Report: TR2005/42

Author: Meg Graeme (Natural Solutions, Marine and Terrestrial Ecologists Ltd.)

Abstract

The seagrass 'Zostera' covers a large area of the harbour flats and provides a significant habitat for invertebrates and fish within the harbour. There is also a population of swans that feed on the seagrass. It is recommended that a watching brief be kept on swan numbers to ensure they do not escalate to densities that may be detrimental to the overall seagrass habitat.

All saltmarsh is significant in Kawhia Harbour due to its limited extent – primarily dictated by the harbour geology. Similarly all remaining freshwater wetlands/swamp forest that adjoin estuarine wetland are significant for their scarcity and habitat value and should be actively preserved and enhanced.

Generally, the bands of saltmarsh and sea meadow are usually only 0.5-1m wide along the coastal edge (which often rises steeply up into a band of coastal forest, gorse/pampas, or pasture).

Weeds are a significant threat to the health and integrity of the harbour’s vegetation. The Department of Conservation is currently undertaking an aerial spraying programme in an attempt to eradicate spartina from Kawhia Harbour.

The other significant estuarine weed is saltwater paspalum. This invasive grass is only just starting to establish in Kawhia Harbour. The survey found only four patches of saltwater paspalum. It particularly threatens low-stature sea meadow communities. These few pioneer populations of saltwater paspalum should be eradicated as soon as possible. This can be undertaken using gallant and so it would be a wise use of resources to co-ordinate the spraying of saltwater paspalum with the spartina control programme.

Access by stock to the harbour is a widespread and serious problem around the harbour.

The protective benefits of the regenerating coastal forest around the harbour edges is degraded by the grazing of the undergrowth by goats.

Estuarine Vegetation Survey - Kawhia Harbour [PDF, 1.4 MB]

Click on highlighted areas on this map for a zoomed in view.