6 Climate impacts on sectors and policies
6.1 Agriculture
Notes:
· The document as it stands now is still largely a compilation of individual contributions of JEO and AI. The introduction will include text linking the different indicators.
· The current version includes some text from the 2008 report and the SOER that will be modifies as the new conclusions and key messages are defined.
· Water limitation indicator will be further developed.
· Some internal comments are included to seek advice from the advisory group. Comments welcome.
· All References are in Zotero group and zoterio citations will be included in this document.
6.1.1 Introduction
The cultivation of crops, their productivity and quality, are directly dependant on different climatic factors. Climate change is already having an impact on agriculture (Peltonen-Sainio et al., 2010; Olesen et al., 2011), and has been attributed as one of the factors contributing to yield stagnation in wheat in parts of Europe (Brisson et al., 2010). Measuring current and future impacts of climate change on agriculture at the continental scale is a significant challenge, but there is growing scientific consensus that climate-induced changes in biodiversity and ecosystem services are occurring. Climate change is expected to continue to affect agriculture in the future (J.E. Olesen et al. 2011; Ana Iglesias et al. 2010), and the effects will vary greatly in space across Europe (M. Trnka, Olesen, et al. 2011; Ana Iglesias, Garrote, Diz, Schlickenrieder, y Martin-Carrasco 2011a), but they may also change over time (Miroslav Trnka, Eitzinger, et al. 2011). It is generally accepted that productivity will increase in Northern Europe due to a lengthened growing season and an extension of the frost free period (Olesen and Bindi, 2002; Trnka et al., 2011a; Iglesias et al., 2011b). In Southern Europe, the impact of climate change on agriculture is likely to affect the productivity of crops and their suitability in certain regions primarily due to extreme heat events and an overall expected reduction in precipitation and water availability (Bindi y Olesen 2010; A Iglesias, Quiroga, y Schlickenrieder 2010; Ana Iglesias et al. 2010). Variability in yields is expected generally to increase, both in Southern and Northern Europe, due to extreme climatic events and other factors, including pests and diseases (Kristensen et al., 2010; Ferrise et al., 2011; Moriondo et al., 2011). Adaptation choices are complex and priorities need to be established at the regional level to respond to specific risks and opportunities (Ana Iglesias, Garrote, Diz, Schlickenrieder, y Martin-Carrasco 2011a; Ana Iglesias, Quiroga, y Diz 2011).
Intensive farming systems in western and central Europe generally have a low sensitivity to climate change, because a given change in temperature or rainfall have modest impact (Chloupek et al., 2004), and because the farmers have resources to adapt and compensate by changing management (Reidsma et al., 2010). However, there may be considerable difference in adaptive capacity between cropping systems and farms depending on their specialisation (Reidsma et al., 2008). Intensive systems in cool climates may therefore respond favourably to a modest climatic warming (Olesen and Bindi, 2002). On the other hand some of the farming systems currently located in hot and dry areas are expected to be most severely affected by climate change. There is a large variation across the European continent in climatic conditions, soils, land use, infrastructure, political and economic conditions. These differences are expected also to greatly influence the responsiveness to climatic change (Olesen et al., 2011; Trnka et al., 2011a).
The indicators selected to evaluate the impact of climate change on agriculture include the rate of change of the crop growing season length, the timing of the cycle of agricultural crops (agrophenology), the size and variability in crop yield, the rate of change of the meteorological water balance, which indicates water requirements and water limitation of crops. The indicators have been chosen based on four key issues: (1) identification of the main drivers of agricultural change, (2) information needed to respond to adaptation policy questions, (3) availability of relevant data, and (4) their ability to clearly show past changes and indicate likely future trends. Table x summarises the
Table X: Summary Agricultural Indicators Observations, Projections, Adaptation options (to be completed)
Indicator / Indicator key aspects / Reasons for Concern / Observations / Projections / AdaptationGrowing season / Rate of change of crop growing season length / Implications for suitability of crop species/cultivars / Growing Season is changing / Likely increase in some parts of Europe / Changes to crop species and cultivars
Changes in management
Agrophenology / Changes in length of crop growth phases or onset / Importance of conditions during growth phases / Flowering is occurring earlier / Shortening of crop growth phases / Changes in crop cultivars
Changes in management
Yield-variability / Yield changes due to climate change / climate events / Food commodity and security implications / Crop yield variability increases observed / Increasing variability due to climate change / Changes in crop cultivars, species
Changes in management
Water requirement (irrigation) / Use proxy, rate of change of the meteorological water balance / Potential changes in irrigation needs have to be taken into account in deciding appropriate crops and is relevant for irrigation infrastructure/ efficiency / Mediterranean and parts of Central Europe experience an increase in the water required from irrigation / Overall expected increases in temperature throughout Europe are likely to increase evapo-transpiration rates, thereby also increasing water requirements / Water use efficiency, distribution efficiency
Changes in management
Water limitation of crops / Crop yield limitation due to water / Water as limiting factor in crop productivity; crop suitability implications / Crop production is at least moderately water limited in many regions and especially in the south / Crop water limitation is projected to worsen across the southern part of Europe / Water use efficiency, distribution efficiency infrastructure improvements
Changes in management
6.1.2 Growing Season for Agricultural Crops
Key messages· Research indicates that the growing season of a number of agricultural crops in Europe is changing
· Studies have shown that the growing season in is likely to increase throughout most of Europe due to earlier onset of growth in spring and later senescence in autumn
Relevance
Increasing air temperatures are significantly affecting the duration of the growing season over large areas of Europe (Scheifinger et al., 2003). The duration of the growing season is for a large part of Europe defined by the duration of the period with temperatures above a certain threshold. In terms of the functioning of many plant species, e.g. for flowering, it is the duration of the frost-free period that is important. However, active growth of plants requires higher temperatures, and for most of the temperate crops grown in Europe a threshold temperature of 5 ºC can be used, although growing of tropical crops like maize and sorghum requires even higher temperatures (Trnka et al., 2011a).
A warming of the climate is reported mainly to result in an earlier start of the growing season in spring and a longer duration in autumn (Jeong et al., 2011; Trnka et al., 2011c). A longer growing season allows the proliferation of species that have optimal conditions for growth and development and can thus increase their productivity or number of generations (e.g., crop yield, insect population). This will in many cases also allow for introduction of new species previously unfavourable due to low temperatures or short growing seasons. This is both relevant for introduction of new crops, but will also affect the spreading of weeds, insect pests and diseases (Roos et al., 2011). Changes in management practices, e.g. changes in the species grown, different varieties, or adaptations of the crop calendar, can counteract the negative effects of a changing growing season (pests) and capture the benefits (agricultural crops).
Past trends
Many studies report a lengthening of the period between the occurrence of the last spring frost and the first autumn frost. This has occurred in recent decades in several areas in Europe and more generally in the northern hemisphere (e.g., Root et al., 2003; Trnka et al., 2011c). Studies of changes in the growing season based on remote sensing shown a spatial pattern in Europe, with western continental areas showing last freeze dates getting earlier faster, some central areas having last freeze and first leaf dates progressing at about the same pace, while in parts of Northern and Eastern Europe first leaf dates are getting earlier faster than last freeze dates (Schwartz et al., 2006). Across all of Europe, the delay in end of the season of the period 1992-2008 by 8.2 days was more significant than the advanced start of the season by 3.2 days (Jeong et al, 2011).
An analysis of the frost free period in Europe between 1975 and 2010 shows a general and clear increasing trend. The trend is not uniformly spread over Europe. The highest rates of change (larger than 0.8 days per year) were recorded in central and southern Spain, central Italy, along the Atlantic shores, and in the British Isles, Denmark, central parts of Europe and in Turkey (Map X1). The map in Figure 1 shows that there are also areas in Europe with an apparent trend for reductions in the frost free period. However, these trends are not significant.
Map X1. The rate of change (number of days per year) of the number of frost-free days per year as actually recorded during the period 1975–2010.
Projections
Following the observed trends and in line with projections for additional temperature increase, a further lengthening of the growing season (both an earlier onset of spring and a delay of autumn) as well as a northward shift of species is projected. The latter is already widely reported (Aerts et al., 2006; Odgaard et al., 2011; Olesen et al., 2011). Results from climate change projections show that the date of last frost in spring will advance by about 5-10 days by 2030 and by 10-15 days by 2050 thoughout most of Europe (Trnka et al., 2011a). The extension of the growing season is expected to be of particular beneficial in northern Europe, where a longer duration for crop growth allows new crops to be cultivated and where water availability is not restricting growth (Olesen et al., 2011). I parts of the Mediterranean area, the cultivation of some crops will under a milder climate be shifted into the winter season (Minguez et al., 2007), which in these areas can offset some of the negative impacts of heatwaves and droughts during summer. Other areas of Europe such as Western France and parts of South-Eastern Europe (Hungary, Bulgaria, Romania, Serbia, etc.) will experience yield reductions from hot and dry summers without the possibility of shifting the crop production into the winter seasons.
Adaptation needs and options
The main adaptations to changes in duration of the growing season and the start and end of the frost free season are changes in the crop species and varieties grown and the timing of crop management operations. A northward shift in cultivation of temperature sensitive species is therefore projected (Olesen et al., 2007). In particular, in southern Europe adaptations may include changes in crop species that relate to major changes in the timing of crop cultivations, e.g. replacing winter with spring wheat) (Minguez et al., 2007). In general, there will be changes in cultivars and sowing dates (e.g. for winter crops, sowing the same cultivar earlier, or choosing cultivars with a longer growth cycle; for summer irrigated crops, earlier sowing for preventing yield reductions or reducing water demand (Olesen et al.., 2007; Kaukoranta and Hakala, 2008).
6.1.3 Agrophenology
Key messages· Flowering of a number of different crops is occurring earlier
· A shortening of phases of crop growth in many crops can be expected, and this is particularly detrimental to grain yield for shortening of the grain filling phase
· Adaptation needs to include changes in management and potential changes in crop cultivars
Relevance
Changes in crop phenology provide important evidence of responses to recent regional climate change (Menzel et al., 2003). Although phenological changes are often influenced by management practices, in particular sowing date and choice of cultivar, recent warming in Europe has clearly advanced a significant part of the agricultural calendar. Specific stages of growth (e.g. flowering, grain filling) are particularly sensitive to weather conditions and critical for final yield. The timing of the crop cycle (agrophenology) determines the productive success of the crop. In general, a longer crop cycle is strongly correlated with higher yields, since a longer cycle permits maximum use of the available thermal energy, solar radiation and water resources. For cereals yields 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. However, shortening of the growth period can also help avoid summer stress conditions in areas prone to drought.
European farmers have already adapted their practices to the changing climate by selecting suitable varieties or adapting the crop calendar, and can be expected to do so increasingly in the future.
Past trends
Several studies have collected data and observed changes in the phenological phases of several perennial crops in Europe, such as the advance in the start of the growing season of fruit trees (2.3 days/10 years), cherry tree blossom (2.0 days/10 years), and apple tree blossom (2.2 days/10 years), in line with increases of up to 1.4 ºC in mean annual air temperature in Germany (Chmielewski et al., 2004). Sowing or planting dates of several agricultural crops have been advanced, by 5 days for potatoes in Finland, 10 days for maize and sugar beet in Germany and 20 days for maize in France (IPCC, 2007).
An analysis of the modelled flowering date for winter wheat in Europe between 1975 and 2010 shows a general and clear increasing trend., which is most pronounced in northwestern Europe (Map X2). In large parts of Europe the modelled flowering date has advanced by more 0.3-0.5 days per year. This modelled advance in flowering date probably exceeds what is observed in practice, where day length responses in the plants and farmers choices of cultivars with longer growth duration will modify this response.