The impact of heat and water stress on food production are analysed in
a paper published in Nature Climate Change this week. Looking
specifically at African maize and its ability to cope with warming,
the work suggests that 1 °C of warming would result in yield losses
for 65% of the current maize-growing region in Africa. Under drought
conditions, 100% of the currently cultivated area would experience
yield losses, with 75% of this area suffering losses of at least 20%.
The impact of climate change on food production remains uncertain,
particularly in the tropics. David Lobell and colleagues used
historical data from over 20,000 African maize trials conducted
between 1999 and 2007, together with daily weather records, to
investigate the impact of heat stress and drought on yield. They found
that for each ‘degree day’ the crop spends above 30 °C — a measure
that accounts for the amount and duration of heat experienced by the
plant — the yield decreases by 1% if the plants are rainfed. This
result tallies with observations for temperate maize varieties in the
United States. Importantly, however, they also show that under drought
conditions, yields decrease by 1.7% for each degree day spent over 30
°C, suggesting that water availability is critical to survival.
