Food security in a warming world
Carbon dioxide encourages plant growth, but this will be at least partly offset by the other consequences of climate change. Higher temperatures are expected to have a positive effect on crop development in cold regions, but further temperature increases in hot regions tend to reduce rates of photosynthesis.
Reductions in average rainfall are being observed in many parts of the world that are already dry, including the Mediterranean. Average rainfall will probably increase in many already wet regions, and extreme rainfall is almost certainly getting more frequent, both of which can damage crops, through impacts such as flooding and physical damages to the plant structure. However, higher levels of CO2in the atmosphere do allow plants to manage moisture better.
The effect of climate change on global rates of photosynthesis, or primary production, is a good measure of the impact on plants generally, including crops. Global photosynthesis will be affected by CO2 fertilisation, temperature increase and rainfall patterns. These competing factors mean that the overall impact of climate change will be positive in some regions and negative in others. Of the three factors, changes to average rainfall patterns are the hardest to predict, and they provide the biggest source of uncertainty. Weeds will also be affected by these changes, potentially affecting competition for space or nutrients. Read more
There will also be implications for crop diseases and pests. The pathogenic fungi which cause the crop disease Fusarium Ear blight are highly sensitive to rainfall fluctuations, so we cannot be certain how climate change will affect them. Fusarium ear blight has the potential to damage staple crops around the world, so it is important that we better understand how it will be affected. There is preliminary evidence that Fusarium ear blight may become more of a problem as the climate warms, including in the UK. Read more