The Three Gorges dam is the most controversial project in the scientific and technological history of modern China. Thousands of China’s leading scientists have worked hard for decades to try and find ways of minimizing the adverse environmental impacts of the project.

“Nobody doubts the Three Gorges dam will be built as planned,” Chen Guojie, senior researcher at the Chengdu Institute for Mountain Hazards and Environment, said in an interview. Along with a number of scientists, however, Prof. Chen continues to insist on the conclusion presented by researchers from the Chinese Academy of Sciences (CAS) in the mid-1980s: that purely from the standpoint of the environmental impacts, the costs of building the Three Gorges dam definitely outweigh the benefits. Prof. Chen and many other scientists believe that it is difficult, with the current level of science and technology, to come up with precise answers and adequate solutions to the uncertainties and hidden problems that the project holds for the environment in the reservoir area.

In early 1984, the Chinese Academy of Sciences organized 700 scientists from a variety of research fields nationwide to take part in an environmental impact study for the proposed Three Gorges dam. Prof. Chen Guojie was in charge of the comprehensive environmental assessment and one of the principal writers of the assessment report, while Chen Weilie and Cao Wenjun were responsible for two separate research programs, on land plants and aquatic life respectively.

According to Chen Weilie, senior scientist from the Institute for Plants, a Beijing-based branch of the Chinese Academy of Sciences, 3,104 plant species exist in the Three Gorges area, of which 46 are considered rare and endangered. For example, an aquatic plant called shuhua shuibaizhi (Myricaria Laxiflora) is found nowhere else in the world apart from along the banks of the Yangtze, at an elevation no higher than 180 metres above sea level, in the three counties of Zigui, Badong and Wushan. This rare plant will be inundated by the water of the reservoir when it begins to rise next June. In an effort to save these rare species, Chen Weilie and colleagues started salvage work as early as 1984, and in 1996 set up a special Three Gorges Rare Plant Resources Conservation Station in a remote mountainous area — the Shengnongjia Forest Conservancy Region in northwest Hubei province, about 100 kilometres north of the Three Gorges area.

Chen Weilie is confident that all of the 30 rare plant species that have been found growing in the reservoir area will be saved and protected properly. But he said, with deep regret, that another four or five plant species that had been recorded in the past have not yet been found. And he said there is now little hope of finding them. “You see, everything has gone, and there is little vegetation left on the cliffs of both banks below 135 metres because of the cleanup campaign,” he said sadly, pointing to the clean-cut cliffs and rocks along the Yangtze River.

Compared with the rare plants, which could be protected in a new resettlement site, aquatic species face greater uncertainties. After the death of Qiqi, the only Yangtze dolphin raised in captivity in China, the spacious Wuhan Yangtze Dolphin Hall looked quiet and deserted, receiving no visitors any more. Dr. Zhang Xianfeng, vice-director of the Biological Diversity Research Centre at the Institute for Aquatic Life of the CAS, refused to comment directly on whether building the Three Gorges dam will drive the Yangtze dolphin to extinction. Choosing his words carefully, he said: “Of course, the effects [of the dam on the Yangtze dolphin] have positive and negative aspects. But to be honest, I have to say that the negative effects are certainly greater than the positive ones.”

Other rare and precious species in the river, such as the Chinese sturgeon (Zhonghua xun), white sturgeon (bai xun) and rouge fish (yanzhi yu), will also be greatly affected by the Three Gorges dam, which will block the migration routes to their spawning grounds.

Cao Wenxuan, a CAS member and senior researcher at the Wuhan-based Institute for Aquatic Life, expressed serious concern about three issues:

• The potential threat to fish migration because of the height of the dam;
• A possible decline in fish population after the dam is closed and prevents natural flooding on the downstream floodplain; and
• The impact of a severe fragmentation of the river valley once other big dams are built on the Jinsha River [as the Yangtze is known upstream of Chongqing].

As Prof. Cao put it, the ecosystem of the Yangtze River has evolved over millions of years. But the big dam will bring about violent and drastic changes to that ecosystem, and aquatic life will have a hard time adapting. Changes in the river regime, such as water velocity and temperature, and sedimentation would significantly affect the fish habitat, especially breeding and feeding conditions. Undoubtedly, all these changes will come as major shocks to the fish living both in the upstream and downstream sections of the river. For instance, when the free-flowing, and even turbulent, river-like Yangtze is transformed into a slower moving – or even still – lake-like reservoir, many species that are used to the turbulent flow will be dramatically affected, leading to a sudden and rapid decline in fish population and diversity in the reservoir area.

Prof. Cao compared the Gezhouba and Three Gorges dams in terms of their impacts on fish migration. While Gezhouba, 40 km downstream of the Three Gorges, has functioned as a barrier for fish, the impact of that much smaller dam was less significant, with more fish living in the upper reaches still able to migrate to the middle and lower Yangtze. By contrast, the Three Gorges dam is much bigger in size, height and reservoir capacity. Fish living in the upper reaches will have little chance of survival if they try to go through the huge structure. And without this migration, fish in the upper reaches and in the downstream area will be blocked by the dam and separated forever, resulting in a profound and unknown impact on the genetic quality of the native fish populations. [Three Gorges Probe editor’s note: Fish that attempt to pass through a dam’s turbines, sluice gates, spillways and shiplocks can die in different ways: They may die on impact with the structure; be cut up by blades; get trapped by currents near the water intakes, and starve to death there or be eaten by bigger fish.]

Fish production will be jeopardized for another significant reason. Fish from the Yangtze River make up half the national freshwater fish supply, with four varieties dominating: variegated carp, silver carp, black carp and grass carp. The Three Gorges project will change the flow of water on the river, with floods controlled according to human will. But it is these same floods that provide a paradise for fish, which spawn in the floods – the bigger the better. The floods that are regarded as disasters in human terms are a necessary condition for fish production. Another problem is that a lower water temperature below the big dam is likely to shorten the fish maturation period. A combination of the above factors, plus other unforeseen changes in the aquatic environment, could seriously undermine the fishery in the river as a whole.

Chinese scientists have been trying to find solutions to these problems, in particular, the impact on fish of reduced flooding. One suggestion has been to create artificial floods in the middle section of the Yangtze, to promote fish production by regulating the water volume in summer and recreating the conditions they need. But this proposal raises concerns about whether such floods would threaten the safety of the dam and the effectiveness of flood-control efforts aimed at protecting humans.

A third impact concerns the fragmentation of the Yangtze River valley. To protect the Three Gorges dam and extend its lifespan, building two more giant dams, known as Xiluodu and Xiangjiaba, has been proposed in order to block silt coming from the Jinsha River, about 1,000 km upstream of the Three Gorges dam. It is unfortunate that the proposed site for the Xiluodu dam is on the outskirts of a national conservation zone for rare and precious fish species. Construction of the two dams is likely to affect at least 100 species in that section of the river. Building the Xiluodu dam alone would block the migration route of the white sturgeon, which, like the Yangtze dolphin, is considered critically endangered. The white sturgeon, and many other species with similar habits, would be doomed.

Prof. Cao said that if the Three Gorges dam does not succeed in driving certain rare species to extinction, constructing more big dams on the Yangtze would finish the job. With more and more dams being built, the river will be broken into several parts. This fragmentation of the river is likely to produce substantial changes and uncertainties in the water environment. Any life form has a threshold beyond which it can no longer adapt and survive. If the environmental changes exceed this threshold, species cannot escape extinction.

Chinese scientists are doing everything possible to protect these rare species. They breed Chinese sturgeon using artificial methods, and put tens of thousands of fry into the Yangtze River each year. A special natural reserve has also been established to accommodate the Yangtze dolphin on a 21-km-long oxbow lake near Shishou city, Hubei province, though no dolphin has yet been caught to take up residence in the zone. Despite all these efforts, it appears that governments have not done enough. As a leading expert on aquatic life in China, Prof. Cao has appealed to various levels of government to create a special fish reserve for rare species in the Chishui River, a tributary of the upper Yangtze, but he has had no response. In fact, Prof. Cao is now very worried that the local government in Guizhou province has been lobbying higher authorities to build a new dam there.

Prof. Cao and many other Chinese scientists have stressed that, along with human beings, other kinds of life also have a basic right to live in the river. It would be a sad consequence if species that have lived in the Yangtze for tens of thousands and even millions of years become extinct at the hands of the current generation because of human activities.

Chen Guojie said that so far we know little about the impending environmental changes, which are surrounded by many uncertainties. An ecosystem is a complex and interrelated system but we have touched on just a small part of it. Chen Guojie maintains that we have only addressed a few main factors affecting the environment in the Three Gorges area, but do not fully understand the ecosystem as a whole and cannot accurately predict the environmental changes to come. He said that a very small alteration in sedimentation in the river, for example, would lead to subtle changes in plankton and algae, which would then have an impact on fish and other aquatic life.

Many Chinese scientists agree that building the Three Gorges dam will accelerate environmental degradation in the reservoir area and in the middle and lower reaches of the Yangtze. During the 20-year period of construction of the Three Gorges dam, the state of the environment in the affected regions will be made worse. The most severe impacts will centre on the following aspects: The population-carrying capacity in the reservoir area will become much smaller, soil erosion will become increasingly severe, and certain endangered species will face critical conditions. The negative impacts began with the formal start of the dam project and will last for 50 and even 100 years after the filling of the reservoir. In some cases the impacts will be hidden, unforeseen and long-term.

This is a Three Gorges Probe translation of an article that appeared in News Weekly magazine on Dec. 4, 2002.