In the waters of the Yunnan Province of China, a team of conservationists is hoping to find a turtle with some very valuable sperm.

The Yangtze giant softshell turtle is one of the most critically endangered species in the world. A male and female are in captivity in the Suzhou Zoo in China, and one wild turtle lives in a Vietnamese lake called Dong Mo. (The Vietnamese turtle is believed to be male, but because they are so elusive, determining its sex has been difficult.)

In February of last year, a fourth turtle — believed to be nearly 100 years old — died in captivity in Vietnam, reducing the world population by a quarter.

Yangtze softshell turtles, also called Red River turtles, are the largest freshwater turtles in the world. They can live for nearly a century and grow to be nearly 200 pounds.

The species dwindled rapidly during the latter half of the 20th century as infrastructure development along China's Red River devastated the turtles' habitat. As China pushes for more renewable energy, dams are being rapidly built in the country's southwest region, which can be massively disruptive to wildlife in the region.

For populations to thrive, the turtles need clean water and beaches to hunt on.

Nearly all species of marine turtles are endangered, as well as many of their freshwater brethren like the Yangtze turtle. Their eggs, meat, and skin leaves them vulnerable to poaching, and their habitat is uniquely susceptible to feeling the adverse effects of climate change. (See "How Thousands of 'Good Luck' Coins Killed a Rare Sea Turtle.")

While rebuilding an entire species from only three turtles is difficult, it's not impossible. Researchers from the Wildlife Conservation Society are searching for a wild Yangtze turtle that they believe to be tucked away deep in the Yunnan Province.

Aimin Wang, a National Geographic grant recipient and director of the China division of the Wildlife Conservation Society, spoke with National Geographic about efforts to bring this species back from the brink of extinction.

What work is being done to find Yangtze softshell turtles in the Yunnan Province?

We are conducting field surveys to search for a Yangtze in the wild. This year from April to May, the team is doing a field survey in the Red River. We have not found one yet, but each year we plan to come to China during this time to try to find one.

What leads you to believe that one can still be found?

We have talked with local people who, based on their description, have probably seen a [Yangtze] turtle. We cannot estimate how many there are, but from speaking with locals, there should be one or two.

What would it mean for the species if one were to be found?

It increases our opportunity [for successful breeding] quite a bit. The male in China is quite old, but the female is young. The turtles are bred using artificial insemination. The last four attempts with the breeding pair in China were unsuccessful. We just tried for a fifth time and got high-quality sperm. We won't know for another month if our results were successful.

Why are these turtles so important to save?

This is a flagship species, and for biodiversity, they're quite important. They serve as an important [indicator of environmental health]. If we can help them survive, that means our ecological system is quite good. If they disappear, that means our ecological system is quite bad.

Is there any hope for this species?