Abstract:
Hydrilla verticillata (L.f.) Royle is one of the major invasive weeds in the world and has been found in four lakes in New Zealand. After establishment in those lakes, H. verticillata caused major negative impacts, covering 30% of one lake, outcompeted native species, reduced oxygen levels and light levels. Biosecurity New Zealand has developed a control programme to eliminate this weed from its current locations; this is ongoing. However, this illustrated that New Zealand could be at risk from further incursions of this species. In order to provide useful information for future control and management of H. verticillata, a spatial risk analysis of New Zealand was carried out, using ecological information available from other studies. Two different approaches were used in this study. 1) Bioclimatic modelling based on known locations of H. verticillata. 2) A spatial model based on known physiological characteristics These two models were also run under different climate scenarios: current climate and future climate change scenarios. The results suggest that there is a strong temperature limitation on the spread of H. verticillata in New Zealand especially in the South Island. Under current climatic conditions, most of lowland North Island and small regions in the South Island are at risk of invasion by H. verticillata. Under future warmer climate conditions, the risk areas could become much wider. These results suggest that long-term and continued surveillance for this species required, and that the surveillance area should be extended.
