Introduction

A scientific understanding of the ocean is fundamental to carry out an effective management of the human activities that affect the marine environment and the biota that it contains. This scientific understanding is also essential to predict or forecast, mitigate and guide the adaptation of societies to cope with the many ways the ocean affects human lives and infrastructures at different spatial and temporal scales.

Ideally, in order to manage human activities so as to achieve sustainable use of the marine environment and its resources, we need to know the geology and geophysics of ocean basins, the physical processes at work as the waters of the world's different oceans and seas move around, the input, distribution and fate of substances (both natural and artificial), the occurrence and distribution of flora and fauna (including the assemblages and habitat dependencies that control the different ecosystems), the biological processes that regulate and sustain the productivity of ecosystems and the way in which all these elements interact. Marine scientific research is the main way in which we can move towards this goal.

From a more fundamental perspective, the ocean is still one of the least known areas of the world. Humanity in its search of understanding has reached beyond our solar system and seeks fundamental answers in the infinitely distant and in the infinitely small. It has been said that we know more about the morphological features on the surface of other planets than of our own ocean. A significant effort of ocean exploration, using the most advanced techniques available today, is still probably one of the most rewarding collective efforts for humanity, as is attested to by the series of achievements of major international scientific programmes of the past.

Sustainability has to do with the mode by which humanity make use of nature. The increasing pressures that we impose on natural systems leave no room for complacency. At any point in time it is possible to extract the best advice that science can provide to completely or partially remove uncertainties around a phenomenon. From a scientific point of view, the need for better information always exists, therefore unresolved uncertainties are not a valid ground for delaying action. There are many improvements that can be made to managing human impacts on the ocean on the basis of current scientific knowledge.