A risk assessment on the potential invasiveness of the biofuel crop, salix viminalis, in New Zealand

Abstract

The rapid pursuit of alternative energy sources is creating strong incentives to distribute plant material. Traits that are identified for being a good biofuel plant also resemble the traits of becoming invasive. Salix viminalis or basket willow has long been used for basket weaving and is now being looked at for biofuel. The goal of this study is to investigate whether an increase of propagule pressure of S. viminalis as a biofuel crop could enhance the chance of it becoming invasive in New Zealand. BIOCLIM built within DIVA-GIS 7.1.7.2 was the ecological niche model used to investigate whether New Zealand is climatically suitability for S. viminalis. A total of 8360 georeferenced locations was used and they form the backbone of this study. Data sensitivities was observed in BIOCLIM as different predictions were observed under different georeferenced location. Low suitability was predicted in New Zealand for S. viminalis under the overall, introduced and Outliers analysis. In contrast, not suitable was predicted under the native and Northern Hemisphere analysis. The Southern Hemisphere and New Zealand only analyses were predicted from georeferenced location in the marginal bioclimate. However, the analyses showed different levels of suitability and is useful in further identify risk areas for S. viminalis. Growing degree days (GDD) was used to identify georeferenced locations that suits the growing conditions of the S. viminalis, which it simulates the occurrence of natural reproduction and as an increase of propagule pressure. Low suitability in New Zealand was predicted for the 5° C condition and not suitable for the 10° C condition. Therefore, It is unlikely that S. viminalis could overgrown and spread even if the growing condition was suitable. The GDD analysis with assumed georeferenced location produced more detailed maps with areas predicted similar to the normal GDD analyses. Although the chance of incursion of S. viminalis is low, the overall conclusion suggested areas most likely for incursions to occur are in Waikato, Manawatu and northern Nelson. The climate change analyses predicted a low suitability and a southern shift of niche for S. viminalis in New Zealand. In contrast, the GDD climate change analyses predicted a southern extension of suitable growing condition of S. viminalis in New Zealand. There is a also a decrease in area of excellent suitability. However, the occupy range of S. viminalis remain relatively unchanged. This highlighted the huge potential of adaptability in S. viminalis. Although the chance of incursion of S. viminalis due to climate change is also low, areas most likely for incursions to occur are in Christchurch/Canterbury regions.