Many people around the globe rely on the low-cost transport of goods and commodities that commercial shipping provides. Indeed, about 90 per cent of the world’s traded goods are transported by sea, with more than 70 per cent of this being containerized cargo (United Nations Conference on Trade and Development, 2017). Shipping densities are illustrated in Figure 1.1, demonstrating the great concentration of traffic along key routes.

The physical impacts that vessels may cause have not generally been emphasized in the past. However, they are becoming more and more apparent (Roberts, 2011), and this chapter offers a brief overview of the physical impacts that ships have on the marine environment. Numerous mechanisms are considered, together with examples of deleterious consequences. Coral reefs and seagrass communities are highlighted. The impacts of various processes, such as sediment suspension, aeration and microorganism mortality, are described.

The DPSIR (drivers, pressures, state, impact and response) framework provides a useful conceptual model for assessing and managing problems arising from the interactions between ships and the environment. The DPSIR framework comprises: drivers – the causes of environmental problem (e.g., ship operations); pressures – the effects of the activity (e.g., ship emissions); state – the environmental parameters and components that are affected (e.g., marine ecosystems); impact – the effect exerted on environmental and biological reservoirs (e.g., invasive species, habitat modification); and responses – mechanisms put into effect to prevent and/or mitigate the environmental impacts (e.g., environmental policies, international conventions). A well-established cycle of processes characterizes the continuous means of protecting the marine environment from the deleterious effects of ships. Both end-of-life events – either by shipwreck or shipbreaking – and routine operational performance of vessels exert, respectively, acute and chronic environmental impacts.