Source: Shipping density data adapted from National Center for Ecological Analysis and Synthesis, A Global Map of Human Impacts to Marine Ecosystems.
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Domains of Maritime Circulation
Oceanic masses and rivers are the two major components of maritime circulation. Oceanic masses account for 71% of the terrestrial surface. The four major oceans relevant to maritime circulation are: the Pacific (165 millions square km), the Atlantic (82 million square km), Indian (73 million square km) and the Mediterranean (2.5 million square km). Although the Pacific is by far the largest ocean, it is not the most significant as far as maritime circulation is concerned. It supports about 25% of the global maritime trade (this share is growing rapidly) and only a small portion of it is used for commercial transportation purposes. The northernmost parts of the Atlantic as well as the southernmost parts of the Atlantic, Indian and Pacific oceans are not much used mainly because of hazardous navigation conditions (mainly ice) and their remoteness to the centers of economic activity.
The shipping density is derived from the paths of mobile data points of a sample of commercial vessels (about 11% of the world fleet) counted over a year on a grid of 1 square kilometer cells. It is not weighted by ship size and is not necessarily fully representative of all commercial activity. Even if maritime transportation has experienced remarkable improvements in its safety and reliability, maritime routes are still hindered by dominant winds, currents and general weather patterns. The North Atlantic and the North Pacific (50 to 60 degrees north) are subject to heavy wave activity during the winter that sometimes impairs navigation, and may cause ships to follow routes at lower latitudes, thereby increasing route lengths. During the summer monsoon season (April to October), navigation may become more hazardous on the Indian Ocean and the South China Sea.
About 50 countries have an inland navigation network of more than 1,000 kilometers. Rivers may not be useful for commercial navigation if their orientation does not correspond to the directions of transport demand. Thus, many of the major rivers of Russia flow north-south, while the main trade and passenger flows are east-west. Shallow draught and extensive obstacles, such as rapids, may also limit navigation. However, many rivers, such as the Rhine or the Chang Jiang, are significant arteries for water transport because they provide access from the oceans to inland markets. Geographically, maritime activities can be divided in two major categories:
  • Interior (Fluvial) Waterways. Fluvial transportation is well suited to transport bulk cargo, has low costs and is the most environmentally friendly. It plays an important role for several industrial countries with large waterway systems such as the Volga, the St. Lawrence / Great Lakes, the Mississippi, and the Rhine. All these networks have a tree-like structure which has been broken by the construction of canals linking different tributaries. Domains of inland navigation in North America, Europe and China are not equivalent in terms of size of ships implying different operational characteristics. Most waterways are solely justified by bulk cargo requirements. However, accelerated integration of industrial and market regions to maritime shipping because of container barge services can be noted, especially in Western Europe. A growth and diversification of activities on the Chinese waterways has also been a dominant trend as China integrated the global economy and as the growth of its domestic economy resulted in a growth of freight shipped on its fluvial network.
  • Transcontinental Waterways. Seaborne trade has experienced very strong growth, especially over the Pacific. This is notably linked to the dependence of developed countries for energy, minerals and agricultural products. There is an increased importance of large maritime companies as well as a division of labor and capital in the maritime industry. Markets, technology and capital are provided by developed countries and labor by developing countries.