VI.

Human Impact

Turtles have been a successful group of animals for over 225 million years, but today the future of many species is in doubt. Though well adapted to survive natural threats, the massive environmental changes caused by human activities are proving to be too much for these long-lived creatures. Some scientists fear that human actions, including destroying turtles’ natural habitats, directly killing turtles, and even removing them from the wilderness areas that remain, may result in the extinction of many turtle species in the next few decades.

Turtles and tortoises are losing vast portions of their original habitats as humans convert wetlands, forests, and grasslands to agricultural fields, grazing lands, and villages and cities. Pollutants from farms and urban areas have degraded many turtle habitats. Turtles are also harmed when humans alter rivers and streams by creating dams and channels, or build sea walls or jetties on the beaches where sea turtles lay their eggs.

Tortoises, which are especially slow moving and easily captured, have long been hunted by humans for food. During the 18th and 19th centuries, whalers captured vast numbers of giant tortoises from the Galápagos Islands to feed to their crews. These ships also harmed tortoises by releasing rats and cats that ate tortoise eggs and young tortoises. By 1900, few tortoises remained, and several forms were already extinct. Efforts by conservationists to breed Galápagos tortoises in protected facilities probably saved them from extinction. Today many smaller mainland tortoise species are also being killed in large numbers and could soon disappear unless efforts are made to save them.

Freshwater and marine turtles may be scattered over their habitats much of the year, but all must return to specific shoreline sites to nest, giving humans the opportunity to take both the female turtles and their eggs for food. These nesting habits leave the turtles vulnerable and nearly all sea turtles and many species of freshwater turtles are now greatly reduced in numbers or even threatened with extinction. Many sea turtles die in fishing nets, and others are killed when they eat garbage that has been thrown into the ocean. Hawksbill sea turtles are killed for their thick carapace scutes, which provide the tortoiseshell used to make combs, curios, and small art objects. Sea turtles are also killed to make leather products. In Southeast Asia and China, turtles are both eaten and used in traditional medicine. A greatly increased Asian turtle trade in recent years has brought many formerly common species to the brink of extinction in this region.

The pet trade, which affects mainly small terrestrial and semi-aquatic species, is another threat to turtles. North American box and pond turtles, as well as the small tortoises found in the Mediterranean region, are particularly valuable to pet trade collectors. In 1975, the United States Food and Drug Agency banned the sale of turtles with shells measuring less than 10 cm (4 in) because many turtles carry a type of bacteria called Salmonella that can infect humans, causing severe gastrointestinal distress. This ban reflects the concern that young children might put these small turtles in their mouths. Larger turtles are still sold as pets in the United States, and turtle farmers can legally sell small hatchling turtles from the United States to overseas markets. Due to the pet trade, slider turtles that are native to the southeastern United States have been spread to many parts of the world. In many instances these pets have escaped human homes and started populations in the wild. In some areas, these feral turtles have taken over habitats once used by native turtles.

Compared to other wildlife, turtles are particularly vulnerable to harm from direct exploitation. Turtles’ slow pace of reproduction is normally compensated by the long lives of mature adults. Thus, it is difficult for populations to recover after numerous mature adults have been killed or removed. In such cases, the turtle population inevitably declines and may eventually disappear.

Many states and countries have passed laws to protect rare turtle species. More than 130 nations have signed a treaty called the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which regulates the international transport of endangered forms of wildlife, including many turtles and tortoises. In addition, the International Union for Conservation of Nature (IUCN) Red List of Threatened Species lists dozens of turtle species as endangered or critically endangered, meaning they are at risk of extinction. Some countries, including the United States, require large-scale shrimp fisheries to use nets that contain turtle excluder devices. These devices help turtles escape from fishing nets. Unfortunately, many wildlife laws are difficult to enforce, and developing nations in particular may lack the necessary resources for preventing the exploitation of turtles. Unless people around the world take steps to preserve turtles and tortoises within their natural environments, many species of these intriguing and ancient animals will probably become extinct during the 21st century.

Scientific classification: Turtles make up the order Testudines in the class Reptilia. Hidden-necked turtles make up the suborder Cryptodira, and side-necked turtles comprise the suborder Pleurodira.