Ingraham, N.L.; Mark, A.F.; Frew, R.D. Fog deposition by snow tussock grassland on the Otago uplands: response to a recent review of the evidence.
We challenge a recent, rather selective ¡¥review of the evidence¡¦ by Davie et al. (2006) explaining the recorded high water yields from snow tussock grasslands on the Otago uplands. We refute their dismissal of the importance to water yield of fog deposition on the fine wispy foliage of the dominant tall tussock plant cover. We stand by the results of our previous study on the stable isotope („·18O and „·2H) values of fog, rain and groundwater from three upland snow tussock grassland sites. We also provide evidence from several direct measures using natural or simulated tussocks at three fogprone upland locations which the reviewers ignored. Overall and importantly, the value of upland snow tussock grassland in maximising water yield is not in dispute, and we continue to endorse the relevance of low evapotranspiration from the dominant tussock cover. The water production capability of the upland snow tussock grasslands is a sufficiently important ecosystem service to justify formal recognition in landuse planning responsibilities of local authorities. Further, this important ecosystem service of upland tall snow tussock grasslands should also feature in central government¡¦s current Sustainable Water Programme of Action and in the development of National Policy Statement and National Environmental Standard for water under the Resource Management Act.