Why the ocean matters

Consider how dependent upon the ocean we are. The ocean is vast – it covers seven-tenths of the planet. On average, it is about 4,000 metres deep. It contains 1.3 billion cubic kilometres of water (97 per cent of all water on Earth). But there are now about seven billion people on Earth. So we each have just one-fifth of a cubic kilometre of ocean to provide us with all the services that we get from the ocean. That small, onefifth of a cubic kilometre share produces half of the oxygen each of us breathes, all of the sea fish and other seafood that each of us eats. It is the ultimate source of all the freshwater that each of us will drink in our lifetimes. The ocean is a highway for ships that carry across the globe the exports and imports that we produce and consume. It contains the oil and gas deposits and minerals on and beneath the seafloor that we increasingly need to use. The submarine cables across the ocean floor carry 90 per cent of the electronic traffic on which our communications rely. Our energy supply will increasingly rely on wind, wave and tide power from the ocean. Large numbers of us take our holidays by the sea. That one-fifth of a cubic kilometre will also suffer from the share of the sewage, garbage, spilled oil and industrial waste which we produce and which is put into the ocean every day. Demands on the ocean continue to rise: by the year 2050 it is estimated that there will be 10 billion people on Earth. So our share (or our children's share) of the ocean will have shrunk to one-eighth of a cubic kilometre. That reduced share will still have to provide each of us with sufficient amounts of oxygen, food and water, while still receiving the pollution and waste for which we are all responsible.

The ocean is also home to a rich diversity of plants and animals of all sizes – from the largest animals on the planet (the blue whales) to plankton that can only be seen with powerful microscopes.