Climate change and food security: risks and responses

The projected impacts of climate change on major crop yields
are now well documented, 
based on two decades of research. Globally, negative impacts are more commonly found than 
positive ones. Observations of the effects of climate trends on crop production indicate that 
climate change has already negatively affected wheat and maize yields in many regions, as
well as globally. 
According to results from major agricultural model inter-comparison projects, despite 
remaining uncertainties related to how models account for the representation of combined 
carbon dioxide fertilization, ozone stress and high temperature effects, there is agreement on 
the direction of yield changes in many major agricultural regions at both low and high latitudes, 
with strong negative impacts especially at higher levels of warming and at low latitudes. IPCC 
has expressed high confidence for crop production to be consistently and negatively affected 
by climate change in the future in low-latitude countries, while climate change may have 
positive or negative effects in northern latitudes. Although some high-latitude regions may 
become more climatically viable for crops, soil quality and water availability might constrain 
sustained agricultural production increases in these locations. 
A recent multi-model study using IPCC’s highest scenario of warming found a mean effect 
on yields of four crop groups (coarse grains, oil seeds, wheat and rice, accounting for about 
70 percent of global crop harvested area) of minus 17 percent globally by 2050 relative to a 
scenario with unchanging climate. The hypothesis for this multi-model assessment combined 
the most extreme radiative forcing scenario with an assumption of limited CO
2
fertilization 
effects in 2050, but has not included the deleterious effects of increased ozone concentrations 
and biotic stresses from a range of pests and diseases, nor the likelihood of increased occurrence 
of extreme events. After 2050, the risk of more severe impacts increases. Overall, findings 
indicate that climate change will also increase crop yield variability in many regions. Potential 
impacts on other crops than major cereals have been less studied.
The models used to make projections of crop yields generally do not take into account the 
impacts of climate change on the functioning of ecosystems, such as the balance between crops, 
weeds and pests, nor the effects on pollinators. Pests and diseases are likely to move, following 
climate change, affecting areas previously immune, and thus less prepared, biologically and 
institutionally, to manage and control them, with potentially higher negative impacts. These 
changes may also counter-balance direct positive effects of climate change. For instance, in 
high-latitude regions, climatic conditions will become more favourable to crops, but also to 
weeds and pests.