Indicator Assessment
Crop-yield variability
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- Climate and its variability are largely responsible for variations in crop suitability and productivity in Europe.
- Since the beginning of the 21st century, the variability of crop yields has increased as a consequence of extreme climatic events, e.g. the summer heat of 2003 and the spring drought of 2007.
- As a consequence of climatic change, such events are projected to increase in frequency and magnitude, and crop yields to become more variable. Changes in farming practices and land management can act as risk-mitigating measures.
Sensitivity of cereal yields to climate change for maize and wheat
Note: A small increase in temperature has a positive impact on cereals yield, while a high increase (3-5 oC) has a negative impact
Easterling, W. E.; Aggarwal, P. K.; Batima, P.; Brander, K. M.; Erda, L.; Howden, S. M.; Kirilenko, A.; Morton, J.; Soussana, J.-F.; Schmidhuber, J. and Tubiello, F. N., 2007. Food, fibre and forest products. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Parry, M. L.; Canziani, O.F.; Palutikof, J. P.; van der Linden, P. J. and Hanson, C. E. (eds.), Cambridge University Press, Cambridge, UK, 273-313.
Past trends
While the area under arable cultivation in most of western Europe has decreased over the past 40 years, crop yields have increased almost continuously (Eurostat). This trend has persisted into the 21st century, although crop-yield variability increased as a consequence of several extreme meteorological events in short succession: a late frost in 2003 followed by a severe drought reduced cereal yields over most of Europe, a drought in 2005 severely affected western Europe (Iberian Peninsula), and an early drought in 2006 was followed by extreme rains during the summer, resulting in lower cereal production, especially in eastern Europe (EC, MARS Bulletins, 2008). Alexander et al. (2006) found a general increase in the intensity of precipitation events observed at the global level. For the Mediterranean area, where climate vulnerability is high, several studies found an increasing trend towards more intense precipitation and a decrease in total precipitation (Alpert et al., 2002; Maheras et al., 2004; Brunetti et al., 2004). In general, it is difficult to separate the climate effects from those of improved agricultural techniques in the development of historic crop yields. Adaptive management is expected to continue to help reduce the risks to agricultural yields from climate change, and to make better use of opportunities.
Projections
The effects on agricultural yields of increasing mean daily temperatures depend on their magnitude and geographic extent. The production areas of some crops could expand northwards in Europe, e.g. for maize. With an increase in mean annual temperature of 2 oC, cereal yields are expected to increase, partly because of the fertilisation effect of the increase in CO2 (Parry et al., 2004). However, an increase of 4 oC or more will shorten the crop cycle and the CO2 effect will not compensate for the resulting loss of yield. Crop yields are also at risk from more intensive precipitation and prolonged periods of drought, particularly in areas bordering the Mediterranean basin. Figure 1 shows the sensitivity of maize and wheat yields to climate change, as derived from the results of 69 published studies. These span a range of precipitation changes and CO2 concentrations, and vary in how they represent future changes in climate variability. Responses include cases without adaptation (red dots) and with adaptation (dark green dots). Adaptation represented in these studies includes changes in planting dates and crop varieties, and shifts from rain-fed to irrigated conditions.
Indicator definition
- Sensitivity of cereal yields to climate change for maize and wheat
Units
Policy context and targets
Context description
In April 2009 the European Commission presented a White Paper on the framework for adaptation policies and measures to reduce the European Union's vulnerability to the impacts of climate change. The aim is to increase the resilience to climate change of health, property and the productive functions of land, inter alia by improving the management of water resources and ecosystems. More knowledge is needed on climate impact and vulnerability but a considerable amount of information and research already exists which can be shared better through a proposed Clearing House Mechanism. The White Paper stresses the need to mainstream adaptation into existing and new EU policies. A number of Member States have already taken action and several have prepared national adaptation plans. The EU is also developing actions to enhance and finance adaptation in developing countries as part of a new post-2012 global climate agreement expected in Copenhagen (Dec. 2009). For more information see: http://ec.europa.eu/environment/climat/adaptation/index_en.htm
Targets
No targets have been specified
Related policy documents
No related policy documents have been specified
Methodology
Methodology for indicator calculation
Methodology for gap filling
http://www.eea.europa.eu/publications/eea_report_2008_4/pp193-207CC2008_ch8_Data_gaps.pdf
Methodology references
No methodology references available.
Uncertainties
Methodology uncertainty
http://www.eea.europa.eu/publications/eea_report_2008_4/pp193-207CC2008_ch8_Data_gaps.pdf
Data sets uncertainty
http://www.eea.europa.eu/publications/eea_report_2008_4/pp193-207CC2008_ch8_Data_gaps.pdf
Rationale uncertainty
No uncertainty has been specified
Data sources
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Cereal crop impacts versus incremental temperature change
provided by Intergovernmental Panel on Climate Change (IPCC)
Other info
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 032
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Temporal coverage
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/crop-yield-variability/crop-yield-variability-assessment-published or scan the QR code.
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