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.     

Population Constraints Associated with the Use of Black Rhinos as an Umbrella Species for Desert Herbivores

The numerous tactics used to conserve biodiversity include the designation of protected areas, political change, and research and education, the latter involving paradigms such as insular biogeography and the "umbrella species concept." In Namibia lands removed from national park status in 1970 and currently under the jurisdiction of indigenous people now contain one of the few unfenced populations of black rhinos (Diceros bicornis) remaining in Africa. Theory predicts that the protection of umbrella species will ensure the survival of other biota that require(s) less space. To gauge how well biodiversity might be retained by examining the spatial needs of a small population of black rhinos, I used data gathered under various ecological conditions to estimate mean and minimum population sizes of six large herbivores of the Namib Desert ranging in size from giraffe (Giraffa camelopardalis) to springbok (Antidorcas marsupialis) and ostrich (Struthio camelus). My results indicate that annual differences in rainfall, both within and between seasons, resulted in wide fluctuations in herbivore population sizes for all species except rhino. Although other herbivores switched to areas of higher rainfall, rhinos did not. The data suggest that under conditions of extreme environmental variance the space used by rhinos alone was unlikely to assure the existence of populations of other species in excess of 250 individuals. Fifty percent of the species failed to exceed 150 individuals 50% of the time and one third of the species never attained populations in excess of 50 individuals. However, by employing assumptions about the spatial needs of rhino populations numbering up to 100 individuals, the mean minimum population sizes attained by any of four desert herbivores is 535. A future challenge in using rhinos and other large-bodied species as umbrellas for organisms of either similar or dissimilar trophic levels will be the refinement of estimates of population viability.     

Variation among populations of the sailfin molly in the rate of concurrent multiple paternity and its implications for mating-system evolution

We examined patterns of concurrent multiple mating in a live-bearing poeciliid fish, the sailfin molly (Poecilia latipinna). We tested whether the probability of multiple paternity was related to female body size or fertility and whether the rate of multiple paternity varied among four populations that differed in their distributions of female body size and fertility. We analyzed data on mother and offspring genotypes for three polymorphic allozymes by three techniques, including a maximum-likelihood estimator that accounts for sampling error in both parental and offspring allele frequencies. The estimated rate of multiple paternity varied between 0.09 and 0.85, and the rate in one population varied seasonally between 0.33 (spring) and 0.85 (autumn). The variation in these rates was not associated with variation in body-size distributions among populations but was closely associated with variation in size-specific fertility: populations with greater variation in female fertility had higher multiple-paternity rates. Within two populations, logistic regression revealed that individual females of larger body size and greater size-specific fertility were more likely to carry multiply sired broods. This result is consistent with observations made in one of the populations 5 years earlier. In general, the results strongly suggest that the mating system varies markedly among conspecific populations of sailfin mollies and that larger, more fertile females are the objects of intermale competition. Received: 6 May 1996 / Accepted in revised form: 5 December 1996     

Phenotypic Alterations, Evolutionarily Significant Structures, and Rhino Conservation

To slow the impending loss of wild black ( Diceros bicornis ) and white ( Ceratotherium simum ) rhinos, three African countries have resorted to dehorning, a practice designed to remove the incentive for poachers to kill the hornless animals. The efficacy of this controversial conservation action remains unknown, in part because much uncertainty exists about the functional significance of rhino horns. We assessed the current utility of horns in Namibian black rhinos from phenotypically altered and intact populations in the Namib Desert, and we collated data on mortal fighting among horned females living in Etosha National Park. Infant mortality was 100% when dehorned mothers were sympatric with spotted hyenas ( Crocuta crocuta ). In contrast, infant survival was 100% for both horned mothers living with hyenas and occasional lions ( Panthera leo ) and 100% for dehorned mothers in the absence of dangerous carnivores. These data suggest that female horns can have direct fitness benefits in terms of calf survival. However, because lethal wounding due to fighting may account for up to 33% of the mortality of horned females, dehorning may improve adult survivorship. Our results (1) suggest that, where the aim of conservation programs is to improve population viability through juvenile recruitment, dehorning is unlikely to be a prudent strategy if practiced in areas with dangerous predators, and (2) illustrate the value of experimental approaches to onerous problems in conservation.     

ANTIDEGRADATION WATER QUALITY CRITERIA FOR THE DELAWARE RIVER: A DISTRIBUTION-FREE STATISTICAL APPROACH1

ABSTRACT: Existing water quality for the Middle Delaware Scenic and Recreational River is significantly better than is required by current standards, leaving a potential for degradation. A method is presented for deriving candidate antidegradation water quality criteria for this segment of the Delaware River using statistical analysis of historic (ambient) water quality data. Data for 34 water quality parameters are first evaluated for data density, serial correlation, trend, seasonality, and other factors. These preliminary analyses are based on observation of data plots and application of distribution-free statistical techniques that are insensitive to outliers and are robust to relatively mild violations of basic assumptions. Data for 12 of the parameters have sufficient density for further analysis and can reasonably be modeled as independent and identically distributed over time (either seasonally or for the entire data sets). For these 12 parameters, distribution-free statistical methods are developed and used to derive intervals within which there is high confidence (usually greater than 95 percent) that the quantiles with potential use as anti-degradation criteria (the 0.85^th, 0.90^th, and 0.95^th quantiles in this study) for a particular parameter lie.     

STATUS AND PROSPECTS OF KAREZ IRRIGATION1

ABSTRACT: The karez is a traditional irrigation water source, consisting of hand-dug horizontal wells, that is still used in parts of South Asia, the Middle East, and North Africa. This paper describes the construction, management, and current problems of karez irrigation systems based on investigations conducted in Baluchistan Province, Pakistan. While karezes have served irrigation needs well in the past, they are now threatened by high costs of labor for construction and maintenance, and by the encroachment of tubewells which lower the water tables on which the karez systems depend. Possible methods for improving karez performance and needs for research are discussed.     

The Influence of Varying Planktonic and Periphytic Algal Biomass On Exposure to Polychlorinated Biphenyls in Mesocosms

Algal populations, either suspended in the water column (planktonic) or present on the walls of an enclosure (periphytic), develop differently depending upon the physical scale of the system. This study determined whether these variations altered the speciation and therefore exposure of polychlorinated biphenyls (PCBs) in estuarine mesocosms. Exposure was defined as the fraction of applied contaminant taken up by plankton after two hours. Using a three phase equilibrium model, the partitioning of a suite of PCBs within variously-sized mesocosms was predicted using laboratory derived distribution coefficients and measured levels of planktonic and periphytic algal biomass. in mesocosms having large wall surface area to volume ratios, sorption of hydrophobic PCBs to periphyton significantly decreased contaminant exposure. However, within the range of planktonic algal biomasses observed in this study, the regulation of PCB exposure was relatively invariant between variously-sized mesocosms. to minimize sorption of hydrophobic organic contaminants (HOCs) to periphyton and reduce artefacts inherent with this partitioning, we suggest using mesocosms with low wall surface area to volume ratios (less than or equal to 1). in addition, periphytic biomass should be quantified regularly and a three-phase equilibrium approach used to predict the actual exposure concentrations.