Upper estuarine systems

The upper estuarine system includes areas with periodic salt water influence, but not at sufficient levels to support saltmarsh vegetation as the dominant riparian plant community. These are extremely important ‘end-of-river’ environments having strong coastal influences setting them apart from freshwater riparian margins higher in the catchment. These influences drive structural and functional properties that produce unique aspects for riparian ecology and management, including providing critical habitat for some species. None is more prominent than our much loved īnanga Galaxias maculatus (a whitebait species) for which these areas are the obligate spawning habitat. End of river environments are also important for a range of recreation and other community values, creating a strong need for an integrated management approach.

In contrast to areas dominated by regular saltwater inundation, subtle changes in salinity regimes can be important in these brackish environments. This is reflected in the zonation patterns of vegetation communities which are often more strongly influenced by salinity ranges than by inundation regimes in these areas. Saltwater intrusion effects are therefore important to understand and can expected to be a major driver of habitat shift and associated impacts under sea level rise. In addition to being a conservation management priority, the location of inanga spawning may be a good indicator of these changes since the location of spawning habitat is known to be strongly influenced by these effects.

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