Cargo and cruise ships are big money makers - but also a big risk to the marine environment

An Environment Ministry and Stats NZ report suggests 22 percent of marine mammals, 90 percent of seabirds and 80 percent of shorebirds are at risk of extinction.

It notes 99.5 per cent of New Zealand imports and exports are transported by sea - with that traffic linked to the introduction of non-native marine species.

It also has other impacts - such as oil and noise pollution - and the risk of hitting marine mammals.