China is what is known as a mega-biodiverse country. It is home to the third-highest number of mammal species in the world, and is ranked fifth for its diversity of both fish and amphibians.

For decades, the country has also been heavily involved in international efforts to safeguard the world’s wildlife. It was one of the original signatories to the UN Convention on Biological Diversity (CBD) at the Rio summit in 1992. This month, China is co-hosting the UN COP15 biodiversity summit alongside Canada.

Yet much of China’s own biodiversity is under threat. After decades of rapid economic development, a huge number of animals and plants in the country are endangered — and the list of extinct species is growing.

The demise of several well-known species has sparked public anguish in China over recent years. In 2022, two large denizens of the Yangtze river — the Yangtze sturgeon and Chinese paddlefish — were declared extinct.

But to really get a sense of the scale of the problem, it’s worth looking at what’s happening in southwest China’s Yunnan province.

A remote, mountainous region, Yunnan is dotted with ancient, high-altitude lakes, which are cut off from each other by the rugged terrain. After millennia of isolation, these lakes have developed into unique ecosystems comparable to the Galapagos Islands — the Pacific islands where Charles Darwin formed his theory of evolution.

Like the Galapagos, Yunnan’s lakes are teeming with endemic species: fish, snails, and plants that can only be found in one lake and nowhere else. Many are so rare, they are known only to a narrow circle of biologists.

Or, rather, were rare. Because dozens of these unique species have quietly disappeared over the past few decades, as rampant overfishing, pollution, and the introduction of invasive species have devastated Yunnan’s lakes. Several other species are critically endangered.

Yunnan is an extreme case, but lakes across China are being similarly destroyed. The rivers flowing into them often run through densely populated areas, where they pick up large quantities of waste — industrial, agricultural, and human — which then build up in the lakewater and sediment.

Lakes are also being depleted by excessive water extraction and droughts, which are becoming more common due to climate change. These shrinking lakes become sinks for pollutants, and traps for the species living in them. Even China’s most iconic and biodiverse lakes, such as Taihu and Poyang, have not been spared.

Chinese authorities have invested billions of dollars in efforts to mitigate the damage in recent years. But as Yunnan’s experience shows, these measures often come too late.

Dianchi

One of China’s largest lakes, Dianchi is about 7 million years old. Stretching north to south for nearly 40 kilometers, it is fed by rivers that run through Kunming, the capital of Yunnan province.

For centuries, the lake has been famous for its rich wildlife. One author, writing during the Tang dynasty around 1,500 years ago, wrote: “There was a large variety of fish in Dianchi Lake, the reeds on the shore were lush and leafy, and wild geese, pheasants, and waterfowl flocked there.”

During the late 18th century, local people began changing the natural environment, cutting down the forest covering the surrounding mountains and converting the grassland into agricultural land. Yet, in the 1970s, Dianchi was still clean enough to provide the people of Kunming with fish to eat, water to drink, and a place to swim.

The destruction started during the 1980s. As Kunming began to develop and grow, the city quickly overwhelmed Dianchi with untreated sewage and industrial waste. Meanwhile, intensive farming in the Dianchi basin flushed vast quantities of fertilizer into the lake.

Fueled by nutrients from the fertilizer and sewage, algae turned Dianchi into a sea of green sludge. By the 1990s, the water had received China’s highest contamination rating — grade five — meaning it was fit only for industrial use. The lake’s biodiversity was devastated.

Dianchi once had 10 species of fish not found anywhere else in the world. Now, only three are left. The rest were driven to extinction by overfishing, pollution, and competition from hardy non-native species like the grass carp and noodlefish — introduced into Dianchi to help local fishers after the stock of native fish collapsed.

One of the last species to disappear was the elongate bitterling — a small, silvery fish that fit into an adult’s hand and lived in the lake’s shallow coastal waters. It has not been seen since the 1990s. Pollution is one reason for its demise. Another is that freshwater mussels — once plentiful in Dianchi — became very rare, with one species going extinct. Without mussels, bitterlings — which lay their eggs in the gills of mussels — cannot survive.

Not only fish have been affected. In the 1980s, the Yunnan newt, which lived only in Dianchi and surrounding streams, vanished. The red-bellied amphibian is one of only three species of salamanders to have gone extinct worldwide.

Authorities have invested billions of dollars trying to bring Dianchi back to life. Wetlands around the lake have been restored, and pollution curbed. Work has just finished on a titanic engineering project — a system of water tunnels stretching hundreds of kilometers — that will flush Dianchi clean with water diverted from the Yangtze.

Development has also been banned on the shores of Dianchi. Recently, a large complex of illegally built villas was torn down. The restored wetlands are now attracting more and more birds — and birdwatchers. One of the surviving endemic fish species — the golden-line barbel — has been reintroduced into Dianchi.

But the lake is still far from the Edenic scene described during the Tang dynasty. The water quality in Dianchi is currently rated grade four — the second-highest contamination level.

Fuxian

Fuxian’s northern shore is located only around 20 kilometers from the southern tip of Dianchi, but the two lakes are very different. Fuxian’s basin does not have urban sprawl and intensive agriculture to contend with — and it was spared heavy pollution. Its water is blue and clear: Rated grade one, it can be drunk untreated.

Many unique species live in Fuxian, and new ones continue to be discovered. Lacunopsis yuxiensis — a new species of snail, named after the Yuxi municipality where Fuxian Lake is located — is a recent example. Two new species of shrimp have also been discovered and named after Fuxian in recent decades, as well as an aquatic fungus.

Yet the clear, deep waters of Fuxian also hide extinctions. The lake has lost five out of its 15 endemic species of fish due to overfishing and the introduction of the noodlefish, which feeds voraciously on the eggs of other fish. The lost species include the Fuxian carp, and a species of snow trout that’s closely related to the famous game fish found in Himalayan rivers.

Another local species of snow trout, known as a kanglang fish, had better luck. Until the turn of the 20th century, kanglang — a silvery fish around 10 centimeters long — was extremely abundant in Fuxian. Eaten with chillies, it was a local staple.

Then, demand exploded, and so did kanglang prices. By the late 2000s, one pound of the fish was selling for up to 3,000 yuan (then $440) in local restaurants — a 125,000% increase over a decade earlier. Soon, kanglang was almost extinct.

A campaign to reintroduce captive-bred kanglang into Fuxian was launched, and the species has now recovered. Photos of shoals of kanglang are touted as evidence of local conservation success.

But the overall picture is far more bleak. Just look at Fuxian’s smaller twin, Xingyun. The lake has lost even more endemic fish species: seven of its nine unique species have gone extinct.

Erhai

Erhai, the seventh-biggest lake in China, lies next to one of the country’s most popular tourist destinations: the ancient town of Dali. Just like Dianchi, Erhai has been decimated by pollution, overfishing, fertilizer runoff, and the spread of invasive species.

Dali’s tourism boom added to the problems, as it resulted in unchecked construction of lakeside hotels that began pumping untreated waste into Erhai. In 2014, large parts of the lake turned milky-white due to the massive pollution.

Only three of Erhai’s eight endemic fish species have survived the onslaught. The lake was once famous among biologists for its four unique species of carp, but only one — the long-pectoral carp — can still be found, and it’s extremely rare. The other three were lost to overfishing and competition from the newly introduced grass carp.

A campaign to save Erhai is now underway. Authorities have built sewage treatment plants, restored coastal wetlands that act as a natural filter for incoming pollutants, and banned all fishing on the lake. They have even demolished all the lakeside hotels. The water quality in the lake has since improved to grade three — deemed good enough for fishing and swimming.

A toxic legacy

In some of Yunnan’s lakes, every single endemic species of fish has become extinct.

In the north, the picturesque Lugu Lake — which drew hordes of tourists before the pandemic — has lost all three of its endemic species of snow trout. In the south, Yilong Lake, which went dry in the 1980s due to excessive water extraction, eventually lost all five of its unique fish species. Cibi and Jianhu lakes in the northeast have lost both their endemic fish species.

Soon, another lake may be added to this list: Qilu Lake, where the last of five local endemic species is barely clinging on.

And then there are countless small lakes that are still being polluted, drained, and built on. In many cases, their unique biodiversity is lost before it’s even discovered.

In 2016, scientists discovered a new species of snail in Shilin County, home to yet another of Yunnan’s tourist hotspots, the Stone Forest. The species, however, was already extinct — all that was left were its shells. The small lake where it had lived had been drained to build villas and a golf course.

The loss of every species matters — even tiny snails — as each species plays a role in its ecosystem. Once a critical number of species is removed, the entire ecosystem can collapse. It’s like removing bolts from a Boeing 747: Taking out one or two might not make a difference, but taking out one too many can lead to catastrophe.

China has recently made great efforts toward protecting its biodiversity, increasing the number of protected areas and launching a sprawling system of national parks. Fishing was banned on the Yangtze and the upper reaches of the Yellow River, and the release of non-native species made a criminal offence.

But none of this can bring back the 28 species of fish already lost in Yunnan — and might not be enough to stop more species disappearing from China’s lakes in the future.

Editor: Dominic Morgan.

(Header image: A boat floats on Fuxian Lake, Yuxi, Yunnan province, Aug. 13, 2022. VCG)