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.     

我国海岛地区土地节约与集约利用研究——以舟山市为例

土地问题是我国现代化进程中的一个带有全局性、战略性的重大问题,土地的节约与集约利用是实现经济社会可持续发展的必然要求;海岛地区独特的自然地理条件决定其土地节约与集约利用必然也具有其特殊性;以浙江省舟山市为例,探讨在海岛这一特殊的地理环境下如何解决经济发展与土地短缺的矛盾,并为海岛地区土地节约与集约利用提出了一些合理的对策建议.     

Why have land use change models for the Amazon failed to capture the amount of deforestation over the last decade?

Land cover change in the Neotropics represents one of the major drivers of global environmental change. Several models have been proposed to explore future trajectories of land use and cover change, particularly in the Amazon. Despite the remarkable development of these tools, model results are still surrounded by uncertainties. None of the model projections available in the literature plausibly captured the overall trajectory of land use and cover change that has been observed in the Amazon over the last decade. In this context, this study aims to review and analyze the general structure of the land use models that have most recently been used to explore land use change in the Amazon, seeking to investigate methodological factors that could explain the divergence between the observed and projected rates, paying special attention to the land demand calculations. Based on this review, the primary limitations inherent to this type of model and the extent to which these limitations can affect the consistency of the projections will also be analyzed. Finally, we discuss potential drivers that could have influenced the recent dynamic of the land use system in the Amazon and produced the unforeseen land cover change trajectory observed in this period. In a complementary way, the primary challenges of the new generation of land use models for the Amazon are synthesized.     

Competition for land in the global bioeconomy

The global land use implications of biofuel expansion have received considerable attention in the literature over the past decade. Model‐based estimates of the emissions from cropland expansion have been used to assess the environmental impacts of biofuel policies. And integrated assessment models have estimated the potential for biofuels to contribute to greenhouse gas (GHG) abatement over the coming century. All of these studies feature, explicitly or implicitly, competition between biofuel feed stocks and other land uses. However, the economic mechanisms governing this competition, as well as the contribution of biofuels to global land use change, have not received the close scrutiny that they deserve. The purpose of this article is to offer a deeper look at these factors. We begin with a comparative static analysis which assesses the impact of exogenously specified forecasts of biofuel expansion over the period: 2006–2035. Global land use change is decomposed according to the three key margins of economic response: extensive supply, intensive supply, and demand. Under the International Energy Agency's “New Policies” scenario, biofuels account for nearly one‐fifth of global land use change over the 2006–2035 period. The article also offers a comparative dynamic analysis which determines the optimal path for first and second generation biofuels over the course of the entire 21st century. In the absence of GHG regulation, the welfare‐maximizing path for global land use, in the face of 3% annual growth in oil prices, allocates 225 Mha to biofuel feed stocks by 2100, with the associated biofuels accounting for about 30% of global liquid fuel consumption. This area expansion is somewhat diminished by expected climate change impacts on agriculture, while it is significantly increased by an aggressive GHG emissions target and by advances in conversion efficiency of second generation biofuels.     

Introduction to the special issue on spatial analysis for agricultural economists

The goal of this special issue is to introduce agricultural economists to new analytical approaches involving spatial data. This paper provides a brief history of the special issue and an introduction to von Thünen's model of the determinants of land use and rent that underlies all spatial analysis.     

Agricultural land use pattern dynamics in the Sudan–Sahel—towards an event-driven framework

While addressing the issue of field encroachment and land use pattern changes in the desert margin regions, the paper proposes to develop a model which recognises land use pattern changes as event-driven. The picture that underpins development efforts and policy papers for environmental improvement in the Sudan–Sahel region often describes changes in agricultural landscape systems as a unidirectional expansion of fields onto marginal land in response to population pressure and resource degradation. It is proposed that models of land use pattern trajectories as well as of resilience of land use systems have to recognise a strong random element related to unforeseeable events.     

土地整理项目PPP模式研究综述

在土地整理中引入PPP模式,能够解决资金不足,项目效率低下等问题。通过文献资料法和比较研究法,对国内外关于土地整理项目PPP模式的研究进行全面综述。从目前研究看,学者多半将重点放在PPP模式运用到公共基础设施中的重要意义、技术问题、成功的关键因素以及项目风险分担等问题,专门关于土地整理项目PPP模式的研究较少,只有一些学者从融资的角度研究PPP模式在土地整理项目中的运用。基于现有研究的基础上,提出了PPP模式运用到土地整理项目需进一步深入研究的方向。     

集体土地所有权法律制度研究

土地所有权问题是我国民法典立法和物权立法所要解决的一个重要方面。集体土地所有权问题更是当前亟需从法律上调整解决的核心问题。明晰农村集体土地所有权主体 ,充分尊重集体土地所有权益 ,实现司法上的“合法财产权一体保护”和土地资源的优化配置 ,关系中国现代化进程中深化土地使用制度改革、保护农民利益、推动经济发展和维持社会稳定的大局。本文试图从法理上廓清集体土地所有权的性质、主体以及权利行使、收益分配问题 ,并提出对农用地、建设用地、宅基地等集体土地使用权流转的相应立法建议。     

Global food demand,productivity growth,and the scarcity of land and water resources: a spatially explicit mathematical programming approach

In the coming decades, an increasing competition for global land and water resources can be expected, due to rising demand for food and bio‐energy production, biodiversity conservation, and changing production conditions due to climate change. The potential of technological change in agriculture to adapt to these trends is subject to considerable uncertainty. In order to simulate these combined effects in a spatially explicit way, we present a model of agricultural production and its impact on the environment (MAgPIE). MAgPIE is a mathematical programming model covering the most important agricultural crop and livestock production types in 10 economic regions worldwide at a spatial resolution of three by three degrees, i.e., approximately 300 by 300 km at the equator. It takes regional economic conditions as well as spatially explicit data on potential crop yields and land and water constraints into account and derives specific land‐use patterns for each grid cell. Shadow prices for binding constraints can be used to valuate resources for which in many places no markets exist, especially irrigation water. In this article, we describe the model structure and validation. We apply the model to possible future scenarios up to 2055 and derive required rates of technological change (i.e., yield increase) in agricultural production in order to meet future food demand.     

Green Light for Green Agricultural Policies? An Analysis at Regional and Global Scales

This paper analyses the effects of introducing biodiversity‐targeted ecological focus area (EFA) requirements on all farms with arable land in the EU by quantifying their global, regional, economic and environmental impacts in a mutually consistent way. To capture these impacts, different spatial scales need to be considered – ranging from on‐farm decisions regarding the EFA in the EU, to supply response around the world. In order to address this challenge, we combine the supply side of the CAPRI model, which offers high spatial, farm and policy resolution in the EU, with the GTAP model of global trade and land use. Both models are linked through a multi‐product, restricted‐revenue function for the EU crop sector. The results predict improved environmental status in the high‐yielding regions of the EU. However, output price increases lead to intensification in the more marginal areas of the EU where little or no additional land is taken out of production. The decrease in arable land in the EU is partially compensated by an increase of crop land, as well as increased fertiliser applications, in other regions of the globe. Thus, the improvement of environmental status in the EU comes at the price of global intensification, as well as the loss of forest and grassland areas outside the EU. Overall, we find that every hectare of land that is taken out of production in the EU increases greenhouse gas emissions in the rest of the world by 20.8 tonnes CO₂ equivalent.     

耕地质量监测预警研究进展

耕地质量是人类社会赖以生存与发展的物质基础,是农业发展的基本生产资料。为发挥监测预警体系在耕地质量建设中的主体作用,实现耕地质量的可持续利用,本文采用文献综述法和系统分析法综述了耕地质量监测和预警体系在国内外的研究进展,并着重对时间序列分析模型、灰色预测模型和回归分析模型三种耕地质量预警模型进行阐述。耕地质量监测预警体系具有实时、动态、全方位的监测与预警功能,对监测预警指标体系、方法、周期、模型和理论实践探究还需要进一步完善,同时还需要借助应用大数据,以期为耕地质量精准化监测预警提供实时的数据及模型支持服务。     

Abstracts of Award-Winning Theses

This thesis determines the tradeoff between producer welfare and the provision of environmental benefits, through reduced soil erosion and fertilizer applications, on agricultural working land. A land-use allocation model of two Iowa counties is formulated as a mathematical programming problem, building upon the Takayama and Judge framework. Slope is used to reflect terrain heterogeneity, such that the spatial allocation of land-use practices impacts economic and environmental outcomes via a yield damage function and differentiated rates of soil erosion. The model differs from prior empirical models in that it includes both crop and livestock production, which gives the model the flexibility to choose whether the two activities are optimally nonseparable.
Price policy analysis indicates that the land use allocation is relatively insensitive to changes in commodity prices, i.e., altering commodity-based support payments is insufficient to attain environmental improvements. Several "green" policy instruments are simulated to estimate the cost to producers of reducing environmental damages. Limiting soil erosion with either a regulatory standard or a per unit tax reduces the average return to land by 10%. Shifting current income support payments into a system of payments for conservation land management practices, similar in essence to the Conservation Security Program, cannot attain the same soil erosion reduction with less cost to producers. Overall, the inelastic response of land use practices to commodity prices indicates that targeting the use of productive inputs, as opposed to commodity outputs, may be a more efficient means of attaining environmental improvements.     

Geographical downscaling of outputs provided by an economic farm model calibrated at the regional level

There is a strong need for accurate and spatially referenced information regarding policy making and model linkage. This need has been expressed by land users, and policy and decision makers in order to estimate both spatially and locally the impacts of European policy (like the Common Agricultural Policy) and/or global changes on farm-groups. These entities are defined according to variables such as altitude, economic size and type of farming (referring to land uses). European farm-groups are provided through the Farm Accountancy Data Network (FADN) as statistical information delivered at regional level. The aim of the study is to map locally farm-group probabilities within each region. The mapping of the farm-groups is done in two steps: (1) by mapping locally the co-variables associated to the farm-groups, i.e. altitude and land uses; (2) by using regional FADN data as a priori knowledge for transforming land uses and altitude information into farm-groups location probabilities within each region. The downscaling process focuses on the land use mapping since land use data are originally point information located every 18 km. Interpolation of land use data is done at 100 m by using co-variables like land cover, altitude, climate and soil data which are continuous layers usually provided at fine resolution. Once the farm-groups are mapped, European Policy and global changes scenarios are run through an agro-economic model for assessing environmental impacts locally.     

土地利用规划模型研究综述

研究目的：以服务土地利用规划编制为目标,针对区域土地利用规划模型研究进行系统回顾。研究方法：文献综述和比较分析法。研究结果：土地利用规划的核心是数量结构和空间布局的调整。作者从模拟与优化两个角度系统地分析了已有区域土地利用规划模型,论述了土地利用规划由传统单一数量结构研究向数量、空间协同研究的发展趋势,并探讨了这些模型在区域土地利用规划应用上的优势与不足。研究结论：基于GIS技术的 “自下而上”与“自上而下”双重耦合空间协同决策模式,是未来区域土地利用规划建模的发展方向,而关于国土空间多尺度转换机理解释是中国构建“多规合一”空间规划体系的关键所在。     

Land use policy in China: Introduction

This themed issue of Land Use Policy builds mainly on papers presented at an international conference on ‘Land Use Issues and Policy in China under Rapid Rural and Urban Transformation’, convened by the Chinese Academy of Sciences in Beijing, China, in October 2012. The conference set out to share and promote new scientific findings from a range of disciplines that advance research on land use policy in China. The contributions to this themed issue provide conceptual–theoretical and empirical takes on the topic, around four main areas of interest to both researchers and policymakers: nation-wide land use issues, the Sloping Land Conversion Program, land engineering and land use, and land use transitions. Various land use issues have been associated with rapid urban–rural transformations in China, giving rise to formulation of new policies directly affecting land use. However, these have contributed to new land use problems due to the nature of the policies and the difficulties in policy implementation constrained by the special ‘dual-track’ structure of urban–rural development in China. In view of this, this themed edition makes a compelling call for more systematic research into the making and implementation of China's land use policy. It also emphasizes the challenges for further research on land use policy in China.     

Organizing anarchy: The food security–biodiversity–climate crisis and the genesis of rural land use planning in the developing world

Shortfalls in global food production, coupled with the growing visibility of climate change's disruptive effects, have underlined for many observers the importance of devoting rural lands to their ‘optimal’ use, where they can make maximal contributions to the global imperatives of feeding the human population and maintaining vital environmental services. In this context observers have endorsed rural land use planning as a way to insure that, at least in theory, lands get devoted to their best uses. In practice, land use planning in the developing world has resembled ‘organized anarchy’. Small landholders with insecure land tenure, overseas investors seeking large land deals, NGOs representing indigenous peoples, government officials, and staff from international environmental NGOs and multilateral organizations have come together in strategic action fields to struggle over and sometimes negotiate land use plans for contested landscapes. These plans represent a strategic, spatially explicit response to the climate change–biodiversity–food security crisis.     

Labour-saving technologies in smallholder agriculture: An economy-wide model with field operations

Labour-saving technologies are relevant for agricultural development. Yet, as this study shows, they are poorly integrated into agricultural production functions of economy-wide models. We report a computable general equilibrium (CGE) model, which explicitly incorporating field operations (e.g. land preparation, weeding or harvesting) in the context of smallholder agriculture. The field operations approach allows to model technological trade-offs in organic and conventional production systems at various stages of the agricultural production process. Simulating a structural change scenario, we compare the performance of the field operations approach with published benchmark production structures by assessing how they replicate empirically observed changes in land and agrochemical use. This benchmark analysis shows that incorporating field operations replicates the observed empirical changes most accurately and allows for more realistic modelling of labour-saving technologies. We use the field operations model to investigate three policy options to mitigate labour shortages in the agricultural sector of Bhutan. Permitting the employment of Indian workers in agriculture has the highest short-term potential in this respect. We find that subsidising agricultural machinery hiring services and removing import tariffs on agrochemical inputs are found to be less effective. Further options for model developments, such as combining field operations and labour market seasonality, are highlighted.     

区域耕地利用变化及对粮食生产的影响--以南宁市为例

土地利用变化及其效应是目前全球变化研究的热点之一.以南宁市为例,探讨耕地利用变化对粮食安全问题的影响,在分析1996-2003年耕地利用变化特点和粮食生产状况的基础上,探讨耕地利用变化包括数量、利用程度和集约度的变化与粮食生产的相关关系,研究表明目前南宁市耕地数量变化对粮食产量影响尚小,但耕地集约度和粮食播种面积对粮食产量影响重大.为此提出南宁市耕地保护的战略应采取以提高粮食播种面积和耕地利用集约度为中心的政策措施,方能达到增强粮食综合生产能力的目的.     

Impacts of increased bioenergy demand on global food markets: an AgMIP economic model intercomparison

Integrated Assessment studies have shown that meeting ambitious greenhouse gas mitigation targets will require substantial amounts of bioenergy as part of the future energy mix. In the course of the Agricultural Model Intercomparison and Improvement Project (AgMIP), five global agro‐economic models were used to analyze a future scenario with global demand for ligno‐cellulosic bioenergy rising to about 100 ExaJoule in 2050. From this exercise a tentative conclusion can be drawn that ambitious climate change mitigation need not drive up global food prices much, if the extra land required for bioenergy production is accessible or if the feedstock, for example, from forests, does not directly compete for agricultural land. Agricultural price effects across models by the year 2050 from high bioenergy demand in an ambitious mitigation scenario appear to be much smaller (+5% average across models) than from direct climate impacts on crop yields in a high‐emission scenario (+25% average across models). However, potential future scarcities of water and nutrients, policy‐induced restrictions on agricultural land expansion, as well as potential welfare losses have not been specifically looked at in this exercise.     

The impact of water scarcity on food,bioenergy and deforestation

We evaluate the impact of explicitly representing irrigated land and water scarcity in an economy‐wide model with and without a global carbon policy. The analysis develops supply functions of irrigable land from a water resource model for 282 river basins and applies them within a global economy‐wide model. The analysis reveals two key findings. First, explicitly representing irrigated land has a small impact on global food, bioenergy and deforestation outcomes. This is because this modification allows irrigated and rainfed land to expand in different proportions, which counters the effect of rising marginal costs for the expansion of irrigated land. Second, changes in water availability have small impacts on global food prices, bioenergy production, land use change and the overall economy, even with large‐scale (c. 150 exajoules) bioenergy production, due in part to endogenous irrigation and storage responses. However, representing water scarcity and changes in water availability can be important regionally, with relatively arid areas and/or areas with rapidly growing populations fully exhausting our estimated maximum irrigation capacity that allows for improved irrigation efficiency, lining of canals to limit water loss, and expanding storage to fully capture average annual water flows.