The surface of our Blue Planet is 71 percent ocean – benign, mysterious and threatening in equal measure.
But today the oceans themselves are in a state of crisis and change as a result of human actions. We harvest the seas for their abundant food, mineral, and energy resources.
But our understanding of their vast domain - over 90 percent of living space on Earth - is still in its infancy.
Ninety-nine percent of all internet communications are transmitted by submarine cables that stretch over hundreds of thousands of kilometres across the seafloor. Marine tourism is a booming multinational industry, touching everywhere from polar to tropical seas.
The coastal regions are home to more than 3 billion people and that figure is set to double by the end of the century. The 10 billion people we expect to populate the planet a hundred years from now will continue to need adequate and sustainable energy, mineral resources, and food supplies.
These are among the most pressing issues of the twenty-first century and for each of them the oceans hold part of the solution.
But the seas are neither so large nor marine ecosystems so robust that they can withstand these pressures without change. The pressures on our coastline from urban sprawl, industrial development, and recreational demand, are without precedent.
From microplastics and waste islands to organo-toxins and dead seas - the dumping of domestic and industrial waste into the oceans is rife. We generate over 15 billion tons annually, with a further 12 billion tons of sewage sludge.
More and more of this waste ends up at sea. David Attenborough’s remarkable TV series has exposed the scourge of plastic waste in our oceans and its appalling effects on wildlife.
Sea levels are on the rise as global climate warms and polar meltdown accelerates. The global average was 20 cm rise for the past century, but is predicted to be around 30-50 cm by 2100.
When this is coupled with subsidence of the land, and particularly of megacities, then the relative rise of sea level is as much as 2-3 cm per year, spelling catastrophe for many of the world’s poorest and most vulnerable.
Ocean acidification, coral bleaching, hotter seas, and extreme weather events are all on the increase. The oceans, rather than the diminishing rainforests, are the true lungs of the world, and yet they are losing oxygen at an alarming rate.
Whatever the societal challenge for the oceans – communications, energy, food, water, minerals, trade, tourism, waste disposal, natural hazards, global warming or the environment – we all need to understand better our ocean world.
As we turn progressively to the oceans for their natural resources, as well as for trade, pleasure and tourism, we need to be fully aware that marine ecosystems are profoundly fragile and that all resources have different limits to their renewability.
Sustainability can only be achieved through a more equitable distribution of resources, a limit to excess, and firm management of the Earth’s environment.
If we understand the oceans and the dramatic changes they are undergoing, and act on this knowledge, then there is a window of opportunity that improved stewardship can lead to a more benign and sustainable future.
In the 1960s, we first became aware of the serious environmental consequences of acid rain. In the 1980s, we first identified the massive thinning of the ozone layer over Antarctica. Since then, collective international measures have successfully combatted the most deleterious effects of acid rain, and should see the ozone layer almost completely recovered by 2050.
The current crises that affect our oceans are multiple and complex. But, we can and should put in place internationally agreed measures to mitigate the worst effects and even reverse the course of change. This requires monumental and collective effort to achieve, but I believe the goal is attainable.
Professor Dorrik Stow FRSE is professor of geoscience at Heriot-Watt University in Edinburgh. He recently chaired the event Oceans in Crisis: A Public Debate at Edinburgh Science Festival, where a panel of technical experts on oceans addressed the challenges posed to the ocean world and answered audience questions on the topic.
Edinburgh Science Festival runs until 21 April, more info on programme and tickets can be found here.