Water has something special and mysterious about it; all living creatures have a high water content, and water also covers 71 per cent of our planet's surface. Life began in the oceans, and without them it could cease. Yet today water evokes images of death and degradation — we think of the thousands of people fleeing conflicts who die every year in a desperate attempt to cross the sea on board inadequate vessels, or of the actual islands of plastic floating in the oceans, which are merely the tip of the iceberg (itself made of plastic).

Why the oceans matter

These vast expanses of salt water — seemingly immutable yet never the same as themselves, like a gigantic snowflake — regulate the climate, produce most of the oxygen we breathe, provide sustenance for millions of people every year, are essential for the production of numerous medicines and are home to an incredible biodiversity. To celebrate and highlight the importance of this priceless common heritage, 8 June marks World Oceans Day, established by the United Nations on 8 June 1992, on the occasion of the Rio de Janeiro environment summit.

Our oceans, our future

The slogan for the 2017 edition is Our oceans, our future, chosen to highlight how the health of these ecosystems is closely linked to that of our own species. The oceans look after us by providing us with precious ecosystem services; we have a responsibility to look after them. In reality, the expression "looking after" might perhaps seem offensive when applied to the oceans — primordial environments that have existed since time immemorial — and it would be more appropriate to substantially reduce our impact on them and on the planet in general. The United Nations' commitment is focused on combating plastic pollution, one of the main threats to seas and oceans.

Plastic in the oceans

It is estimated that approximately eight million tonnes of plastic end up in the water every year. This waste gradually breaks down into smaller pieces and is absorbed by numerous marine organisms, entering the food chain (which also includes humans who eat fish). According to a study published last year in Proceedings of the National Academy of Sciences, up to 90 per cent of seabirds worldwide have plastic residues in their gut.

Not just plastic: the other threats

The health of the oceans is in serious danger due to direct and indirect human impact, brought to its knees not only by pollution but also by climate change, the overexploitation of fish stocks, unsustainable aquaculture practices and the introduction of non-native species. The enormous quantity of greenhouse gases released into the atmosphere is rapidly increasing the acidity of the oceans; according to the Royal Society, this phenomenon could increase by up to 300 per cent during this century. Researchers say it would represent a threat to the biology of the planet equal to, or perhaps greater than, climate warming. Currently less than 4 per cent of the oceans is protected, with marine protected areas making up a minimal portion of the total surface area. Yet protecting the oceans would bring great benefits, from an economic standpoint as well.