Abstract:
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.
