Ship anchors could seriously alter underwater ecosystems

NIWA has observed the ship anchors causing scarring on the seabed in real time, with the anchor moving around due to wind and currents.

The effects can remain on the sea floor for 15 years.

NIWA geophysicist Dr Sally Watson says this is just the tip of the iceberg - as the shipping industry's set to be four times bigger than it is now, by 2050.

She says it could result in habitat loss and changes to the seabed.