Response Doctoral Program

Apple orchards across many parts of the world are under stress due to a rapidly-changing climate characterized by more frequent and intense extreme weather events such as heat waves, droughts and episodes of spring frost. Despite being the most produced fruit in Europe, can apples withstand the changing environmental conditions that accompany climate change? What have local farmers done so far and what should they do in the future to adapt to these changing circumstances? Laurent Giguère, is a PhD student at ETH Zurich, as well as a RESPONSE fellow in the PhD program Science and Policy. He sought to answer these questions using mixed methods involving econometric modelling, index-based hazard assessment as well as both quantitative and qualitative surveying.

Future apple yields will suffer from higher summer temperatures
He applied this approach to 32 French apple-growing departments from the years 1989 to 2020 to analyze how climate change has so far affected apple yields, and the extent to which production systems could adapt to its effects. On the one hand, apple production systems have performed well at harnessing the benefits of rising spring temperatures. Meanwhile, they have not adapted as well to increasing temperatures in the summer, especially in early summer, when the apple fruit is most sensitive to heat stress. As a result, past changes in climate have already caused yield losses in the southern French departments surrounding the Mediterranean Sea. Given the current adaptation capacity of production systems, a total of 11 departments are expected to undergo yield losses as a consequence of increasing heat stress by 2050. These conclusions are in spite of the widespread use of irrigation in the departments studied. Hence, new strategies to adapt to the consequences of climate change, such as canopy architecture allowing for natural shading of apple trees and the introduction of heat-tolerant apple varieties in orchards, will likely be needed in the future.

The type and level of climate hazard faced by apple growers will depend on greenhouse gas concentrations
Laurent also conducted finer-scale analyses in Switzerland to understand the evolution of climate hazards to apple production systems while considering the biophysical vulnerability of these systems, such as water availability for irrigation and soil characteristics. The results indicate decreases in spring frost hazard and increases in heat, and to a lesser extent, drought hazard across all Swiss apple-growing regions over the coming decades. Under a intermediate-emissions scenario (RCP 4.5; climate change scenario in the future with 4.5 W/m² of radiative forcing given projections of greenhouse gas concentrations), by the mid-21st century, these trends could lead to summer heat becoming the dominant source of hazard in Valais and in the area surrounding Lake Geneva. On the other hand, in north-eastern growing areas such as Lake Constance, spring frost should remain the most important factor of climate hazard. Conversely, if a high-emissions scenario (RCP 8.5; climate change scenario in the future with 8.5 W/m² of radiative forcing given projections of greenhouse gas concentrations) were to come true, extreme heat would become the main climatic hazard in all Swiss apple-growing areas by the end of the century, thereby exposing around 60% of current Swiss apple surfaces to either high or very high climate hazard. 

“[talking about whether he could picture himself making new investments on his farm to adapt to climate change]…I just don’t see the returns from the industry, which is very, very depressing.” (British apple grower)

Supply chains will need to better support the shift to climate-resilient apple production
Laurent assessed the supply chain environment of apple production to determine its influence on apple grower’s capacity for resilience to climate change. In the process, he also distinguished between the type of resilience favored by growers, namely intrinsic versus extrinsic resilience. Intrinsic resilience refers to a process whereby production systems rely on their internal features such as soil, cultivars grown, biodiversity and the interaction between these to lessen their sensitivity to climate hazards. Meanwhile, extrinsic resilience depends on the incorporation of inputs such as irrigation, fertilizers and pesticides into the system to guarantee stability of production in the face of climate hazard. For this study, Laurent conducted structured surveys as well as semi-structured interviews in Switzerland and Great Britain. His results show that the open market environment in which British growers operate has so far been more conducive to overall climate adaptation, despite the higher level of financial pressure they are subject to compared with their Swiss counterparts. In the vast majority of cases, extrinsic resilience has been favored over intrinsic resilience, a likely sign of the path dependency of the large-scale input-based growing systems that characterize the British fruit sector. Nevertheless, despite being largely industrial, the British apple sector has already seen a significant share of its growers take up adaptation measures tied to intrinsic resilience, like climate-resilient cultivars and rootstocks, which indicates a certain degree of complementarity between input-based adaptation measures like irrigation and more sustainable ones. When it comes to fostering intrinsic climate resilience, the Swiss apple sector only performs better than its British counterpart on one measure – cultivar diversity in the orchards. This has likely been made possible by the more coordinated nature of the Swiss supply chain. However, when combined with the fact that Swiss growers are sheltered from foreign competition through import tariffs, this feature has also created a relatively low-risk business environment which can disincentivize the foresight needed for building long-term climate resilience. The final conclusion that Laurent drew from this comparative case study is that in order for apple growers to invest in building intrinsic climate resilience on their farm, value-based collaborative supply chains are needed in which producers and other food system actors agree on the kind of financial and commercial support needed to encourage the redesign of production systems along agroecological lines. 

Learnings from the secondment
During the secondment, Laurent collaborated with the Schweizer Obstverband (Association of Swiss Fruit Growers, located in Zug), an experience which allowed him to gain insights into the socio-economic realities of fruit-growers in Switzerland and to carry out a structured survey on how Swiss apple growers adapt to climate change. This was of utmost importance to understand how climate change has an impact on the livelihoods of farmers and to put the need to adapt to climate change into the context of the relations apple farmers enjoy with supply chain actors. 

Policy recommendations from these learnings
Laurent calls for policies that support apple farmers in adopting more heat-tolerant varieties and production systems in which apple trees are provided with more shade to effectively manage the negative effects of heat stress. He also emphasizes another need of the hour – to rectify the imbalance in market power between producers and food distributors, so that apple growers receive the necessary economic support to make their orchards more resilient to climate change. 

This article is co-authored by Laurent Giguère and Mary Ann George (University of Zurich, RESPONSE Program office assistant).

This featured image was created using Leonardo.Ai on 20 August 2024 at 3:27 PM. Text: “A high-contrast, horizontal photograph of a serene apple orchard with lush green grass and vibrant trees, their branches stretching towards the sky, capturing the warm sunlight filtering through the leaves, with a sick and unhealthy apple placed prominently in the foreground, its wrinkled, brown skin and wilted stem standing out against the otherwise idyllic backdrop, the camera’s shallow depth of field blurring the background trees, drawing attention to the lone, afflicted fruit, the image exuding a sense of contrast between the orchard’s natural beauty and the apple’s decay, shot in a naturalistic style with muted earth tones, and a subtle play of light and shadow.”