Pollution havens and industrial agglomeration

This paper examines the pollution haven hypothesis using a spatial-economy model of two countries and two sectors. The manufacturing sector generates cross-border pollution which reduces cross-sectoral productivity of agricultural goods, and lowers local income. We derive a demand-reducing effect that discourages firms to move to the country with laxer environmental regulations, in the absence of any comparative advantage. Our analysis also demonstrates that manufacturing agglomeration forces can alleviate the pollution-haven effect: a pollution haven may not arise if environmental regulation is slightly more stringent in the larger country.     

Environmental pollution and biodiversity: Light pollution and sea turtles in the Caribbean

We examine the impact of pollution on biodiversity by studying the effect of coastal light pollution on the sea turtle population in the Caribbean. To this end we assemble a panel data set of sea turtle nesting activity and satellite-derived measures of nighttime light. Controlling for the surveyor effort, the local economic infrastructure, and spatial spillovers, we find that nighttime light significantly reduces the number of sea turtle nests. According to data on replacement costs for sea turtles raised in captivity, our result suggests that the increase in lighting over the last two decades has resulted in the loss of close to 1800 sea turtles in the Caribbean, worth up to $288 million. Incorporating our empirical estimates into a stage-structured population model, we discover that the dynamic effect of nighttime light on future generations of sea turtles is likely to be much larger, with a cost of approximately $2.8 billion for Guadeloupe alone. More generally, our study provides a new approach to valuing the cost of environmental pollution associated with species extinction.     

Effects of learning and adaptation on population viability

Cultural adaptation is one means by which conservationists may help populations adapt to threats. A learned behavior may protect an individual from a threat, and the behavior can be transmitted horizontally (within generations) and vertically (between generations), rapidly conferring population-level protection. Although possible in theory, it remains unclear whether such manipulations work in a conservation setting; what conditions are required for them to work; and how they might affect the evolutionary process. We examined models in which a population can adapt through both genetic and cultural mechanisms. Our work was motivated by the invasion of highly toxic cane toads (Rhinella marina) across northern Australia and the resultant declines of endangered northern quolls (Dasyurus hallucatus), which attack and are fatally poisoned by the toxic toads. We examined whether a novel management strategy in which wild quolls are trained to avoid toads can reduce extinction probability. We used a simulation model tailored to quoll life history. Within simulations, individuals were trained and a continuous evolving trait determined innate tendency to attack toads. We applied this model in a population viability setting. The strategy reduced extinction probability only when heritability of innate aversion was low (<20%) and when trained mothers trained >70% of their young to avoid toads. When these conditions were met, genetic adaptation was slower, but rapid cultural adaptation kept the population extant while genetic adaptation was completed. To gain insight into the evolutionary dynamics (in which we saw a transitory peak in cultural adaptation over time), we also developed a simple analytical model of evolutionary dynamics. This model showed that the strength of natural selection declined as the cultural transmission rate increased and that adaptation proceeded only when the rate of cultural transmission was below a critical value determined by the relative levels of protection conferred by genetic versus cultural mechanisms. Together, our models showed that cultural adaptation can play a powerful role in preventing extinction, but that rates of cultural transmission need to be high for this to occur.     

The effect of competition on toxic pollution releases

We examine how competition affects toxic industrial releases, using five years of data from thousands of facilities across hundreds of industries. Our main result indicates that competition reduces toxic releases at the facility level. On average, each percentage-point reduction in the Herfindahl Index (HHI) results in a nearly two-percent reduction in a facility׳s toxic releases. At the same time, we find no evidence that competition increases aggregate pollution. Further analysis sheds some light on the mechanisms through which firms reduce pollution releases due to increased competition. In particular, we find suggestive evidence that this relationship is due to both reduced output and increases in abatement. We find no evidence that our result is driven by: consumer aversion to pollution, regulations changing with competition, or technologies introduced by new firms. Taken together, our results indicate that competition may be good, at least for public health in areas near polluting facilities, and fail to provide support for the hypothesis that competition leads to more socially undesirable behavior.     

Sexual selection on alleles that determine body size in the swordtail Xiphophorus nigrensis

Summary In a natural population, we document changes in the frequencies of alleles influencing body size and size-correlated alternative male reproductive tactics, and we examine the possible role of sexual selection in producing these changes. Male swordtails (Xiphophorus nigrensis, Rio Choy) exhibit three body size classes (small, intermediate, and large) that primarily derive from allelic variation (s, I, L) at the Y-linked pituitary (P) locus. Some XX individuals are male. They are small and can be fathered either by XX or XY males. We compared the frequencies of Y-linked P alleles across two generations in a natural population. There was a significant decrease in the Y-s genotype relative to Y-I and Y-L genotypes. Laboratory experiments suggest that the disadvantage of Y-s resulted, at least in part, from female preference for larger courting males relative to small chasing males. All larger courting males are of the Y-I or Y-L genotypes. Although the frequency of Y-linked P alleles changed across generations, there was no change in the distribution of male body size classes. The stability of the phenotypic distribution across generations, despite changes in P allele frequencies, was maintained by the production of small XX sons by Y-I and Y-L males. Offprint requests to: M.J. Ryan     

Evaluating the Effects of Anthropogenic Stressors on Source‐Sink Dynamics in Pond‐Breeding Amphibians

Although interwetland dispersal is thought to play an important role in regional persistence of pond‐breeding amphibians, few researchers have modeled amphibian metapopulation or source‐sink dynamics. Results of recent modeling studies suggest anthropogenic stressors, such as pollution, can negatively affect density and population viability of amphibians breeding in isolated wetlands. Presumably population declines also result in reduced dispersal to surrounding (often uncontaminated) habitats, potentially affecting dynamics of nearby populations. We used our data on the effects of mercury (Hg) on the American toad ( Bufo americanus) as a case study in modeling the effects of anthropogenic stressors on landscape‐scale amphibian dynamics. We created a structured metapopulation model to investigate regional dynamics of American toads and to evaluate the degree to which detrimental effects of Hg contamination on individual populations can disrupt interpopulation dynamics. Dispersal from typical American toad populations supported nearby populations that would otherwise have been extirpated over long time scales. Through support of such sink populations, dispersal between wetland‐associated subpopulations substantially increased overall productivity of wetland networks, but this effect declined with increasing interwetland distance and decreasing wetland size. Contamination with Hg substantially reduced productivity of wetland‐associated subpopulations and impaired the ability of populations to support nearby sinks within relevant spatial scales. Our results add to the understanding of regional dynamics of pond‐breeding amphibians, the wide‐reaching negative effects of environmental contaminants, and the potential for restoration or remediation of degraded habitats. Evaluación de los Efectos de Estresantes Antropogénicos sobre la Dinámica Fuente‐Vertedero en Anfibios que se Reproducen en Charcas     

Integral projection models for finite populations in a stochastic environment

Continuous types of population structure occur when continuous variables such as body size or habitat quality affect the vital parameters of individuals. These structures can give rise to complex population dynamics and interact with environmental conditions. Here we present a model for continuously structured populations with finite size, including both demographic and environmental stochasticity in the dynamics. Using recent methods developed for discrete age-structured models we derive the demographic and environmental variance of the population growth as functions of a continuous state variable. These two parameters, together with the expected population growth rate, are used to define a one-dimensional diffusion approximation of the population dynamics. Thus, a substantial reduction in complexity is achieved as the dynamics of the complex structured model can be described by only three population parameters. We provide methods for numerical calculation of the model parameters and demonstrate the accuracy of the diffusion approximation by computer simulation of specific examples. The general modeling framework makes it possible to analyze and predict future dynamics and extinction risk of populations with various types of structure, and to explore consequences of changes in demography caused by, e.g., climate change or different management decisions. Our results are especially relevant for small populations that are often of conservation concern.     

Double dividend hypothesis, golden rule and welfare distribution

This paper analyzes the double dividend issues within the framework of overlapping generations models. We characterize the necessary conditions for obtaining a double dividend, i.e. an improvement of environmental and non-environmental welfare when the revenue from the pollution tax is recycled into a change in the labor tax rate. We show that, depending on the initial capital stock and on the intertemporal elasticity of substitution, conditions may be defined to simultaneously allow (i) the obtaining of a long-term double dividend, (ii) the economy to move closer to the modified golden rule and (iii) in the short term, an improvement in the welfare of the two present generations.     

Renewable Resources in an Overlapping Generations Economy Without Capital

We incorporate a renewable resource into an overlapping generations model without capital and with quasi-linear preferences. Besides being an input for production the resource serves as a store of value. We characterize the dynamics, efficiency, and stability of the steady-state equilibria. The stability properties are sensitive to the type of resource growth. For constant growth there is only one steady-state equilibrium which is stable and efficient. In the general case of the concave growth function, there are usually at least two steady-state equilibria, one of which is stable and the other one unstable. The unstable steady state is efficient, but the stable one may or may not be. We study the robustness of our results by assuming a logarithmic utility function. We show that for the Cobb–Douglas production function the steady state is unique and stable regardless of whether the equilibrium is efficient or inefficient. Our analytical results are illustrated by numerical calculations.     

The tragedy of the commons and socialization: Theory and policy

We revisit the Tragedy of the Commons in a dynamic overlapping generations economy populated of shepherds who decide how many sheep they let graze on a common parcel of land, while relying on different forms of rationality (Nash players and Kantian players). We examine the dynamics of moral behaviors and land congestion when the prevalence of different types evolves over time following a vertical/oblique socialization process à la Bisin and Verdier (2001). We study the impact of a quota and of a tax on the congestion of land, and we show that introducing a quota may, in some cases, reduce the proportion of Kantians, and worsen the Tragedy of the Commons with respect to the laissez-faire. Ignoring the dynamics of moral traits may lead governments to implement policies that make the Tragedy worse than at the laissez-faire, even though such policies would work well for a fixed population composition.     

Modelling of stem biomass accumulation in Pinus densiflora seedlings exposed to aqueous-phase OH radicals generating mist

The present study aimed to evaluate the short-term biomass accumulation of forest trees exposed to wet acidic depositions. A hierarchical Bayesian model of tree growth was developed based on the data of a short-term experiment in which 2-year-old Japanese red pine (Pinus densiflora Sieb. et Zucc.) seedlings were exposed to aqueous phase OH radicals generated by an iron-oxalate-H₂O₂ mist (a pseudo-polluted dew) over two growing periods. We conducted a statistical comparison of tree growth between the control and pollution treatment groups by using the growth model incorporated the random effects due to the unknown characteristics of each seedling. The variability among seedlings is expressed in this model by the posterior probabilistic distributions of unobserved dry weight of a stem cohort before exposure treatment. The analysis of the effects of pollution treatment on the stem growth revealed that this treatment decreases the biomass allocation in the current year stems. However, the effects on the relative growth rate of pre-existing stems were unclear. Based on these results, we can speculate that in a polluted environment, the short-term growth of the young stems in the seedlings inhibited by pollution treatment, thereby resulting in the slowdown of long-term biomass accumulation. This can explain the patterns observed in the declining Japanese red pine forests that are subjected to OH-generating dews in the polluted area of western Japan.     

Modelling the spatial population dynamics of the green oak leaf roller (Tortrix viridana) using density dependent competitive interactions: Effects of herbivore mortality and varying host-plant quality

Cyclic population dynamics of forest insects with periods of more than two generations have been discussed in relation to a variety of extrinsic and intrinsic forces. In the present study, we employed the selection pressure of density dependent competitive interactions according to Witting's equations (Witting, 2000) as driver for a discrete spatiotemporal model of the green oak leaf roller (Tortrix viridana). The model was successfully parameterised to rebuild the cyclic population dynamics of an empirical data set of a 30-year leaf roller monitoring in Russia. Our analysis focussed on the role of herbivore mortality and host plant food quality, which have a significant effect on T. viridana population dynamics. An additional egg or larvae mortality lowers population density and can lead to selection pressures that favour individuals with higher growth rate. This increased population growth rate can not only compensate the additional mortality, but also can lead to higher average moth abundances in subsequent generations. Furthermore, we analysed the effect of inter- and intraspecific variation in host plant quality on herbivore population dynamics and the spatial distribution of abundance and defoliation patterns. We found significant effects of the qualitative composition of a trees neighbourhood on the herbivore population of the respective tree. Also, the patchy damage patterns observable in reality have been reproduced by the present model. The applicability of the model approach and the putative genetic processes underlying Witting's model are discussed.     

The effect of pollution on crime: Evidence from data on particulate matter and ozone

We estimate the effect of short-term air pollution exposure (PM_2.5 and ozone) on several categories of crime, with a particular emphasis on aggressive behavior. To identify this relationship, we combine detailed daily data on crime, air pollution, and weather for an eight-year period across the United States. Our primary identification strategy employs extremely high dimensional fixed effects and we perform a series of robustness checks to address confounding variation between temperature and air pollution. We find a robust positive effect of increased air pollution on violent crimes, and specifically assaults, but no relationship between increases in air pollution and property crimes. The effects are present in and out of the home, at levels well below Ambient Air Pollution Standards, and PM_2.5 effects are strongest at lower temperatures. The results suggest that a 10% reduction in daily PM_2.5 and ozone could save $1.4 billion in crime costs per year, a previously overlooked cost associated with pollution.     

Pollution control in a simplified general-equilibrium model with production externalities

Pollution externalities of the producer-producer type are considered in a positive two-sector model with stationary capital and labor. By assumption, output from the polluting sector can be diverted to pollution abatement. Environmental authorities attempt to control the level of pollution to some minimum “acceptable” standard by requiring polluters to depollute through the mechanism of a uniform tax on production. Following discussion of short-run considerations, the stability of the tax-adjustment scheme is examined and the dynamic nature of growth paths in the economy is explored.     

Rapidly Shifting Baselines in Yangtze Fishing Communities and Local Memory of Extinct Species

Abstract: Local ecological knowledge can provide a unique source of data for conservation, especially in efforts to investigate the status of rare or possibly extinct species, but it is unlikely to remain constant over time. Loss of perspective about past ecological conditions caused by lack of communication between generations may create “shifting baseline syndrome,” in which younger generations are less aware of local species diversity or abundance in the recent past. This phenomenon has been widely discussed, but has rarely been examined quantitatively. We present new evidence of shifting baselines in local perception of regional species declines and on the duration of “community memory” of extinct species on the basis of extensive interviews with fishers in communities across the middle‐lower Yangtze basin. Many Yangtze species have experienced major declines in recent decades, and the Yangtze River dolphin or baiji (Lipotes vexillifer) and Yangtze paddlefish (Psephurus gladius) may have become extinct during the 21^st century. Although informants across all age classes were strongly aware of the Yangtze ecosystem's escalating resource depletion and environmental degradation, older informants were more likely to recognize declines in two commercially important fish species, Reeves’ shad (Tenualosa reevesii) and Yangtze pufferfish (Takifugu fasciatus), and to have encountered baiji and paddlefish in the past. Age was also a strong predictor of whether informants had even heard of baiji or paddlefish, with younger informants being substantially less likely to recognize either species. A marked decrease in local knowledge about the Yangtze freshwater megafauna matched the time of major population declines of these species from the 1970s onwards, and paddlefish were already unknown to over 70% of all informants below the age of 40 and to those who first started fishing after 1995. This rapid rate of cultural baseline shift suggests that once even megafaunal species cease to be encountered on a fairly regular basis, they are rapidly forgotten by local communities.     

Inefficient environmental instruments and the gains from trade

The primary result from the trade and environment literature is that countries never lose from trade liberalization as long as they implement optimal pollution targets or if they hold emissions constant. These results are derived in models where the regulators use efficient instruments such as tradable permits or emission taxes. Regulators, however, continue to prefer command and control instruments. I show that regulation under these inefficient instruments (such as design standards or concentration standards) can lead to net losses under trade liberalization even if emissions are optimally adjusted for trade. Furthermore, holding the line on emissions need not guarantee welfare improvements either. The problem is that institutional distortions, the excess costs of inefficient instruments, can rise with trade and offset the material gains from trade. Hence the presumption that we can achieve gains from trade by considering only the level of emissions fails to recognize that the mode of regulation also matters.     

Intergenerational aspects of ecotax reforms – An application to Germany

In a model of overlapping generations and majority voting, we analyze an ecotax reform consisting of the tax rate and the budgetary rule. Revenue can be recycled through a lump-sum transfer or a reduction in pension contributions. Our theoretical results as well as the calibration of our model to the German economy show that the median voter's preferred tax rate may exceed the efficient rate. This holds whenever income of the decisive voter is sufficiently high compared to the average income, as rich individuals benefit more from a reduction in pension contributions than they are harmed by an increase in ecotaxes. The calibration confirms that the median voter prefers the earmarking of tax revenue for reductions in pension contributions to the alternative lump-sum transfer. This is quite an accurate prediction of the situation in Germany. Aging of society as expected for Germany lowers the ecotax in the political equilibrium below its optimal level.     

Evaluating mortality rates with a novel integrated framework for nonmonogamous species

The conservation of wildlife requires management based on quantitative evidence, and especially for large carnivores, unraveling cause‐specific mortalities and understanding their impact on population dynamics is crucial. Acquiring this knowledge is challenging because it is difficult to obtain robust long‐term data sets on endangered populations and, usually, data are collected through diverse sampling strategies. Integrated population models (IPMs) offer a way to integrate data generated through different processes. However, IPMs are female‐based models that cannot account for mate availability, and this feature limits their applicability to monogamous species only. We extended classical IPMs to a two‐sex framework that allows investigation of population dynamics and quantification of cause‐specific mortality rates in nonmonogamous species. We illustrated our approach by simultaneously modeling different types of data from a reintroduced, unhunted brown bear (Ursus arctos) population living in an area with a dense human population. In a population mainly driven by adult survival, we estimated that on average 11% of cubs and 61% of adults died from human‐related causes. Although the population is currently not at risk, adult survival and thus population dynamics are driven by anthropogenic mortality. Given the recent increase of human‐bear conflicts in the area, removal of individuals for management purposes and through poaching may increase, reversing the positive population growth rate. Our approach can be generalized to other species affected by cause‐specific mortality and will be useful to inform conservation decisions for other nonmonogamous species, such as most large carnivores, for which data are scarce and diverse and thus data integration is highly desirable.     

Effects of different levels of song overlapping on singing behaviour in male territorial nightingales (Luscinia megarhynchos)

In signalling interactions, animals can directly address information to a specific individual. Vocal overlapping is such a signalling strategy used in songbirds, anurans, and insects. In songbirds, numerous studies using high rates of song overlap to simulate an escalating situation have shown that song overlapping is perceived as a threatening signal by interacting and by listening (eavesdropping) individuals, indicating a high social relevance of song overlapping. Here we present a playback experiment on nocturnally singing male territorial nightingales (Luscinia megarhynchos). Using three different rates of song overlap (1, 25, or 50%), we tested whether or not lower levels of song overlapping act as a signal of aggressive intent and if birds would increase the intensity of their response with increasing level of song overlapping. Subjects did not vary song duration in response to the different playback treatments but increasingly interrupted their singing with increasing overlap by the three playback treatments. The effects persisted even after the playback ceased to overlap and switched to an alternating singing mode. These results expand on previous studies by showing that song overlapping is interpreted as an aggressive signal even when it is used at low or moderate levels. They suggest that, within the range tested here, increasing levels of song overlapping are perceived to be increasingly aggressive.     

Temporal displacement of environmental crime: Evidence from marine oil pollution

We provide evidence for temporal displacement of illegal discharges of oil from shipping, a major source of ocean pollution, in response to a monitoring technology that features variation in the probability of conviction by time of day. During the nighttime, evidence collected by Coast Guard aircraft using radar becomes contestable in court because the nature of an identified spot cannot be verified visually by an observer on board of the aircraft. Seasonal variation in time of sunset is used to distinguish evasive behavior from daily routines on board. Using data from surveillance flights above the Dutch part of the North Sea during 1992–2011, we provide evidence for a sudden increase in illegal discharges after sunset across the year. Our results show that even a tiny chance of getting caught and a mild punishment can have a major impact on behavior.