The 'hidden hunger' caused by climate change

Lewis Ziska in SciDev.net: Researchers are focusing much attention on how to adapt agriculture to ensure steady food supplies in the face of climate change. But it is equally important to preserve the quality of these supplies as well as the quantity. Researchers, policymakers and the public are increasingly aware that climate uncertainty — characterised by shifting rainfall patterns, increased desertification and warming temperatures — threatens to decrease people's ability to grow food sustainably in many parts of the developing world.

But few know that rising levels of carbon dioxide (CO2) — the principal greenhouse gas — is also expected to affect the nutritional value of many basic food crops. At first glance this may seem counter-intuitive, since CO2 stimulates plant growth in several basic crop species such as wheat and rice, cereals that supply the bulk of calories for most of the world's poor.

But the nutritional value of these potentially bumper yields is unlikely to improve because extra CO2 is often converted into carbohydrates such as starch, meaning that the relative levels of other components may fall. For example, the 20 per cent or so rise in atmospheric CO2 since 1960 may have already caused a significant decline (5–10 per cent) in protein concentration in wheat flour.

And a recent study, by researchers in Southwestern University, Texas, of major food crops including barley, wheat, soya bean and potato, reveals a significant decline (10–15 per cent) in protein content if atmospheric CO2 reaches 540–960 parts per million — a range anticipated by the middle to end of this century.

In addition to 'diluting' protein levels, rising CO2 levels may reduce water flow through a crop plant, affecting the uptake of micronutrients from the soil, lowering concentrations of key nutrients such as sulphur, magnesium, iron, zinc and manganese…..

Barley (Hordeum vulgare) on a field near Höchberg, Germany, shot by Carport, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 3.0 License