Spartina almost eradicated

The Department of Conservation (DOC) and Council are continuing a decades-long effort to eradicate common cordgrass (Spartina Anglica) from Motuweka/Havelock Estuary.

Spartina is an introduced grass that lives in intertidal areas with soft sediment, spreading through seed and underground rhizomes. It displaces native species causing accelerated sedimentation in estuaries.

Spartina was introduced to the estuary in the 1950s for agriculture, to reclaim the wetland and use its large roots to stabilise stopbanks and muddy areas for grazing stock.

DOC’s Senior Biodiversity Ranger Phil Clerk said due to its root mass, the invasive grass can change the estuary dynamic for native habitats.

“DOC has a vested interest in the estuary, with protected birds that call the estuary home and juvenile fish that nurse in its waters,” he said.

The joint programme began in 2004 with aerial spraying of the main infestations, centred in the Pelorus Sound around Havelock and Kaituna estuaries.

Spartina is an invasive species of regional significance, Council’s Biosecurity Manager Liam Falconer said.

“We’ve seen major improvements in biodiversity since removing dozens of hectares of Spartina,” he said.

Today, all Spartina infestations have been managed to very low levels. In early 2025 DOC found only one plant during its annual monitoring, and again one plant was found over the 2026 season. Council and DOC jointly fund the operation, where DOC has concluded that eradication is not only feasible, but could be achievable well within a decade at the current levels of funding and management.

Collaboration is at the heart of this programme and why it has been so successful, Mr Falconer said.

“There’s been a strong commitment from dedicated DOC staff involved in the programme for many years. This work is very physical in tough conditions. Council recognises the effort the DOC field teams have put into delivering results.”