Urban awa

It is somewhat inevitable that natural remnants are pushed towards the margins of our cities. Streamsides, coastal cliffs, saltmarshes and historically infertile ground (such as gumlands) all sit just outside the bounds of use – at least for a time.

One nationally threatened herb, Leptinella tenella, has managed to continue its existence along two of our urban awa (waterways), including a Hillsborough gully that we have written about within this journal before.

As part of research (together with David Straight) into the relationship between rare plants and water’s editing influence within our cities, rural landscapes and wild places, we visited another site on Auckland’s North Shore to find this attractive, fine-leaved species.

This population differed markedly from the Hillsborough site, where the plants cling to the hard mudstone banks of a gully adjacent to a small torrent. At the North Shore streamside population, Leptinella tenella is much more vigorous and widespread – extending from harder, consolidated stone banks into the soft, eroded mudstone.

The common thread that maintains this rare species’ ecological niche at both sites is the periodic scouring of competing vegetation from the flood zone of stream banks (as shown below), in addition to the effect of brackish water in parts of this awa. In other words, it is dynamism that allows Leptinella tenella to remain – a point worth remembering with respect to how we design (and preserve) our urban landscapes.