Weeds vs. Crops: the winner of climate change

Climate change is projected to bring increased temperature, increased carbon dioxide (CO2) and altered rainfall amount, frequency, and intensity. However, changes in climate may positively affect the potential for agricultural production in northern regions by extending the length of the growing season (60-90 days in Norway) and the latitude at which some crops might be grown. Therefore, in these areas, yields can be increased. These changes may also benefit weeds and other plant pests leading to higher weed and pests’ pressure in agriculture. Plants, both crops and weeds, are affected by many climate change effects with temperature and CO2 being among the most important, especially CO2 concentration as CO2 represents the source of carbon for photosynthesis. Competition between weeds and crops may also be affected by increased CO2 and studies suggest that the positive impact of increased CO2 on crops may be nullified by higher responses from weeds.

The magnitude of photosynthesis, growth and reproductive response to increased CO2 varies among plant photosynthetic types. In C3 plants, the photosynthetic rate is approximately doubled when plants are exposed to double atmospheric CO2 concentration. However, the sensitivity of photosynthesis to the increased CO2 is temperature dependent. C4 plants, however, are photosynthetically saturated at the current CO2 level and rising atmospheric CO2 would have no major impact on their carbon fixation rate, biomass production and yield. This little CO2 stimulation in C4 plants is irrespective of temperature.

In northern climatic regions most of the crops grown and most of the troublesome weeds use the C3 photosynthesis pathway which is not particularly well adapted to drought and high temperatures. However, there are some problematic C4 weed species such as barnyard grass (Echinochloa crus-galli) which may, unfortunately, spread further north by benefiting from higher temperatures.

Weeds vs. Crops: the winner of climate change

The action plan for sustainable use of pesticides in Norway (2021-2025) emphasizes that climate change can lead to greater problems with plant pests (weeds, diseases, and insects) in Norway. This will increase the need for new plant protection measures and knowledge about the effects of climate change on new and established plant pests establishing, spreading, and population dynamics.

“Weeds vs. Crops: the winner of climate change” is a three-year “Investing in the future” project financed by NIBIOs base funding from the Research Council of Norway (project number 342631/L10). The project’s main goal is to build competence on the effects of climate change on competition between weeds and crops that will be used to inform integrated weed management.

Within the project

1. we will develop a methodology to assess the effect of future climate with higher temperature and CO2 levels on competition between selected C3 and C4 weeds and crops,
2. we will gain knowledge that can inform weed warning models used to develop Decision Support System (DSS) for integrated weed management
3. we will develop a multidisciplinary network and a significant project portfolio on the effects of climate change on weeds and adaptation strategies for weed management, to contribute to increasing and maintaining the crop potential in Norway, especially at northern latitudes.