Modeling climate change and agriculture: an introduction to the special issue

This issue of Agricultural Economics is a special issue containing articles on model performance in assessing the effects of climate change, bioenergy policy, and socioeconomics on agriculture. The contributions present results from a global economic model intercomparison activity undertaken as part of the AgMIP Project ( www.agmip.org ). The origins of the comparison activities can be traced to a project that was organized by the OECD in late 2010 to compare results from three models. The current phase of the research includes 10 models and was designed in part to support of the IPCC fifth assessment report (AR5). The special issue includes seven peer‐reviewed articles that present thematic results from a range of modeling strategies, with partial and general equilibrium modeling as a high level distinction but a myriad of differences within these two model types. A central common element is harmonization on biophysical effects using crop models and socioeconomic effects using drivers from the Shared Socioeconomic Pathways developed as part of the AR5 process. The special issue provides broad insights into how the modeling communities approached the interactions of climate, socioeconomics, bioenergy policy on agricultural outcomes, including land use, prices, consumption, and production.     

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.     

人工湿地植物能源化利用的机遇、挑战与展望

综合概述了利用人工湿地植物进行能源化再生产的方式、优势、存在问题和发展趋势。人工湿地植物具有生长不需额外施肥、较高的生物量、物种多样化等优势,是一种较好的生物质资源,可通过生物质固体成型燃料技术、沼气技术和燃料乙醇技术加以利用,进而建立人工湿地植物生物质能源化利用模式,实现应对能源挑战、进行污水处理和强化环境保护三者的有机统一。     

Why do global long‐term scenarios for agriculture differ? An overview of the AgMIP Global Economic Model Intercomparison

Recent studies assessing plausible futures for agricultural markets and global food security have had contradictory outcomes. To advance our understanding of the sources of the differences, 10 global economic models that produce long‐term scenarios were asked to compare a reference scenario with alternate socioeconomic, climate change, and bioenergy scenarios using a common set of key drivers. Several key conclusions emerge from this exercise: First, for a comparison of scenario results to be meaningful, a careful analysis of the interpretation of the relevant model variables is essential. For instance, the use of “real world commodity prices” differs widely across models, and comparing the prices without accounting for their different meanings can lead to misleading results. Second, results suggest that, once some key assumptions are harmonized, the variability in general trends across models declines but remains important. For example, given the common assumptions of the reference scenario, models show average annual rates of changes of real global producer prices for agricultural products on average ranging between ?0.4% and +0.7% between the 2005 base year and 2050. This compares to an average decline of real agricultural prices of 4% p.a. between the 1960s and the 2000s. Several other common trends are shown, for example, relating to key global growth areas for agricultural production and consumption. Third, differences in basic model parameters such as income and price elasticities, sometimes hidden in the way market behavior is modeled, result in significant differences in the details. Fourth, the analysis shows that agro‐economic modelers aiming to inform the agricultural and development policy debate require better data and analysis on both economic behavior and biophysical drivers. More interdisciplinary modeling efforts are required to cross‐fertilize analyses at different scales.     

Woody biomass potential for energy feedstock in United States

The production reliability and relatively low costs of sustainably harvested woody biomass such as logging residue and low value roundwood could make it a significant component of the Renewable Fuel Standards portfolio. This research explored a set of woody biomass harvesting combinations of different sources and wood types using a cost minimizing linear programming model populated with disaggregated regional inventory, yield, and cost data, and projected future conventional wood demand of the United States. The model pre-satisfied conventional wood demand before harvesting roundwood as woody biomass. Findings suggest that collecting forest residue and non-merchantable (small sized) timber may provide the largest initial contribution in woody biomass supply. Regional estimations imply that not all regions have the capacity to develop bioenergy plants without using merchantable (medium sized) wood. Within a reasonable range of harvesting costs, demand for roundwood is expected to increase with higher energy production targets. Harvesting merchantable natural softwood as woody biomass has a relatively small impact on marginal supply costs. This will result in little or no disturbance to merchantable natural softwood timber management and operations if demand for woody biomass increased.     

The effect of spatial variables on the economic and environmental performance of bioenergy production chains

The aim of this paper is to understand the impacts of spatial variables on the performance of bioenergy production chains (BPCs). Even though the strong debates continue on the use of first generation biomass for bioenergy production, many countries continue to utilize it as an alternative energy source. Several studies have been carried out on biomass transformation efficiency, on environmental impacts of using crop in biofuel production, and on its negative effects on increasing food prices. However, less attention has been paid to the role played by the spatial variables on the performance measures of BPCs.In this paper, we analyse how three spatial variables, i.e. cultivation area size, land dispersion, and accessibility to cultivation areas, can affect the performance of energy-balanced BPC, which produces its own electric and thermal energy demand. The chain is represented as a network of processes, where all inputs and outputs are geographically referred and analysed in a theoretical case example. We propose an enterprise input-output (EIO) model, which can be used as an accounting tool to compute the main materials and energy flows-related costs and as a planning tool to evaluate the chain performance in different scenarios. Finally, the proposed model is applied to an actual case study, to investigate the opportunity to establish a sunflower-based BPC in Apulia region (Italy) and to assess its performance.Results show that higher land dispersion degree and less area accessibility levels reduce the economic and environmental performance of the BPCs. The construction of the energy-balanced chain reduces the negative environmental impacts caused by fossil energy use in the processes of the BPC. Managerial implications can also be obtained from actual case study about the biodiesel plant location decisions.     

An assessment of the influence of bioenergy and marketed land amenity values on land uses in the Midwestern US

There is substantial concern that bioenergy policies could swamp other considerations, such as environmental values, and lead to large-scale conversions of land from forest to crops. This study examines how bioenergy and marketed environmental rents for forestland potentially influence land use in the Midwestern US. We hypothesize that current land uses reflect market values for environmental benefits of forestland, so that the marketed component of the environmental value of land can be captured as the difference between Census land values and value of land as a timber asset. We use a multinomial logit model to estimate the land use shares of forests, crops and urban in Ohio, Indiana, and Illinois. The results show that marketed environmental rents increase forestland relative to cropland. To examine the effects of biofuels on land use, we conduct policy analysis by altering future land rents. Our baseline scenario projects that urban development uses mostly cropland, but with higher crop rents resulting from increased demand for bioenergy, there will be significant losses of forestland to urban and cropland. On the other hand, if marketed environmental rents grow while crop rents are maintained at their baseline value, urban growth will occur, primarily at the expense of cropland.     

A study on the bioenergy crop production function of land use in China

Based on the analysis of the bioenergy crop production function of land use,combined with the status quo of Chinese land use,the cultivation of energy plants and the bioenergy crop production function of land use had been analyzes and discusses in this paper.Results show that there were a lot of unused lands and marginal lands which can be planted bioenergy crops to perform the bioenergy crop production function of land use with great potentials; and currently there were no food production problems.Therefore,it was very important for China to emphasize bioenergy crops planting in order to fully use land resources in our country,moderate the energy crisis and increase peasants＇ income.     

A multi-sector intertemporal optimization approach to assess the GHG implications of U.S. forest and agricultural biomass electricity expansion

This study applies an intertemporal partial equilibrium model of the U.S. Forest and Agricultural sectors to assess the market, land use, and greenhouse gas (GHG) implications of biomass electricity expansion. Results show how intertemporal optimization procedures can yield different biomass feedstock portfolios and GHG performance metrics at different points in time. We examine the implications of restricting feedstock eligibility, land use change, and commodity substitution to put our results in the context of previous forest-only modeling efforts. Our results highlight the importance of dynamic considerations and forest and agricultural sector interactions on projecting the GHG effects of biomass electricity expansion in the U.S.     

Beyond biofuels: Assessing global land use for domestic consumption of biomass: A conceptual and empirical contribution to sustainable management of global resources

Consumption of natural resources should not exceed sustainable levels. The increasing use of biofuels and to some extent biomaterials, on top of rising food and feed demands, is causing countries to use a growing amount of global land, which may lead to land use conflicts and the expansion of cropland and intensive cultivation at the expense of natural ecosystems. Selective product certification cannot control the land use change triggered by growing overall biomass consumption. We propose a comprehensive approach to account for the global land use of countries for their domestic consumption, and assess this level with regard to globally acceptable levels of resource use, based on the concept of safe operating space. It is shown that the European Union currently uses one-third more cropland than globally available on a per capita basis and that with constant consumption levels it would exceed its fair share of acceptable resource use in 2030. As the use of global forests to meet renewable energy targets is becoming a concern, an approach to account for sustainable levels of timber flows is also proposed, based on the use of net annual increment, exemplified with preliminary data for Switzerland. Altogether, our approach would integrate the concept of sustainable consumption into national resource management plans; offering a conceptual basis and concrete reference values for informed policy making and urging countries to monitor and adjust their levels of resource consumption in a comprehensive way, respectful of the limits of sustainable supply.