Weed Population Dynamics under Climatic Change

This paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in crops. Elevated CO₂ levels may have positive effects on crop competitiveness with C₄ weeds, but these are generally outnumbered by C₃ species in weed populations. Moreover, higher temperatures and drought will favor C₄ over C₃ plants. The implementation of climate change adaptation technologies, such as drought-tolerant germplasm and water-saving irrigation regimes, will have consequences for crop?weed competition. Rainfed production systems are thought to be most vulnerable to the direct effects of climate change and are likely to face increased competition from C₄ and parasitic weeds. Biotic stress-tolerant crop cultivars to be developed for these systems should encompass weed competitiveness and parasitic-weed resistance. In irrigated systems, indirect effects will be more important and weed management strategies should be diversified to lessen dependency on herbicides and mechanical control, and be targeted to perennial rhizomatous (C₃) weeds. Water-saving production methods that replace a weed-suppressive floodwater layer by intermittent or continuous periods of aerobic conditions necessitate additional weed management strategies to address the inherent increases in weed competition. Thus, climatic conditions have a great effect on weed population dynamics all over the world.