The complex network of global cargo ship movements

TL;DR

This study analyzes the global cargo ship movement network using real-world data, revealing distinct patterns among ship types and providing insights into global trade and bioinvasion risks.

Contribution

It introduces a detailed network analysis of cargo ship movements, highlighting differences among ship categories and improving understanding beyond gravity models.

Findings

Ship network exhibits heavy-tailed distributions of port connectivity.

Container ships follow regular, repeating routes.

Bulk dry carriers and oil tankers have less predictable movement patterns.

Abstract

Transportation networks play a crucial role in human mobility, the exchange of goods, and the spread of invasive species. With 90% of world trade carried by sea, the global network of merchant ships provides one of the most important modes of transportation. Here we use information about the itineraries of 16,363 cargo ships during the year 2007 to construct a network of links between ports. We show that the network has several features which set it apart from other transportation networks. In particular, most ships can be classified in three categories: bulk dry carriers, container ships and oil tankers. These three categories do not only differ in the ships' physical characteristics, but also in their mobility patterns and networks. Container ships follow regularly repeating paths whereas bulk dry carriers and oil tankers move less predictably between ports. The network of all ship movements possesses a heavy-tailed distribution for the connectivity of ports and for the loads transported on the links with systematic differences between ship types. The data analyzed in this paper improve current assumptions based on gravity models of ship movements, an important step towards understanding patterns of global trade and bioinvasion.