Core Ideas CLIMEX model projections match known Palmer amaranth distribution. Sub‐Sahara Africa and Australia are at risk for Palmer amaranth establishment. Future climate scenarios indicate the potential for poleward range expansion. Herbicide‐resistant weeds are increasingly becoming a major challenge for agricultural production worldwide. Palmer amaranth [Amaranthus palmeri (S.) Wats.] is an invasive annual forb that has recently emerged as one of the most widespread and severe agronomic weeds in the United States, due in part to its facility for evolving herbicide resistance. It has invaded several parts of the world, including key agricultural production regions in South America. Climate change will likely exacerbate the challenges of managing this species. To assess this, we developed a process‐oriented bioclimatic niche model of Palmer amaranth to examine its potential global distribution under current conditions and future climate scenarios. The model agreed well with all credible current distribution data. Projected future increases in temperatures will expand potential Palmer amaranth range northward into portions of Canada and Europe. Model projections under current and future climates highlight several agricultural production regions of increasing and emerging risk from this weed.
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