Importance of the sea

It is bizarre our planet got called ‘Earth’ and not ‘Water’, there being so much more water on it than land. Oceans and seas cover about 71 % of the earth’s surface. “Sea” is the word usually indicating the large body of salt water covering the earth’s surface. To make things easier some parts of this huge volume of water were given specific names like the ‘Northsea’, the ‘Mediterranean Sea’, etc. “Ocean” is the word used for the largest and deepest parts of sea. We distinguish four of them: the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the smallest one, the Arctic Ocean (sometimes considered a sea of the Atlantic Ocean). All oceans and seas together are called the ‘World Ocean’.

Life on earth started in the ocean. Through electric charges, for example from lightning bolts, some particles in the ocean can melt together to form different particles, amino-acids. These particles are the ‘bricks’ that build life on earth. They appear in all plants and animals. Over millions of years this process very likely is responsible for creating the first bacteria and single cell organisms from which ‘higher’ lifeforms like plants, crustaceans and molluscs, fish and reptiles developed. Followed by marine mammals.


The world ocean englobes 99% of the biosphere, the viable space on earth. We’ve only seen and explored 5 % of it. It should be no surprise then that we’ve always believed that biodiversity – the number of different lifeforms – was poorer in the ocean than on land. But nothing is further from the truth. New technologies made it possible to document life in the ocean from the most bright coral reefs to the darkest and deepest oceans. In the year 2000 a ten year program was launched to assess life in the ocean. Thousands of scientists from 82 countries participated in this effort. The Census of Marine Life program was ended in 2010 and led to the discovery of thousands of species. So far about 250,000 species are found and formally described. This is far less than on land where mainly plants and insects know a large biodiversity.

But because life in the ocean is more ancient than on land, there are more marine species on higher taxonomic levels. So it is that there are 14 unique biological animal tribes in the ocean where there is only one unique tribe on land. This means that animals out of these 14 tribes are found only in the ocean and not in fresh water or on land.
Life not only started in the ocean; the ocean also maintains life on earth. It regulates earth’s temperature, provides us with oxygen, food, drinking water, energy, raw materials medication and even recreation and culture. All these benefits mankind gets from marine ecosystems like estuaries, coastal lines and open ocean are known as ecosystem services. More than a third of the world population lives in coastal areas. All over the world these people, but inland people too, are directly or indirectly depending on the services of the ocean for food, survival and general well being.
We can distinguish 4 kinds of services: provisioning services, regulating services, supporting services and cultural services.

Ecosystem Services

Provisioning Services

Amongst others the ocean provides us with food, water, wood and fiber. Over a billion people worldwide depend on fish as a source of protein. The fishing industry and accessory industries directly employ 38 million people and another 162 million are supported indirectly. Other examples of provisioning services are building materials harvested from mangrove forests and pharmaceutical components extracted from marine invertebrates and algae. The ocean also provides drinking water in the form of rain. Rain is formed by the evaporation of seawater. The vapor rises up and comes together in the air to form clouds. When the vapor in the cloud cools down, it drops down as rain. When the air is very cold the vapor transforms into snowflakes or hail. Every year millions of liters of water evaporate from the oceans. Most of which drops right back into the ocean, but the other part drops over land on fields, in lakes and rivers. Eventually this water flows back to the ocean through rivers and underground streams. This circular movement of water is known as the water cycle. Without this cycle and water to drink and to grow food life on earth would be quite different.

Regulating services

The ocean, together with the sun, regulates earth’s temperature and climate. The ocean’s circulation plays an important part in this. As an example, the Gulf stream sends warmed water from the Gulf of Mexico our way over the Atlantic Ocean. That warm water warms our air. Without the Gulf stream Western-Europe would be a lot colder. Seawater can also store warmth from the sun. During the summer the sea absorbs this warmth. Without that process the earth would become too hot. During the winter the sea releases this warmth thus tempering the climate, mostly on coastal areas. Therefore the sea can be considered to be a climate regulator. A heating in the winter and air conditioning in the summer.
Beside the climate, the ocean regulates more things essential to a viable world, like the quality of water and the fixation of carbon dioxide. Wetlands, such as the Wadden Sea in the Netherlands, play a major part in preserving the quality of water by filtering inland sediments and organic matter before they reach the ocean. On a global scale the fixation of atmospheric CO² by phytoplankton and the later setting on the seabed probably are the most important regulating service. It is an extremely important part of the global carbon cycle and buffers a large part of the climate change.

Cultural services

We are not often aware of this but the sea has had an important influence on the culture of many people. The sea appears in many works of art, history books, songs, movies, etc… Moreover humans more and more seek out the sea for recreation. Watersports, cruises, deepseadiving, paddling, whale watching, etcetera. These are all forms of recreation made possible by the sea. Coastal tourism, with or without joint ecotourism, is the fastest growing sector in the global tourist industry and plays a major part in the economy of small island states. For example, the value of tourism generated by coral reefs is estimated at a yearly participation of 30 billion dollars to the global economy. So, in economical terms as well the protection of our ecosystems is extremely important.

Supporting Services

The services of soil formation, photosynthesis and the transformation of nutrients are in their turn enabling other services. Therefore they are called supporting services. Mangrove forests and seagrass beds for example are important ecosystems because they are like maternity wards for young fish and invertebrates. These animals, once they are adults, can be fished or harvested by local communities, commercial fisheries or recreational fishermen. The value of photosynthesis too is not to be underestimated. The oceans are sometimes known as the blue longs of the earth, because they are responsible for the biggest part of primary oxygen production. It is the phytoplankton (algae and seaweeds) that we owe our thanks to. Algae and seaweed, like other green plants on land, make their own food from sunlight. They get their energy to grow from photosynthesis. During this process oxygen is freed. Part of this oxygen ends up in the air; the other part stays in the water, since fish and other marine animals also need oxygen to live.


  • Van Lier, Bas en Annie Meussen. 2003. Het Zeeboek. Ploegsma.
  • Crist, D.T., G. Sowcroft en J. M. Harding. 2009. World Ocean Census: A global survey of marine life. Firefly Books.
  • UNEP. 2006. Marine and Coastal Ecosystems and Human Well-being: A synthesis report based on the findings of the Millenium Ecosystem Assessment. UNEP.
  • The Encyclopedia of Earth.

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