Water-limited crop productivity (CLIM 032) - Assessment published Nov 2012

Key policy question: How is climate change affecting the water-limited productivity of agricultural crops across Europe?

Projected changes in effective solar radiation from two climate models

Note: The map shows the mean changes in effective solar radiation (MJ m-2), which is an indicator for water-limited crop productivity, for the period 2031–2050 compared with 1975–1994 for the RACMO (KNMI) and HadRCM3 (Hadley Centre.HC) projections under the A1B emission scenario.

Data source:

• Changes in flowing and maturity time of cereals in Northern Europe under climate change provided by University of Aarhus

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Projected changes in water-limited crop yield

Note: This figure shows the mean relative changes in water-limited crop yield simulated by the ClimateCrop model for the 2050s compared with 1961–1990 for 12 different climate models projections under the A1B emission scenario.

Data source:

• Looking into the future of agriculture in a changing climate provided by Universidad Politecnica de Madrid

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Simulated change in water-limited wheat production

Note: The figure shows the simulated change in water-limited wheat production for 2030 compared with 2000 for the A1B emission scenario using a cold (ECHAM5) (left) and a warm (HADCM3) (right) climate change projection. The simulation was performed on a 25x25 km grid (assuming current area of wheat cropping) but the results are presented here at the NUTS-2 level.

Data source:

• Assessing agriculture vulnerabilities for the design of effective measures for adaption to climate change (AVEMAC project) provided by Joint Research Centre (JRC)

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Key assessment

Past trends

A global analysis of yields of cereal crops (wheat, maize and barley) has shown yield decreases due to increasing mean temperatures [i]. Similar effects have been observed for various countries in Europe [ii]. Increasing temperatures have also been attributed as one of the main causes for the lack of yield increase of winter wheat in France despite improvements in crop breeding [iii]. Grain yields in maize have been steadily increasing in northern Europe, whereas yields in southern Europe seem to have been stagnating. There is also a tendency for increasing variability of grain yields in France and Italy, linked to occurrence of heat waves and droughts [iv]. These climatic extremes affected the crop production in large areas of southern and central Europe in 2003 and 2007. In contrast to cereals and oilseed crops, potato and sugar beet seem to have responded positively to the increasing temperatures by increasing yields, most likely due to longer growing seasons [v].

Projections

The impact of future changes in climate on crop yield depends on the characteristics of the climatic change within a region as well as on a combination of other environmental, economic, technological and management factors [vi]. The index of effective solar radiation sum has been developed as a proxy for the effects of environmental changes on crop productivity [vii], and it integrates the daily solar radiation on those days where neither temperature nor soil moisture is limiting for growth. This index estimates the potential for rain-fed crop production using a standard soil across the entire continent, although this may be greatly modified by local soil conditions. Figure 1 shows the projected changes in effective radiation sum for the 2040s for climate projections from two different climate models. Both projections show reduced production potential in large parts of southern Europe and increases in the far north, but they differ substantially for areas in-between. A broader analysis of climate change scenarios for agricultural productivity in Europe has provided a clear picture of deterioration of agroclimatic conditions from increased drought stress and a shortening of active growing season across large parts of southern and central Europe [viii]. Results also suggest a risk of an increasing number of unfavourable years for agricultural production in many European climatic zones, resulting in increased variability of crop yield from droughts and heat waves.

The estimates shown in Figure 1 do not consider the effects of enhanced atmospheric CO₂ levels on crop productivity. The ClimateCrop model was applied to explore the combined effects of projected changes in temperature, rainfall and CO₂ concentration across Europe, considering certain management changes thus incorporating effects of adaptation. The mean projected changes in Figure 2 show the same overall picture as Figure 1 of decreases in yields along the Mediterranean and large increases in Scandinavia. However, throughout large parts of western and central Europe mean changes in crop yields are likely to be small.

Figure 3 shows changes in water-limited wheat production in Europe by 2030 for climate projections from two different climate models [ix]. The results that also include effects of enhanced CO₂ concentrations indicate that different climate models can lead to large differences in projected impacts, with both yield increases and decreases possible in northern and southern Europe. The same study showed large differences in simulated yield changes between different crops, climate model projections and time horizons. Neither of these model estimates considers adaptation to climate change, such as changes in crop species and varieties and changes in crop management. It is therefore likely that negative yield impacts will be smaller and positive effects bigger following adaptation in the farming systems.

[i] David B Lobell and Christopher B Field, „Global scale climate–crop yield relationships and the impacts of recent warming“, Environmental Research Letters 2 (März 2007): 014002, doi:10.1088/1748-9326/2/1/014002.

[ii] K. Kristensen, K. Schelde, and J. E. Olesen, „Winter wheat yield response to climate variability in Denmark“, The Journal of Agricultural Science 149, Nr. 01 (2011): 33–47, doi:10.1017/S0021859610000675.

[iii] Nadine Brisson et al., „Why are wheat yields stagnating in Europe? A comprehensive data analysis for France“, Field Crops Research 119, Nr. 1 (Oktober 9, 2010): 201–212, doi:10.1016/j.fcr.2010.07.012.

[iv] J.E. Olesen et al., „Impacts and adaptation of European crop production systems to climate change“, European Journal of Agronomy 34, Nr. 2 (Februar 2011): 96–112, doi:10.1016/j.eja.2010.11.003.

[v] Pirjo Peltonen-Sainio et al., „Coincidence of variation in yield and climate in Europe“, Agriculture, Ecosystems & Environment 139, Nr. 4 (Dezember 2010): 483–489, doi:10.1016/j.agee.2010.09.006.

[vi] P. Reidsma et al., „Adaptation to climate change and climate variability in European agriculture: The importance of farm level responses“, European Journal of Agronomy 32, Nr. 1 (Enero 2010): 91–102, doi:10.1016/j.eja.2009.06.003.

[vii] M Trnka et al., „Expected changes in agroclimatic conditions in Central Europe“, Climatic Change 108 (März 5, 2011): 261–289, doi:10.1007/s10584-011-0025-9.

[viii] Trnka et al., „Expected changes in agroclimatic conditions in Central Europe“.

[ix] M. Donatelli et al., Assessing agriculture vulnerabilities for the design of effective measures for adaption to climate change (AVEMAC project) EUR 25249 (Luxembourg: European Commission, Joint Research Centre, 2012), http://ec.europa.eu/agriculture/analysis/external/avemac/full_text_en.pdf.