Author:Donald Morrisey, Catherine Beard, Mark Morrison, Rupert Craggs, Meredith Lowe
Source:Auckland Regional Council
The present review provides a baseline of information on mangroves in New Zealand to inform the debate on their management.
What are mangroves and are they native to New Zealand?
Mangroves are a taxonomically diverse group of halophytic (salt-tolerant) plants that, worldwide, comprise approximately 70 species within some 19 families. They are typically woody trees or shrubs taller than 0.5 m, and inhabit the intertidal margins of low-energy coastal and estuarine environments over a wide range of latitude. The New Zealand mangrove, or Manawa, is one of several taxa within the genus Avicennia. Avicennia are true mangroves in that their habitat is defined solely by the intertidal zone, and they also possess specialised physiological and reproductive adaptations which allow them to grow there. Manawa is presently ranked as a sub-species (Avicennia marina (Forsk.) Vierh subsp. australasica (Walp.) J. Everett) within Avicennia marina (grey mangrove), a species occurring in both northern and southern hemispheres of the globe.
Avicennia marina subsp. australasica qualifies as an indigenous member of the New Zealand flora, given that its existence here can be dated some thousands of years before humans inhabited, or even visited, these islands. Mangroves have inhabited New Zealand coastlines for approximately 19 million years, as indicated by the presence of Avicennia-type silicified woods associated with lower Miocene rocks from the Kaipara Harbour. The origin of New Zealand’s mangroves remains in question. It has been suggested that some populations may have arisen from sporadic introductions of propagules (the young plantlets) rafting across the Tasman Sea.
Auckland Regional Council technical publication TP325 May 2007