It’s been an exciting couple of weeks, with the recent publication of a couple articles in the latest issue of The Lancet Planetary Health, so I thought I’d put together a couple blog posts about the articles.
The first, “Combining the effects of increased atmospheric carbon dioxide on protein, iron, and zinc availability and projected climate change on global diets: a modelling study“, is the product of more than a year of collaborative research across multiple institutions (IFPRI, Harvard, USDA, EPA, RTI, and CSIRO). In this study we tried to look at a wide range of climate change induced impacts on crop growth.
A lot of work that I’ve contributed to has looked at the impacts of shifting temperature and precipitation patterns on crop yields, and how changes in crop productivity can lead to changes in commodity prices, agricultural trade flows, consumer demand and food security. For example, Ignaciuk and Mason-D’Croz (2014), Nelson et al. (2014), and Wiebe et al. (2015) all of which focused primarily on assessing the impacts of changes in mean temperature and precipitation on crop productivity. In another recent study we looked at how changes in economic growth and climate change could impact the supply of nutrients. In this latest article, we tried to expand on this previous work to consider the role of atmospheric CO2 on crop growth and nutrient supply.
Changing CO2 concentration levels can have multiple effects on the environment, beyond its impact as a greenhouse gas. Varying levels of CO2 in the atmosphere has multiple effects on plant chemistry.
- CO2 Fertilization CO2 is a critical input into plant photosynthesis, the biochemical process which plants use to convert sunlight into carbohydrates that serve as food for the plant, with Oxygen another key by-product. More CO2 (assuming there aren’t water and nutrient constraints), should lead to more photosynthesis, and more plant biomass. In theory, CO2 fertilization could help offset some of the negative yield impacts of changes in temperature and precipitation.
- Shifting nutrient balance Greater availability of carbon can also change the nutrient balance in crops. More carbohydrates from photosynthesis dilutes the concentration of many micronutrients like iron and zinc. Changes in the carbon cycle can also impact the chemistry of building protein and vitamins, often contributing to a decline in the nutrient content of many crops.
Adding these additional impact pathways on crop productivity and nutritional quality, continues to show the climate change will have a negative impact on our food supply, not only by reducing crop yields, but also by reducing the nutritional quality of the foods we grow. Perversely, the regions most likely to be negatively impacted by these changes are also those regions least responsible for higher CO2 levels. These findings suggest that while we cannot ignore the productivity losses climate change may cause, the situation is more complicated than just a food supply (quantity) question. We need to also consider more broadly issues of food quality and nutrition.