Agriculture: European scale
Length and intensity of Europe's thermal growing season
The agricultural potential and suitable conditions for forest growth in a certain part of the world can be expressed by two measures that describe the growing conditions for crops and trees in the summer season: the length and intensity of the so-called thermal growing season. Thermal growing season is the length of the growing season for crops and trees. It is defined to start when the daily mean temperature rises above a selected threshold in spring, and end as the mean temperature falls below that level in autumn. The intensity of the thermal growing season is represented by the effective temperature sum, also termed temperature accumulation or the growing degree day sum; this sum is calculated by summing the daily mean temperature excesses above the threshold during this season (41).
The commonly used base temperature for the thermal growing season is 5°C in boreal and temperate climate conditions (42) and 10°C in warmer climate zones (43).
Global warming leads to a prolongation and intensification of the thermal growing season. Prolongation and warming of this season has already been noticed in many regions: in northern Europe thermal growing season has lengthened by about 1week between 1951 and 2000 (44). The intensity of this season (expressed as growing degree day sum) has increased all over Europe after 2000 (45).
Projections of future changes have been calculated for Europe for the end of the 21st century, based on 22 - 23 global climate models under a moderate and high-end scenario of global warming, respectively (the so-called RCP4.5 and RCP8.5 scenarios). According to these results, in most of Europe the thermal growing season will last 1.5 - 2 months longer in 2100 compared to the reference period 1971 – 2000 for the high-end scenario of climate change, and 20 - 40 days longer for the moderate scenario of climate change; results are similar for the 5°C and 10°C baseline. Lengthening is anticipated to be slightest in southeastern European Russia and largest in coastal areas and central Europe (41).
For the high-end scenario the intensity of the thermal growing season with respect to the 5°C baseline (growing degree day sum) will be 60 - 100% higher in 2100; the increase is somewhat smaller for the moderate scenario. In absolute terms, the increase of the intensity of this season is largest in the south. In relative terms, however, the increase is largest in cold areas (41).
The prolongation and intensification of the thermal growing season is beneficial for especially northern Europe. It enables the introduction of new species and cultivars in agriculture (46), allows a more extensive utilization of double-crop rotation (47) and enhances timber growth in forests (48). Besides, the mildness of the dark season facilitates the overwintering of fruit trees and other vulnerable perennial plants (49), and high autumn and winter temperatures accelerate the decomposition of litter and the release of nutrients in boreal forest, a factor that may already have enhanced timber growth (48).
On the other hand, long growing seasons and mild winters also favour pests and fungi in arable lands and forests, and higher temperatures in late autumn are of little use for plant photosynthesis in northern Europe due to the scantiness of the light. Also, annual cereal crops are harvested in early autumn and thus do not benefit from the autumn lengthening of the thermal growing season. In late autumn, the harvesting conditions would in any case be unfavourable owing to high moisture, even more so as precipitation is projected to increase and the low amount of solar radiation can no longer alone dry the harvest crop (41).
To conclude, the prolongation and intensification of the thermal growing season offers several benefits for northern European forestry and agriculture, but adaptation (plant breeding and pest control) is still necessary. In southern Europe, negative impacts dominate, particularly as a result of excessive heat and the reduced availability of water (41).
Effects of climate extremes on global yields
Climate extremes, such as droughts or heat waves, will occur more often, last longer and become more intense. It is important to understand how this impacts crop yields on a global scale so the resilience of the global food system can be enhanced. The vulnerability of crop yields on a global scale has been assessed for the period 1961 to 2008, and for the four major food crops maize, soybeans, rice, and (winter and spring) wheat. According to the authors, their study is the first global study on climate extremes impacts on crop yields based on yield data at sub-national scale (129).
Their results show that almost half of the variability in global maize (49%) and spring wheat (46%) yields can be explained by climate variability and climate extremes during the growing season. For the variability in rice and soybean yields this is about one quarter (rice: 28%) to one fifth (soybeans: 20%). More than half of this explained yield variability for maize, rice and soybeans, and nearly half of it for spring wheat can be related to climate extremes. The variability that cannot be related to climate variations is due to several other factors, such as soil properties, management decisions (irrigation rate, fertiliser use) and market factors (129).
For winter wheat the observed variations in yields can be explained only for a minor part by climate variability and climate extremes. This is likely due to the comparatively long growing season spanning several seasons (129).
Variations in temperature are more important as a driver of yield variations than variations in precipitation (such as extreme precipitation or drought). Possibly, droughts only influence yields if they occur at larger spatial and temporal scales than the ones in this study, or droughts should be defined differently (as hydrological or agricultural droughts) than the definition used in this study (meteorological droughts). Anyway, the negative yield effects of high temperatures are intertwined with water stress and can be mitigated by irrigation (129).
Hotspot regions that are critical for global food production and particularly susceptible to the effects of climate extremes include North America for maize, spring wheat and soy production, Asia in the case of maize and rice production, and Europe for spring wheat production (129).
Vulnerabilities and opportunities - global yields
Maize, rice, soy and wheat are the four crops that make up a major part of the scientific literature on climate impacts on crops. These crops collectively account for approximately 20% of the value of global agricultural production, 65% of harvested crop area, and just under 50% of calories directly consumed (63).
Crop production losses due to climate change so far
Technological improvements have increased crop yields during the last half-century. Climate change, however, has slowed down the increasing yield trends compared to the yields we would have had without global warming. The impacts so far of climate change on the global average yields of maize, rice, wheat and soybeans has been estimated in a study focused on two situations: the yields for the actual conditions in the period 1981 - 2010, and a counterfactual simulation representing a preindustrial climate without human influences on the global climate (104). These estimates include both yields under rainfed and irrigated conditions. In this study, a single combination of a climate model and a crop model was used.
Negative impact on crop yields: The model simulations suggest that without climate change, current global mean yields of maize, wheat and soybeans would have been 4.1, 1.8 and 4.5% higher, respectively. For rice, no significant impacts were detected. The uncertainties in these estimated yield impacts are large, however. For maize, the 90% probability interval is -8.5 to +0.5% (- indicating a yield loss, + an increase). For wheat and soybeans these intervals are -7.5 to +4.3%, and -8.4 to -0.5%, respectively. These estimates include the uncertainties related to the positive impact of higher concentrations of CO2 on crop yields (104).
Economic production losses: The estimated yield impacts were converted into economic production losses. This was done for the period 2005 – 2009. The estimated annual global production loss so far due to global warming is largest for maize: -22.3 Billion US$. Estimated annual production losses for wheat and soybeans are -13.6 and -6.5 Billion US$, respectively. Again, the uncertainties in these estimates are large, reflecting the uncertainties in the yield impacts (104).
Geographical variation: On a global scale, global warming so far seems to have increased crop yields at the mid and high latitudes, and decreased at the low latitudes. This pattern was observed for all of the crops. In the low latitudes current temperatures are already high, and warming has led more crops to be exposed to physiologically critical temperatures (105). In the high latitudes, where low temperatures and snow cover are the primary limiting factors for crop production, the warming has benefited crop growth. The mid-latitudes are in the transition zone between the changes that have occurred in the low and high latitudes. The role of temperature change on yield impacts seems to dominate over that of precipitation change, consistent with earlier studies (106). In Europe, precipitation changes (more droughts) are very important in the Mediterranean, however.
Global warming so far has had a negative impact on recent yields in 31% of the global areas where maize is being grown today, according to this study. For wheat and soybeans these numbers are 14 and 25%, respectively. By contrast, in 5 - 9% of the harvested area worldwide crop yields have benefitted from climate change (104).
Still, yields are increasing: The aforementioned negative impacts of climate change do not imply that crop yields have actually decreased over the last decades. On the contrary, crop yields have increased globally during the last half-century, driven by technological improvements. A negative yield impact as a result of global warming implies that the increasing yield trends have slowed down compared to the yields we would have had without global warming (104).
Overview published results (including IPCC) wheat, maize, rice and soybean
There is medium confidence that climate trends have negatively affected wheat and maize production for many regions; there is also medium confidence for negative impacts on global aggregate production of wheat and maize. Changes in temperature caused reduction in global yields of maize and wheat by 3.8 and 5.5% respectively from 1980 to 2008 relative to a counterfactual without climate change, which offset in some countries some of the gains from improved agricultural technology (32). Effects on rice and soybean yields have been small in major production regions and globally (31). There is limited direct evidence that unambiguously links climate change to impacts on food security (31).
Global yield impacts of climate change and adaptation have been evaluated by analysing a data set of more than 1,700 published simulations for three crops: wheat, rice and maize (21). This is the largest pool of data from diverse modelling studies ever used for a global synthesis of this kind; the results have contributed to the food security and food production systems chapter of the Fifth Assessment Report (AR5) of the IPCC (22,31). The results show that without adaptation, losses in aggregate production are expected for wheat, rice and maize in both temperate and tropical regions by 2°C of local warming. The results also show that crop-level adaptations increase simulated yields by an average of 7-15%, with adaptations being more effective for wheat and rice than maize. Yield losses are greater in magnitude for the second half of the century than for the first. Even moderate warming may reduce temperate crop yields in many locations.
For around 1-3°C warming, the data show both positive and negative yield responses, whereas the previous Fourth Assessment Report (AR4) had primarily positive responses at these temperature changes. For all three temperate crops the new data set shows a greater risk of yield reductions at moderate warming than AR4. The results show that adaptation provides clear benefits for wheat and rice: the central tendencies indicate that most yield loss in wheat may be avoided, or even reversed, in tropical regions up to 2-3°C of local warming and in temperate regions across a broad range of warming (21).
In the more than 1,700 published simulations there is a majority consensus that yield changes will be negative from the 2030s onwards. More than 70% of projections indicate yield decreases for the 2040s and 2050s, and more than 45% of all projections for the second half of the century indicate yield decreases greater than 10%. The magnitude of the yield impact generally increases with time. These projections include simulations with adaptation, suggesting that farmer adaptation earlier in the twenty-first century can ameliorate some, but not all, risk of yield reductions. It looks like increases in yield variability become increasingly likely as the century progresses (21).
There are a number of limitations with respect to this meta-analysis, however, such as: the lack of simulation of pests, weeds and diseases, the frequent assumption of water availability into the future despite ongoing changes in many regions, inaccuracies in representing adaptations, and structural, parameter and bias correction uncertainty in both crop and climate models (21).
Global potato yields
Global projections based on 5 global climate models indicate potato crop yield reductions for the temperate regions of North America, Eastern Europe, and Asia, and a yield increase for Western Europe. This geospatial pattern of yield change due to climate change was found for 2055 under an intermediate (RCP 4.5) and high-end scenario of climate change (RCP 8.5), and for 2085 under the intermediate scenario of climate change. Yields declined for most of the world by 2085 for the high-end scenario of climate change. Under the intermediate scenario, global potato yields are projected to decline by 2.1% and 1.8% by 2055 and 2085, respectively. For the high-end scenario, the projections indicate a global yield decline of 5.6% and 25.8% by 2055 and 2085, respectively (108).
The impact of ozone versus global warming
Global demand for food is expected to increase by at least 50% from 2010 to 2050 mainly as a result of population growth and a shift towards a more `westernized' diet in developing regions (28). Both temperature extremes and surface ozone, formed through the photochemistry of precursor gases mainly arising from human activities, are detrimental to crop yields (27). The impact of global warming and surface ozone concentration has been projected for 2050 compared with 2010 for two greenhouse gasses emission scenarios: an intermediate pathway with a global reduction in surface ozone due to pollution control measures worldwide (RCP4.5) and a more `pessimistic', energy-intensive pathway with a worldwide increase in ozone except in the US and around Japan (RCP8.5) (27). According to these projections, more severe ozone pollution (scenario RCP8.5) leads to substantial crop damage on a global scale, reducing global total crop production by 3.6%. In this scenario, ozone pollution and climate change combine to reduce global crop production by 15% between 2010 and 2050. Aggressive pollution control worldwide, however, (scenario RCP4.5) leads to an overall 3.1% increase in global production. According to these results, ozone pollution control (scenario RCP4.5) has the potential to partially offset the negative impact of climate change, leading to a smaller combined global crop production decrease of 9.0%.
Cereal yield reduction from ozone could reach 6 and 10% in 2030 for the European Union with the B1 and A2 scenarios, respectively (33).
Vulnerabilities and opportunities - global impacts under 1.5 °C and 2 °C warming
Paris Agreement: Crop productivity changes at 1.5°C and 2°C global warming
Following the adoption of the Paris Agreement, there has been an increasing interest in quantifying impacts at global mean temperature increase of 1.5°C and 2°C above pre-industrial levels. The results of a global study on the four major staple crops wheat, maize, rice, and soybean indicates that impacts of warming on crop production will be consistently higher at 2°C compared to 1.5°C (78). However, uncertainties related to potentially positive effects of increasing CO2 fertilization on crop productivity are found to dominate over this warming increment. Thus, changes in temperature alone are insufficient to characterize impacts of anthropogenic greenhouse gas emissions on crop productivity (78).
While some high latitude regions like Northern Europe see some benefits under future warming up to 1.5°C, warming benefits beyond 1.5°C remain limited. Tropical and sub-tropical regions are affected most strongly, with median reductions in total crop productivity of 3%-5% projected for regions such as Central America and the Caribbean, the Sahel or East Africa. Rice productivity is particularly affected in water-scarce regions such as the Mediterranean or West Asia (78). These findings of consistently reduced productivity under scenarios of increased warming align well with existing literature estimating the impacts of warming on crop productivity (79). For instance, a recent study found warming to reduce global yields of wheat by 6.0 ± 2.9%, rice by 3.2 ± 3.7%, maize by 7.4 ± 4.5% and soybean by 3.1% ± 5% per °C global mean temperature increase (80).
Wheat, with about a 2.1 million km2 total harvested area, is the most abundant crop in the world: it is the first rain-fed crop after maize and the second irrigated crop after rice (65). It contributes to about the 20% of the total dietary calories and proteins worldwide (66).
Higher than optimal temperatures during the growing season generally
- accelerate the progress of the plant phenological stages and reduce the final yield (67),
- increase the atmospheric demand for water and reduce the crop water-use efficiency (68), and
- leads to plant damages by inducing perturbations in cellular structures and metabolic processes (69).
Besides, isolated occurrences of extreme high temperatures around a sensitive stage of crop development, such as flowering and grain filling, can reduce grain yield considerably (70), while a prolonged period of extreme high temperatures might result in almost total yield loss (71). The detrimental effect of the heat stress on wheat yield may worsen when coinciding with drought (72). On the other hand, extreme amounts of precipitation and water excess in the soil can also be responsible for wheat loss due to proliferation of pests and diseases, leakage of nutrients, inhibition of oxygen uptake by roots, and interference with agronomical practices (e.g waterlogging during harvest) (64).
Global wheat production approximately doubled from 1970 to 2015, and increased by about 50% in the period 1980–2010 (64). This increase was mostly due to improved management and higher yielding crop varieties (64). Without these adjustments, changes in temperature and precipitation in this period would have led to a 5.5% reduction of global wheat production (73).
With respect to the impacts of extreme events on wheat yield anomalies, heat stress is often the most important predictor, in general as important as drought. As a prominent exception, in the Mediterranean countries drought carries a larger detrimental effect on wheat yield than heat stress. Wheat yield is sensitive to water excess, rather than to drought, in especially tropical regions and in some regions of the mid/high latitudes. While heat stress globally remains the most important factor determining the yield anomalies, water stress, and in particular water excess, is essential to explain yield anomalies of important wheat producers such as China and India (64).
Maize and soybean
Maize and soybean are among the most important food crops worldwide. 10 countries represent 84 % and 94 % of the world’s maize and soybean production respectively. This includes 4 European countries: France, Romania, Italy and Ukraine (38). A modeling study has shown that global warming results in reduced growing season lengths and ultimately reduced yields for both crops, with maize being more negatively impacted than soybean (37).
Even a small increase in temperature of about 0.5 °C (compared to the period 1961 - 1990) will have negative impacts on global maize yield, the severity of which will increase with increasing temperature. For maize, under no adaptation, large (>30 %) reductions in national average yield were simulated for all the major producing countries under +4 degree warming, and for most under +2 degree warming. The results indicate a global yield reduction of 10 - 20 % for every 1 °C increase in temperature without adaptation. These impacts are stronger than previous estimates of a yield reduction of 3 - 8 % for every 1 °C increase in temperature (39).
Use of farmer-instigated adaptation strategies through changing planting date and crop variety may alleviate the effects of a 0.5 °C warming for maize yields; however, temperatures greater than 1 °C will negatively affect yield in most countries. The response to adaptation strategies is country-specific: of these 10 countries adaptation seems to be most effective for France, demonstrating no decrease in yield under a 4 °C increase in temperature with adaptation measures (37).
Small temperature increases of 0.5 °C had no effect on soybean yield, although yield decreased as temperature increased. These negative effects, however, were partly compensated for by the implementation of adaptation strategies including planting earlier in the season and changing variety. For soybean, adaptation can be effective at temperatures up to 4 °C but that response is country-dependent (37).
Paris Agreement: Crop productivity changes versus biofuel expansion at 1.5°C and 2°C global warming
1.5° to +2°C global warming, the Paris targets, will impact crop yields and food prices. The impact of a mitigation policy where croplands are being used for bioenergy crops may be stronger, however.
Possible implications of +1.5° and +2°C global warming for global food production have been assessed for yields of maize, wheat, rice, and soy (99). Crop yield changes were quantified and compared with the reference situation (1980-2009). Several global climate models and crop models were combined, and a range of changes in atmospheric CO2 concentrations was included. Four crops were studied: maize, wheat, rice, and soy. The distinction between maize on the one hand, and wheat, rice, and soy on the other is particularly relevant since these crops have different photosynthetic carbon cycles. Hence, they respond differently to changes in atmospheric CO2 concentrations.
Rainfed crop yields in a +1.5°C World: Maize yields decline in most areas in a +1.5°C World. Wheat yields also decline (<5%) in major wheat belts of the North American Great Plains and Europe. Larger losses are evident in the northern Murray-Darling Basin of Australia, eastern South Africa, and northern Argentina, while western Asia and the North China Plain see substantial yield increases.
Rice yield changes are small over the major production regions in Asia, while increases are projected over tropical Africa and South America. Soy yields are projected to improve over much of Eastern Europe and northwestern Asia, and slightly decrease over the interior of North America and equatorward portions of South America and East Asia.
Rainfed crop yields in a +2°C World: When global warming moves from +1.5° to +2°C, maize yields decline further (median model results: -5%), compared with the current situation. Wheat and rice yields increase slightly (median of +1 to +2%), and soybean yields increase more substantially (median of + 8%).
Irrigated crop yields: Irrigated crops respond in much the same way as rainfed crops. In both the + 1.5° and + 2°C Worlds, irrigated maize losses are large over much of North America, China, and southern Europe, while yields are reduced for the irrigated wheat basket of South Asia.
The benefits of higher CO2 concentrations: CO2 effects are widely understood to be positive even as the magnitude of this benefit is uncertain (100). Overall there is strong agreement that crops like wheat, rice, and soy benefit more from higher CO2-levels than crops like maize.
Without CO2 effects, the production of all four crops would be lower in a + 2°C World compared with the current situation. Thanks to the CO2 effects, however, wheat, rice, and soy yields improve in the + 2°C World: in nearly all world regions the CO2 fertilization effect largely overcomes negative impacts of temperature and precipitation (101). For maize yields, this beneficial CO2 effect is much lower and yields decline further as temperatures rise to the +2°C World.
Global market responses: In the +1.5°C World, reductions in maize and rice production drive up their prices, increasing cropped area to make up for production gaps. Wheat prices and area also increase despite nearly flat global production levels, likely carried upward by pressure on maize and rice. Increases in soy production may lead to declining area and lower prices.
Maize production declines further in the +2°C World. The production of wheat, rice, and soy increases, however, compared to a future without climate change. This results in continued upward pressure on maize prices and area whilst prices and area for wheat, rice, and soy may decline.
Disturbing effects of mitigation policy: The implications of stabilizing global warming at +1.5° and +2°C go beyond the direct impacts of changes in temperature and precipitations, and the response to higher CO2-levels. Ambitious mitigation policy to achieve this climate stabilization may lead to croplands being used for bioenergy crops. This may affect food production and disturb food prices. In fact, bioenergy expansion may be more disruptive to land use and crop prices than the climate change impacts alone. This would require substantial intensification in remaining agricultural systems to meet food demands.
Land use competition from bioenergy crops may lead to higher food crop prices compared with a no-mitigation scenario. Thus, the costs of mitigation to achieve + 1.5° and + 2°C Worlds may likely exceed the costs of adaptation to those new climate conditions (102). This may also lead to a corresponding increase in hungry populations and food insecurity (103) compared to climate change alone.
Paris Agreement: Economic and biophysical impacts on agriculture under 1.5°C and 2°C global warming
Agriculture is affected by climate change in different ways. First, there is an impact of changes in temperature and precipitation. Second, crops respond to increasing levels of CO2 in the atmosphere in different ways, where in general a higher concentration of CO2 has a ‘fertilizing effect’ on crops. And there are additional impacts, including extreme heat, flood events, pests and disease, and ozone damages, which would be increasingly important at higher levels of climate change.
In addition to these climate and biophysical effects there is economics: the economic response where agricultural production is stimulated in regions that are relatively well-off, and trade flows of imports and exports change between these regions and regions with significant crop yield declines. Trade responsiveness will influence the difference in agricultural impacts between 2°C and 1.5°C global warming, and therefore must be included in an assessment on the benefits of achieving the Paris Agreement targets for global food production. This was done in a recent study on the combined effects of higher temperatures, higher atmospheric CO2 levels and trade effects (107). Focus was on seven crop types: temperate corn, soybean, wheat, sugarcane, cotton, tropical corn, and tropical soybean.
In this global study, the scientists concluded they were unable to distinguish the regional agricultural impacts occurring with 1.5°C warming from those occurring with 2°C warming. The uncertainties in the contributing impacts of climate, CO2 and trade, and how they counteract or reinforce one another are simply too large. Especially the uncertainty in the effect of CO2 fertilization on crop yield dominates the results. Without these effects, the agricultural sector is generally worse off in the 2°C scenario than in the 1.5°C scenario, but the associated higher CO2 levels may increase yields through its fertilizing effect. As a result, due to the CO2 fertilization effects on crop yield, economic impacts may be worse in the 1.5°C scenario than they are in the 2°C scenario (107).
Thus, when all of these uncertainties are included, it cannot be concluded whether 1.5°C is better or worse than 2°C warming in terms of global agricultural impacts (107).
Vulnerabilities and opportunities - global yield potential under sustainable irrigation
Closing the gap between actual and maximum crop yield
Global crop production depends on water received both as precipitation (or ‘green water’) and irrigation (or ‘blue water’) from surface water bodies and aquifers. The actual yield that a farmer currently achieves is often less than the potential yield he could achieve if the circumstances for a crop cultivar were optimal, that is, a situation with non-limiting water and nutrient supplies, and with pests, weeds, and diseases effectively controlled. The difference between this potential yield and the actual yield is called the crop yield gap. Additional irrigation will be needed in many places in order to close the yield gap and to maximize food production (94).
Closing this gap with sustainable water use
In some regions, the development of irrigation is limited by the availability of blue water resources. In other places, more water is needed for irrigation than can be replenished on rainy days. Using this water for irrigation may not be sustainable: too little water may be left to sustain aquatic habitats (95) and groundwater resources may be depleted (96).
For the world’s existing croplands, the irrigation water demand under current and maximized crop production has been quantified (93). This was done for 16 major crops that account for 73% of the planet’s cultivated areas and 70% of global crop production. These numbers were compared to local renewable freshwater availability, accounting for the volumes of water that are needed to sustain aquatic habitats, the so-called ‘environmental flows’. Thus, world regions could be identified where irrigation can be expanded into currently rainfed croplands without threatening freshwater ecosystems. The results are hopeful.
Hopeful results: an additional 2.8 billion people can be fed sustainably
Global water consumption for irrigation could sustainably increase by 48%, the results show. Thus, 37% more calories could be produced, enough to feed an additional 2.8 billion people. If current unsustainable blue water consumption practices were eliminated, a sustainable irrigation expansion and intensification would still enable a 24% increase in calorie production. Collectively, these results show that the sustainable expansion and intensification of irrigation in selected croplands could contribute substantially to achieving food security and environmental goals in tandem in the coming decades (93).
The results are hopeful for many regions where food security is under pressure. Sustainable irrigation could increase national food self-sufficiency in many countries that today meet large fractions of their domestic food demand through international trade (97). According to this study, China has the greatest potential to sustainably increase crop production by intensifying and expanding irrigation, thereby feeding an additional 382 million people. Africa currently produces enough calories to feed 400 million people, making it the continent with the largest gap between crop production and demand (98). An increase in yields through investments in irrigation expansion could sustainably feed an additional 450 million people and substantially reduce the continent’s dependence on food imports (93).
What needs to be done
Adequate and informed investments in irrigation infrastructure can help to feed billions more people, avoid agricultural expansion into natural habitats, and safeguard local boundaries of freshwater allocation for human and natural systems. More needs to be done than just installing more irrigation infrastructure, however. In addition, nutrient (fertilizer) supply needs to be improved, crop switching or increased cropping frequencies may be needed, and rainwater should be stored for its use during the dry seasons.
Vulnerabilities and opportunities - European yields according to review studies
Review Knox et al. (2016)
Climate impacts in Europe are not necessarily all negative. They could be beneficial for many crops and areas of production. This message was sent by the authors of a recent study in which they combined results of 41 scientific publications (59). Their study confirms that climate change is likely to increase the yield of Europe’s major agricultural cropping systems, with more favourable impacts in northern and central Europe.
The projected impacts of climate change on the yield of seven major crop types have been assessed. These crops are wheat, barley, maize, potato, sugar beet, rice and rye. Compared with the period 1961-1990, the projected change in average yield in Europe for these seven crops by the 2050s is a yield increase by 8%. Only for maize a reduction by 6% is projected. For wheat and sugar beet, projected average yield increase is highest: 14% and 15%, respectively. These increases are largely due to rising atmospheric CO2 concentrations, enhancing both crop productivity and resource use efficiency. Evidence of climate impacts on yield was extensive for wheat, maize, sugar beet and potato, but very limited for barley, rice and rye (59).
The findings of this study show strong regional differences with average crop impacts by the 2050s in northern Europe being higher (+14%) and more variable compared to central (+6%) and southern (+5) Europe (59).
Projections for northern Europe show significant higher average yields for maize and potato in the 2050s (+12% and +18%, respectively) and 2080s (+19% and +14%, respectively), compared with the reference period 1961-1990. Positive impacts for most crops apart from maize were also reported for central and southern Europe. The project decrease in average yield for maize in central Europe is 9% for the 2020s and 15% by the 2080s. Maize is projected to suffer the largest mean decrease in southern Europe, up to 28% by the 2080s (59).
The findings of this study corroborate other studies that show how crop productivity impacts in higher-latitude temperate regions, such as northern Europe, are generally expected to be less severe than in lower-latitude more tropical regions (60). The findings also illustrate that a lot of knowledge is available on projected crop yield changes for wheat and maize, but far less so for climate impacts on important crops such as barley, rice and rye. In addition, the study confirms there is extensive evidence on climate impacts on crop production for northern and central Europe, but much fewer studies for southern Europe (59).
Review Iglesias et al. (2012)
Recently, Iglesias et al. inventorized the overall impact of climate change on farming across agro-climatic zones in Europe within a time-frame of 2050 to 2080, based on 300 references that have been published in the period 1995 - 2010 (1). Their subdivision in agro-climatic zones is shown in figure 1. The risks and opportunities according to their inventory are summarized in figure 2. The text below is based on their paper unless stated otherwise.
The effects of climate change and increased atmospheric carbon dioxide are expected to lead, overall, to small increases in European crop productivity at moderate warming (2). On a regional scale, impacts on crop yields are expected to vary across Europe due not only to changes in the mean of climate variables but also due to the increase in climate variability or extreme events.
Figure 1. Agro-climatic regions considered by Iglesias et al. (2012).
Figure 2. Summary of risks and opportunities in the agro-climatic areas of Europe (from Iglesias et al., 2012).
Increased temperatures may increase both the cultivable area and crop yields within the entire zone, as well as provide opportunities for increased livestock production. However, the soil types in this zone may limit the potential for increased agricultural production. In addition, increased rainfall may lead to increased waterlogging, flooding risk and perhaps also a decrease in water quality.
There is potential for increased agricultural production in the Atlantic north region, especially in the livestock sector, but soil type may limit this potential. Measures need to be introduced to enable adaptation to drier summers, as currently summer rainfall usually enables unrestricted growth of crops and forage.
Particularly vulnerable to flooding from rising sea levels is the Atlantic central region and attention needs to be given to measures that will reduce this risk. Some increases in agricultural production are possible from increased yields of cereals and the introduction of new crops. However, it may be difficult to maintain the yields of more moisture- or temperature-sensitive crops if summer rainfall decreases and insufficient water is available for irrigation.
The priority for the Atlantic south region will be to conserve water to reduce the risk of decreases in crop yields and to avoid conflict with other water users. There may also be opportunities to grow crops more tolerant to heat and drought.
In the Continental north region the increase in the northern range of crops and longer growing season offers the potential for increased crop and livestock production. However water stress in summer and infertile soils may limit this potential. Flooding is also a serious risk. Priority needs to be given to manage water supplies to reduce the risk of flooding and to conserve water to increase availability for agriculture.
Agriculture in the Continental south region is likely to be adversely affected by hotter drier summers with yields of crops such as potatoes, sugar beet and forage crops most likely to be reduced. Priority needs to be given to ensuring water supplies for agriculture and also promoting the growth of crops, such as soya, that could replace vulnerable crops.
Changes in precipitation pattern and increased frequency of extreme events appear to pose the greatest risks in the Alpine region. There may be opportunities for increased production of both crops and livestock but the realisation of these opportunities will depend upon the continued availability of water at critical periods of crop growth. However, changes in precipitation pose some of the greatest risks in this zone, together with an increased risk of extreme weather events. There may be benefits from a longer growing season and the ability to grow some crops at higher altitudes, but this potential may not be realised due to soil limitations.
In the Mediterranean north region the forecast risks greatly outweigh any potential benefits. Forecast decreases in total annual rainfall make water conservation a priority and careful attention needs to be given to avoiding conflicts over water use.
For the Mediterranean south region eight of the risks are considered to be high priority. The main risks directly concern the consequences of potential reductions in total precipitation. Hence strategies need to be considered to conserve as much water as possible over winter to maintain supply during the summer. The risk of reduced yields was also assessed as high and strategies need to be developed to adopt cultivars or crops better suited to reduced water availability and heat stress. No significant opportunities were identified in this zone, which is not well placed to benefit from the forecast changes in climate. The impacts of climate change are forecast to be so serious that it may lead to land abandonment.
Vulnerabilities and opportunities - European yields other sources
European wheat production
With 25% of the global wheat area and 29% of global wheat production (24), Europe is the largest producer of wheat. The increased occurrence and magnitude of adverse and extreme agroclimatic events are considered a major threat for wheat production. A recent study (25) showed that, by 2030, we should expect a twofold increase in the global wheat-growing area threatened by extremely high temperatures during critical developmental stages in a typical year, and a more than threefold increase of the area at risk by 2050.
From climate change projections (based on the relative extreme high-end scenario RCP8.5) it was shown that the occurrence of adverse conditions for the main European wheat-growing areas might substantially increase by 2060 compared to the present (1981–2010), which is likely to result in more frequent crop failure across Europe. This would have profound repercussions given the importance of European wheat production in the global food trade (23). The adverse agroclimatic conditions that have been studied are: severe winter frost without snow cover, late frost, excessive soil moisture with water logging from sowing to anthesis, high precipitation event with the possibility of widespread lodging, severely dry growing season (sowing–maturity), severe drought event between sowing and anthesis, severe drought event between anthesis and maturity, heat stress at anthesis, heat stress during grain filling, adverse conditions during sowing, adverse conditions during harvest. The climate projections indicate that sowing dates will move forward on average by 15 +/- 7 days in 2060 compared to the present, whereas anthesis and maturity dates will be two weeks earlier (23).
For winter wheat growth duration is reduced, because any changes in sowing date in autumn would have little effect on duration of the vegetative and reproductive phases in the following spring and summer. This response concurs well with observed response of winter wheat yields in Denmark, where the largest reductions were related to high temperatures during the grain-filling phase (54).
Climate change is likely to increase cereal yields in Northern Europe but decrease yields in Southern Europe (31).
Northward expansion crops
Arable farming in the Northern region of Europe is projected to be the main winner in the course of this century under both low-end and high-end climate change as higher temperatures increase the growing season and the options for growing a wider range of arable crops. Increases in arable land and food production are also projected for the Alpine region under high-end climate scenarios. This was concluded from an assessment study focused on differences in impacts between low-end (RCP 2.6) and high-end (RCP 8.5) climate change scenarios on Europe for six sectors (agriculture, forestry, biodiversity, water, coastal and urban) and their cross-sectoral interactions (128). Intensive farmers in Southern and Atlantic regions of Europe lose as food production and arable land is projected to decrease under both low-end and high-end climate change due to more productive agriculture moving northwards where greater yields are possible per unit of land area (128).
Warming has already caused a northward expansion of the area of silage maize in northern Europe into southern parts of Scandinavia, where the system of grass and silage maize for intensive dairy production has largely replaced the traditional fodder production systems (50). Very recently grain maize has started to be grown in southern parts of Denmark, reflecting the warming trends (51). Analyses of the effects of observed climate change on yield potential in Europe have shown positive effects for maize and sugar beet, which have benefited from the longer growing season for these crops (52). Yield benefits have been greatest in northern Europe. The warming may also have contributed to higher potato yields in northern regions of Europe. In contrast, warmer and more variable climatic conditions with increased occurrence of drought have reduced crop yields in parts of central Europe (53).
The projections for a range of SRES climate change scenarios show a 30 to 50% increase in suitable area for grain maize production in Europe by the end of the 21st century, including Ireland, Scotland, southern Sweden and Finland (4). Moreover, by 2050, energy crops show a northward expansion in potential cropping area, but a reduction in suitability in southern Europe (5).
Although human population growth and increased affluence in some regions, along with changing diets, will lead to higher demand for food products, crop, fish and livestock yields are projected to decline in many areas due to climatic and other stress factors. In addition to the effects of drought, extreme events such as heat waves, frost or heavy rainfall during critical phenological stages may bring unexpected losses due to crop diseases, yield reductions and increased yield variability (109,110).
In some crops, yield increases may occur, due to CO2-fertilization effects that could increase water- use efficiency and biomass productivity (109). These yield increases are expected to be combined with decreased quality (for example, lower protein content in cereals (111). Pests and diseases, as well as mycotoxins, could also represent a serious threat under unfavourable climate conditions (112).
Barley is an important cereal crop for the arid and semi-arid Mediterranean environments. Europe produces about 63% of the world’s barley with most of it under rainfed conditions (124). Future climate projections show that Mediterranean countries will get drier and hotter. Depending on the climate projection, the impacts of changing agronomic practices might offset the negative impacts of climate change. This was studied for 9 locations across the Mediterranean focused on 2050, by using the output of a large number of climate models (GCMs) based on a moderate scenario of climate change (RCP 4.5). Overall, model results indicate a 9% reduction in grain yield under climate change in 2050. It was concluded that the impact of future climate on barley yield in the Mediterranean is negative; some locations will be less affected than others, however (123).
Chilling and forcing: cold and heat requirements olive orchards
Olive production in Europe is concentrated in the Mediterranean countries Spain (53% of total production in Europe), Italy (24%), Greece (15%) and Portugal (7%) (114). There are usually two main thermal factors influencing plant development: cold (chilling) and heat (forcing) requirements (115). Chilling refers to an extended accumulation of cold weather, which enables plants to leave the dormancy stage and allowing them to properly set buds and produce fruit when warmer temperatures arise. Following this stage, heat accumulation plays a major role, forcing plant phenological development and growth. A certain accumulation of warm temperatures is indeed necessary for plants to achieve a proper ripening. Higher winter temperatures may be detrimental, as insufficient chilling may cause delayed budding and foliation, resulting in low fruit set/yields (116). Additionally, increased temperatures during the growing season may result in faster and unbalanced fruit ripening, which may lead to implications in fruit quality, fruit set and yields (113).
For olive trees, chilling plays an important role for flowering and fruit set (117). Although olive trees exposed to insufficient chilling may indeed flower, it tends to result in low fruit set percentage (118). The projected future reduction in chilling in the Mediterranean region may threaten this crop; flowering and fruit set may be reduced due to insufficient chilling (119). This was concluded from simulations with a large number of models based on a moderate and high-end scenario of climate change (RCP4.5 and RCP8.5 scenarios) (113). Projected higher thermal (heat) forcing may also lead to advances in the timing of each phenological stage, affecting fruit yields and quality (120). Certain varieties of olive trees are more resilient to the negative impacts of the changes in heat and chill conditions, however (121).
Pests and diseases
Between 10 and 16% of global crop production is lost to pests, with similar losses postharvest (10). From an analysis of published observations of 612 crop pests and pathogens it was concluded that the average poleward shift in recorded incidences of these pests and pathogens since 1960 is 2.2 ± 0.8 km/year for the Northern Hemisphere and 1.7 ± 1.7 km/year for the Southern Hemisphere (11). The results indicate significant positive latitudinal shifts for many important groups of crop pests and pathogens. Overall, there has been a significant trend of increasing numbers of pest and pathogen observations at higher latitudes, globally and in both the Northern and Southern hemispheres. For all pests combined, the mean latitudinal shifts were not significant, however, but this seemed to be due to large variability among pest groups. Although recent climate change is implicated as an important driver of these observations, other factors could bias the results. For instance, new crop varieties and agricultural technologies have extended the agricultural margin northward in the USA, and deforestation has increased production in the tropics, thus providing new opportunities for pest invasions at high and low latitudes (11).
Global increase at 2°C global warming
Insect pests damage crop yields directly from pest infestations and indirectly from pesticides applied to reduce pest damage (91). Global warming will change the impacts of pest species on crop yields. These impacts have been estimated for the major grain crops maize, rice, and wheat, which together account for 42% of direct calories consumed by humans worldwide. These estimates are based on simulations with several climate models fed by a high-end scenario of climate change (RCP8.5) (90).
There are two ways in which the impacts of insect pests will change in a warmer climate: (1) an individual insect’s metabolic rate accelerates with temperature, and an insect’s rate of food consumption must rise accordingly (92), and (2) the number of insects will change, because population growth rates of insects also vary with temperature. In the estimates, these two effects are combined (90).
The results show that crop production losses to pests increase globally with rising temperatures. When average global surface temperatures increase by 2°C, the median increase in yield losses owing to pest pressure is 46, 19, and 31% for wheat, rice, and maize, respectively. The impact for wheat is relatively high: wheat is typically grown in relatively cool climates where warming will increase pest population growth and overwinter survival rates, leading to large population increases in the growing season. The impact for rice is relatively low: rice is grown in relatively warm tropical environments where warming reduces insect population growth rates because current temperatures there are already near optimal. The impact for maize is in between wheat and rice: this crop is grown in some regions where insect population rates will increase and in other regions where population rates will decline, in nearly equal measure (90).
In temperate regions, warming increases both the size of insect populations and their per capita metabolic rate. As a result, the increase in pest-related crop loss is consistently larger than in tropical regions, where the increasing metabolic rate is offset by declining population growth rates, resulting in a smaller overall rise in crop damages. This broad geographic pattern holds across all three crops. France, the United States, and China, countries that produce most of the world’s maize, are also among the countries projected to experience the largest increases in pest-related crop losses. In addition, France and China are responsible for a considerable fraction of global wheat and rice production, respectively, and are projected to suffer large increases in yield loss of these grains owing to climate impacts on pests (90).
Future irrigation water demand
Crop irrigation is responsible for 70% of humanity’s water demand. Globally, the area equipped for irrigation grew six fold to nearly the size of India between 1900 and 2005 (13). This expansion occurred rapidly at a rate of nearly 5% per year during the period 1950s–1980s, but it has slowed down since the late 1990s when the growth rate decreased to <1% per year. For the coming decades, the global area of irrigated land is not expected to expand dramatically due to limited land and water available (14).
For Europe, by the end of the century (2080s: mean of 2069-2099), compared to the present (2000s: mean of 1980-2010), irrigation water demand is projected to decrease for Eastern Europe under scenarios for moderate climate change (12). Under more severe climate change scenarios irrigation water demand in Europe is projected to increase substantially (>20%) (15); according to the IPCC (31) there is high confidence that irrigation demand will increase by more than 40% across Europe. Future irrigation water demand, however, will also be determined strongly by the growing world population and altering lifestyles and dietary habits (15).
Future yield estimates for changes in climate, atmospheric CO2 concentration and technological development
From an analysis of a global data base of yield impact studies compiled for the IPCC Fifth Assessment Report (62) it was concluded that CO2 fertilization fully offsets negative impacts of warming up to 1-2° for the global average yield effect for both maize, wheat, and rice (61).
The impact of projected changes in climate, atmospheric CO2 concentration and technological development on crop yield has been studied for 25 EU countries for the period 2041–2064 compared with the period 1983–2006. This has been done for grain maize, potatoes, sugar beet, winter barley and winter wheat, and for a selection of General Circulation Models (GCMs) and three emission scenarios (SRES B1, A1B and A2) that span the range of changes in temperature and precipitation by the mid-21st century (16).
The results suggest that in these countries the negative effects of climate change on crop yields range between 12% and 34% depending on the crop and region. Climate change effects are less pronounced for winter cereals (barley and wheat) as compared to tuber crops (potatoes and sugar beet) or other spring crops (maize). One possible explanation, still subject of further investigation, is the longer vegetative period for winter crops which may allow the winter crops to better cope with extreme events such as drought spells in spring. Also, changes in growing season length due to temperature increase will be relatively smaller in winter as compared to spring crops. The simulations with the driest scenario A1B resulted in the strongest negative influence on yields (16).
The results also suggest that increasing atmospheric CO2 concentration stimulate yields in wheat, barley, sugar beet and potatoes by 14%, 11%, 14% and 7%, respectively. However, most substantial yield changes were projected when considering the effect of technology development. The yield decreasing effect of climate change was compensated and partially superseded when atmospheric [CO2] elevation and technology development were taken into account which is in good agreement with earlier research (17).
For the winter cereals yield increases of 30% and more are projected compared to the baseline for most European regions under the combined impacts of climate change, increasing atmospheric CO2 concentration and technology development. There are small areas on the Iberian and Italic peninsulas were yield decreases are projected compared to the baseline. These declines are mainly due to the pronounced negative climate change effect which could not be compensated for by the positive effects of increasing atmospheric CO2 concentration and technology. For potatoes and sugar beet yield increases are also simulated for most regions in Europe except for some areas in Southern Europe (Italy, Greece and Spain), and few regions in Poland and Finland, but in most of the cases the decreases do not surpass 10% in relation to the baseline period. For grain maize the spatial variability in yield changes ranges between <−30% to >30%. Yield increases are highest in South-western Europe and yield declines are mainly projected for Eastern Europe (16).
For a site in Austria, representative for confined livestock buildings for growing-fattening pigs in Central Europe, the impact of global warming on the thermal conditions inside confined livestock buildings for growing-fattening pigs was estimated. This was done by calculating heat stress over the period 1981 – 2017. It was shown that heat stress has increased over this period, stressing the need for adaptation measures (122).
Wetter winters and an increased likelihood of fields remaining waterlogged into spring mean that the housing period of ruminant livestock may need to be increased, with the animals remaining inside for longer in the spring. Hotter summers forecasted may also mean that ruminants need to be housed in summer to reduce problems from heat stress or because pastures may not remain productive during the summer months. The grazing season may be lengthened in autumn and into the early winter period, and therefore may at least partially compensate for the reduced grazing opportunities in early spring and late summer.
Increased temperatures and decreased rainfall in summer are also likely to reduce forage yields, especially on pastures grazed during summer (3). Adaptation measures include growing a new range of forage crops, such as soya, or making increasing use of forage grown during early spring and late autumn. Reduced yields of current forages could also be compensated for by the introduction of more drought and heat resistant forage varieties (3,77).
The longer growing season, greater grass production and warmer temperatures all mean that livestock housing costs could be reduced. For ruminants this will be due to a longer growing season, which will enable livestock to graze longer. For carnivores, the reduction in housing costs will be due to a reduced need for heating over winter. A further cost reduction may accrue from the increased potential to grow forage legumes.
The spread of bluetongue virus in sheep across Europe has been partly attributed to climate change (34) through increased seasonal activity of the Culicoides vector (35).
Adaptation measures - Overview
Zoning and crop productivity
Changing planting dates, optimisation of crop varieties and planting schedules, improving cultivar tolerance to high temperature, irrigation optimisation and diversification of activities are climate adaptation options for cropping systems summarized by the IPCC (31).
Some predictions foresee a greater potential for overall crop productivity from a longer growing season in some parts of the EU, a northward shift in the cultivable zone, and increased CO2 concentrations in the atmosphere. Increased average temperatures and a longer growing season may offer the opportunity to grow a wider range of crops over a greater area.
Changing crop sowing days may ensure that maturation occurs before peak temperatures and thus reduce possible negative effects on productivity. Growing the most heat resistant cultivars or those that become more suitable for the specific climate— present new opportunities for farmers (31). While a warmer climate poses a risk to some traditional fruit growing practices, opportunities will also be presented to grow new types of fruit.
Farm-level actions are needed to improve soil drainage to reduce waterlogging and the consequent impacts on stock health. However, improving drainage from fields, by increasing the rate at which water is discharged to streams and rivers may increase the risk of flooding downstream. In consequence adaptation to this risk should focus on disseminating information on minimising the adverse impacts of waterlogging and on recommending farmers move stock from those fields vulnerable to waterlogging.
The majority of adaptation measures proposed would be implemented at the farm level and range from improving soil structure to contour ploughing. Providing ‘breaks’ such as hedges and increasing the area of undrained farm woodlands would help to buffer peak rainfall events, slowing the movement of water from soil to watercourse. This will help balance the increase in water transfer from soils to watercourses brought about by improved drainage.
Improved on-farm management alone may not fully adapt to the risk; infrastructural adaptation including ‘hard’ defences and drainage systems is likely needed.
Drought, Water Scarcity and Irrigation
Farm level actions such as changing land use in areas that are more susceptible to drought, changing cropping by switching to less water intensive crops, and investing in rain water harvesting equipment are needed. Measures to adapt to the expected decrease in water availability and drought risk may include measures to increase the water-holding capacity of soils (increasing the organic matter content of soils); measures that increase the collection of rainwater over winter to increase the supply for subsequent irrigation; measures to improve the efficiency with which irrigation water is applied.
Earlier sowing, of both Autumn and Spring-sown crops, will result in the maturation phase occurring earlier and before the occurrence of peak temperatures in the summer. Also, crops may be shifted to areas where the climate is more suitable for their cultivation.
If the agriculture industry aims to adapt by increasing irrigation, the water resources necessary may need to be supplied from within the farm. This may be achieved by on-farm rainwater harvesting and establishing small-scale water reservoirs on farmland while improving the efficiency with which irrigation water is used. Irrigation may be used more efficiently by a range of approaches from irrigating at night to use of trickle irrigation.
Government agencies and regulators may provide an incentive for farmers to take action by re-negotiating water abstraction licenses and/or introducing charging/tradable permit schemes to promote efficient use of reduced water resources.
Crop husbandry adaptation measures include intercropping (where available space between rows is used by different crops to allow maximum use of the soil moisture); altering row and plant spacing (to increase root access to available soil moisture); and introducing or changing fallow and mulching practices to retain soil moisture and organic matter (Iglesias et al. 2006). In response to forest fires during summer drought, the introduction and maintenance of firebreaks (where areas are cleared or burnt under controlled conditions) with access to water for fire fighting, will limit fire spread and damage.
Water quality may be polluted by fertilizers through increased point-source and diffusive pollution (more runoff). Fertilizer efficiency and application methods need to be improved and farmers should be made aware of best practices regarding the application of manures and fertilizers and the control of soil erosion. The use of buffer strips (hedgerows, vegetative rows) beside water courses can be effective in reducing nutrient leaching.
Glaciers and permafrost
Mountain communities that depend upon melt waters for their domestic and agricultural supply will need to invest in water capture and storage systems to compensate for the projected changes in seasonal water availability that will affect these regions.
The threat from rising sea levels is the one that most requires an infrastructural approach. National governments will need to decide the balance between constructing ‘hard’ flood defences and allowing land to be abandoned to inundation.
Pests and diseases
The introduction of resistant or less-susceptible varieties is one approach. To deal with new crop pests a sustainable integrated pesticides strategy should be developed. The use of new pesticides needs to be carefully evaluated with respect to the potential impacts on water quality. Within greenhouses the use of thermostats and rapid cooling may be used to reduce pest and disease infestation. Livestock disease adaptation measures include vaccination of both the domestic and wild populations (31). An increased use of pesticides is expected due to climate change (36).
Adaptation potential - Global
Global climate change impacts on crop yields up to the 2050s can be small (but negative) for rice and wheat, and modest for maize, provided farmers adopt practices and technologies such as improved varieties, planting at optimal times, and improved water and fertilizer management. This conclusion was drawn from a review of 157 studies from across the world (125).
Over the last decades, a large number of scientific studies have been carried out on climate change impacts on crop yields. In a review study, the results of 157 of these studies from across the world, published in the period 1984 to 2016, were combined to assess climate change impacts on the yields of three major crops: wheat, maize and rice. In addition to potential impacts, also the effects of different adaptation strategies to mitigate these impacts were studied. This was done for every country across the world (125).
No adaptation, high yield losses
Without adaptation, losses in crop yields due to climate change are high and increase with time. Mean global wheat and rice yield losses increase from 6% in the 2020s to 12% - 15% by 2080s, compared with the reference period of 1960-1990. Similarly, for maize, the combination of 157 studies shows an increase from 9% losses in the 2020s to 20% in the 2080s. Low latitudes generally show higher yield losses except for wheat, which shows only a small reduction until the 2050s (125).
Mitigation through adaptation
Adaptation can significantly mitigate these impacts. After considering farmers’ adaptation, climate change yield losses are relatively small, especially for wheat and rice. For wheat, global yield losses are 1 ± 0.03% in the 2020s and 4 ± 0.16% in the 2080s. For rice and maize global yield losses are 3 ± 0.08% (2020s) to 6 ± 0.23% (2080s), and 6 ± 0.24% (2020s) to 13 ± 0.6% (2080s), respectively. With adaptation, climate change impacts are not major issues for the production of wheat, rice and maize for many countries until the 2050s (125).
Several previous studies have shown that food security under climate change is less vulnerable in temperate, high-income countries than in tropical, low-income countries of Asia, Africa and Latin America (126). The global assessment of these 157 studies shows that such differences may not necessarily be large or significant across political, economic and climatic regions if the right adaptation measures are implemented. Adaptation can help to reduce inter-regional differences. Out of the assessed adaptation measures, the most effective are dynamic nutrient and irrigation application. These measures can largely reduce climate change impacts on maize, rice and wheat yields. Other measures, such as changing planting dates and cultivars, are less effective (125).
Strongest impacts in Middle East and Africa
There will still be food production gaps (supply rates lower than projected demand) in the future, according to the assessments; for wheat in top-producing countries in Europe and Asia, Sub-Saharan Africa, and North America, and for rice in a few Central Asian countries. For wheat and rice, the additional impact of climate change, after adaptation, is small however. For maize, many countries of Sub-Saharan Africa and South Asia are primary hotspots where the production gap may increase due to climate change. For all crops combined, yields in the Middle East and Africa will be significantly more impacted compared to other regions (125).
Good news, with a side note
The good news is that with adaptation, climate change doesn't have to add significantly to the challenge of food production for the majority of countries except for some potential hotspots distributed around the world. Especially in vulnerable, low-latitude countries there is considerable scope for increasing yields. However, massive investment, policy, and institutional support will be needed to facilitate adoption and scaling-out of such practices, and to address climatic variability. The economic costs and institutional support for these adaptation strategies could be a constraint for many lower-income countries (125).
Adaptation potential - Europe
The adaptation potential of European agriculture in response to climate change has been assessed for a number of crops (29). It was shown that adaptation potential is high for maize and (to a lesser extent) sugar beet and oilseed, and limited for wheat and barley. For instance, maize yields are projected to decline by 9% in 2040 relative to 1975 without adaptation but adaptation has the potential to cut this to just over 1%. Barley yields, on the other hand, are projected to decline by 22% in this period but this loss could be cut to 15% with adaptation.
Under climate change, average farm profits across Europe would increase modestly (1.5%) with adaptation but could decline by 2.3% without adaptation (29). However, warmer regions in southern France, Spain, Italy, Greece and Portugal already beyond the temperature optimum of 16°C could see substantial residual damages from climate change of over 10% even after adaptation. Without adaptation even cooler regions in central France and Germany could see declines in profitability due to warming by 2040. In agreement with several previous studies, the authors found that projected temperature changes are more important than precipitation changes in determining the impacts of climate change over the next few decades (30). They found that the impact of mean temperature change on yield is around 5-10 times larger than the impact of precipitation by 2040; projected precipitation changes tend to be small compared with projected temperature changes. It should be noted, however, that these estimates do not include a number of moderating influences that may limit climate change impacts such as potential yield gains in southern Scandinavia or the CO2 fertilization effect (29).
Autonomous vs planned
Two types of adaptation are generally discriminated (8):
- autonomous adaptation often occurs at short time-scales and small spatial scales (e.g. farms). Autonomous means that no other sectors (e.g. policy, research) are needed in their development and implementation. Examples of such adjustments are changes in varieties, sowing dates and fertilizer and pesticide use. In particular, in southern Europe, autonomous adaptations may include changes in crop species (e.g. replacing winter with spring wheat, (6)), changes in cultivars and sowing dates (e.g. for winter crops, sowing the same cultivar earlier or choosing cultivars with longer crop cycle; for summer irrigated crops, earlier sowing for preventing yield reductions or reducing water demand) (8). In northern Europe, new crops and varieties may be introduced only if improved varieties will be introduced to respond to specific characteristics of the growing seasons (e.g. length of the day) (4).
- planned adaptation refers to major structural changes to overcome adversity caused by climate change. This involves changes in land allocation and farming systems, breeding of crop varieties, new land management techniques, etc. It requires longer time than autonomous adaptation and often concerns regions or nations. A different allocation of European agricultural land use seems to represent one of the major planned adaptation strategies available (8).
From an analysis of a global database of yield impact studies compiled for the IPCC Fifth Assessment Report (62) it was concluded that there is little evidence in the existing literature that farm-level adaptations will substantially reduce the negative impacts of climate change on yields. The potential for within-crop, farm-level adaptations that improve yields in the future climate more than in the present climate appears limited, at least as currently represented within the studies included in the meta-analysis (61).
The ability to adapt agricultural practices is strongly influenced by social and economic factors. Farmers who have been historically exposed to variable climatic conditions, such as in the Mediterranean region, tend to be more prepared to cope with climatic change. Adaptive decisions ought to occur at the farm level in response to local conditions, which makes it impossible to prescribe a single strategy at global level (9).
The world’s cereal producing regions have been identified that are likely to become vulnerable to climate change over the 21st century by identifying those regions that will be [a] exposed to climatic stress and [b] have a limited capacity to adapt (8). Model projections on available soil moisture were made to identify regions likely to be exposed to drought under the SRES A1B and B2 emissions scenarios for the 2050s and 2080s. These regions were compared with model projections of adaptive capacity based on agricultural, meteorological and socio-economic data. These projections were compared with the baseline period of 1990–2005. “Vulnerability hotspots” were identified for wheat and maize, a vulnerability hotspot being defined as a region where both a decline in adaptive capacity and in available soil moisture is projected. The results suggest there are perhaps five wheat and three maize growing regions likely to be both exposed to worse droughts and a reduced capacity to adapt. The “vulnerability hotspots” for wheat are: southeastern USA, southeastern South America, the northeastern Mediterranean, and parts of central Asia. For maize, the suggested vulnerability hotspots are: southeastern South America, parts of southern Africa, and the northeastern Mediterranean. This analysis did not consider the effects of available ground water on adaptive capacity, however (8).
Differences between Eastern and Western Europe
The same scenario of climate change will have different effects on agriculture in Eastern and Western Europe. These differences arise because today agriculture in Eastern Europe is not at the same high level as agriculture in Western Europe, and because the options to adapt to future climate change are not the same in these two regions (55). The big difference of agriculture today between Eastern and Western Europe is illustrated by the difference in agricultural labour productivity: between 2011 and 2013 this productivity in Eastern Europe was only 19% of productivity in Western Europe (56). This is despite investment of approximately 20 billion euro of European Union (EU) and national funds to modernize Eastern European agriculture between 2000 and 2012 (57). Apparently, transition of agriculture in Eastern Europe is a slow process.
Due to these big differences, Eastern and Western Europe do not have the same adaptive capacity or climate response, and thus face different climate change impacts. A farmer in Eastern Europe that is faced with a negative impact on a certain crop, for instance, has fewer options to adapt than a farmer in Western Europe facing the same impact for the same crop. Farmers will continue to adapt to changing circumstances to maximize their profit. This profit-maximization has different outcomes for Eastern and Western Europe. This hypothesis has been tested for changes in temperature and precipitation between now and 2071-2100 under scenarios of a moderate change in climate (55). For this test two assumptions have been assessed:
- What if Eastern and Western European regions were to adapt in isolation, not being able to benefit from adaptation options the other region might offer? If agriculture in Eastern and Western Europe were to adapt in isolation, and thus farmers in Eastern and Western Europe could only benefit from adaptation options in their respective regions, this would negatively affect farmers in Eastern Europe. After all, the number of potential adaptation options is smaller in Eastern than in Western Europe: the variation in Eastern European farms is smaller, and agriculture is less developed, modernized, and capital-intensive than in Western Europe (55).
- What if farmers in both regions have full access to adaptive capacity in the other region? The results show that if farmers in Eastern Europe have full and easy access to the adaptive capacity of Western Europe, Eastern Europe will respond more positively to changes in climate. Vice versa, having full access to the adaptive capacity of Eastern Europe does not increase the adaptive capacity of Western Europe (55).
Both extremes are not realistic at this moment, however. Adaptation will not take place in isolation. There is an exchange of knowledge and expertise that strengthens adaptation capacity in Eastern Europe. Eastern European countries are continuing to re-adjust their institutions according to Western European templates, and Eastern European farmers have access to EU farm subsidies. The other end of the spectrum, where Eastern Europe gains access to the same level and quantity of adaptation options as Western Europe, is also unrealistic at this moment. Complex behavioural, technical, societal and institutional costs and adjustments at all levels of the society are required to make this happen (58). Even though market principles are now predominant all over the European Union, and Eastern Europe has made a lot of progress to close the gaps, the countries in this region continue to face significant socio-economic setbacks that decrease the countries’ options to respond to the current and future climate (55).
Assessments of future impacts of climate change show that the region with the lowest adaptive capacity, Eastern Europe, suffers the most from climate change. This is because Eastern Europe cannot fully apply the same adaptation options as Western Europe. Autonomous adaptation will not bridge the existing adaptation gap. Planned adaptation in Eastern Europe is needed. The European Union, national governments, and regional policy must attempt to overcome the barriers to adaptation in Eastern Europe and increase Eastern European adaptive capacity by providing more information on adaptation opportunities and climate change, by enlarging the adaptation options and resource inventory and by creating a favourable implementation and management environment, by encouraging knowledge and skills transfer between all European farmers, and by guiding farmers in making efficient adaptation decisions (55).
Adaptation measures – Risk management policies
Risk management instruments in agriculture, such as crop insurance and disaster assistance programme, and especially how they are designed, will affect incentives to adapt (19). Three types of crop production insurance are: individual yield, area-yield and weather index insurance. In addition to these insurance schemes governments may decide to assist farmers financially after climate extremes that caused a lot of damage to their yields (ex post assistance) (18):
- Traditional individual-yield crop insurance makes an indemnity payment when the farm incurs a yield loss. This can help to manage production risk but it is known to be expensive and will diminish incentives to adapt to climate change (18).
- Area-yield crop insurance is a crop insurance scheme in which both indemnities and premiums are based on the aggregate yield of a geographical area. The indemnity equals the difference in value, if positive, between the area yield and some predetermined critical yield level. Participating producers in a given area would receive the same indemnity per insured unit of land, regardless of their own crop yield, and all would pay the same premium rate (20). Under changing climate conditions, area yield insurance would have the advantage of maintaining incentives to adapt (18).
- Weather index insurance is an insurance scheme where a threshold in the proxy variable marks the point at which payments begin. Once the threshold is reached, the payment increases incrementally as the value of the index worsens. The payment rate is independent of the actual loss incurred by a policyholder (18).
- Ex post payments are highly variable and can be extremely high in some years (18).
Weather index insurance or area yield insurance, which do not require on-farm verification, can help keep administrative costs down as compared to individual yield insurance, and they do not discourage adaptation since indemnities are paid independently of actual loss incurred by a policyholder. However, they are not a means for structural adaptation. Farmers will incorporate any insurance subsidies or ex post disaster payments to their production decisions, which may favour insurance over crop diversification or other risk management and adaptation strategies (18).
European wheat production
From a study on adverse weather conditions for European wheat production (23) it was concluded that the adaptation strategies must be a compromise between using early-ripening cultivars to avoid stress as much as possible and maintaining a growing season length with the highest possible effective global radiation to sustain current yields or minimize yield decrease. With early-ripening cultivars adverse condition risk can be reduced; shortening the growing season, however, reduces the effective global radiation and therefore yield potential. The authors from this study stress the importance of regionalization of adaptation strategies: in Northern Europe, by using late-ripening cultivars the growing season is longer without the penalty of increased exposure to adverse agroclimatic conditions; in central Europe, by switching to late-maturing cultivars the risk of adverse event frequency significantly increases. They state that diversity of wheat varieties for different regions and season-specific threats should be promoted to enhance climate resilience (26).
In addition to changes in planting dates, cultivar use, and planting locations, farmers will need to make changes such as introducing new crop rotations, to maintain yields in the face of rising insect pest pressure. Without wider attention to how climate warming will affect crop breeding and sustainable pest management strategies, insect-driven yield losses will result in reduced global grain supplies and higher staple food prices (90).
Adaptation measures – Specified for the Boreal zone
In the Boreal zone, farming will mainly need to adapt to increased rainfall. The rapid removal of water from agricultural land, by increasing stream flow, may increase the risk of flooding downstream, however. Hence there will need to be an assessment of the impacts of any programme to improve farm drainage on the requirement for hard flood defences in vulnerable zones (1).
The opportunities in the Boreal zone (including the greater area of land available for a range of crops, longer growing seasons and increased temperatures) offer the potential to improve the productivity and/or profitability of all agricultural sectors. Farmers will need access to information on new cultivars and their husbandry in order to maximise those opportunities. Careful consideration also needs to be given to the potential impacts that increasing agricultural production may have on biodiversity and the overall landscape quality (1).
Adaptation measures – Specified for the Atlantic zone
The whole Atlantic zone presents improvements on land availability, longer growing season and higher temperatures. Farmers will need access to information on new farming techniques and species to benefit from those opportunities. Nevertheless, farming in the Atlantic zones will have to adapt to the risks of intensification of winter rainfall as well as reduced summer rainfall and, under warmer conditions, the likely introduction of new pests and disease. Farm-level measures are needed to allow rainwater harvesting and improve drainage to reduce waterlogging while improving crop growth and stock health and reducing the risk of pollution from run-off and fertilizer leaching (1).
The risk of sea level rise is more pronounced in the Atlantic Central zone where measures will need to be put in place to give up or protect land from salt water intrusion and to improve drainage. The impacts of improved farm drainage and the need for hard flood defences from sea and rainwater flooding in vulnerable zones will have to be assessed (1).
In the Atlantic South zone adaptations need to prioritise efficiency in the water supply. Improving water supplies, introducing less water-demanding crops and screening fruit and orchard crops from direct sunlight are possible farm-level measures. Potential risks (heat waves) and opportunities (rise of forage productivity) can be anticipated for livestock and more shade and shelter will be needed to avoid heat stress. Using woodland for this will provide co-benefits by increasing rainfall retention in soils and therefore help reduce the risk of winter flooding and run-off (1).
Adaptation measures – Specified for the Continental zone
Adaptation to winter flooding and summer drought by the agricultural sector is a top priority in the Continental North zone. Farm level measures to capture additional winter rainfall will reduce flood and water quality risk and allow farmers to respond to summer drought. Changing to new cultivars and different crop varieties at farm level will allow farmers to make the most of increasing temperatures and CO2.
The greatest risks in the Continental South zone are likely to be a decrease in water supply due to a decline in annual rainfall, reduced crop yields and increased heat stress to livestock. The priorities for adaptation measures will be to identify suitable new crops and new cultivars that can be grown in place, or in combination with, those currently cultivated. Priority should be given, by farmers, to conserving water on their farms to provide a source for irrigation and to apply efficient irrigation schemes (1).
Adaptation measures – Specified for the Alpine zone
Farming will need to adapt to an intensification of winter rainfall and altered hydrological cycles in rivers, as well as flash floods and summer drought. Farm level measures are needed to improve natural buffering to reduce erosion and landslides. Drainage to reduce waterlogging is also an important measure. Flood prevention plans may need to be put in place along with the appropriate infrastructure. Win-win measures include the collection of winter rainfall for summer irrigation. Again, in this area, longer growing season and higher temperature offer the possibility to improve the productivity and profitability of agriculture (1).
Adaptation measures – Specified for the Mediterranean zone
It is essential to improve irrigation efficiency to adapt to future climate and socioeconomic change globally and in major arid regions (89). One of these regions is the Mediterranean, spanning over southern Europe, Northern Africa, and the Middle East. Strategies have been evaluated to adapt the Mediterranean’s water and land management in view of future change (81). This was done for 2050 compared with 2010, for a large number of downscaled global climate model projections driven by an intermediate scenario of climate change (the RCP 4.5 scenario). Population projections were derived from the so-called Shared Socioeconomic Pathways SSP2 scenario. The Mediterranean is densely populated, water stress is high, and food production strongly depends on irrigation (82). Irrigation amounts to 69% of total water withdrawal in thisregion (83). Climate change will probably increase aridity and decrease freshwater resources, thus impacting future crop production (84).
Irrigation efficiency needs to improve
The evaluation shows that the efficiency of the irrigation systems in the Mediterranean region needs to be improved substantially in order to continue satisfying the region’s future food demand with irrigated crops. Still, this would not allow for expanding irrigated cropland in areas where there is no cropland today, or where cropland is being managed with low intensity. After all, water withdrawal for irrigation most likely needs to be reduced, because the availability of water resources will reduce under climate change whilst water stress is already a major issue in this region. In fact, the share of irrigated cropland in future crop production needs to be considerably lower, despite improvements in irrigation efficiency (81).
Rain-fed cropland yields need to increase
As a result, and in addition to improving irrigation efficiency, the productivity of existing rain-fed cropland systems needs to be improved. The less progress is made in improving irrigation efficiency, the more difficult it will be to successfully increase rain-fed crop yields. Low improvements to irrigation efficiency require extremely high increases in crop production in rain-fed land systems. Such increases seem unrealistic, considering projected climate change and variability in precipitation (81).
Current multifunctional land use is effective
Maintaining multifunctional mosaic land systems, as well as introducing additional activities to low intensity croplands can be considered as an additional adaptation strategy to scarce water resources. These systems are mostly satisfying the increased demand for livestock and partially for crops. Such traditional systems may play a significant role in mitigating and preventing other negative consequences of intensive agriculture, such as soil erosion (85) or biodiversity loss (86), and are particularly adapted to the hilly areas with high variability in environmental conditions. Increasing and maintaining the extent of such land systems will be difficult. Local studies demonstrate that these areas are subject to abandonment and loss due to intensification (87). Moreover, future climate change might reduce the crop and livestock productivity of these systems (88).
Adaptation measures - Irrigation to offset heat stress crops
A study based on observations in Kansas (USA) has shown that dryland wheat yields decrease about eight percent for every one-degree Celsius increase in temperature, yet irrigation completely offsets this negative impact (76). According to this study, precipitation does not provide the same reduction in heat stress as irrigation. Water scarcity not only reduces crop yields through water-deficit stress, but also amplifies the negative effects of heat stress. A caveat to these results is that future increases in CO2 concentrations might limit plant transpiration, thereby reducing the plant’s ability to cool itself and the efficacy of irrigation in reducing heat stress.
Adaptation measures - Livestock
Livestock production systems are of major economic, environmental and cultural importance to the EU, producing outputs worth EUR 168 billion in 2014 and accounting for 28 % of land use (75). Livestock production systems are many and varied. In the EU in 2014, there were 355 million livestock, consisting of pigs (42 %), cattle (25 %), sheep (28 %) and goats (4 %) (74).
There is much uncertainty about the response of livestock production to climate change. Some of the climate effects, their impacts on livestock, and adaptation options are summarized below for (A) intensified livestock systems and (B) wide-value systems (from (74)).
(A) Intensified livestock systems (reduced or zero grazing)
1. Climate effect: Increased temperatures and temperature extremes
- Challenge: Housed animals are protected from extremes, but higher productivity animals are more susceptible to heat stress; extra heat is also produced from animals being in close proximity.
- Adaptation: Improve ventilation and housing conditions; genetic approaches for breeds that have better resilience against heat stress.
2. Climate effect: Spread and increased incidence of pathogens and pathogen vectors
- Challenge: Housed animals avoid many pathogens, but large numbers of animals kept in close proximity to each other increases potential hazards
- Adaptation: Use of antibiotics (but limited by increasing resistance); new medical interventions, including use of feeds and supplements; monitoring of health status; genetic approaches for resilient breeds
3. Climate effect: Increased pressure on water supplies
- Challenge: Intensive systems use large amounts of water, increasing use of feed concentrates increases water demand
- Adaptation: More efficient collection, storage and transport of water; regulation to minimise water demand; improve water governance
(B) Wide-value systems (grazing)
1. Climate effect: Increased temperatures and temperature extremes
- Challenge: Grazing animals are exposed to temperature extremes, but lower productivity animals are more resilient to heat stress; droughts will have effects on pasture productivity
- Adaptation: Provision of shaded areas in pasture; trees for shade can also improve the resilience of swards to extremes; genetic approaches for breeds that have better resilience against heat stress
2. Climate effect: Spread and increased incidence of pathogens and pathogen vectors
- Challenge: Grazing animals expected to be more susceptible to liver-fluke and other pathogens under climate change (increased risk), but smaller herd sizes and more diversity reduce hazards
- Adaptation: Use of antibiotics (limited by resistance); new medical interventions; monitoring of health status; genetic approaches for resilient breeds; land management to reduce pathogen impact
3. Climate effect: Increased pressure on water supplies
- Challenge: Provision of water in the field may be difficult and inefficient; drought may reduce grassland productivity
- Adaptation: Provision of shade can reduce water demand; more efficient storage and transport of water; improve water governance.
It is not likely that the breeds of cattle present in the temperate climate zone can adapt to significant changes in climate. It is widely assumed that breeds that evolved in the tropical zone are adapted to warm conditions. It was not shown that warm climate breeds are likely to reach the performance of temperate climate cattle. The productivity of cattle in temperate countries will decline due to heat stress unless counteracting steps are adopted. Measures should focus on increasing convective heat loss by structure design and forced air flow by fans. Convective heat loss diminishes with increasing air temperatures. Evaporative heat loss remains the alternative. Evaporative cooling of the ambient requires partial enclosing of the space surrounding the animals and is limited by the humidity in ambient air. An alternative was developed of coupling forced ventilation with wetting of animal surface. The exchange of ambient air flowing on animal surface makes the evaporation practically independent of air humidity and the loss of heat from animal surface practically independent of the surface to air temperature gradient. The coupling of forced ventilation with wetting combination may be attained in various parts of the dairy farm, the holding area of the milking parlour, the feeding trip and the resting area (127).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Europe.
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