An Appraisal of Factors Controlling the Latitudinal Distribution of Mangrove (Avicannia marina var. resinifera) in New Zealand
Keywords:Climate, dispersal, littoral drift, manawa, tidal currents, wind drift
The latitudinal distribution of mangroves (Avicennia marina var. resinifera) in New Zealand has traditionally been considered to be controlled by climatic stress, particularly air temperature. This paper reviews the influence of climate factors, particularly frost, and the dispersal of mangrove propagules on the present-day mangrove distribution. There is no strong evidence to show that the southern limit of mangroves in New Zealand is a function of climatic conditions, or that the present mangrove distribution is in equilibrium with climatic conditions. It is probable that coastal processes affecting propagule dispersal are more important controls on the mangrove distribution within New Zealand than climatic factors. In particular, tidal asymmetry inhibits mixing of east and west coast mangrove populations around northern-most New Zealand, and low coastal current velocities and large distances between suitable habitats makes natural establishment south of present limits unlikely.