Climate change and pesticides

More rainfall and higher temperatures

According to current research at the Rossby Centre at the Swedish Meteorology and Hydrology Institute (SMHI), climate change will result in a wetter and warmer climate, with rainfall and temperature predicted to increase more during the winter months. Extremely high intensity rainfall events are also predicted to become more frequent. Changes in the amount and intensity of precipitation can increase the risk of leaching due to increased flow through soil macropores and in surface runoff following high-intensity precipitation events. However, these effects may be counteracted by increased temperatures leading to faster decomposition. Diffuse losses are the dominant agricultural source of pesticides to the aquatic environment. Climate change is likely to increase these diffuse losses, mainly as a result of indirect effects, by affecting pesticide use patterns. 

Mostly indirect effects

There are several conceivable indirect effects of climate change:

1. A longer growing season can allow earlier application of pesticides, which can be beneficial since there may be more time available for degradation. However, autumn spraying can also be expected to be delayed owing to the greater area of winter crops grown, which may increase leaching, as precipitation in autumn/winter is predicted to increase.
2. A need for new pesticide compounds may arise due to changes in land use, crop rotations and the introduction of new crops and varieties.
3. A wetter and warmer climate will increase the pressure from pests, and probably result in an altered weed flora, which is expected to increase the need for pesticides. Most of the pesticides used within agriculture today are herbicides, but climate change may result in a greater need for insecticides and fungicides in the future.

Research and advisory services are incredibly important tools when it comes to reducing the use of pesticides, particularly in the light of climate change. Monitoring pesticides in the aquatic environment will continue to be important and may need to be intensified, with denser sampling during the growing season and also during the winter season, and including more northern ‘type catchment areas’ in the program.

Links

• Publication from 2015 on direct and indirect effects of climate change on herbicide leaching by Steffens et.al.