基于超循环理论的土地利用结构预测模型与实证研究

研究目的：将超循环理论引入土地利用变化模型研究,构建一个新的用于土地利用结构预测的数值模型。研究方法：类比法,超循环模型,马尔科夫模型,数值拟合。研究结果：（1）土地利用系统是典型的达尔文系统,符合超循环模型描述的演化机制;（2）马尔科夫模型是超循环模型的特例,其土地利用类型转移概率矩阵方法可计算部分超循环模型参数;（3）深圳市的实证表明,在大部分土地利用类型预测中超循环模型比马尔科夫模型更加贴近现实,参数?值的可变性使得超循环模型更能表示外生因素的影响。研究结论：超循环模型是一个具有可行性和较强灵活性的土地利用变化模型,在未来具有一定应用前景。     

THE EFFECT OF FERTILISER ON RISK: A HETEROSCEDASTIC PRODUCTION FUNCTION WITH MEASURABLE STOCHASTIC INPUTS

The sources of production risk are many and diverse in nature. Estimating risk as a black box, without explicit recognition of its sources, can lead to inferior estimates of optimal inputs under risk aversion. In this paper, a method is presented for estimating production functions with measurable stochastic inputs and for generating the parameters of the probability distributions of yield for various environments and input levels. Based on this method, it appears that moderate risk aversion can account for a 6.7 per cent to 16.7 per cent reduction in nitrogen use (relative to the risk-neutral solution) for selected rice producing areas of the Philippines. Estimating optimal inputs without environment specific information about the sources of risk leads to large errors. This underscores the value of collecting information about the sources of risk and of exercising caution when such information is not available.     

A look into the nature of complex systems and beyond "Stonehenge" economics: coping with complexity or ignoring it in applied economics?

Real-world economic systems are complex in general but can be approximated by the "open systems" approach. Economic systems are very likely to possess the basic and advanced emergent properties (e.g., self-organized criticality, fractals, attractors) of general complex systems. The theory of "self-organized criticality" is proposed as a major source of dynamic equilibria and complexity in economic systems. This is exemplified in an analysis for self-organized criticality of Danish agricultural subsectors, indicated by power law distributions of the monetary production value for the time period from 1963 to 1999. Major conclusions from the empirical part are: (1) The sectors under investigation are obviously self-organizing and thus very likely to show a range of complex properties. (2) The characteristics of the power law distributions that were measured might contain further information about the state or graduation of self-organization in the sector. Varying empirical results for different agricultural sectors turned out to be consistent with the theory of self-organized criticality. (3) Fully self-organizing sectors might be economically the most efficient. Finally, empirical implications of the results are discussed. Complexity theory should be considered as a valuable supplement to the existing analytical toolbox.     

An Evaluation of the Actuarial structure of manitoba crop Insurance Program and its Implications

Very little research has been done in evaluating the basic principles and assumptions of the actuarial structure for premium ratemaking in crop insurance programs. Therefore, the objectives of this study are: (a) to examine the Pearson probability distribution of actual crop yields as compared with an application of normal-curve theory to crop yields as compared with an application of normal-curve theory to crop yield distributions and in turn to crop insurance ratemaking which was suggested by Botts and Boles in 1958 [1]; (b) to evaluate the pure premium rates derived from estimated Pearson probability distributions for wheat yields in 14 crop districts of the province of Manitoba; and to establish an experience rating system for the crop insurance program based upon the estimated Pearson distribution of actual crop yields on the individual farm.     

Evaluating environmental policies under uncertainty through application of robust nonlinear programming

Environmental policy evaluation is characterised by a paucity of information. The novel technique of robust mathematical programming is introduced as a means to proactively account for this uncertainty in policy analysis. The procedure allows identification of expected bounds on the range of abatement costs associated with environmental policy. It also has the advantage of not limiting conclusions to realisations of specific point estimates or probability distributions. Empirical insights are provided in an application to a New Zealand inland lake threatened by nitrate pollution from dairy farming. Overall, this novel framework is demonstrated to have several key advantages, including explicit treatment of severe uncertainty, capacity to bound the range of expected abatement costs accruing to a given policy instrument, and the opportunity to identify robust plans that are immune to parametric variation.     

20 years of stated preference valuation of non-timber benefits from Fennoscandian forests: A meta-analysis

Stated preference (SP) surveys have been conducted to value non-timber benefits (NTBs) from forests in Norway, Sweden and Finland for about 20 years. The paper first reviews the literature and summarises methodological traditions in SP research in the three countries. Second, a meta-regression analysis is conducted explaining systematic variation in Willingness-to-Pay (WTP). Two important conclusions emerge, with relevance for future research: (1) WTP is found to be insensitive to the size of the forest, casting doubt on the use of simplified WTP/area measures for complex environmental goods; and (2) WTP tends to be higher if people are asked as individuals rather than on behalf of their household.     

Crop-Yield Distributions Revisited

This article revisits the issue of crop-yield distributions using improved model specifications, estimation, and testing procedures that address the concerns raised in recent literature, which could have invalidated previous findings of yield nonnormality. It concludes that some aggregate and farm-level yield distributions are nonnormal, kurtotic, and right or left skewed, depending on the circumstances. The advantages of utilizing nonnormal versus normal probability distribution function models, and the consequences of incorrectly assuming crop-yield normality are explored.     

Ranking Crop Yield Models: A Comment

This comment discusses key specification issues that may have affected the performance and, therefore, the ranking of parametric models that were compared in a recent AJAE article. A procedure to obtain the most flexible parametric model specification possible, given the particular probability distribution function on which the model is based is presented. These specifications also allow for standardized and, therefore, more valid comparisons across parametric models that are based on different probability distributions. Finally, the comment cautions against generalization of the rankings in that AJAE article and recommends that these more flexible specifications be adopted in future comparisons and applications.     

Efficiency effects of agricultural economics research in the United States

Allocations of research funds across programs are often made for efficiency reasons. Social science research is shown to have small, lagged but significant effects on U.S. agricultural efficiency when public agricultural R&D and extension are simultaneously taken into account. Farm management and marketing research variables are used to explain variations in estimates of allocative and technical efficiency using a Bayesian approach that incorporates stylized facts concerning lagged research impacts in a way that is less restrictive than popular polynomial distributed lags. Results are reported in terms of means and standard deviations of estimated probability distributions of parameters and long‐run total multipliers. Extension is estimated to have a greater impact on both allocative and technical efficiency than either R&D or social science research.     

Statistical Modelling of Incentive Design Under Limited Information ‐ The Case of Public Access to Farmland

This paper explores the use of statistical modelling to aid efficient policy design for the provision of environmental goods on farms under conditions of adverse selection. The specific case of incentive‐based schemes to enhance the supply of public access to farmland is used as an example. A range of site willingness‐to‐pay (WTP) distributions are used to explore the benefits derived from policies designed under different levels of information. Where no individual farm information is available, low payment rates are optimal, but efficient market creation may not be possible. Increasing the information set allows discretion in pricing and entry: optimal payment rates and net benefits are higher and the pay‐off from procuring improved information can be substantial. Such benefits are reduced where there is a welfare cost associated with increased government expenditure. Optimal policies are sensitive to the skewness of the WTP distributions. Mechanisms for increasing the information set available to policy makers are discussed.     

The distribution of returns from land efficiency improvement in multistage production systems

This paper assesses the distributional consequences of technical changes that improve the efficiency of land and of other inputs in a multifactor crop‐production system. We introduced an equilibrium displacement model (EDM) by using the specification of a factor‐augmenting approach. Given the uncertainty about the EDM parameters, a Monte Carlo simulation is used to produce a distribution of possible return measures. We found that land suppliers (likely farmers) receive a larger share (73%) of total benefits from the adoption of land‐technical change than they do from the adoption of other input technologies. Each input supplier receives a larger share of total benefits from technical change in her own input. However, this result is sensitive to the value of the parameters, especially the value of the elasticity of substitution. We applied the EDM to the case of no‐tillage (NT) to provide insight into how the aggregate return from the adoption of NT was distributed among different groups on the Canadian Prairies. The results of this study can be used by policymakers and funding agencies in order to influence landowners and farming communities to adopt environmentally sound land technologies to achieve both greater agricultural productivity and sustainability.     

Wilderness Canoeing in Ontario: Using Cumulative Results to Update Dichotomous Choice Contingent Valuation Offer Amounts

This study used cumulative results to update the distributions from which offer amounts were drawn in a dichotomous choice contingent valuation of user benefits from wilderness canoeing in Ontario's wilderness parks. An empirical model demonstrates the efficiency gains from using this procedure. Results allow comparison of variation in average daily willingness to pay (WTP) by trip length, indicating decreasing average benefits per trip-day. Two payment vehicles were used. Canoeists indicated ranges of WTPs which conformed to expected hypotheses when the payment vehicle was an increase in general trip costs. However, the same respondents indicated an upper bound on WTP when the payment vehicle was an increase in the provincial park backcountry permit price.     

Differentiating the consumer benefits from labeling of GM food products

Although recurrent evidence is found that consumers have different willingness to pay for GM and non-GM products, there is disagreement in the scientific community about the size of consumer benefits from GM labeling. In this article we use a theoretical model based on a standard constant elasticity of substitution (CES) to explain the importance of the quality effect. It is shown that failing to consider the quality effect may yield an overestimation of benefits from GM labeling, voluntary or mandatory.     

Stochastic Technology, Risk Preferences, and Adoption of Site-Specific Technologies

A model of farmer decision making is developed to determine the extent to which uncertainties about soil fertility and weather affect the value of site-specific technologies (SSTs) using jointly estimated risk and technology parameters. Uncertainty can lead risk-averse farmers to apply more fertilizers and generate more pollution than in the certainty case. Ignoring uncertainty and risk aversion would overestimate the economic and environmental benefits of SSTs and underestimate the subsidy required to induce adoption. Accounting for uncertainties and risk preferences might explain the low observed adoption rates of SSTs. Improving the accuracy of SSTs would increase the incentives for adoption.     

Costs and benefits of controlling quarantine diseases: a bio-economic modeling approach

This article describes a bio-economic model to quantify the costs and benefits of controlling plant quarantine diseases. The model integrates the epidemiology and economic consequences of a quarantine disease. It allows for ex ante evaluation of control scenarios for their cost-effectiveness, taking into account potential export losses resulting from presence of the disease. The model is applied to brown rot of potato in the Dutch potato production chain. Simulation results show that under the current (2006) control policy, the average yearly costs of brown rot are 7.7 million euros. Reducing monitoring frequency increases the costs to 12.5 million euros, 60% of which are export losses. It is also shown that, due to potential long-term effects of a strategy, conclusions on cost-effectiveness of a strategy depend on the length of the period over which that strategy is observed. These applications illustrate the potential of the bio-economic model to facilitate the development of cost-effective and soundly based control policies.     

Impacts of changing water inflow distributions on irrigation and farm income along the Drâa River in Morocco

Irrigation water is essential for agriculture in the arid Drâa River basin in Morocco but climate change leads to increasingly unreliable water supply in the area. This article analyzes impacts of changing water inflow distributions on irrigation and farm income extending a conjunctive river basin model toward a stochastic modeling approach. Regional climate scenarios are used to derive a maximum likelihood density estimate of current and future water supplies. Based on these distributions, Monte Carlo simulations are performed to obtain stochastic model results on surface and groundwater irrigation as well as economic indicators for six oases along the river. The probability of farmers to receive revenues below the subsistence level is around 2% under current conditions, but this is likely to rise to rates of 6% to 15% depending on the underlying climate change scenario. The composition of water sources for irrigation will shift to more groundwater use. The river basin model is able to represent complex spatial interactions between oases as well as a partial complementarity between groundwater and surface water irrigation due to salinity management effects. Interestingly, the value of groundwater is not necessarily increasing under future climatic conditions as salinity problems are aggravated with expanded groundwater use.     

Theoretical analysis and model design of search for ecological conservation redlines based on the sensitivity assessment of ecosystem services

Most small-scale social economies are characterised by their deficiency, lack, and/or difficulty in matching natural data. Against this backdrop, this paper builds a relatively uniform theoretical framework and designs a more economical and objective method for demarcating ecological conservation redlines (ECR) based on sensitivity assessment of ecosystem services. The results show that the sensitivity assessment model designed in this study can identify sensitive zones effectively, and that the ECR in Hubei Province are well within the sensitive zones so identified. The delimited areas based on the sensitive assessment of ecosystem services have great similarities (95%) with the actual ECR areas in Hubei Province. The most ecologically important functional zones (EIFZ) can also be identified using the regional ecological sensitivity coefficient. When the threshold of EIFZ is set higher, the probability that it falls within the ecologically sensitive areas is greater and the ECR delimited by the method proposed in this study will be more reliable. Theoretically, the delimitation of ECR can be inserted at any evaluation level with a grid resolution higher than that of the land use data, which can be used as a supplement to the ECR delimitation method in ecology or geography.     

Factors determining intercropping by rubber smallholders in Sri Lanka: a logit analysis

Variables related to farmers' awareness and attitudes towards intercropping of immature rubber (Hevea brusiliensis) stands, extension contacts, education level, and experience with farming other crops are positively associated with the probability of adoption. Higher levels of off‐farm income are associated with reduced intercropping in immature rubber stands. Farmers who are sole owners of the land and engaged in full or part‐time rubber farming show lower adoption rates than other land ownership groups. Social participation, family size, experience with farming rubber, immature and mature rubber stands size, and the nature of the land (flat/sloped) do not significantly influence adoption. These conclusions were obtained from a logit model estimated by employing the results of a survey of 588 smallholder rubber farmers from five major rubber‐growing regions in Sri Lanka.     

Economic Returns to Feed Barley Yield-increasing and Disease Resistance Research at the Alberta Field Crop Development Centre

The Alberta Field Crop Development Centre (FCDC) at Lacombe has carried out an extensive research and development program on feed barley since 1973. Prior to 2002, FCDC released 11 hulled and six hull-less barley varieties that have been adopted by farmers. The primary objective of this study is to estimate an economic rate of return to the FCDC barley research and development program from 1973 to 2001. A secondary objective is to include benefits arising from research that improved feed barley disease resistance in new cultivars in addition to benefits from purely higher-yielding cultivar research. The analysis uses an ex post economic surplus methodology. Benefits are identified and empirically investigated for three separate FCDC feed barley research thrusts:
• benefits arising from FCDC research that developed new, higher-yielding feed barley cultivars that give a yield advantage
• benefits arising from FCDC research that improved feed barley disease resistance in new cultivars that result in yield loss avoidance from disease
• benefits arising from FCDC research that developed new feed barley cultivars that yield higher silage production.
Of the total benefits from research on feed grain varieties, 52% can be attributed to yield advantage research and 48% to yield loss avoidance research. The overall internal rate of return with base elasticity parameters is estimated at 27%, ranging between 23% and 31%, depending on the assumptions made about the yield advantage and base variety. The IRR was sensitive to changes in supply elasticities and ranges from 20% (∈= 1.5) to 54% (∈= 0.1).