Cindy Lee Van Dover in her review of the Bismarck Sea mining project (Nature 470, 31–33; 2011) accepts the inevitability of interest in excavating the sediments of hydrothermal vents for minerals such as copper, zinc, gold and silver. Many of the hundreds of these sites are accessible, and the issue is widely seen as not whether mining should proceed, but how it can be done profitably and safely.

I approach the issue with a strong bias, based on efforts over decades to figure out how to keep the world working as a biophysical system capable of serving indefinitely as a human habitat. On the overall issue I am not optimistic. On one topic, however, I am certain: the integrity of the oceanic biophysical system is being lost now and the human cost is overwhelming.

The fact is that intrusions into the global environment have passed a limit of acceptability and this one must be seen for the twofold attack on the global commons that it is.

Hydrothermal vents are one of the wonders of Earth: communities of autotrophic organisms that survive on Earth's energy as opposed to photosynthetic energy from the Sun, the source of energy of almost all other life. Each vent site may have its own high degree of endemism, essentially unique life. The mere fact that the sites are commercially attractive as ore is not an adequate reason to exploit them, any more than the existence of the giant redwoods of the Sierra Nevada justifies harvesting them for shingles. The vents are a window onto the history of life. By what right do we destroy them for corporate profit?

Worse, mining of marine sediments mobilizes the noxious minerals they contain, including those that are toxic to other marine life. Suddenly, we have another contribution to the chemical disruption of the ocean. We are well aware of the process and its effects. Do we need more research to confirm our experience?

Global problems all have local origins. Here we have the beginning of another process we shall never be able to stop, once started. Another mountain-top mining. Another Tar Sands of Alberta. Another North Slope oil development. Scientists who join the programme are offering tacit approval of it, no matter what their perspectives. The world is too small for this further destructive intrusion — it should be stopped now before it becomes another corporate atrocity, too big and too valuable to stop.