Uncertainty and sustainability in the management of rangelands

We analyze a dynamic and stochastic ecological-economic model of grazing management in semi-arid rangelands. The ecosystem is driven by stochastic precipitation. A risk averse farmer chooses a grazing management strategy under uncertainty such as to maximize expected utility from farming income. Grazing management strategies are rules about which share of the rangeland is given rest depending on the actual rainfall in that year. In a first step we determine a myopic farmer's optimal grazing management strategy and show that a risk averse farmer chooses a strategy such as to obtain insurance from the ecosystem: the optimal strategy reduces income variability, but yields less mean income than possible. In a second step we analyze the long-run ecological and economic impact of different strategies. We conclude that a myopic farmer, if he is sufficiently risk averse, will choose a sustainable grazing management strategy, even if he does not take into account long-term ecological and economic benefits of conservative strategies.     

基于Moran过程的PPP项目承包商机会主义行为演化动态

在PPP项目中,由于政府部门和承包商的目标不一致以及信息不对称等原因的存在,使得在其全寿命周期过程中,承包商的机会主义行为屡见不鲜。本文基于随机演化博弈理论,建构基于Moran过程的博弈模型,旨在探讨推动PPP项目承包商不采取机会主义行为策略的有利条件。研究表明,承包商数目不断扩大,通过降低承包商之间的举报成本,增大惩处力度,可使降低机会主义行为发生概率的效果显著。进一步,借助数值算例,对研究结果进行验证并给出相应的管理对策。     

Optimal Management of Environmental Externalities with Time Lags and Uncertainty

Many environmental externalities occur with time lags that can range from a few days to several centuries in length, and many of these externalities are also subject to uncertainty. In this paper, we examine the key features of an optimal policy to manage environmental externalities that are both lagged and stochastic. We develop a two-period, two-polluter model and obtain closed-form solutions for optimal emissions levels under different combinations of damage functions and stochastic processes. These solutions show that it is not obvious whether greater control should be exerted on polluters that generate externalities with longer lags or on polluters that generate externalities with shorter lags. We find that the optimal ranking of polluters with respect to the length of the time lag associated with their externality will depend on (a) the discount rate, (b) conditional expectations of future states of the polluted resource, (c) persistence of the pollutant, and (d) initial conditions.     

An options based bioeconomic model for biological and chemical control of invasive species

The management of non-native invasive species is a complex but crucial task given the potential for economic and environmental damages. For many invasions the development of socially optimal control strategies requires more than is offered by the single-species, single-control models that have dominated this area of research. We develop a general stochastic optimal control framework that accommodates multiple interacting species while accounting for uncertainty in the temporal population dynamics. This extension to the current line of bioeconomic control models allows for the design of optimal integrated pest management strategies that utilize both chemical and biological controls in an environment of uncertainty and irreversibility. We demonstrate the benefits of combining chemical and biological controls in long term management strategies through a case study of the hemlock wooly adelgid (Adelges tsugae) infestation in the eastern United States. In this application we find that the introduction of natural predators is usually sufficient to manage the infestation, though chemical insecticides can play an important role when detection of the infestation is delayed or when the biological control agent does not sufficiently increase mortality of the invasive species.     

Pitfalls and potential of institutional change: Rain-index insurance and the sustainability of rangeland management

Rain-index insurance is strongly advocated in many parts of the developing world to help farmers to cope with climatic risk that prevails in (semi-)arid rangelands due to low and highly uncertain rainfall. We present a modeling analysis of how the availability of rain-index insurance affects the sustainability of rangeland management. We show that a rain-index insurance with frequent payoffs, i.e. a high strike level, leads to the choice of less sustainable grazing management than without insurance available. However, rain-index insurance with a low to medium strike level enhances the farmer's well-being while not impairing the sustainability of rangeland management.     

Ecological-economic viability as a criterion of strong sustainability under uncertainty

Strong sustainability, according to the common definition, requires that different natural and economic capital stocks be maintained as physical quantities separately. Yet, in a world of uncertainty this cannot be guaranteed. To therefore define strong sustainability under uncertainty in an operational manner we propose to use the concept of viability. Viability means that the different components and functions of a dynamic, stochastic system at any time remain in a domain where the future existence of these components and functions is guaranteed with sufficiently high probability. We develop a unifying and general ecological-economic concept of viability that encompasses the traditional ecological and economic notions of viability as special cases. It provides an operational criterion of strong sustainability under a mild form of uncertainty and for medium spatial and temporal scales. We illustrate this concept and demonstrate its usefulness by applying it to livestock grazing management in semi-arid rangelands.     

可持续发展的代际资源管理

资源在代际之间的永续利用是可持续发展的核心问题。这一问题在当代人利益激励和后代人主体缺位的条件下是不可能自然实现的。所以,对世代赖以生存的自然资源进行公平合理的代际管理和分配,是实现可持续发展的必由之路。     

Ecological services to and from rangelands of the United States

The over 300 million ha of public and private rangelands in the United States are characterized by low and variable precipitation, nutrient-poor soils, and high spatial and temporal variability in plant production. This land type has provided a variety of goods and services, with the provisioning of food and fiber dominating through much of the 20th century. More recently, food production from a rangeland-based livestock industry is often pressured for a variety of reasons, including poor economic returns, increased regulations, an aging rural population, and increasingly diverse interests of land owners. A shift to other provisioning, regulating, cultural, and supporting services is occurring with important implications for carbon sequestration, biodiversity, and conservation incentives. There are numerous goods and services possible from rangelands that can supply societal demands such as clean water and a safe food supply. The use of ecologically-based principles of land management remains at the core of the ability of private land owners and public land managers to provide these existing and emerging services. We suggest that expectations need to be based on a thorough understanding of the diverse potentials of these lands and their inherent limits. A critical provisioning service to rangelands will be management practices that either maintain ecological functions or that restore functions to systems that have been substantially degraded over past decades. With proper incentives and economic benefits, rangelands, in the U.S. or globally, can be expected to provide these historical and more unique goods and services in a sustainable fashion, albeit in different proportions than in the past.     

Understanding the Opportunistic Approach to Disinflation

One approach to achieving price stability is to undertake a deliberate path to an ultimate goal of low inflation—deliberate disinflation. In contrast an opportunistic strategy for disinflation has gained credence in recent years though on the face of it suboptimal. Our procedure is to seek a set of sufficient conditions under which the opportunistic strategy is optimal for a central bank maximising the preferences of the representative agent. We find that such a sufficient set of conditions consists of adaptiveness in expectations and an asymmetry in the Phillips curve of a specific sort.

     

Monitoring as a partially observable decision problem

Monitoring is an important and costly activity in resource management problems such as containing invasive species, protecting endangered species, preventing soil erosion, and regulating contracts for environmental services. Recent studies have viewed optimal monitoring as a Partially Observable Markov Decision Process (POMDP), which provides a framework for sequential decision making under stochastic resource dynamics and uncertainty about the resource state. We present an overview of the POMDP framework and its applications to resource monitoring. We discuss the concept of the information content provided by monitoring systems and illustrate how information content affects optimal monitoring strategies. Finally, we demonstrate how the timing of monitoring in relation to resource treatment and transition can have substantial effects on optimal monitoring strategies.     

论市场体制与我国区域可持续发展战略实施

市场经济条件下，实施可持续发展具有新的特点。市场机制的作用存在缺陷，与可持续发展目标实现存在背反。政府主体方面与生产主体方面因市场缺陷的影响易产生短期行为，给区域可持续发展带来不利影响，而我国的政治体制、管理模式、法规制度不完善，人的素质、经济发展水平低下，使我国市场体制下区域可持续发展具有特殊性，文章分析了当前市场体制下区域可持续发展存在的问题，也指出了我国是社会主义市场体制，有高度统一的市场规则，有计划体制的宏观管理经验，可以采用强有力的宏观调控手段，防止市场失灵、约束生产主体行为，推进区域可持续发展。     

Social security and risk sharing

In this paper we identify conditions under which the introduction of a pay-as-you-go social security system is ex ante Pareto-improving in a stochastic OLG economy with capital accumulation and land. We argue that these conditions are consistent with realistic specifications of the parameters of the economy. In our model financial markets are complete and competitive equilibria interim Pareto efficient. Therefore, a welfare improvement can only be obtained if agents? welfare is evaluated ex ante, and arises from an improvement in intergenerational risk sharing. We also examine the optimal size of a given social security system as well as its optimal reform.     

Stochastic technical change,non-renewable resource and optimal sustainable growth

We develop a stochastic endogenous growth model involving a non-renewable resource, in which innovation arrivals are governed by a non-stationary Poisson process. Using a CRRA analytical example, we characterize the optimal trajectories of the model and analyze the effects of uncertainty in the sense of Rothschild and Stiglitz by computing a mean-preserving spread. We show that increased variability in the innovation process always implies a smaller optimal R&D effort, since this leads to a reduced marginal rate of return. Effects on the other variables of the model may also be unambiguously identified depending upon the relative risk aversion of agents, the social discount rate and the marginal arrival rate of innovations. Finally, we investigate the conditions under which, on average, the economy reaches a sustainable growth path.     

走向可持续的工业遗产景观保护—— 英国布莱纳文工业景观保护实践

对可持续发展理论、工业遗产保护可持续发展原则 进行了分析。从景观概况,运营、范围、目标、策略、经济和 评估可持续方面对英国布莱纳文工业景观保护实践的经验、教 训进行了剖析。在此基础上,结合中国的国情、国策和现实问 题,从工业遗产景观保护的理论、制度、层级、目标、模式和 主体等方面对我国可持续的工业遗产景观保护路径进行了思 考,提出了在我国建立面向可持续的,地区发展综合目标、整 体系统规划管理、多元伙伴机制耦合的工业遗产景观保护新格 局的建议。     

Optimal stationary consumption with stochastic production and resources

Uncertainty about technology and resources is represented in terms of uncertainty about an (exogenous) environment whose successive states form a stationary stochastic process, with probabilities that are unaffected by economic decisions. The successive states of the economy depend both on the environment and on the decisions taken with regard to production and consumption. It is shown that, under conditions that are natural extensions of “neoclassical” conditions in the case of certainty, (1) Capital saturation is possible, i.e., an optimal stationary stochastic program exists, and (2) An optimal program can be sustained by a price system that takes the form of a stationary stochastic process of price vectors. In other words, an optimal stationary program can be sustained by a stochastic “equilibrium,” in which at each date the optimal production decisions maximize expected intertemporal profit, and the optimal aggregate consumption vector has minimum cost among all aggregate consumption vectors yielding no less (social) utility.     

Renewable resource management with environmental prediction: the importance of structural specification

Environmental variability can substantially influence renewable resource growth, and as the ability to forecast environmental conditions improves, opportunities for adaptive management emerge. Using a stochastic stock‐recruitment model, Costello, et al. ( 2001 ) show the optimal management response to a prediction of favourable growth conditions is to reduce current harvests. We find this result may be reversed when environmental variability and stock are substitutes in growth, a possibility that has been ignored by resource economists. As an example, we analyze the South Carolina white shrimp fishery, finding the optimal response to a prediction of favourable overwinter conditions is to increase fall harvests.     

Asset allocation under stochastic interest rate with regime switching

We investigate an optimal asset allocation problem in a Markovian regime-switching financial market with stochastic interest rate. The market has three investment opportunities, namely, a bank account, a share and a zero-coupon bond, where stochastic movements of the short rate and the share price are governed by a Markovian regime-switching Vasicek model and a Markovian regime-switching Geometric Brownian motion, respectively. We discuss the optimal asset allocation problem using the dynamic programming approach for stochastic optimal control and derive a regime-switching Hamilton–Jacobi–Bellman (HJB) equation. Particular attention is paid to the exponential utility case. Numerical and sensitivity analysis are provided for this case. The numerical results reveal that regime-switches described by a two-state Markov chain have significant impacts on the optimal investment strategies in the share and the bond. Furthermore, the market prices of risk in both the bond and share markets are crucial factors in determining the optimal investment strategies.     

Control and the management of a spreading invader

We consider the problem of management of an aquatic invader spreading in a lake system. We assume that each year the invader can be removed from a certain proportion of invaded lakes, which depends on the selected intensity of control. Control decisions are generated and compared for an optimally controlled system and for a static optimization across asymptotic steady states. Control close to eradication of the invasive species is always optimal for invasions with relatively high damages, low rates of density dependent spread and/or low chance of additional random introductions. Control to a highly invaded steady state is optimal for those invasions with low relative damages, high chances of random introduction and high levels of uncertainty in species location. In all other cases the optimal outcome depends upon initial conditions. Comparing the relative performance of the optimally controlled system and the static optimization demonstrates situations when the differences are small and when not. When invasions are acted upon in their later stages and across certain parameter combinations a static optimization provides a reasonable approximation of an optimally controlled system. The flip-side is that optimal policies directed at an invasion in its early stages tend to provide significantly savings. The savings vary across parameter combinations, yet in these situations little useful insight will be generated without consideration of a dynamically optimized system.     

Optimal Intertemporal Consumption under Uncertainty

We analyze the optimal consumption program of an infinitely lived consumer who maximizes the discounted sum of utilities subject to a sequence of budget constraints where both the interest rate and his income are stochastic. We show that if the income and interest rate processes are sufficiently stochastic and the long run average rate of interest is greater than or equal to the discount rate, then consumption eventually grows without bound with probability one. We also establish conditions under which the borrowing constraints must be binding and examine how the income process affects the optimal consumption program. Journal of Economic Literature Classification Number: D91.     

福建省自然保护区可持续管理研究

如何有效实现自然保护区可持续管理是当前福建自然保护区所面临的最为现实问题。本文首先从管理条件、管理措施、科研基础和管理成效4个方面对福建自然保护区的管理现状进行系统评析,进而指出要实现自然保护区的可持续管理,核心在于如何协调好保护管理与资源开发、自然保护与社区参与两方面的关系。