Analysis of climate change impact on resource intensity and carbon emissions in protected farming systems using Water-Energy-Food-Carbon Nexus

Highlights

• Climate change affected the trade-off among irrigation requirement, productivity, and energy for heating.

• We constructed a WFE-Carbon nexus reflecting characteristics of protected farming system.

• We found that heating temperature of protected farming system is key component of WEF-Carbon nexus.

Abstract

As the uncertainty and importance of securing resources increase, the nexus concept is used for integrated sustainable use management planning. In particular, because protected farms are most affected by temperature change, the connection between the heating temperature variable and resources must be analyzed. In this study, a water-energy-food-carbon nexus model that reflected the agricultural characteristics of protected farms was constructed. The crop yield, irrigation amount, and heating energy were simulated, and a sensitivity analysis was performed according to climate change scenarios and heating temperature variables. There was no significant decrease in the yield of food resources even at heating temperatures lower than 12 °C. In contrast, the growing period shortened as the heating temperature increased above 12 °C, which decreased the irrigation amount but tended to increase the heating energy. In addition, lowering the heating temperature standard from 12 °C to 8 °C (or less) is suitable for efficient resource management.

Introduction

Globally, the demand for food, water, and energy resources has increased with population growth and economic development, and food shortages are predicted owing to decreased agricultural population, aging population, labor shortage, and stagnant farm income (Cansino-Loeza et al., 2020; Ryu et al., 2015; Tilman et al., 2011). In addition, disasters caused by climate change are being reported worldwide, and damage and climate variability are predicted to increase owing to climate change. Protected farms with controlled climates are proposed to solve these agricultural and food problems, such as food supply instability, and to overcome the limitations of climate-dependent agricultural systems (FAO, 2013; Lipper et al., 2014). In addition, the importance of water, energy, and food resources to the agricultural sector is increasing, although these resources are extremely vulnerable to climate change. Water and energy demand is predicted to increase simultaneously with food security issues (Daher and Mohtar, 2015; Howells et al., 2013). Therefore, efficient resource management is an important element of climate change adaptation and mitigation (Alsaidi and Elagib, 2017; Wu et al., 2021). However, the absence of an integrated resource management system leads to inappropriate policy decisions, inefficient resource use, and reduced availability of water, food, and energy resources (Howells et al., 2013; Keulertz and Mohtar, 2019; Mohtar et al., 2015).

Owing to population growth and the uncertainty of climate change, food production is required even in the winter when the external temperature is low, and food production through protected cultivation is essential to ensure year-round food security (Ryu et al., 2015; Tilman et al., 2011). Protected cultivation has high productivity and few temporal and spatial constraints. With the focus on food security, protected cultivation areas are increasing gradually (Kim et al., 2011; MAFRA, 2018; Oh and Lee, 2000). Unlike field cultivation, protected cultivation is less affected by external weather conditions because of controlled humidity, temperature, and light inside the greenhouse. In addition, whereas the water used in field cultivation is largely obtained from the effective rainfall, the water used in protected cultivation (for crop growth and environmental control) is supplied artificially. Moreover, crop yield in field cultivation is directly affected by external weather conditions, and crops are cultivated 1–2 times according to the appropriate growing season. In contrast, the productivity and total yield in protected cultivation are high through year-round cultivation by controlling the appropriate growing environment for each crop. However, protected cultivation differs from field cultivation in that energy (cooling and heating, water curtain, ventilation, and drip irrigation) is required to create an appropriate growing environment for the crops (Kim et al., 2011; RDA, 2018; Shin and Nam, 2016). Protected cultivation is thus a water and energy resource-intensive agricultural practice, and input and output resources change according to weather and environmental conditions (FAO, 2013; Lipper et al., 2014; Oh and Lee, 2000; Udink ten Cate, 1983). In South Korea, because the external temperatures in the winter fall below zero, heating is necessary to create a growing environment suitable for crop growth in greenhouses. Therefore, a comprehensive analysis of the appropriate heating temperature, heating energy use, water consumption, and crop yield in the winter is necessary.

The increasing uncertainty of future resource supply due to climate change has increased the importance of resource security (Wu et al., 2021). Accordingly, comprehensive discussions on resource management in relation to resource security and sustainability have been conducted worldwide at various forums. The concept of a nexus to interpret the connection among water, energy, and food resources and to present an integrated management plan for these resources was embodied at the World Economic Forum in 2011 (Ringler et al., 2013). The water-energy-food (WEF) nexus encompasses three important resources (water, food, and energy) that require efficient and integrated management. This concept helps us analyze the interconnections and trade-offs according to changes in each element by considering their interrelationships. Water and energy are required for food production; additionally, energy is required for water intake, water treatment, and distribution. Water is additionally used to produce energy, and in agriculture, energy input through fertilization, cultivation, harvesting, transportation, and irrigation is essential (Mohtar and Daher, 2012; Ringler et al., 2013). In other words, the interrelationships among these nexus systems affect the stress and pressure on each resource. In addition, as the relationship between resources is affected by external environmental conditions such as climate change and economic and population growth, it is necessary to comprehensively analyze and quantitatively evaluate the trade-offs among resources (Cansino-Loeza et al., 2020; Chen et al., 2013; Qin et al., 2022). The nexus used for protected cultivation differs from the general nexus framework for existing paddy fields or field cultivation, and a new nexus framework is required to reflect the agricultural systemic characteristics of protected cultivation. In other words, we can effectively implement resource-specific changes and perform resource-to-resource correlation analysis only by using nexus variables and various scenarios that reflect the particular characteristics of protected cultivation.

The term nexus was coined at the 2008 World Economic Forum meeting, and the term “water-food-energy nexus” was coined at the 2011 Bonn conference under the theme of “Initiating Integrated Solutions for the Green Economy,” emphasizing the need for integrated management of water, energy, and food security (Daher and Mohtar, 2015). The concept of such a nexus begins with the understanding that limited resources are available to achieve the goals of economic growth and human well-being and strives to identify the relationship between resources as well as increase resource efficiency for sustainable development in present and future generations (Hoff, 2011; Keulertz et al., 2016). The water-food-energy nexus is a concept for the integrated management and efficient use of each resource to analyze the trade-off and synergy among water, food, and energy resources. Since the Sustainable Development Goals (SDGs) were proposed in 2015, the relationship between resources has been actively researched. The WEF nexus-related research conducted so far can be divided into scenario-based assessment, integrated assessment modeling, decision support, and data-based models (Namany et al., 2019). Some research studies are focused on conceptual approaches to understanding nexus thinking (Bazilian et al., 2011; Biggs et al., 2015; Ringler et al., 2013; Zhang et al., 2018), and other types of relationships have been identified, including food-energy (Chen et al., 2013; Fingerman et al., 2011; Gheewala et al., 2011) and water-energy (Pittock et al., 2016; Siddiqi and Anadon, 2011; Valek et al., 2017; Vilanova and Balestieri, 2015; Zhou et al., 2019). Mohtar and Daher (2012) analyzed the relationship among the water, food, and energy resource systems constituting the nexus and the effects of external factors and quantitatively presented the water-energy, water-food, and food-energy relationships. In addition, case studies of the trade-offs and synergies using the water-food-energy-environment nexus have been presented for India (water-energy-environmental conflict), Ethiopia (water-energy-environmental synergy), Jordan (energy-water-economic relations), and the United States (energy-environmental conflict) (McCornick et al., 2008). Lawford et al. (2013) constructed a water-food-energy nexus for watersheds in terms of watershed water management and analyzed the quantity and quality of rivers, both nationally and on the border. In addition, climate, land use, energy, water strategies, an integrated and efficient resource management model of water, food, energy, and land resources, was constructed and analyzed by applying climate change scenarios and energy scenarios related to bioethanol production (Howells et al., 2013). Recently, a study was conducted to analyze the interdependence of water, energy, and food through a user-defined scenario-based platform (Daher and Mohtar, 2015), which evaluated the response measures to natural and social conditions based on trade-offs between resources (Daher et al., 2019; Degirmencioglu et al., 2019; Lee et al., 2019; Wen et al., 2022). Studies assessing future resource security using resource index and sustainability were conducted (Cansino-Loeza et al., 2020; de Vito et al., 2017; Fabiani et al., 2020), and Nhamo et al. (2020) developed a WEF nexus analytical model defining WEF nexus sustainability indicators. Wu et al. (2021) quantitatively analyzed the trade-offs and synergy among food, groundwater, hydropower, and greenhouse gas (GHG) emissions using a system dynamics approach and simulated the effect of climate and external conditions on resource sensitivity. In addition, studies were also conducted to calculate and compare the relationship and pressure between the nexus resources and external conditions such as climate change and human activities by adding an ecology system, climate, and land productivity to the WEF nexus structure (Qin et al., 2022). In particular, Duan et al. (2019) analyzed the linkage between resources when the resources are limited, such as in a transboundary region, and the change due to the application of scenarios related to external environmental conditions. Studies including a review of additional methodologies and perspectives for applying the WEF nexus and extended nexus are being conducted (Endo et al., 2017; 2020; Naidoo et al., 2021; Purwanto et al., 2021; Scardigno, 2020).

Therefore, in this study, a WEF-carbon nexus model for protected farms reflecting the agricultural characteristics was constructed. Compared to the open field, protected farms have high productivity but require the input of a large amount of water and energy resources. Among the meteorological factors affected by climate change, changes in temperature have the greatest effect on protected farms, and the heating temperature affects various parameters such as crop yield, irrigation amount, and heating energy. In addition, considering the increase in the uncertainty of weather conditions owing to climate change and the importance of food security, a nexus analysis was performed on the resources according to the heating temperature variable in a protected farm. To analyze the effect of climate change on resources, a sensitivity analysis for each resource according to the heating temperature variable and climate change scenario was performed. Using the AquaCrop model and heating energy load formula, the crop yield, irrigation amount, and heating energy were simulated according to climate change. In addition, resource efficiency and carbon emissions were calculated according to economic and environmental evaluation standards, trade-offs between resources according to climate change and heating temperature variables were analyzed, and appropriate heating temperature standards were presented. Many existing studies focus on analyzing changes in agricultural resources due to climate change or the relationship between the two resources, and nexus studies of various resources compare the simulations for each resource and the productivity or index of resources using statistical data at the national or regional level. However, in this study, based on the physical models, the meteorological conditions, yield, water use, and energy use inside the protected farm were simulated in detail. Based on the greenhouse heating temperature variable, which plays an important role in a protected farm, the effects of variables and climate change on the water-energy-food-carbon (WEFC) nexus were analyzed in terms of resource intensity and environmental impact.