Reducing climate change impacts on agriculture: Global and regional effects of mitigation, 2000–2080

What are the implications for agriculture of mitigating greenhouse gas emissions? By when and by how much are impacts reduced? Where does it matter most? We investigated these questions within the new A2 emission scenario, recently developed at the International Institute of Applied Systems Analysis with revised population and gross domestic product projections. Coupling an agro-ecological model to a global food trade model, two distinct sets of climate simulations were analyzed: 1) A non-mitigated scenario, with atmospheric CO₂ concentrations over 800 ppm by 2100; and 2) A mitigation scenario, with CO₂ concentrations stabilized at 550 ppm by 2100. Impacts of climate change on crop yield were evaluated for the period 1990–2080, then used as input for economic analyses. Key trends were computed over the 21st century for food demand, production and trade, focusing on potential monetary (aggregate value added) and human (risk of hunger) impacts. The results from this study suggested that mitigation could positively impact agriculture. With mitigation, global costs of climate change, though relatively small in absolute amounts, were reduced by 75–100%; and the number of additional people at risk of malnutrition was reduced by 80–95%. Significant geographic and temporal differences were found. Regional effects often diverged from global net results, with some regions worse off under mitigation compared to the unmitigated case.     

Probabilistic temperature change projections and energy system implications of greenhouse gas emission scenarios

This paper explores the implications for global average temperature change of a set of reference and mitigation scenarios in a probabilistic framework. First, we use published probability density functions for climate sensitivity to investigate the likelihood of achieving targets expressed as levels or rates of global average temperature change. We find, for example, that limiting warming to 3 C above pre-industrial levels with at least a medium likelihood requires cumulative emissions reductions on the order of 30-60% below one unmitigated reference scenario by 2100, while a more favorable baseline scenario requires no reductions at all to achieve this outcome with the same likelihood. We further conclude that the rate of temperature change may prove to be more difficult to control, especially if most of the mitigation effort is postponed until later in the century. Rate of change targets of 0.1–0.2 °C/decade are unlikely to be achieved by a target for the long-term level of climate change alone. Second, we quantify relationships between mitigation costs and the likelihood of achieving various targets and show how this depends strongly on the reference scenario. Third, we explore relationships between medium-term achievements and long-term climate change outcomes. Our results suggest that atmospheric concentrations and the share of zero-carbon energy in the middle of the 21st century are key indicators of the likelihood of meeting long-term climate change goals cost-effectively. They also suggest that interim targets could be an effective means of keeping long-term target options open. Our analysis shows that least-cost mitigation strategies for reaching low climate change targets include a wide portfolio of reduction measures. In particular, fundamental long-term structural changes in the energy system in these scenarios are a necessary but not sufficient condition to achieve high likelihoods for low temperature targets. The cost-effective portfolio of emissions reductions must also address demand-side measures and include mitigation options in the industry, agriculture, and the forest sector.     

Long-term global water projections using six socioeconomic scenarios in an integrated assessment modeling framework

In this paper, we assess future water demands for the agricultural (irrigation and livestock), energy (electricity generation, primary energy production and processing), industrial (manufacturing and mining), and municipal sectors, by incorporating water demands into a technologically-detailed global integrated assessment model of energy, agriculture, and climate change — the Global Change Assessment Model (GCAM). Base-year water demands – both gross withdrawals and net consumptive use – are assigned to specific modeled activities in a way that maximizes consistency between bottom-up estimates of water demand intensities of specific technologies and practices, and top-down regional and sectoral estimates of water use. The energy, industrial, and municipal sectors are represented in fourteen geopolitical regions, with the agricultural sector further disaggregated into as many as eighteen agro-ecological zones (AEZs) within each region. We assess future water demands representing six socioeconomic scenarios, with no constraints imposed by future water supplies. The scenarios observe increases in global water withdrawals from 3710 km³ year^− 1 in 2005 to 6195–8690 km³ year^− 1 in 2050, and to 4869–12,693 km³ year^− 1 in 2095. Comparing the projected total regional water withdrawals to the historical supply of renewable freshwater, the Middle East exhibits the highest levels of water scarcity throughout the century, followed by India; water scarcity increases over time in both of these regions. In contrast, water scarcity improves in some regions with large base-year electric sector withdrawals, such as the USA and Canada, due to capital stock turnover and the almost complete phase-out of once-through flow cooling systems. The scenarios indicate that: 1) water is likely a limiting factor in meeting future water demands, 2) many regions can be expected to increase reliance on non-renewable groundwater, water reuse, and desalinated water, but they also highlight an important role for development and deployment of water conservation technologies and practices.     

An analysis of public adaptation to climate change using agricultural water schemes in South America

This paper provides an analysis of public adaptation to climate change using agricultural water schemes in South American farms. Unlike other studies of adaptation, this paper examines the differences between private irrigation and public irrigation schemes based on around 1400 farm surveys collected across seven countries in South America which recorded detailed water schemes. We analyze the choice of water schemes in the first stage and the land values for each scheme in the second stage. We find that public irrigations do not increase in response to a warmer climate, but private irrigations do. On the other hand, we find that public irrigation schemes are provided primarily as a response to water scarcity. Moreover, we find that private irrigations are taken gradually while public irrigations are provided as a lump sum, resulting in either too much or too little provision. Therefore, public adaptations to climate change will likely involve two inefficiencies. No provision of irrigation in a hotter climate may result from a lack of knowledge. Overprovision of irrigation in dry zones may result from a lump-sum provision of a public good.     

An integrated analysis of the effects of local water institutions on irrigated agriculture outcomes in the arid western United States

Irrigation water rights and their governance structures constitute the foundation of local water institutions and profoundly influence water resource allocations, irrigated agricultural productivity and other consumptive water uses in the arid climate zones. This article explores the regional structures of irrigation water rights and water governance and empirically analyses the priority effects of water rights on irrigated agriculture at the micro level in Idaho, an arid and semiarid state in the western United States. We integrate a unique data set of water rights and water supplies with agricultural features and environmental characteristics into our empirical analysis. Results indicate that seniority in water resources allocation has significant, positive effects on both the average crop revenue and crop water use efficiency. Local water rights structures differ significantly in seniority and water sources from region to region. In response to the heterogeneity in local water rights structures, the aforementioned effect of allocative priority of water rights on average crop revenue per hectare and crop water productivity varies significantly, reaching up to an 87% difference, when measured across regions. In addition, the priority effects of water rights are nonlinear, which reflects the influence of historical patterns of water rights establishment on water institutions to date.     

Geographically explicit global modeling of land-use change, carbon sequestration, and biomass supply

This study aims to determine whether carbon sequestration policies could present a significant contribution to the global portfolio of climate change mitigation options. The objective is to model the effects of policies designed to induce landowners to change land use and management patterns with a view to sequester carbon or to reduce deforestation. The approach uses the spatially explicit Dynamic Integrated Model of Forestry and Alternative Land Use (DIMA) to quantify the economic potential of global forests. The model chooses which of the land-use processes (afforestation, reforestation, deforestation, or conservation and management options) would be applied in a specific location, based on land prices, cost of forest production and harvesting, site productivity, population density, and estimates of economic growth. The approach is relevant in that it (1) couples a revised and updated version of the Special Report on Emissions Scenarios with the dynamic development of climate policy implications through integration with the Model for Energy Supply Strategy Alternatives and their General Environmental Impact (MESSAGE); (2) is spatially explicit on a 0.5° grid; and (3) is constrained by guaranteeing food security and land for urban development. As outputs, DIMA produces 100-year forecasts of land-use change, carbon sequestration, impacts of carbon incentives (e.g., avoided deforestation), biomass for bioenergy, and climate policy impacts. The modeling results indicate that carbon sequestration policies could contribute to a significant part of the global portfolio of efficient climate mitigation policies, dependent upon carbon prices.     

Local irrigation response to ethanol expansion in the High Plains Aquifer

Global ethanol production has grown rapidly due to national renewable fuel programs. Concern has grown over impacts that land conversion and crop displacement driven by ethanol feedstock production might have on water resources. In this paper, we examine irrigation decisions of agricultural producers in the Kansas portion of the High Plains Aquifer in response to local ethanol market expansion. To identify the effects of ethanol expansion on irrigation decisions, we examine field-level data on irrigation water use, irrigated acreage, and crop decisions for the years 2003–2017 for nearly 23,000 fields in Kansas. We measure the response of three irrigation decisions, (i) irrigated acreage, (ii) irrigation per acre, and (iii) total water use to the introduction and capacity expansion of an ethanol plant. We find that ethanol market expansion did lead to increases in irrigation water use. Specifically, a 10 % increase in ethanol capacity within 50KM increases annual water use by 0.22 % per field (4.8 acre-inches/field). We predict that ethanol markets accounted for about 4% of total irrigated water use in 2017.     

Climate change and spatial agricultural development in Turkey

This paper investigates the impact of climate change on the spatial distribution of agricultural production in Turkey between 2004 and 2019. Our findings show that climate change has a pervasive impact on agricultural development. The empirical results show that the average temperature is negatively associated with agricultural land use, grain, and legume production. Moreover, regional variability analyses reveal the nonmonotonic relationships between climatic factors and agricultural output. Climate change hurts agricultural production in northern and central regions the most. This finding points out the ineffectiveness of one-size-fits-all-type policies for mitigating the adverse effects of climate change in topography with sizeable spatial dissimilarities. Overall, our results suggest that climate change will significantly threaten the evolution of agricultural activities that are critical for regional development. In addition, findings show that spatial spillovers and heterogeneity will be crucial for designing climate change policies for rural and agricultural development.     

An analysis of irrigated agricultural outcomes under the prior appropriation doctrine: hypotheses and applications

This article measures irrigated agricultural outcomes under the prior appropriation doctrine by developing a model of farmers’ land allocations in response to water supply change. The modelling approach considers the institutional factors of water rights and permits the inclusive determination of water and land allocations. We utilize farm-level data of irrigated agriculture in Water District #1 in Idaho to examine the predictions from our theoretical model. The water rights priority date is consolidated at the farm level and used to differentiate farmers’ responses. We test a set of hypotheses that relate to water supply and crop revenue. Our results suggest that the water rights priority has a profound impact on agricultural outcomes, indicating strong institutional effects and weak influence of market-based approaches. Farmers respond to both long-term and seasonal water supply change and variation, and they respond to seasonal water supply forecasts in varied ways depending on their water rights portfolios, thus signalling a disproportionate distribution of potential impacts of water supply change.     

Economywide impacts of climate change on agriculture in Sub-Saharan Africa

Two possible adaptation scenarios to climate change for Sub-Saharan Africa are analyzed under the SRES B2 scenario. The first scenario doubles the irrigated area in Sub-Saharan Africa by 2050, compared to the baseline, but keeps total crop area constant. The second scenario increases both rainfed and irrigated crop yields by 25% for all Sub-Saharan African countries. The two adaptation scenarios are analyzed with IMPACT, a partial equilibrium agricultural sector model combined with a water simulation module, and with GTAP-W, a general equilibrium model including water resources. The methodology combines the advantages of a partial equilibrium approach, which considers detailed water-agriculture linkages, with a general equilibrium approach, which takes into account linkages between agriculture and nonagricultural sectors and includes a full treatment of factor markets. The efficacy of the two scenarios as adaptation measures to cope with climate change is discussed. Due to the limited initial irrigated area in the region, an increase in agricultural productivity achieves better outcomes than an expansion of irrigated area. Even though Sub-Saharan Africa is not a key contributor to global food production (rainfed, irrigated or total), both scenarios help lower world food prices, stimulating national and international food markets.     

低碳农业发展核心目标:减缓和适应气候变化

减缓和适应是人类应对气候变化行动中两种相辅相成的措施。中国农业在应对气候变化中,减缓和适应同等重要:一方面,农业在减缓气候变化中具有独特的作用;另一方面,农业适应气候变化比减缓气候变化更为现实的迫切。积极发展低碳现代农业实现减排增汇,中国农业生态系统可以作为一种非常重要的固碳增汇措施,纳入全球CO2减排措施中去。中国低碳农业在减缓和适应气候变化中具有巨大潜力。     

Adoption of climate change mitigation practices by risk-averse farmers in the Ashanti Region,Ghana

Uncertainty and risk-aversion are notably absent in the modeling of farmers' adoption of climate change mitigation practices in developing countries even though most of the agricultural mitigation practices also have effects on yield variability. The objective of this paper is to explore the implications for climate change mitigation projects of modeling farmers as risk neutral while in actuality they behave as risk-averse agents. Results indicate that when risk averse farmers are modeled as risk-neutral agents, the size of the incentives needed to induce participation to a carbon sequestration program is miscalculated with serious implications either for the success for projects that aim at compensating for climate change mitigation services or for the economic efficiency of such projects.     

International climate regimes: Effects of delayed participation

This paper analyses how delayed participation by regions can affect international climate regimes in terms of the feasibility, costs, timing, magnitude and nature of the long-term mitigation response. We use the energy-systems optimization model MESSAGE to construct several climate change mitigation scenarios with various levels of regional participation in short-to-mid term. By comparing these with a global scenario that assumes full spatial and temporal flexibility throughout the century, we are able to evaluate how participatory decisions affect the mitigation response as well as the costs and technology choices. We find that short-term postponement of participation from some regions can often lead to a delay of mitigation measures on the global level. However, if the regional delay lasts until mid-century, participants of the regime are likely to increase their efforts in the short term. Mitigation costs are found to substantially increase as a result of delayed participation—the extent of the increase depends on the relative importance of the region that postpones its participation, the stringency of the climate target and the ability to reorganize mitigation measures. Our analysis also shows that a region's decision to delay its participation in an international climate regime can lead to accumulated inertia in its energy system and thus to a delayed ‘technological transition’ toward a low-carbon future.     

The projected costs and benefits of water diversion from and to the Sultan Marshes (Turkey)

The Sultan Marshes in the Develi Basin, Anatolia, one of twelve internationally important wetlands of Turkey, have been severely affected by the construction of an irrigation project in 1988. Intensive use of surface and ground water in irrigation has caused more than a 1 m decline in water levels and has affected the wetlands' ecological characteristics. Previous studies indicate that Sultan Marshes will need more water to restore viable ecological conditions. In this study, we analyze how economic benefits from agriculture and wetlands would be affected if moderate amounts of water were diverted from agriculture back to wetlands in the Develi Basin. By estimating total and marginal costs and benefits associated with water diversions, we determined the optimum or economically-efficient amount of water diversion. When only direct-use values of the wetland (animal grazing, plant harvesting, and ecotourism) were included in the analysis, the optimum amount of water diversion to the wetlands was found to be 5.2 million m³ year^− 1 (165 L sec^− 1), which compares to about 62 million m³ year^− 1 (1,957 L sec^− 1) used in irrigation. When wastewater treatment benefits (an indirect-use value) were added, the optimum amount rose to 7 million m³ year^− 1. Overall, the analysis showed that water diversion from agriculture to the Sultan Marshes is economically preferable.     

Basin impacts of irrigation water conservation policy

Climate change, uncertain future water supplies, growing population, and increased water demands continue to raise the importance of finding cost-effective water conservation measures. Irrigated agriculture is the world's largest water user, so governments, donor organizations, water suppliers, and farmers continue to look for measures that would produce more crop per drop. Despite the importance of promoting water conservation in agriculture, little work has been done that integrates hydrologic, economic, institutional, and policy dimensions of water conservation. This paper presents an integrated basin scale analysis of water conservation subsidies for irrigated agriculture. A dynamic, nonlinear programming model is developed and applied for the Upper Rio Grande Basin of Colorado, New Mexico, and Texas, USA. Several potential public subsidies of drip irrigation are analyzed for their economic and hydrologic impacts at both the farm and basin levels. Results indicate that water conservation subsidies for drip irrigation produce several effects. These include greater on-farm implementation of water-conserving technology, less water applied to crops, more water consumed by crops, increased farm income, greater crop production, more land irrigated, and increased total water-related economic benefits for the basin. Findings provide a framework for designing and implementing water conservation policies for irrigated agriculture.     

Scenarios of long-term socio-economic and environmental development under climate stabilization

This paper presents an overview of the greenhouse gas (GHG) emissions scenarios that form the analytical backbone for other contributions to this Special Issue. We first describe the motivation behind this scenario exercise and introduce the main scenario features and characteristics, in both qualitative and quantitative terms. Altogether, we analyze three ‘baseline’ scenarios of different socio-economic and technological developments that are assumed not to include any explicit climate policies. We then impose a range of climate stabilization targets on these baseline scenarios and analyze in detail the feasibility, costs and uncertainties of meeting a range of different climate stabilization targets in accordance with Article 2 of the United Nations Framework Convention on Climate Change. The scenarios were developed by the IIASA Integrated Assessment Modeling Framework that encompasses detailed representations of the principal GHG-emitting sectors—energy, industry, agriculture, and forestry. The main analytical findings from our analysis focus on the implications of salient uncertainties (associated with scenario baselines and stabilization targets), on feasibility and costs of climate stabilization efforts, and on the choice of appropriate portfolios of emissions abatement measures. We further analyze individual technological options with regards to their aggregated cumulative contribution toward emissions mitigation during the 21st century as well as their deployment over time. Our results illustrate that the energy sector will remain by far the largest source of GHG emissions and hence remain the prime target of emissions reduction. Ultimately, this may lead to a complete restructuring of the global energy system. Climate mitigation could also significantly change the relative economics of traditional versus new, more climate friendly products and services. This is especially the case within the energy system, which accounts for the largest share of emissions reductions, but it is also the case in the agriculture and forestry sectors, where emissions reduction and sink enhancement measures are relatively more modest.     

Substitution between water and other agricultural inputs: Implications for water conservation in a River Basin context

Substitution of irrigation water with other agricultural inputs could be an important means to conserve water in the face of growing pressures on water resources from both nonagricultural water demands and environmental water requirements. This paper discusses the potential of such substitution through an empirical analysis based on a multiple-input crop production function at the field and farm scales complemented with a numerical modeling exercise at the basin scale. Results from the crop production function analysis show that under both crop yield and net profit maximization, water is a substitute to other crop inputs for high-value crops, and is a complement to water for low-valued crops. At the basin scale, an integrated economic-hydrologic river basin model is used to analyze the role of other factors in crop input substitution, including the spatial connections among water sources and demands, hydro-agronomic conditions, and institutional settings for water allocation. Results show that in the case study area, the Maipo River basin in Chile, where water is very scarce, moving from the current, input-constrained, situation to full optimization of water resources leads to an increase in all crop inputs, including water. In that case, 301 million m³ of additional water use results in additional net profits of USD 11 million. However, if the water fee is raised by a factor of eight while overall basin irrigation profits are maintained at the original, baseline level, a reduction of water withdrawals by 326 million m³ is traded off with costs of USD 43.2 million for other inputs. Irrigation districts with a high share of low-value crops have a low potential for substituting water with other crop inputs. Therefore, investments for water substitution should also be kept low in these areas.     

Estimating a socially optimal water price for irrigation versus an environmentally optimal water price through the use of Geographical Information Systems and Social Accounting Matrices

This article develops a method for establishing water prices and their effects in order to provide policy makers an environmentally and socially optimal range of regional prices for irrigation water. Two prices are determined. The “environmentally optimal price” of water is defined as the one that internalizes the environmental costs generated by agricultural consumption. The “social optimally price” of water is defined as the one that maximizes levies on water for agriculture without affecting the regional economy. The environmentally optimal price is calculated with an economic model built over a Geographical Information System (GIS) that allows the economic quantification and valuation of the environmental cost of water in different basins. The optimal price is calculated with a demand curve for irrigation water introduced into a Social Accounting Matrix (SAM) to observe if the regional economy can accept higher prices without affecting the regional GDP. Potential water prices are established, ranging from prices that minimize the negative impact in the regional economy to those that totally internalize the environmental cost of water.     

Willingness to Pay for Ancillary Benefits of Climate Change Mitigation

Assessing the Willingness to Pay (WTP) of the general public for climate change mitigation programmes enables governments to understand how much taxpayers are willing to support the implementation of such programs. This paper contributes to the literature on the WTP for climate change mitigation programmes by investigating, in addition to global benefits, the ancillary benefits of climate change mitigation. It does so by considering local and personal benefits arising from climate change policies. The Contingent Valuation Method is used to elicit the WTP for ancillary and global benefits of climate mitigation policies in the Basque Country, Spain. Results show that WTP estimates are 53–73% higher when ancillary benefits are considered.     

The water footprint of energy from biomass: A quantitative assessment and consequences of an increasing share of bio-energy in energy supply

This paper assesses the water footprint (WF) of different primary energy carriers derived from biomass expressed as the amount of water consumed to produce a unit of energy (m³/GJ). The paper observes large differences among the WFs for specific types of primary bio-energy carriers. The WF depends on crop type, agricultural production system and climate. The WF of average bio-energy carriers grown in the Netherlands is 24 m³/GJ, in the US 58 m³/GJ, in Brazil 61 m³/GJ, and in Zimbabwe 143 m³/GJ. The WF of bio-energy is much larger than the WF of fossil energy. For the fossil energy carriers, the WF increases in the following order: uranium (0.1 m³/GJ), natural gas (0.1 m³/GJ), coal (0.2 m³/GJ), and finally crude oil (1.1 m³/GJ). Renewable energy carriers show large differences in their WF. The WF for wind energy is negligible, for solar thermal energy 0.3 m³/GJ, but for hydropower 22 m³/GJ. Based on the average per capita energy use in western societies (100 GJ/capita/year), a mix from coal, crude oil, natural gas and uranium requires about 35 m³/capita/year. If the same amount of energy is generated through the growth of biomass in a high productive agricultural system, as applied in the Netherlands, the WF is 2420 m³. The WF of biomass is 70 to 400 times larger than the WF of the other primary energy carriers (excluding hydropower). The trend towards larger energy use in combination with an increasing contribution of energy from biomass will enlarge the need for fresh water. This causes competition with other claims, such as water for food.