In May of this year CNOOC reported a mid-sized oil field discovery, the Liuhua 20-2 field, in the Eastern South China Sea. Liuhua 20-2 is located in the Pearl River Mouth basin of the South China Sea, at an average water depth of about 390 m. The discovery well (LH20-2-1) was drilled to a depth of about 2,970 m.
This is only the latest South China Sea oil and gas field to be opened. In the last decade a large number of fields have been discovered, explored and commercially exploited. Hong Kong in fact receives some of its gas via a direct pipeline from a gas field southeast of Hainan Island.
Oil and gas prospecting, however, relies on seismic surveys. This involves sending powerful sound or shock waves through the water to the seabed to measure and analyse the echo received back. For the echo to give valuable data on lower rock layers they must be powerful enough to penetrate through thick sediment and into the rocks below. There are a few ways that can be done some including TNT or electricity to create imploding plasma bubbles. But the result is always a loud sound or explosion.
In the last few years Hong Kong has seen a number of more unusual whale strandings including deep-water species like sperm whales, Pygmy sperm whales and short-finned pilot whales, as well as other whales normally rarely if ever seen in Hong Kong such as Omura’s whales. Toothed whales rely heavily on echolocation (seeing by sound) for navigation, so the idea arises whether increased seismic survey activity in the South China Sea is part of the cause for these strandings.
Unfortunately, I am not aware of any scientific investigations into the effects of seismic surveys on whales and dolphins in the South China Sea. Research in this area is very difficult because it is hard to track whales and dolphins in the first place, and because their navigation sense is poorly understood. There are also multiple possible reasons for strandings, including disease and injuries so making a causal link between seismic surveys and whale strandings is very difficult even in the best of circumstances. However, intuitively, it seems right to restrict the use of loud explosions in the habitat of rare marine animals with very sensitive hearing organs that are also essential for their navigation. Particularly as sound conducts much better in water than in air.
When I took part in a research cruise to the Weddell Sea in Antarctica (back in 2005) there was actually a restriction on even the scientific use of small seismic surveys for marine geological baseline research. Special permits had to be applied for from the relevant government ddepartments of participating nations – in the end the only country that granted a permit was Russia.
There are also (as far as I am aware) reasonable restrictions on using seismic surveys in the North Atlantic by Europe, the U.S. and Canada, that require observers to check (as far as possible) that no whales are in the area before the survey starts.
I am not aware of any such restrictions in the South China Sea, although my knowledge of PRC laws and regulations is poor and perhaps such rules exist after all (feel free to point out any errors in the comments below).