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Crop risk maps

by Marco Moriondo and Marco Bindi

Aim of the work

Since agricultural practices are climate-dependent and yields vary from year to year depending on the weather, agricultural sector is particularly exposed to changes in climatic mean values and variability. Additionally, the agricultural sector represents the major land use across the globe and consequently is the major economic, social, and cultural activity, providing a wide range of ecosystem services. The summer heat wave of 2003 (Schär et al. 2004), taken as an indicator of the future climate change, accompanied by precipitation deficits, has led to agricultural damages of more than €13 billion, 30% reduction in gross primary production of terrestrial ecosystems, numerous and extensive wild fires (390,000 ha in Portugal), and problems in water supply and energy production (IPCC, 2007). In Poland, the six-week (mid-June to end of July) period of deficient precipitation in 2006 caused high agricultural damage.

As a consequence, understanding the potential impacts on agriculture of climate change in general and increasing climate extreme events in particular has become increasingly important and is of main concern especially for the sustainability of agricultural system and for policy-making purposes.

Adaptation is certainly an important component of any policy response to climate change in this sector (Mizina et al. 1999; Reilly and Schimmelpfennig 1999). Studies show that without adaptation, climate change may create considerable problems related to agricultural production and agricultural economies and communities in many areas; but with adaptation, vulnerability can be reduced and there are numerous opportunities to be realized (Nordhaus 1991; Rosenzweig and Parry 1994; Smit and Skinner, 2002, Wall and Smit, 2005).

Effective adaptation strategies may be adopted bearing in mind that climate change includes not only long-term changes in mean conditions, but also a change in the year-to-year variation in growing season conditions, and the frequency and magnitude of extreme weather events (Hulme et al. 1999; IPCC 2007, Moriondo et al., 2009). Crop yield is largely determined by average climate conditions, but is also affected by irregular or extreme conditions deviating from the mean growing season conditions, in particular - droughts, heat waves, and floods (Mearns, 1984, Reilly 1995; Risbey et al. 1999). Major concerns result from model-based climate projections for the 21st century, which show increases in both the number of consecutive dry days and precipitation intensity in many regions, with potential adverse consequences on agriculture. According to these models, heat waves are shown to increase, in duration and magnitude, in future scenarios (Semenov, 2007; Moriondo and Bindi; 2006; IPCC, 2007) resulting in severe yield loss especially when occurring during sensible phenological stages.

On these premises, this study aims at assessing the impact of a 2°C warming on EU agriculture, accounting changes in both mean climate ad climate variability. Specifically, the results of a GCM statistical downscaling were coupled with a process-based crop model to simulate responses of sunflower, soybean spring and winter wheat to climate change. Additionally, different adaptation options were tested to alleviate the expected adverse impacts or to exploit possible positive spin-off effects of climatic change.

Due to the coarse GCM resolution, firstly an empirical downscaling procedure was set up in order to reproduce, on a scale suitable for impact assessment, the future climate at the time of average global warming of 2°C over the entire European domain. This procedure, based on the use of a weather simulator (LARS WG, cf. Semenov and Barrow, 1997), allowed considering both change in mean climate as well as changes in the climate variability for future climate simulations.

Crop growth model used in this work (CropSyst) incorporates the effect of environmental variables (temperature, rainfall, soil type, CO2 concentration) and management practices (ploughing, sowing time, fertilization, irrigation) on crop growth and yield. Additionally, both the impact of drought stresses and heat waves (following Moriondo et al., 2009) occurring at anthesis and grain filling are simulated. 

The impacts of changes in climate regime of both winter and summer crops are considered in this work. At the same time, the performances of different adaptation strategies are compared the including advanced or delayed sowing time, shorter- or longer-cycle cultivar and irrigation.

The results are discussed in terms of which mechanisms are underlying the processes of adaptation to climate change in agriculture.

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