Climate change impacts and vulnerability in Europe 2016

Climate change impacts on society
5.3.4 Water-limited crop yield
Key messages
• Yields of several rainfed crops are levelling off (e.g. wheat in some European countries) or decreasing (e.g. grapes in
Spain), whereas yields of other crops (e.g. maize in northern Europe) are increasing. These changes are attributed partly
to observed climate change, in particular warming.
• Extreme climatic events, including droughts and heat waves, have negatively affected crop productivity in Europe during
the first decade of the 21st century.
• Future climate change could lead to both decreases and increases in average yield, depending on the crop type and the
climatic and management conditions in the region. There is a general pattern of projected increases in productivity in
northern Europe and reductions in southern Europe, but with differences between crop types.
• Projected increases in extreme climatic events are expected to increase crop yield variability and to lead to yield
reductions in the future throughout Europe.
Relevance
The production of biomass in crops is the result of
the capture and conversion of solar energy through
the process of photosynthesis. However, this process
may be restricted by low (or high) temperatures or
by water limitations (Trnka, Olesen, et al., 2011).
Crop yields are affected by the combined effects of
changes in temperature, rainfall and atmospheric
CO 2 concentration (Box 5.2). In practice, the
response depends on soil type, which can differ
greatly in capacity for storing soil moisture, and on
the possibilities for supplementary irrigation. Crop
yield also depends on the timing of the crop growth
and yield formation. Yields in cereal and oilseed
crops respond particularly to the duration of the
grain‐filling period (Kristensen et al., 2011). The
impacts of unfavourable meteorological conditions
and extreme events vary considerably, depending on
the timing of occurrence and the development stage
of the crops (Moriondo et al., 2011; Trnka et al., 2014;
Eyshi Rezaei et al., 2015). Changes in the occurrence
of extreme events such as heat waves, droughts,
heavy precipitation and floods will greatly affect crop
yield leading to increased variability and economic
consequences (Ciscar et al., 2011).
Past trends
A global analysis of yields of cereal crops (wheat,
maize and barley) has shown that increasing mean
temperatures in recent decades have had a negative
effect on yield (Lobell and Field, 2007). Similar effects
have been observed for various countries in Europe
(Peltonen-Sainio et al., 2011). Increasing temperatures
have been identified as one of the main causes of
the lack of yield increase in winter wheat in France,
despite improvements in crop breeding (Brisson
et al., 2010). Grain yields in southern Europe seem
to have been levelling off. There is also a tendency
for an increasing variability of grain yields in France
and Italy, linked to the occurrence of heat waves and
droughts (Olesen et al., 2011). Similar effects of heat
haves and droughts have been observed globally,
whereas floods and intense rainfall have not been
seen to affect overall crop production (Lesk et al.,
2016). In Italy and southern-central Europe, the
potential crop yields of potato, wheat, maize and
barley significantly decreased over the time period
1976–2005 owing to temperature and radiation
change effects (Supit et al., 2010). In north-east Spain,
grape yield has been declining because of increasing
water deficits since the 1960s (Camps and Ramos,
2012). Droughts and heat waves affected the crop
production in large areas of southern and central
Europe in 2003 and 2007 (Peltonen-Sainio et al.,
2010). An increase in climate-induced variability in
maize yield has been observed over recent decades in
France (Hawkins et al., 2013).
Climate change has also shown positive effects
on yields. Potato and sugar beet have responded
positively to increasing temperatures through an
increase in yields, most likely due to the longer
growing seasons (Peltonen-Sainio et al., 2010, 2011).
In Scotland, increasing temperatures are estimated
to have increased the potential potato yield by up
to 39 % over the period 1960–2006 (Gregory and
Marshall, 2012). In parts of the United Kingdom and
parts of northern-central Europe, the yield potential of
wheat, sugar beet and maize has increased since 1976
(Supit et al., 2010). Grain yields in maize have been
steadily increasing in northern Europe, most likely
linked to the warmer climate (Olesen et al., 2011).
232 Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report