Emerging Weed Problems under Changing Climatic Condition: A Review

Climate is a major force in earth’s environmental system, and even minor changes in climate can have complex and serious effects on the environment. Atmospheric CO2, temperature and precipitation are major important abiotic variables that directly affect weed physiology and growth. Weeds are more genetically diverse than crops, hence show enhanced growth and reproductive stability than crops. Among the C3 and C4 weeds in cropped field, C3 weeds have more response in photosynthesis to increased CO2 level in atmosphere. The elevated CO2 under sufficient soil moisture condition will leads the higher C3 weed competitiveness in C4 crops. So weed growth is favoured as CO2 is increased. Temperature changes resulted in an expansion of weeds, and shifting of weeds. Based on the differences in temperature, the C4 spp. able to tolerate high temperature than C3 spp. Therefore, C4 weeds benefit more than the C3 crops from temperature increases that accompany elevated CO2 levels. Due to global warming, weeds expand their range into new areas. Precipitation is also one of the important climate variable that influences the growth and distribution of weeds growth. Even though CO2 concentration level and temperature rise in future are predictable, amount, distribution, and intensity of rainfall patterns remains much more uncertain. Moisture is a key factor required for weed seed germination, growth and development. Climate change can affect the frequency and intensity of rainfall and result in occurrences of extreme events such as floods and droughts; consequently, weeds adapted to these conditions will have a higher competitive advantage.