Methods


We used species distribution modelling as the basis for assessing the threat posed by 541 non-native naturalised and invasive plants under current and future climates within Australia. Species records were downloaded from Australia's Virtual Herbarium and the Global Biodiversity Information Facility in June of 2012 for naturalised species and July of 2013 for invasive species. A combination of five bioclimatic variables and one soil variable was used to build models of suitable habitat. We used seven global climate models (GCMs) and two greenhouse gas emission scenarios (RCPs 4.5 and 8.5) to assess future climate in the years 2035 and 2065, and WorldClim baseline climate conditions (1950-2000) to find areas of current suitable habitat. Gridded maps of the seven GCM projections were averaged to produce average suitability for each future scenario. Areas that were considered highly suitable or very good quality habitat were also calculated.

Additionally, we calculated species-level habitat suitability information and species observation data within the following spatial scales and jurisdictions: national; states and territories; protected areas (using the Collaborative Australian Protected Area Database, CAPAD); Local Government Areas (LGAs); wetlands of international importance (RAMSAR); Natural Resource Management regions (NRMs); and Interim Biogeographic Regionalisation for Australia (IBRA7) areas.

We collated information on the non-native plant species from national and international plant databases. Information compiled included growth form, longevity, seed dispersal morphology, and location and habitat of exotic ranges. Species profiles were created by compiling key trait data, observation records, and maps of current habitat suitability and projected change in suitability across Australia. These profiles serve as the basis to evaluate how climate change may influence the distribution of these species in the future. Search our species profile database.

Finally, we developed screening tools for naturalised and invasive plants. The screening tool for naturalised plants identifies species as having low, medium or high potential for population establishment and expansion now and in the future. For invasive plants, we developed a method of classifying species into three classes to reflect their modelled response to climate scenarios under RCP 8.5 in 2065 compared to current climate at the national level. These tools are designed to assist managers in prioritising naturalised and invasive species for which more comprehensive assessments and management are needed.

Further details on modelling methods can be found in:

  • Duursma DE, Gallagher RV, Roger E, Hughes L, Downey PO, Leishman MR (2013) Next-Generation Invaders? Hotspots for Naturalised Sleeper Weeds in Australia under Future Climates. PLoS ONE 8(12): e84222. doi:10.1371/journal.pone.0084222 [PDF available]
  • Prioritising naturalised plant species for threat assessment: developing a decision tool for managers [PDF available]