Figure 13-6: Change in water-limited yield for wheat (a) and potential yield for grapevine (b), using HadCM2
scenario for 2050 (Harrison and Butterfield, 1999).
Agriculture accounts for only a small part of GDP in Europe. Therefore, the vulnerability of the overall economy to changes that affect agriculture is low (Reilly, 1996). Locally, however, effects on society may be large. Europe as a whole is noted for its substantial output of arable crops and animal products (FAOSTAT, 1998).
Trends in European agriculture are dominated by the EU’s Common Agricultural Policy (CAP). This occurs because EU member states account for a large proportion of agricultural production in Europe and because several countries currently are seeking membership in the EU and in this process are adjusting their policy to match the CAP. The EU seeks to integrate concerns for environmental protection and countryside livelihood into the CAP.
Many studies have assessed the effects of climate change on agricultural productivity (e.g., Ryszkowski and Kedziora, 1993; Harrison et al., 1995b; Semenov and Porter, 1995; Alexandrov, 1999; Cuculeanu et al., 1999; Harrison et al., 1999). Relatively little work, however, has been done to link these results across sectors to identify vulnerable regions and farming systems. Such assessments are needed to identify appropriate policy responses to climate change. More extensive information than the summary presented in this section appears in the agriculture chapter of the European ACACIA report (Bindi and Olesen, 2000).
Figure 13-6: Change in water-limited yield for wheat (a) and potential yield for grapevine (b), using HadCM2 scenario for 2050 (Harrison and Butterfield, 1999). |
Cereals of different species and varieties are grown throughout Europe. Climatic warming will expand the area of cereals cultivation (e.g., wheat and maize) northward (Kenny et al., 1993; Harrison and Butterfield, 1996; Carter et al., 1996a). For wheat, a temperature rise will lead to a small yield reduction, whereas an increase in CO2 will cause a large yield increase; the net effect of both for a moderate climate change is a large yield increase (Nonhebel, 1996; Harrison and Butterfield, 1999). Drier conditions and increasing temperatures in the Mediterranean region and parts of eastern Europe may lead to lower yields and the need for new varieties and cultivation methods. Yield reductions have been estimated for eastern Europe, and yield variability may increase, especially in the steppe regions (Alexandrov, 1997; Sirotenko et al., 1997). Figure 13-6a shows the response of wheat yields to change of climate and CO2 concentration for a GCM scenario for 2050 that resembles the A1 scenario. The largest increases in yield occur in southern Europe—particularly northern Spain, southern France, Italy, and Greece. Relatively large yield increases (3–4 t ha-1) also occur in Fenno-Scandinavia. In the rest of Europe, yields are 1–3 t ha-1 greater than at present. There are small areas where yields are predicted to decrease by as much as 3 t ha-1, such as in southern Portugal, southern Spain, and Ukraine. For maize, future climate scenario analyses carried out for selected sites in Europe suggest mainly increases in yield for northern areas and decreases in southern areas (Wolf and van Diepen, 1995). This is a result of a small effect of increased CO2 concentration on growth (maize is a C4 plant that responds less positively to CO2 increases than C3 plants such as wheat and barley) and a negative effect of temperature on the duration of growing season. The latter effect, however, can be largely prevented by growing other maize varieties (Wolf and van Diepen, 1995).
Seed crops generally are determinate species, and the duration to maturity depends on temperature and day length. A temperature increase therefore will shorten the length of the growing period and possibly reduce yields (Peiris et al., 1996). At the same time, the cropping areas of cooler season seed crops (e.g., pea, faba bean, and oilseed rape) probably will expand northward into Fenno-Scandinavia, leading to increased productivity of seed crops there. There also will be northward expansion of warmer season seed crops (e.g., soybean and sunflower). Harrison and Butterfield (1996) estimate this northward expansion for sunflower; they also found a general decrease in water-limited yield of sunflower in many regions, particularly in western Europe. Analysis of the effect of climatic change on soybean yield for selected sites in western Europe suggests mainly increases in yield (Wolf, 2000a). This is a result of a positive effect of CO2 concentration on growth and only a small effect of temperature on crop duration.
Vegetables cover a wide range of species with a large variation in type of yield components, including leaves, stalks, inflorescence, bulbs, roots, and tubers. Most vegetables are high-value crops that are grown under ample water and nutrient supply. Their response to changes in temperature and CO2 varies among species, mainly depending on the type of yield component and the response of phenological development to temperature change. For determinate crops such as onions, warming will reduce the duration of crop growth and hence yield (Harrison et al., 1995b), whereas warming stimulates growth and yield in indeterminate crops such as carrots (Wheeler et al., 1996). Onion yields are sensitive to the degree of warming (Harrison et al., 1995b), with a yield decrease for warmer scenarios and a yield increase for cooler scenarios. There also is a spatial gradient, with yield increases in northwest Europe to decreases in southeast Europe. For lettuce, temperature has been found to have little influence on yield, whereas yield is stimulated by increasing CO2 (Pearson et al., 1997). For cool-season vegetable crops such as cauliflower, large temperature increases may decrease production during the summer period in southern Europe because of decreased yield quality (Olesen and Grevsen, 1993). Root and tuber crops are expected to show a large response to rising atmospheric CO2 because of their large underground sinks for carbon and apoplastic mechanisms of phloem loading (Farrar, 1996; Komor et al., 1996). On the other hand, warming may reduce the growing season and enhance water requirements, with consequences for yield. Climate change scenario studies performed with crop models show increases in potato yields in northern Europe and decreases or no change in the rest of Europe (Wolf, 2000b). Simulation results show an increase in potato yield variability for the whole of Europe, which enhances the risk for this crop. However, crop management strategies (e.g., advanced planting and cultivation of earlier varieties) seem to be effective in overcoming these changes (Wolf, 2000b). Indeterminate root crops such as sugar beet may be expected to benefit from warming and the increase in CO2 concentrations. A study performed by Davies et al. (1996) for England and Wales indicates that the area of suitability for the growth of the crop moves westward.
Forage crops, including maize and whole crop cereals for silage, as well as root crops such as sugar beet and some Brassica species, also are described under cereals and root crops. When these crops are grown as forage crops, yield components and quality may change. Thus, there is a larger emphasis on total biomass yield and on digestability of biomass. The effects on production and quality of wheat whole crop silage will depend on the relative magnitudes of changes in CO2 and temperature (Sinclair and Seligman, 1995). Yields of the different forage crop types will be affected differentially. Yields of indeterminate crops such as sugar beet and silage maize can be expected to show a larger increase than the yields of whole crop cereals, especially in northern Europe. This probably will lead to changes in the types of forage crops grown. Studies indicate an increase in suitability of the north and west UK to forage maize (Cooper and McGeechan, 1996; Davies et al., 1996).
Perennial crops (e.g., grapevine, olive, and energy crops) have been relatively less studied in the context of climate change impacts. A study on the potential cultivation of grapevine in Europe under future climate scenarios has shown that there is potential for expansion of the wine-growing area in Europe and an increase in yield (see Figure 13-6b). Yet detailed predictions made for the main EU viticultural areas have shown an increase in yield variability (fruit production and quality). The quality of wine in good years is not guaranteed, and the demand for wine in poor years is not met, implying a higher economic risk for growers (Bindi et al., 1996; Bindi and Fibbi, 2000). For olive, it was shown that in a 2xCO2 case, the suitable area for olive cultivation could be enlarged in France, Italy, Croatia, and Greece as a result of changes in temperature and precipitation patterns (Bindi et al., 1992). For indeterminate energy crops that are favored by the longer growing season and by increased WUE resulting from higher CO2 levels, higher temperatures and CO2 concentrations generally would be favorable. A study of willow production in the UK found that warming generally would be beneficial for production, with increases in yield of as much as 40% for a temperature increase of 3°K (Evans et al., 1995). Livestock systems may be influenced by climate change directly by means of its effects on animal health, growth, and reproduction and indirectly through its impacts on productivity of pastures and forage crops. Heat stress has several negative effects on animal production, including reduced reproduction and milk production in dairy cows and reduced fertility in pigs (Furquay, 1989). This may negatively affect livestock production in summer in currently warm regions of Europe. Warming during the cold period for cooler regions is likely to be beneficial as a result of reduced feed requirements, increased survival, and lower energy costs. Impacts probably will be minor for intensive livestock systems where climate is controlled. Climate change may affect requirements for insulation and air-conditioning, however, and thus change housing expenses (Cooper et al., 1998). The impact of climate change on grasslands will affect livestock living on these pastures. In Scotland, studies of the effect on grass-based milk production indicate that these effects vary by locality. For herds grazed on grass-clover swards, milk output may increase regardless of site, as a result of the CO2 effect on nitrogen fixation (Topp and Doyle, 1996b).
Pest-disease-weed-host relationship can be affected by climate change in different ways. Pests, diseases, and weeds that currently are of minor significance may become key species, thereby causing serious losses. The distribution and intensity of current key pest, diseases, and weeds may be affected, leading to changed effects on yield and on control measures such as pesticides and integrated pest management. Competitive abilities in weed-plant interactions may be affected through changes in ecophysiology (i.e., CO2 fertilization effects on C3 and C4 species). Pests and diseases generally will migrate as crops migrate (e.g., Lipa, 1997, 1999).
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