2 The global cargo ship network The ability to travel, trade commodities, and share information around the world with unprecedented efficiency is a defining feature of the modern globalized economy. Among the different means of transport, ocean shipping stands out as the most energy efficient mode of long-distance transport for large quantities of goods (Rodrigue et al. 2006). According to estimates, as much as 90% of world trade is hauled by ships (International Maritime Organization 2006). In 2006, 7.4 billion tons of goods were loaded at the world’s ports. The trade volume currently exceeds 30 trillion ton-miles and is growing at a rate faster than the global economy (United Nations conference on trade and development 2007). The worldwide maritime network also plays a crucial role in today’s spread of invasive species. Two major pathways for marine bioinvasion are discharged water from ships’ ballast tanks (Ruiz et al. 2000) and hull fouling (Drake & Lodge 2007). Even terrestrial species such as insects are sometimes inadvertently transported in shipping containers (Lounibos 2002). In several parts of the world, invasive species have caused dramatic levels of species extinction and landscape alteration, thus damaging ecosystems and creating hazards for human livelihoods, health, and local economies (Mack et al. 2000). The financial loss due to bioinvasion is estimated to be $120 billion per year in the United States alone (Pimentel et al. 2005). Despite affecting everybody’s daily lives, the shipping industry is far less in the public eye than other sectors of the global transport infrastructure. Accordingly, it has also re- ceived little attention in the recent literature on complex networks (Wei et al. 2007, Hu & Zhu 2009). This neglect is surprising considering the current interest in networks (Al- bert & Barabasi 2002, Newman 2003a, Gross & Blasius 2008), especially airport (Barrat et al. 2004, Guimer` a & Amaral 2004, Hufnagel et al. 2004, Guimer` a et al. 2005), road (Buhl et al. 2006, Barthelemy & Flammini 2008) and train networks (Latora & Marchiori 2002, Sen et al. 2003). In the spirit of current network research, we take here a large-scale perspective on the global cargo ship network (GCSN) as a complex system defined as the network of ports that are connected by links if ship traffic passes between them. Similar research in the past had to make strong assumptions about flows on hypothetical networks with connections between all pairs of ports in order to approximate ship move- ments (Drake & Lodge 2004, Tatem et al. 2006). By contrast, our analysis is based on I. INTRODUCTION