|dc.description.abstract||Climate change, land use change and invasive species are transforming global biodiversity at multiple scales. Projections are for threats to biodiversity from these global changes to continue into the future, with varied and discernible distribution changes for many species. Concomitantly, these global changes will interact with each other to further exacerbate the problem, as exemplified in this study. In New Zealand, climate change is expected to affect landscapes, fragmented and disturbed by land use change, further increasing the potential invasibility of these landscapes for a suite of existing and emerging invasive species.
This thesis is concerned with the combined effects of climate and land use changes on the spatial distribution of the sub-tropical invasive plant, Tradescantia fluminensis (Vell.). The contribution of this thesis is to undertake an integrated assessment of the distribution change for this species in New Zealand. On the basis that climatic variables affect species distribution at larger scales, while land use, habitat, disturbance and dispersal mechanisms affect distribution at smaller scales, two separate analyses were undertaken. At the national scale BioCLIM and the Ecological Niche Factor Analysis (ENFA) were implemented using the variables: minimum temperature (July-August), MTminJ-A, and annual water deficit (November-February). At the landscape scale, only ENFA was implemented, using the variables: MTminJ-A, ECOSAT riparian classes (habitat) and proximity to roads, urban areas and streams (disturbance and dispersal sources). Three scenarios of climate change (CCSR B1-Low, CSIRO9 A1B-Mid and HadCM A1FI-High) and two scenarios of land use change (SmartGrowth and Buildout) were developed to the year 2050, using the CLIMPACTS Open Framework Modelling System and Geographic Information Systems, GIS, techniques respectively. The baseline species distribution model was extrapolated in ENFA, using the 2050 scenarios. Changes to potential threat from this species to protected areas at the landscape level were assessed spatially at the landscape level. This approach and its results are novel for this species.
At the national scale the results for the modelling show that climate change will increase the potential habitat suitability of Tradescantia under all combined scenarios of CCSR, CSIRO9 and HadCM for mean minimum temperature (July-August), MTminJ-A and Annual Water Deficit, AWD. At the case study landscape, in the Western Bay of Plenty and Tauranga also the modelling results showed that climate change and land use changes will increase the suitability for Tradescantia by 2050.
The 'core' or highest suitability areas increase under all future scenarios. At the national level core suitability increased by about 13% for the CCSR:B1-Low and CSIRO9:A1B-Mid and 22% for HadCM:A1FI-High combined scenario on the North Island. On the South Island, core areas increased by a much lower margin - 1.4%, 2.3% and 2.9% for CCSR:B1-Low, CSIRO9:A1B-Mid and HadCM:A1FI-High combined scenarios respectively. At the landscape level core areas increased by 5%, 8% and 21% for the CCSR:B1-Low+SmartGrowth, Darlam:A1b-Mid+SmartGrwoth and HadCM:A1FI-High+Build-out combined scenarios, respectively. This is true also for the Protected areas within the case study landscape, and indicate that the increasing if Tradescantia is able to track both climate and land use change through its dispersal and migration within the landscape 9 primarily in the inland and upland direction), then is will pose a greater risk to native habitats than at present.
Integrated assessments and the outputs they produce are essential to exploring anticipated changes (through scenario-building) and in understanding the change spatial context and magnitude of projected changes from the combined effects of climate and land use changes into the future and need to be integrated into biodiversity-biosecurity management at multiple scales.||en_NZ