On 1 July 2025, NIWA merged with GNS Science to become Earth Sciences New Zealand.

Hornwort Ceratophyllum Demersum

HORNWORT (Ceratophyllum demersum) New Zealand’s worst submerged weed. Can grow up to 8m tall (taller than a two story building). Spread throughout North Island. Eradicated from South Island – not seen there since 2008.