Mankind has continually abused the sea, regarding it as an inexhaustible source of food and minerals, and a dumping ground for rubbish. Now it is more widely accepted that the oceans are finite, and there is a need to use and manage them carefully, especially as globally environmental pressures are mounting because of the burgeoning human population. Pollution is important enough to be discussed separately. The Carbon Dioxide Regarded by some people as a pollutant, this is a key substance in natural cycles and so cannot be treated like man-made substances. As a greenhouse gas, increasing concentrations of carbon dioxide in the atmosphere threaten climate change globally, modify ocean circulation, and so reduce the viability of many marine species. Sharp reductions in emissions per capita (>60%) are needed to avoid irreversible changes, bearing in mind the rate at which the human population is growing and future industrial expansion by the developing world, especially China. No one of the suite of solutions, which range from improving energy efficiency and switching to renewable energy sources, to capturing carbon dioxide and storing it somewhere—for instance, in deep geological deposits that formerly contained offshore oil and gas is likely to be sufficient.
