This damage is caused by:
- Transfer of invasive alien species: through ballast water and on ship hulls
- Air pollution: through emission of sulphur dioxide, nitrogen oxides, and carbon dioxide
- Physical and other damage: through dropping of anchors, noise and wave disturbances, and striking of whales and other marine mammals
The threats posed by shipping are not spread evenly across the oceans, but rather concentrated in busy shipping lanes and ports.
As shipping lanes become more and more congested, the level of pollution caused by shipping increases - as does the chance of spills and accidents.
Increased shipping traffic also threatens natural habitats around ports and near shipping routes. Seagrass meadows, wetlands, and mudflats - which are increasingly recognized as fundamental elements of a country's natural environment and economic resource base - are often located near or in maritime port locations.