Weeds vs. Crops: the winner of climate change

Summary: In subarctic climatic regions, increasing temperature due to climate change may positively affect the potential for agricultural production by extending the growing season and the latitude at which some crops might be grown. However, these changes may also benefit weeds that are acknowledged as the primary contributors to crop yield loss. A changing climate is also projected to bring an elevated CO₂ - e(CO₂) - concentration that is known to affect plant growth and reproductivity as CO₂ represents the source of carbon for photosynthesis. Competition between weed and crop may also be affected by e(CO₂) and studies suggest that the positive impact of e(CO₂) on crops may be nullified by higher responses from weeds. In subarctic climatic regions most of the crops grown and most of the troublesome weeds use C3 photosynthesis pathway and this has a disadvantage in drought and high-temperature environments. C4 photosynthesis plants, however, have an advantage in drought and high-temperature environments. Recently the  C4 weed barnyard grass (Hønsehirse) have established well in the southern part of Norway and other subarctic climatic regions and it may, unfortunately, spread further north by benefiting from higher temperatures and e(CO₂). Together with increased problems with herbicide resistance, this may threaten our future food safety. By studying biological, physiological, and molecular changes of selected C4-C3  weed-crop competition systems exposed to higher temperature and CO₂ levels and selected herbicides as well as predicting the responses using mathematical and statistical models, we may reveal acclimatory and evolutionary changes of these weeds and their management in a near future climate. The gene expression regulation associated with plant responses to e(CO₂) is a novel research topic that until now has only been explored for a few model plants but never considered for weed-crop competition systems or interaction of e(CO₂) and herbicide.