia Commons / CC BY 2.0 The radiated tortoise (Astrochelys radiata) is native to southern Madagascar but is also found in smaller numbers in other parts of the island. Once abundant throughout the island, the species is now listed as Critically Endangered by the IUCN. The radiated tortoise is locally extinct in approximately 40% of areas on the island where it had previously lived, and one study has estimated that if further conservation efforts are not undertaken, the species will become extinct within the next 50 years. The most severe threats to the radiated tortoise include habitat loss and poaching. As the forests where the tortoises live are cut down for the collection of timber and to make room for agricultural land, the possible range of the tortoise becomes increasingly limited. Furthermore, the tortoises are often caught by poachers who sell them as pets both within Madagascar and internationally. Poachers also kill the tortoises and sell their meat as food. Customs officials have discovered these tortoises in the luggage of smugglers returning from Madagascar multiple times, including at Suvarnabhumi Airport in Bangkok in 2013 and at Chhatrapati Shivaji Maharaj International Airport in Mumbai in 2016.

2 of 11 Painted Terrapin Daiju Azuma / Wikimedia Commons / CC BY-SA 2.5 The painted terrapin (Batagur borneoensis) is found in Brunei, Indonesia, Malaysia, and Thailand. The IUCN lists it not only as Critically Endangered but also as one of the 25 most endangered freshwater turtles on earth. Habitat destruction caused by palm oil harvesting operations and shrimp fisheries is one of the most serious threats to the species. Poachers will also capture the painted terrapin to sell as food or as pets and will harvest the turtles' eggs for human consumption, further contributing to declining population numbers.

3 of 11 Angonoka Tortoise Hans Hillewaert / Wikimedia Commons / CC BY-SA 4.0 The angonoka tortoise (Astrochelys yniphora), also known as the ploughshare tortoise, is found only in the Baly Bay region of northwestern Madagascar. Currently listed as Critically Endangered by the IUCN, the angonoka tortoise is considered to be the most threatened tortoise on earth by the Durrell Wildlife Conservation Trust. The current wild population is estimated to contain around 200 adults, but it may be as low as 100 adults if not lower. The species is especially threatened by poachers who illegally catch and sell the tortoises as pets. Highly valued in the illegal pet trade, a single adult angonoka tortoise can sell for tens of thousands of dollars. In last-ditch efforts to save the few remaining individuals, conservationists have carved letters and numbers into the shells of some specimens in hopes of making them undesirable to poachers who value the tortoises for their beautiful shells. While the illegal pet trade poses the biggest threat to this species, angonoka tortoises also suffer from habitat loss and from fires started by ranchers to clear land for cattle grazing and other agricultural uses.

4 of 11 Kemp's Ridley Sea Turtle USFWS Endangered Species / Flickr / CC BY 2.0 The Kemp's ridley sea turtle (Lepidochelys kempii) is found in the Atlantic Ocean along the east coast of the United States. Although the species is found as far north as New Jersey, populations are most abundant in the Gulf of Mexico. Listed as critically endangered, the Kemp's ridley is the rarest species of sea turtle on earth. Once abundant in the Atlantic Ocean, the species has declined in population by more than 80% over the past three generations. Shrimp trawls are the biggest danger to this species, as the turtles frequently become entangled in these fishing nets and die. Habitat loss and pollution, such as that caused by the 2010 Deepwater Horizon oil spill, also pose major threats to the survival of the species. The harvesting of Kemp's ridleys' eggs for human consumption was previously a major concern until the 1990s when successful efforts were made to reduce egg harvesting.

5 of 11 Philippine Forest Turtle Pierre Fidenci / Wikimedia Commons / CC BY-SA 2.5 The Philippine forest turtle (Siebenrockiella leytensis), which is found only on the Filipino island of Palawan, has a unique history. First described as a species in 1920, only two specimens were known to exist, and no more could be found by herpetologists until 1988 when one more specimen was discovered. Due to the lack of available specimens, scientists feared that the species was extinct until 2001 when herpetologists surveying Palawan discovered populations of the turtle living there. These scientists soon realized that the original specimens discovered in the 1920s were erroneously described as originating from the island of Leyte. Thus, the efforts to locate the species over the past 80 years, which were conducted exclusively on Leyte, had been futile since the species actually lived on Palawan. Today, the species is listed as critically endangered by the IUCN. Due to its enigmatic nature and history, the Philippine forest turtle is highly valued by exotic animal collectors, and thus poachers frequently target the species to sell as pets. The turtle is so popular in the illegal pet trade that it is one of the endangered species most commonly discovered in poachers' possession. Filipino authorities only confiscate five other endangered species more often from poachers. In addition to poaching, habitat loss also poses a major threat to the survival of the species.

6 of 11 Flattened Musk Turtle Eugene van der Pijll / Wikimedia Commons / CC0 1.0 The flattened musk turtle (Sternotherus depressus) has an incredibly limited habitat. It lives in a single drainage system of small rivers and streams in Alabama, which is only about 7% of its historical habitat. The IUCN thus lists the species as critically endangered. The biggest threat to the flattened musk turtle is habitat destruction and pollution, mostly caused by nearby coal mining operations, which introduce toxic chemicals into the streams and induce siltation. Agricultural operations and construction also contribute to the pollution of the turtle's habitat. Such pollution not only hurts the turtles directly but also contributes to declining population numbers of certain mollusks that serve as food sources for the turtles. Siltation amplifies the erosion of the rocky areas where the turtles live, further restricting their range. Disease may also contribute to declining population numbers. An outbreak of an immune-compromising disease in the mid-1980s caused the flattened musk turtle population in the river of Sipsey Fork to drop by more than 50% in one year.

7 of 11 Yellow-Headed Box Turtle Cuora / Wikimedia Commons / CC BY-SA 3.0 The yellow-headed box turtle (Cuora aurocapitata) is native to the central Chinese province of Anhui. Currently listed as critically endangered by the IUCN, it is considered one of the 25 most endangered species of turtles in the world. The species was first described in 1988 and immediately became a highly valued animal in the pet trade. Poachers began capturing the turtles to sell as pets, causing population numbers to plummet within a decade. It was not until 2004 that another specimen was observed by scientists in the wild. Today, there are fewer yellow-headed box turtles living in the wild than there are in captivity. In addition to suffering from overexploitation in the pet trade, the species is also threatened by water pollution and habitat destruction caused by hydroelectric dams.

8 of 11 Indochinese Box Turtle Torsten Blanck / Wikimedia Commons / CC BY-SA 3.0 The Indochinese box turtle (Cuora galbinifrons) is a freshwater turtle found in Southeast Asia in high altitude woodland areas. Population numbers for the species have been sharply declining by more than 90% over the past 60 years, causing the IUCN to list the species as critically endangered. The turtles are highly valued both in the illegal pet trade and as a food source. The golden coin turtle (Cuora trifasciata) is the only turtle from Laos and Vietnam that fetches a higher price on the black market. The bones of the Indochinese box turtle are also sometimes used to make glue.

9 of 11 McCord's Box Turtle Cuora / Wikimedia Commons / CC BY-SA 3.0 McCord's box turtle (Cuora mccordi) is native to the Chinese province of Guangxi. Currently listed as critically endangered by the IUCN, this species is rarely observed in the wild and is one of the most threatened turtles in China. McCord's box turtle was first described in 1988 by American herpetologist Carl Henry Ernst, who obtained it from a pet seller in Hong Kong. Scientists were unable to find any specimens of the species in the wild until 2005 when Chinese herpetologist Ting Zhou led an expedition for the turtle in Guangxi and finally observed members of the species in their natural habitat. McCord's box turtle is seriously threatened by poaching and habitat destruction. It is a highly sought-after species both in the pet trade and in traditional Chinese medicine, with a single turtle selling for several thousand dollars. Waterways in Guangxi are also becoming increasingly polluted, posing additional threats to the few remaining members of this species.

10 of 11 Roti Island Snake-Necked Turtle Mark Newman / Getty Images The Roti Island snake-necked turtle (Chelodina mccordi) is found on Roti Island in Indonesia as well as in the island country of Timor-Leste. Listed as critically endangered by the IUCN, the species is so endangered that it may be extinct in many parts of its natural habitat. Populations have plummeted by more than 90% since the 1990s, and no specimens have been observed on Roti Island by scientists since 2009, although individuals have been recently documented in Timor-Leste. The greatest threat to the Roti Island snake-necked turtle is the international pet trade, as the rare and strange-looking turtle is highly sought-after by collectors. Habitat destruction caused by climate change, deforestation, and the conversion of wetlands into agricultural rice fields has also proven to be a serious threat, especially when compounded by pollution from agricultural pesticides and garbage dumping. Invasive species such as pigs and predatory fish also contribute to declining population numbers by eating juveniles and destroying their nests.