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Keywords:

  • climate change;
  • CLIMEX;
  • climate modelling;
  • scotch broom;
  • invasive alien species

Summary

Cytisus scoparius is a serious weed of pastoral systems, natural ecosystems and plantation forestry, which has become invasive in a number of countries. CLIMEX™ was used to infer the climatic requirements of C. scoparius from its native range, as well as its current range as an exotic in the United States and New Zealand. The parameterised model was used to examine the invasive potential of C. scoparius under current and future climatic conditions, assuming a range of climate-change scenarios. The modelled global potential distribution of C. scoparius compared favourably with the known distributions, in both the fitted and validation dataset, encompassing almost all temperate and Mediterranean regions. The predicted distribution also included most sub-tropical regions and extended into continental areas in North America and Europe and savanna regions in Africa. Under current climate, the projected potential distribution exceeded the known distribution. Places most at risk from range expansion include China, Australia, Argentina and North America, as C. scoparius is already present, but has not yet colonised all areas with apparently high climatic suitability. Climate change is likely to lead to a poleward shift in the range of C. scoparius and a contraction of areas of suitable climate for the species in southern Europe, central Africa, Australia, China, Brazil and the southern United States. With climate change, currently uncolonised areas within northern Scandinavia, southern Canada and western regions of the Russian Federation are projected to become climatically suitable.