land development and preservation over time and under uncertainty a review and a research agenda abstract the combination of a rising interest in sustainable natural resource use and the increasingly fractious nature of the interactions between developers and preservationists has led to renewed interest in the question of appropriate natural resource management in this paper i consider the question of land development and preservation over time and under uncertainty i first review the extant literature and then i discuss its shortcomings next i propose a research agenda which will enable us to shed light on some important management questions faced by land developers

nonrenewable resources with switching costs abstract this paper considers a firm s decision to commence or to suspend extraction of a nonrenewable resource when there are start up or shut down costs for a given level of reserves the critical price that would cause an inactive mine to be opened exceeds the price that would induce an active mine to be closed as one would expect greater switching costs cause firms to be less inclined to change status this impact can be substantial even for modest switching costs possible implications of switching costs are considered including the potential for firms to abandon mines with economically valuable remaining reserves

search bioprospecting and biodiversity conservation abstract to what extent can private sector bioprospecting incentives be relied upon for the protection of biological diversity the literature contains dramatically different estimates of these incentives from trivial to quite large we resolve this controversy by isolating the fundamental source of the discrepancy and then providing empirically defensible estimates based on that analysis results demonstrate that the bioprospecting incentive is unlikely to generate much private sector conservation thus other mechanisms are likely required to preserve the public good of biodiversity

fixed costs efficient resource management and conservation this article develops a framework to analyze the impacts on resource development of efficient management practices that account for possible resource conserving technological changes compared with the traditional management practice ignoring these changes efficient management may not delay or reduce resource development depending on the level of the changes under efficient management a higher probability of resource conserving technologies may not delay or reduce resource development these ambiguities are due to the existence of fixed and increasing marginal costs in resource development

flexibility and uncertainty the preserving of flexibility when faced with uncertainty is a neglected aspect of behaviour under risk yet it is an important factor in decisions to hold liquid assets or delay irreversible investment this paper formalizes the notion of flexibility in a sequential decision context and relates its value to the amount of information an agent expects to receive a rudimentary money demand model is developed embodying these ideas and the history of flexibility as an economic concept is traced choices are frequently made between alternatives that imply different degrees of future commitment between a short term investment that leaves future options open for example and a long term one that by its very nature forecloses those options the relative attractiveness of the two depends on their probability distributions of payoffs over time a basic consideration in this choice is the recognition that beliefs about the risks governing these payoffs may change current doubts may be partially resolved in the near future this prospect decreases the attractiveness of the longer term commitment in that one is able to respond less fully to new information and even if it does not directly affect the risks associated with shorter term choices enhances their appeal this paper formalizes the above remarks by establishing connections between the following two partial orderings the first is an ordering based on variability of beliefs one set of beliefs is more variable than another if more final risk is resolved at an intermediate stage the more one expects to learn by an intermediate period relative to what one knows today the more variation one is anticipating in beliefs about the final outcome the second is an ordering of current actions or positions based on flexibility one position is more flexible than another if it leaves available a larger set of future positions at any given level of cost these two orderings are incorporated in a simple sequential decision model to suggest the following behavioural principle the more variable are a decision maker s beliefs the more flexible is the position he will choose this principle potentially applies whenever i there will be opportunities to act after further information is received and ii current actions influence either the attractiveness or availability of different future actions

what to preserve an application of diversity theory to crane conservation this paper attempts to demonstrate how diversity theory can be applied to the analysis of real world conservation policies the specific example chosen to serve as a paradigm concerns preservation priorities among the fifteen species of cranes living wild throughout the world the example is sufficiently actual to show how diversity theory can be used operationally to frame certain critical conservation questions and to guide us toward answers by providing informative quantitative indicators of what to protect at the same time the cranes example is rich enough that it illustrates nicely some broad general principles about the economics of diversity preservation

the irreversibility effect in environmental decisionmaking we provide a new more general definition for the irreversibility effect and demonstrate its relevance to problems involving environmental and other decisions under uncertainty we establish several analytical and numerical results that suggest both that the effect holds more widely than generally recognized and that an existing result epstein s theorem giving a sufficient condition for determining whether the effect holds can be applied more widely than previously indicated in particular to problems involving intertemporally nonseparable benefit functions we further show that a low elasticity of intertemporal substitution will however result in failure of the effect

evaluating natural resource investments notwithstanding impressive advances in the theory of finance over the past 2 decades practical procedures for capital budgeting have evolved only slowly the standard technique which has remained unchanged in essentials since it was originally proposed see dean 1951 bierman and smidt 1960 derives from a simple adaptation of the fisher 1907 model of valuation under certainty under this technique expected cash flows from an investment project are discounted at a rate deemed appropriate to their risk and the resulting present value is compared with the cost of the project this standard textbook technique reflects modern theoretical developments only insofar as estimates of the discount rate may be obtained from crude application of single period asset pricing theory but see brennan 1973 bogue and roll 1974 turnbull 1977 constantinides 1978 the inadequacy of this approach to capital budgeting is widely acknowledged although not widely discussed its obvious deficiency is its the evaluation of mining and other natural resource projects is made particularly difficult by the high degree of uncertainty attaching to output prices it is shown that the techniques of continuous time arbitrage and stochastic control theory may be used not only to value such projects but also to determine the optimal policies for developing managing and abandoning them the approach may be adapted to a wide variety of contexts outside the natural resource sector where uncertainty about future project revenues is a paramount concern

global warming irreversibility and learning a number of economists have argued that the literature on the irreversibility effect implies that current abatement of greenhouse gas emissions should be greater when there is the possibility of obtaining better information in the future about the potential damages from global warming than when there is no possibility of obtaining better information in this paper we show that even the simplest model of global warming does not satisfy either of epstein s 1980 sufficient conditions so it is not possible to use epstein s analysis to tell whether the irreversibility effect applies to models of global warming we derive an alternative sufficient condition for the irreversibility effect to hold

optimal and open access harvesting of multi use species in a second best world expansion of human populations and activities has caused increased conflicts between wildlife and humans as a result the distinction between resource and pest species has become blurry we propose an economically based classification of species based on a multi use bioeconomic model the classification of the steady state population of a species is shown to depend on both species density and economic factors we extend earlier work on multi use resource pest species by applying the theoretical model to a developing country context where property rights to wildlife are imperfectly enforced so that second best trade measures are often applied by the international community to promote conservation upon calibrating the model using data for the african elephant we derive three further results first when comparing the optimal stock of a multi use species to the open access stock we find that the ranking in terms of abundance is ambiguous second and consistent with existing literature on resource management in a second best world our case study supports the idea that trade bans have ambiguous effectson wildlife abundance third due to a bifurcation effect characterizing the multi use model s solution strategic and temporary subsidizing by the north may enable them to free ride on conservation efforts of the south henceforth

risk aversion intergenerational equity and climate change the paper investigates a climate economy model with an iso elastic welfare function in which one parameter measures relative risk aversion and a distinct parameter measures resistance to intertemporal substitution we show both theoretically and numerically that climate policy responds differently to variations in the two parameters in particular we show that higher but lower leads to increase emissions control we also argue that climate economy models based on intertemporal expected utility maximization i e models where may misinterpret the sensitivity of the climate policy to risk aversion

a multinomial choice model of neighborhood effects this paper provides a model of individual decisionmaking in the presence of neighborhood effects by neighborhood effects we refer to interdependencies between individual decisions and the decisions and characteristics of others within a common neighborhood as such neighborhood effects are forms of social interactions in fact the terms would seem to be interchangeable in many contexts within economics there has developed an increasing recognition that neighborhood effects play a possibly major role in explaining a range of individual behaviors rich empirical and theoretical literatures have developed a failing of much of this work is the absence of strong connections between theory and empirics this paper addresses this limitation by providing a model of multinomial choice with neighborhood effects the model represents a generalization of the binary choice model of william brock and steven durlauf 2001a b the model is econometrically implementable and so has the potential of allowing for structural estimation of neighborhood effects section i outlines a basic choice model with neighborhood effects section ii specializes the structure using a multinomial logit framework section iii considers econometric implementation section iv discusses some limitations of the framework and proposes some research directions proofs of all theorems may be found in brock and durlauf 2001c

quasi option value some misconceptions dispelled abstract we discuss a couple of important issues in the recent literature on quasi option value we show that the assertion that quasi option value can be negative in a model with independent learning is based on confusion between quasi option value which is always positive and the net benefit of preservation of a natural environment subject to development which is not we also explore the significance of different assumptions about the nature of learning and show that the result that quasi option value is positive is surprisingly robust

the role of spatial scale in the timing of uncertain environmental policy the spatial scale of an environmental problem is dictated by boundaries physical boundaries limit the extent of impacts while the scale of decision making creates perceived boundaries beyond which impacts are ignored by decision makers while it is well understood that uncertainty and irreversibility will alter policy decisions aimed at alleviating environmental impacts the effect of spatial scales both physical and perceived is less understood when spatial scale is included in a real options model of environmental policy adoption results indicate that the importance and influence of spatial considerations depends on the level of uncertainty stringency of the proposed policy and flexibility of the policy decision recognizing spatial scale may force policy adoption to take place within a window of current damage when spatial scale is small or uncertainty high this window for policy adoption can close precluding policy adoption entirely this undermines well known results demonstrating that changes in uncertainty will only alter the timing of policy adoption in other instances the policy adoption window remains open but the option value increases faster than the benefits of the policy creating a scenario where it is always preferable to delay here the inclusion of an option value can prevent adoption of policies that would be adopted according to traditional cost benefit analysis in general policy decisions will be most affected by spatial considerations when the spatial scale is small damage is spreading fast and the uncertainty in damage spread is high

on the valuation of uncertainty in welfare analysis thisarticle developsa general model of private and public choice under temporal uncertainty the model incorporatesthe effectsof ris k preferencesand the pros pect of future learning into both the individual and aggregate valuationsof public projects the analys isprovidesnew ins ightson individual valuation itsimplicationsfor benefit cos t analys isand the characterization of paretoefficiency under uncertainty it also resolves some of the confusion in the option value and quasioption value literature private and public decisions typically involve many sources of uncertainty including uncertainty about prices income technology environmental quality health etc temporal uncertainty is also common where some of the risk 1 getsresolved over time due to learning additionally private and public decisions often exhibit some form of irreversibility implying that current choicescan affect the ability of decision makers to be flexible and to adjust their future choices in response to forthcoming information when uncertainty and irreversibility are both present welfare analys isgainscomplexity and importance although considerable progress has been made since weisbrod s seminal article a better understanding of the roles of uncertainty and irreversibility in welfare analys improve our ability aseconomis ts to communicate the importance of risk in project evaluation to public decision makers

uncertain irreversibility information and transformation costs abstract the problem of allocation of a given stock of land between two alternatives uses preservation and development is analyzed in a two period model with initial uncertainty about future benefits of those uses and about the irreversibility of development arrival of information at the end of the first period and costs of changing the allocation of the resource it is shown how the consideration of those costs may imply results that do not coincide with the ones presented in the previous literature on irreversibility

looking for a guide to protect the environment the development of the precautionary principle abstract if the precautionary principle is to become the guide of the international community for environmental protection policies an economic interpretation of the principle is in order the analysis of case studies and a survey of the recent decision theoretic literature show the lack of a fully satisfactory economic model more generally various theoretical and empirical results show that the principle cannot be assumed to apply a priori though it has been proposed by international treaties as a rule of thumb for situations of scientific uncertainty the precautionary principle could actually be inefficient

modeling ecological constraints on tropical forest management comment abstract we offer this comment on 1 recent model of ecological constraints on tropical forest management in order to emphasize the complexity of the subject and to qualify the usefulness of her method albers structures her model in a highly asymmetric manner in favor of preservation we contend that the results of a truly general empirically defensible model of tropical forest management are inherently ambiguous spatial and intertemporal dimensions clearly matter but they do not point as neatly in favor of preservation as albers would have us believe

fundamental irreversibilities in stock externalities abstract this paper concerns the irreversibility effect in stock externalities in an environment of uncertainty with learning taking place one may wish to under emit today to avoid potential environmental irreversibilities alternatively one may wish to under invest in pollution control capital avoiding investments in sunk capital that turn out to be wasted the paper develops theoretical results on the tension between these two effects and separates risk aversion from the irreversibility effect the paper also presents a simple example in climate change policy

forest conservation in costa rica when nonuse benefits are uncertain but rising stochastic dynamic programming is used to investigate optimal holding of primary tropical forest in humid costa rica when future nonuse benefits of forest conservation are uncertain and increasing the quasi option value of maintaining primary forests is included as a component of investment in natural capital although the impact of uncertainty on conservation incentives is substantial our results indicate that a rising trend in future benefits and compensation by the international community for beneficial spillovers are more important factors in determining optimal holdings of forest stocks without compensatory payments however further deforestation may be warranted

valuing research leads bioprospecting and the conservation of genetic resources bioprospecting has been touted as a source of finance for biodiversity conservation recent work has suggested that the bioprospecting value of the marginal unit of genetic resources is likely to be vanishingly small creating essentially no conservation incentive this result is shown to flow specifically from a stylized description of the research process as one of brute force testing unaided by an organizing scientific framework scientific models channel research effort toward leads for which the expected productivity of discoveries is highest leads of unusual promise then command information rents associated with their role in reducing the costs of search when genetic materials are abundant information rents are virtually unaffected by increases in the profitability of product discovery and decline as technology improvements lower search costs numerical simulation results suggest that under plausible conditions the bioprospecting value of certain genetic resources could be large enough to s

network effects in public transit use evidence from a spatially autoregressive mode choice model for new york this article empirically tests for positive network effects in transit use by applying a spatial autoregressive logit mode choice model with 1997 98 work trip data from new york city positive network effects exist when people prefer to use transit together with other people as a result of social spill over although these network preferences should differ for each person because of statistical restrictions in the model individual network preferences cannot be obtained however it is possible to derive econometrically a measure of aggregate network preference this paper can be seen in the wider context of other recent work focusing on the analysis of spatial dependencies and network effects in travel

environmental and resource economics a canadian retrospective the paper reviews research contributions to environmental and resource economics by scholars in canada we focus mainly on work from the past 25 years but also highlight earlier pathbreaking work we begin by looking at broad trends in research both internationally and within canada we then review canadian contributions to various topics in the field canadians have played a leading role in the development of the field especially in resource economics international environmental economics and the valuation of environmental amenities

asset retirement with infinitely repeated alternative replacements harvest age and species choice in forestry abstract at what age should productive assets be retired how should replacements be chosen when they differ in their uncertain ability to generate future incomes as a particular version of that problem we study the tree harvesting decision with two possible replacement species whose values as timber are stochastic and whose growth functions are deterministic in the single rotation wicksell problem starting with a bare piece of land an empty shop it is optimal to choose and plant one species immediately if its current value is sufficiently high relative to that of the other species the alternative equipment however if the species are insufficiently price differentiated it is preferable to leave the land vacant the shop empty despite the opportunity cost of doing so in the repeated version of the problem it is never optimal to leave the land bare provided the cost of replacement is null furthermore the optimal harvest tree retirement age not only depends on the price and current productivity of the trees in place but also on the price and productivity of the other species because it may replace the current one the harvest age reaches a peak at some critical threshold of the relative price that signals the necessity to switch to the alternative species indeed this is when the opportunity cost of choosing one alternative replacement over the other is the highest the land value and also the value of the firm is similar to an american option with free boundary infinite expiry period and endogenous payoff the paper highlights the opportunity cost of alternative replacement options and the central role of their volatility in both asset retirement and replacement choice decisions all results are derived analytically a numerical treatment by the penalty method completes the resolution

introduction to intertemporal equilibrium theory indeterminacy bifurcations and stability institute of economic research kyoto university yoshida honmachi sakyoku kyoto 606 japannishimura kier kyoto u ac jpthis paper provides an overview of the basic concepts of intertemporal equi librium theory and discusses the frameworks and techniques used in this subject it then goes on to introduce the main themes discussed in the papers included inthis symposium issue journal of economic literature classification numbers c61 d90 o41

learning and stock effects in environmental regulation the case of greenhouse gas emissions abstract this paper concerns the optimal regulation of greenhouse gases that lead to global climate change in particular we focus on uncertainty and learning which over time resolves uncertainty we present an empirical stochastic model of climate economy interactions and present results on the tension between postponing control until more is known vs acting now before irreversible climate change takes place uncertainty in our model is in the damage caused by global warming the results suggest that a temporary carbon tax may dominate a permanent one because a temporary tax may induce increased flexibility

flexibility learning and irreversibility in environmental decisions a bayesian approach the bayes decision is characterized and studied for a two period decision problem involving a proposed resource development project it is assumed that development is irreversible and that expectations about benefits and costs during the second period vary with experiences resulting from the first period action the amount and types of learning achieved depend upon the particular action taken during the first period flexible sequential decision procedures are compared with fixed once and for all decisions it is shown that under this specification optimal development decisions are not necessarily more conservative when a sequential procedure is used the possibility of reneging on a fixed decision is formally specified and studied

valuing biodiversity for use in pharmaceutical research biodiversity prospecting has been touted as a mechanism for both discovering new pharmaceutical products and saving endangered ecosystems it is unclear what values may arise from such activities however evidence from transactions is incomplete and existing theoretical models are flawed we calculate an upper bound on the value of the marginal species even under favorable assumptions this bound is modest slightly modified assumptions lead to drastically lower estimates we extend our findings to the value of the marginal hectare of habitat and find that the incentives for habitat conservation generated by private pharmaceutical research are also at best very modest

the biodiversity bargaining problem we employ cooperative bargaining theory and nash s rational threats idea to cast light on the biodiversity bargaining problem the problem of global environmental negotiations is argued to be of the nature of a bargaining problem in which bargainers must agree on the distribution of cooperative surplus in order to move to the bargaining frontier we discuss the importance of both efficiency bargaining frontier and fairness recognition of characteristics of bargainers in the choice of the appropriate contract we show that the incremental cost contract used to resolve the biodiversity bargaining problem is of the form of an extreme point contract that fails to recognise the contributions of the south to the production of cooperative surplus a rational response to such a contract is the use of threats of biodiversity destruction contracts must evince both efficiency and fairness in order to represent lasting solutions

discrete choice with social interactions this paper provides an analysis of aggregate behavioural outcomes when individual utility exhibits social interaction effects we study generalized logistic models of individual choice which incorporate terms reflecting the desire of individuals to conform to the behaviour of others in an environment of noncooperative decisionmaking laws of large numbers are generated in such environments multiplicity of equilibria in these models which are equivalent to the existence of multiple self consistent means for average choice behaviour will exist when the social interactions exceed a particular threshold local stability of these multiple equilibria is also studied the properties of the noncooperative economy are contrasted with the properties of an economy in which a social planner determines the set of individual choices finally a likelihood function based on the theoretical model is given and conditions for the econometric identifiability of the model are established

strategic exploitation with learning and heterogeneous beliefs abstract we study the effect of learning with heterogeneous beliefs on the exploitation of a renewable common pool resource to that end we extend the great fish war model of levhari and mirman 1980 to a learning environment in which several agents interact strategically and learn about the distribution of the stochastic evolution of the resource we find that the effect of anticipation of learning with heterogeneous beliefs is twofold first the anticipation of learning makes future payoffs more uncertain which induces the agents to decrease present exploitation due to the precautionary motive second under heterogeneity of beliefs there is a differential informational externality that induces the agents to increase or decrease present exploitation we also perform a comparative analysis on the cournot nash equilibrium with learning by studying the effect of optimism and riskiness on resource exploitation

information and the concept of option value this paper examines the arrow fisher henry concept of option value and analyzes its properties including its relationship to the value of information and the effects of increasing uncertainty about the future consequences of irreversible development it is shown that this option value is distinct from but bounded by the value of information in the overall decision problem also it is distinct from a concept of option value that appears in b s bernanke quart j econom 98 85 106 1983 however when there is a continuum of development levels rather than a binary choice between full development and no development some of these conclusions need to be modified

uncertainty learning and heterogeneity in international environmental agreements this paper concerns the formation of international environmental agreements under uncertainty about environmental damage with different models of learning complete learning partial learning or no learning the results of the existing literature are generally pessimistic the possibility of either complete or partial learning generally reduces the level of global welfare that can be achieved from forming an iea relative to no learning that literature regards uncertainty as a parameter common to all countries so that countries are identical ex ante as well as ex post in this paper we extend the literature to the case where there is no correlation between damage costs across countries each country is uncertain about a particular parameter in our case the benefit cost ratio drawn from a common distribution but ex post each country s realized parameter value is independently drawn consequently while countries remain identical ex ante they may be heterogeneous ex post we show that this change reinforces the negative conclusions about the effects of partial learning on international environmental agreements but under certain conditions moderates the negative conclusions about the effects of complete learning

a note on option value and the expected value of consumer s surplus abstract in roughly contemporaneous papers cicchetti and freeman quart j econ 1971 and schmalensee amer econ rev 1972 reached apparently conflicting conclusions about the sign taken by option value cicchetti and freeman conclude that option value is always non negative schmalensee concludes that option value may be either positive or negative depending upon the circumstances this paper reconciles these seemingly contradictory conclusions it is demonstrated that cicchetti and freeman s unambiguous conclusions concerning the sign of option value are the result of two special strong assumptions not imposed by schmalensee

an open access fishery with rational expectations explain the evolution of the fish stock and the boat fleet as well as determine their equilibrium levels 2 while the changes in the fish stock are described by a biological rule entry and exit from the fishing industry are determined by how expectations are formed we examine a general model in which entry and exit are proportional to the present value of expected profits and compare two special cases of adaptive myopic expectations and rational expectations although both expectations mechanisms lead to the same equilibrium values they lead to different adjustment paths where expectations solely depend on current values myopic expectations it is well known that boats enter the fishery only when the fish stock is greater than its steady state stock 3 with rational expectations however boats may enter when the fish stock is much lower than its steady state value provided the boat fleet is sufficiently small this difference in adjustment is observable and in principle leads to an obvious test on how agents form expectations section 2 develops a general dynamic model for studying fisheries in section 3 we show that the model standardly used in the literature is equivalent to a myopic adaptive expectations model a rational expectations model is analyzed in section 4 the standard and rational expectations models are compared in section 5 section 6 illustrates this comparison using a simulation based on a schaefer model of the pacific halibut fishery section 7 presents the conclusions

permanent and temporary policy incentives for conservation under stochastic returns from competing land uses rapid conversion of private land for agricultural and urban use has raised concern worldwide over the loss of ecological services to inform conservation policy we model privately optimal land use decisions using a real options framework that assumes both the ecological and commercial values of land are stochastic and that land conversion is irreversible we analyze permanent and temporary land conservation policy incentives using this dynamic framework to guide policy makers interested in designing efficient payment mechanisms to achieve ecological preservation goals we find that while the financial cost of temporary policy incentives is generally much lower than permanent policy incentives this difference is very small in scenarios with high discount rates and lower uncertainties in conversion returns and lower expected trend in conservation returns alternately the financial cost of temporary conservation is substantially lower than that of permanent conservation when the expected trend in conservation returns and uncertainties in conservation and conversion returns is high and the discount rate is low comparison with net present value and single source uncertainty models indicates that the presence of a second uncertainty increases the option value of delaying conversion and shows that permanent and temporary policy incentives based on either of the two simpler models can be seriously misguided if multiple uncertainties are present we illustrate the analytical results with a case study of tropical deforestation in indonesia where private landowners can either conserve forests and earn carbon credits or convert to palm oil agriculture and earn profits from the sale of palm oil

optimal environmental management in the presence of irreversibilities abstract we consider an environment of a fixed size that can be converted to another use this conversion can be made in steps but it is irreversible the future benefits per unit from the original use and from the alternative use follow a diffusion process for a fairly general case we show that the value function must be the unique viscosity solution to the associated hamilton jacobi bellman equation we also exhibit several properties of the solution for the case of constant relative risk aversion between 0 and 1 and a log linear diffusion for the benefits journal of economic literature classification numbers c61 d90 q30

an analysis of the world s environment and population dynamics with varying carrying capacity concerns and skepticism abstract because of the open access nature of the environment we consider an ad hoc adjustment of people s environmental footprint to the quality of the environment the adjustment is motivated by environmental concern but hindered by skepticism about announced changes in the state of the environment changes in the quality of the environment affect earth s carrying capacity by expanding the lotka volterra predator prey model to include these features we show that despite skepticism the environment does not deteriorate to a state in which humans cannot exist we also show that in the ideal case of no skepticism the interplay between the non optimally changing environmental concerns and carrying capacity leads the world s environment and human population to a unique interior steady state along an oscillating course these results require no further technological social or international progress

hedging in incomplete markets with hara utility in the context of merton s original problem of optimal consumption and portfolio choice in continuous time this paper solves an extension in which the investor is endowed with a stochastic income that cannot be replicated by trading the available securities the problem is treated by demonstrating using analytic and in particular viscosity solutions techniques that the value function of the stochastic control problem is a smooth solution of the associated hamilton jacobi bellman hjb equation the optimal policy is shown to exist and given in a feedback form from the optimality conditions in the hjb equation at zero wealth a fixed fraction of income is consumed for large wealth the original merton policy is approached we also give a sufficient condition for wealth under the optimal policy to remain strictly positive

risk management instruments for debt driven conservation efforts the case of india s project tiger abstract project tiger has been india s premier case of conservation success since mid 1990s select project tiger reserves in india were chosen for intensive funding by the global environment facility the international development agency ida and the government of india under the india eco development project this project marked a modest shift towards debt based funding the gef project has become a benchmark for tiger conservation in india both in terms of management outcomes and scale and scope of funding however in the absence of large scale budgetary support or self generating income flows it becomes difficult for the gef type of project to be replicated in other tiger reserves of the country debt instruments hold promise as enablers of conservation finance the paper proposes issue of tiger bonds to meet the financial requirements of tiger reserves though attractive as a debt instrument a tiger bond could nevertheless entail interest rate and default risks bioprospecting activities form good revenue sources for tiger reserves to pay off their debts however bioprospecting activities do not provide assured returns to tiger reserves pharmaceutical companies that prospect for genetic resources and practice real options approach to r d investment planning adopt multi phased investment systems and sequential searches that gives them the flexibility to abandon r d projects from the point of view of genetic resource providing entities like project tiger reserves the postponement value generated by real options enables a drug company to tap substitutes for the genetic resources that form the subject matter of bioprospecting contracts to obviate possible repayment risks by tiger reserves the paper advocates the institution of put bonds as a risk management tool for project tiger reserves in order to hedge themselves against loan defaults arising from possible loss in bioprospecting income the paper also brings out the mechanics of the issue of tiger bonds in the indian context it is argued that a put bond not only hedges default risks but would also aid value discovery and payment for ecosystem services as far as the project tiger reserves of india are concerned

optimal conservation extinction debt and the augmented quasi option value abstract optimal conversion defines rules that determine the rate at which land is irreversibly moved out of conservation into production what are the implications on these rules of allowing for a feedback between conversion decisions and the stochasticity of conservation benefits we address this question using the well known ecological mechanism of extinction debt as an illustration this yields a model with a controlled diffusion process at its core we solve this model using a real options approach which leads to the conventional conversion rule as a special case calibrating the model to a specific case costa rica we demonstrate the presence of an augmented quasi option value the size of this value depends on the strength of the feedback

the economics of sequential choice applied to quasi option value abstract this paper develops a general model that can be used to determine the value of sequential forecasts the model is used 1 to examine the interacting effects of strategies for coping with environmental uncertainty and 2 to explore the relationship between the theories of sequential choice and quasi option value the framework presented bridges these two schools of thought and provides a tool for evaluating one time e g climate change or repetitive e g pollution forecasts of environmental damage

valuing environmental damage the purpose of this paper is to review the most important parts of the economic theory and measurement of environmental damage the paper is structured as follows section 2 introduces the willingness to pay concept and money measures such as the compensating variation and the equivalent variation this section also offers an interpretation of money measures in terms of the outcome of a referendum section 3 defines the total value of an environmental asset in order to give the reader an idea of the complexity of the money measures used in recent empirical studies section 4 and 5 introduce risk or uncertainty and discuss the choice of money measure in a risky world in section 6 three frequently employed methods for the estimation of money measures are introduced the paper ends with some remarks regarding the limitations of these approaches to decision making copyright 1990 by oxford university press

biodiversity and international stakes a question of access abstract this paper examines three main questions is it possible to create a market for genetic resources is it a perfectly or an imperfectly competitive market what impact could this market have on the management of biodiversity in the context of sustainable development i analyse the conditions for access and use of knowledge of genetic resources and the genetic resources themselves i then consider the consequences on the management of genetic resources and social welfare trends in the context of sustainable development i present product and technology transfers in terms of access and user rights i show that the lack of information on the quality of biological resources and on their value on both the demand and supply sides lead to an imperfect market model i examine how benefit sharing can be achieved via public research institutions in developed countries and the conditions of their access to private patent licences my main conclusion is that a valorisation of developing countries genetic resources is a means among others of accomplishing a sustainable management of biodiversity by an equitable access and benefit sharing from the use of biodiversity direct use of natural and biological resources valorisation of genetic resources development of new economic sectors etc furthermore it enables taking part in the economic and social development of these countries increasing the social welfare in a context of sustainable development by widening the access to genetic resources

species preservation and biodiversity value a real options approach abstract we evaluate biodiversity in a real options framework when the resources in use are substitutable we examine optimal conservation decisions given that a biodiversity loss is irreversible and that future use values are uncertain while species substitutability has been shown to reduce the value of diversity we show that the flexibility associated with substitutability is a source of value marginal species value is decreasing in the number of species but rising and convex in the value of the marginal species as we show in the two species homogenous model increased volatility raises biodiversity value and a positive correlation between species values both reduces the value of the pool of species and the value of biodiversity the role played by the correlation between the value of a species and the value of other species is reminiscent of the beta of a financial asset just like an asset with a negative beta derives additional value by providing insurance against fluctuations in the market portfolio a species whose value tends to move in the opposite direction as the species in use derives additional value from its higher probability to be available for substitution if the value of the species in use diminishes

switching to perennial energy crops under uncertainty and costly reversibility we study a farmer s decision to convert traditional cropland into land for growing dedicated energy crops taking into account sunk conversion costs and uncertainties in crop returns the optimal decision rules differ significantly from the expected net present value rule which ignores uncertainties and from real options models that allow only one way conversion into energy crops these models also predict drastically different patterns of land conversions into and out of energy crops over time using corn soybean rotation and switchgrass as examples we show that the model predictions are sensitive to assumptions about stochastic processes of the returns government policies might have unintended consequences subsidizing conversion costs into switchgrass may not much affect proportions of land in switchgrass in the long run

optimal investment in ecological rehabilitation under climate change ecological rehabilitation is subject to a variety of risks affecting the likely return on investment we propose an options approach to allocating scarce conservation funds that explicitly allows for the irreversibility of investment and risks to investment payoffs the approach captures ecosystem dynamics from extinction debt as well as ecological and climatic risks at the project scale climatic risks are introduced through three channels the effects of climate change on species loss future rehabilitation benefits and frequency of catastrophic events our results suggest that allocating voluntary rehabilitation contracts on the basis of real options criteria increases cost efficiency and delivers greater value for money for the government when compared with the conventional cost effectiveness criterion as it is illustrated for the case of box gum grassy woodland rehabilitation in australia

scientific progress and irreversibility an economic interpretation of the precautionary principle abstract we consider the problem of the optimal use of a good whose consumption can produce damages in the future scientific progress is made over time that provides information on the distribution of the intensity of damages we show that this progress induces earlier prevention effort only if prudence is larger than twice absolute risk aversion this paper thus identifies the class of quite restrictive but plausible conditions such that scientific uncertainties justify an immediate reduction of the consumption of a potentially toxic substance

confronting the food energy environment trilemma global land use in the long run economic agronomic and biophysical drivers affect global land use so all three influences need to be considered in evaluating economically optimal allocations of the world s land resources a dynamic forward looking optimization framework applied over the course of the coming century shows that although some deforestation is optimal in the near term in the absence of climate change regulation the desirability of further deforestation is eliminated by mid century although adverse productivity shocks from climate change have a modest effect on global land use such shocks combined with rapid growth in energy prices lead to significant deforestation and higher greenhouse gas emissions than in the baseline imposition of a global greenhouse gas emissions constraint further heightens the competition for land as fertilizer use declines and land based mitigation strategies expand however anticipation of the constraint largely dilutes its environmental effectiveness as deforestation accelerates prior to imposition of the target

population technology and growth from malthusian stagnation to the demographic transition and beyond this paper develops a unied growth model that captures the historical evolution of population technology and output it encompasses theendogenous transitionbetween three regimes that have characterized economic development the economy evolves from amalthusianregime wheretechnologicalprogressis slow andpopulationgrowthprevents anysustainedriseinincomepercapita intoapost malthusianregime wheretechnological progress rises and population growth absorbs only part of output growth ultimately a demographic transition reverses the positive relationship between income and population growth andtheeconomyentersamoderngrowthregimewithreducedpopulationgrowth

taking one for the team is collective action more responsive to ecological change debate persists around the timing of risk reduction strategies for large scale ecological change for three reasons risks are difficult to predict they involve irreversibilities and they impact multiple jurisdictions the combination of these three factors creates a general class of filterable spatial dynamic externalities fsde in which one person s risk reduction investments reduce or filter undesirable events experienced by others and underestimates the option value placed on being able to respond to new information about the consequences of ecological change by focusing on the optimal intervention decision we illustrate how and when the opposing forces created by an fsde will lead to a divergence in private and collective risk reduction strategies we use bioinvasions as our motivating example the bioinvasion first hits one jurisdiction and that jurisdiction s risk reduction investment reduces the risk faced by all other jurisdiction we find that efforts to internalize the full benefits of risk reduction investments may have unintended consequences on the responsiveness of environmental policy there is a social welfare gain from asking the first jurisdiction to delay a risk reduction investment to internalize the option values of all at risk jurisdictions

an algorithm for optimal pigouvian taxes without benefits data the pigouvian prescription to internalize external diseconomies and to achieve the optimum social equilibrium is well known a unit tax on polluting activities equal to the marginal social damage arising at the after tax optimal level of activity if an authority imposes an effluent fee on emissions equal to the marginal social damage the resulting equilibrium is pareto efficient it has not been possible to translate the pigouvian dictum into actual because of the problem of quantifying such a tax and its heavy subjective information requirements this makes the monetary value of the damage difficult to determine in order to overcome this difficulty this paper develops a different theoretical approach the main goal is to provide the environmental authority with an algorithm which allows policy makers to base decisions on technical data i e firms production functions rather than on subjective information i e individuals utility functions the paper illustrates advantages offered by this approach providing some theoretical and practical conditions useful in calculating the optimal tax

valuing insurance services emerging from a gene bank the case of the greek gene bank abstract we develop a conceptual framework for determining insurance values associated with a gene bank and we apply the methodology to the greek gene bank ggb the largest ex situ conservation program in greece to evaluate the insurance value generated by the holdings of the ggb genetic resources the current study examined scenarios for alternative arrival probabilities of an adverse event that would negatively affect production of seven major staple crops held at the ggb within the next 100 years within the range of our estimates it is indicated that insurance values considerably exceed the current operating costs of maintaining the ggb

the social value of biodiversity for r d the value of genetic resources for use in research and development r d activities has been the subject of a literature modelling the activity as onewhere individual firms engage in optimal search here we develop a moregeneralised framework in which genetic resources are used in r d at thebase of an industry that addresses recurring problems of resistance as inthe pharmaceutical or plant breeding industries the r d process is onein which firms are engaging in a continuing contest of innovation againsta background of both creative destruction schumpeterian competition andadaptive destruction natural selection and adaptation this frameworkdemonstrates that the search model is conceptually inadequate because itfails to incorporate the important dynamic characteristics of biologicalphenomena we then demonstrate the important differences between firm based valuation of genetic resources and the social value of geneticresources for use in this contest of innovation there are six externalitiesin private patent based genetic resource valuation and five of theseindicate that private valuations will under estimate social values

on impatience economic growth and the environmental kuznets curve a dynamic analysis of resource management the paper presents a dynamic analysis of natural resource management and investigates some key factors that affect optimal management and resource conservation using a recursive specification of time preferences we show how endogenous discounting and impatience can affect the motivation for both capital investments and environmental preservation we examine the relationships between economic growth and environmental quality endogenous discounting provides new insights in the economic dynamics underlying the environmental kuznets curve by treating growth as endogenous we examine how externalities and economic growth interact with each other we investigate how economic development can contribute to an increased demand for environmental preservation as an important new result we also show how poverty can contribute to environmental degradation

from malthus to sustainable energy theoretical orientations to reforming the energy sector abstract the main purpose of this article is to consider macro level theories for understanding the urge for reform as well as the process of societal change both in general terms and more specifically within the energy sector the aim is also to consider the energy sector in a wider context and analyse its recent development as a potential part of this reform the scope and logical framework of this article is the following the state of the global environment is approaching a point where the whole of humankind is in danger the article reviews and discusses humankind s limits of existence and dialectics of the human nature relationship by contrasting malthusian and boserupian theoretical views this creates both practical and scientific needs the long societal process of change is discussed according to the three layer 3l model of societal chance the production of energy has traditionally been one of the core issues concerning the effect humankind has on the environment and with regards to potential change related to it reforming the energy sector is in a key position this article reviews and discusses the way the already established renewal of the energy sector corresponds to the 3l model and the diverse potentials of the anticipated further progress

on modeling and interpreting the economics of catastrophic climate change with climate change as prototype example this paper analyzes the implications of structural uncertainty for the economics of low probability high impact catastrophes even when updated by bayesian learning uncertain structural parameters induce a critical tail fattening of posterior predictive distributions such fattened tails have strong im plications for situations like climate change where a catastrophe is theoretically possible because prior knowledge cannot place sufficiently narrow bounds on overall damages this paper shows that the economic consequences of fat tailed structural uncertainty along with unsureness about high temperature damages can readily outweigh the effects of discounting in climate change policy analysis

irreversible investment with uncertainty and scale economies abstract optimal irreversible investment policy is analyzed when profits undergo multiplicative geometric brownian shocks the marginal product of capital increases initially and then decreases in the latter range it is optimal to add capacity gradually as the shock rises to a threshold where the expected return on the marginal unit is a multiple of its cost reflecting the option value of waiting the optimal policy in the increasing marginal product range obeys the same multiple now applied to the total return on an optimal discrete capacity addition implications for economic growth and suboptimal equilibria under external economies are examined

stochastic economic assessment of afforestation on marginal land in irrigated farming system we analysed the economic viability of afforestation on marginal irrigated croplands in irrigated drylands of uzbekistan the revenues derived from a combination of diversified agricultural production carbon sequestration nitrogen fixation and avoided irrigation water use were analysed considering uncertainty associated with on farm activities such as crop production and short rotation forestry at the per hectare scale variability in land use revenues would necessitate substantial increases in carbon prices for afforestation to be as profitable as crop cultivation on marginal lands assuming an abundant irrigation water supply in contrast at the farm scale the analysis results revealed that afforestation can be attractive financially even without carbon payments due to farm production constraints variable land use returns and the benefits of land use diversification increased carbon prices would promote carbon sequestration by motivating farmers to plant high biomass producing tree species but would have an ecosystem service trade off by reducing the appeal of nitrogen fixing species that are essential for nitrogen self sufficiency of afforestation efforts given the modest irrigation needs of afforestation efforts compared to the cultivation of annual crops tree plantations could become a primary income source for farms during periods of drought irrigation water saved from replacing crops with trees on marginal farmland would enhance the cultivation of commercial crops on productive lands thus increasing farm income