Herbicide resistant weeds are increasingly becoming a major challenge for agricultural production worldwide. Palmer amaranth (Amaranthus palmeri) is an invasive annual forb that has recently emerged as one of the most widespread and severe agronomic weeds in the United States (US), due in part to its facility for evolving herbicide resistance. Originally from arid regions of southwestern US and northwestern Mexico, this highly adaptive weed has spread across the US due to human-assisted dispersal of its seeds. It has also invaded portions of Africa, Europe, and South America. The distribution and growing season of a weed species like Palmer amaranth will undoubtedly change as a consequence of climate change, adding additional challenges to managing this species. In this study, we developed a process-oriented bioclimatic niche model of Palmer amaranth using CLIMEX, to examine its potential global distribution under both current climatic conditions and possible future climate under the RCP 8.5 emission scenario for the year 2050.
Results/Conclusions
The CLIMEX model was validated with independent widespread distribution data in its non-native US range, as well as more limited data from Europe, Africa, and South America. The model agreed with all credible Palmer amaranth distribution data. Model projections indicated that key row-crop production regions in Africa and Australia are at high risk for Palmer amaranth invasion in terms of both current and future climate scenarios. Model outputs also suggest the potential for substantial range expansion and infill in Europe, North America, and South America. In the Northern Hemisphere, projected increases in temperature will likely enable Palmer amaranth to expand its range northward into Canada and northern Europe. In the United States alone, suitable range for Palmer amaranth would increase by 21.22% by mid-century, particularly in the central and western states. The results of this study show that the likely range expansion of this weed under future climate change should be considered routinely in Palmer amaranth security planning and weed management programs.