A pest is a pest is a pest? The dilemma of neotropical leaf-cutting ants: Keystone taxa of natural ecosystems

Leaf-cutting ants of the generaAcromyrmex andAtta are considered the principal polyphagous pests of the Neotropics Although some members of these genera are of economic importance, have a broad geographic distribution, and are extremely good colonizers, others are endemic and closely interact with native ecosystems. Control is generally practiced against any colony, irrespective of its taxonomic status. Indiscriminate control coupled with habitat destruction threatens endemic species with extinction, and, through habitat simplification, favors other pest species. As nests ofAtta are large, having several square meters of nest surface, the endemic taxa can be easily used as environmental indicators for natural ecosystems Likewise, the pest species can be used to detect environmental disturbance As these ants are keystone species and easily identified by nonspecialists, efforts should be made to integrate these into viable conservation programs     

Analyzing injury severity factors at highway railway grade crossing accidents involving vulnerable road users: A comparative study

Objective: The main objective of this study is to identify the main factors associated with injury severity of vulnerable road users (VRUs) involved in accidents at highway railroad grade crossings (HRGCs) using data mining techniques.

Methods: This article applies an ordered probit model, association rules, and classification and regression tree (CART) algorithms to the U.S. Federal Railroad Administration's (FRA) HRGC accident database for the period 2007–2013 to identify VRU injury severity factors at HRGCs.

Results: The results show that train speed is a key factor influencing injury severity. Further analysis illustrated that the presence of illumination does not reduce the severity of accidents for high-speed trains. In addition, there is a greater propensity toward fatal accidents for elderly road users compared to younger individuals. Interestingly, at night, injury accidents involving female road users are more severe compared to those involving males.

Conclusions: The ordered probit model was the primary technique, and CART and association rules act as the supporter and identifier of interactions between variables. All 3 algorithms' results consistently show that the most influential accident factors are train speed, VRU age, and gender. The findings of this research could be applied for identifying high-risk hotspots and developing cost-effective countermeasures targeting VRUs at HRGCs.     

A stakeholder driven process to reduce vulnerability to climate change in Hermosillo,Sonora, Mexico

While there is a growing body of knowledge on potential impacts of climate change on water availability, there has been much less empirical research on exploring the viability of particular adaptation options. The participation of stakeholders in defining appropriate adaptation strategies is increasingly recognized as a critical element in the translation of climate change impact research into effective actions to reduce future vulnerability, yet the process by which stakeholders are included in such initiatives is not well-defined. This article presents the results of a pilot project in which a participatory approach was employed to identify and evaluate adaptation options to climate change scenarios for Sonora’s capital city, Hermosillo. In an iterative process, stakeholders representing different water users and managers in the city met to discuss climate change scenarios, identify specific adaptation options, and evaluate a subset of options for possible future implementation. This process enabled the focus of the investigation on those adaptations that addressed not only concerns with the potential future impacts of climate change but also the immediate and pressing concerns about development patterns and water use in the city. Two of the adaptations to climate change identified by stakeholders would also reduce energy demand. The simplicity of the approach makes it a feasible model for adaptation initiatives in other regions of Mexico and in other countries in Latin America.

Farming dynamics and social capital: A case study in the urban fringe of Mexico City

Urban development has important implications for farmland preservation and natural resource management in local peri-urban communities. Social science research on recent changes in rural landscape of mega-cities tends to be limited to case studies in Latin-American nations. This study analyses the socioecomic dynamics of farming land use and the interactions between multiple cultural variables and the environment. Fieldwork was carried out during the 2002–2003 period in rural livelihoods of the five high mountain towns of south Mexico City. Data obtained from participatory survey and ethnographic techniques were integrated to assess changes in rural landscape and resource management and how urbanization, deforestation and market oriented agricultural production result in different livelihoods within a similar urban fringe context. The dynamic of mixture of urban and rural landscapes is based on farm productivity and social capital factors. The study concludes that policy support for regional agricultural production systems through enhancing ecosystems services, environmental protection and economic development is needed for sustainable development of local communities. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue     

An index to quantify street cleanliness: The case of Granada (Spain)

Urban surfaces receive waste deposits from natural and human sources, which create a negative visual impact and are identified as potentially significant contributors to water and air pollution. Local councils are usually responsible for the sweep of roads and footpaths to keep the environment clean and free of litter. Quality controls are useful in order to check whether the services are being executed according to the quantity, quality and performance standards that are provided. In this sense, several factors might affect the efficiency of the management of cleaning and waste collection services; however, only a few contributions are available in the literature on the various aspects associated with the level of street cleanliness. In this paper, the suitability of a Cleanliness Index has been checked, for the case of Granada (South of Spain), in order to contribute to the proper management of public expenditure, improving the quality and cost of an essential service for any municipality. Results have concluded that the city exhibits a good level of cleanliness, although the standard of cleaning varied from one area of the city to another. The Cleaning Index fits well to the general situation of the different districts of Granada and thus, it could be considered a useful tool for measuring the level of cleanliness of the streets of the city and for evaluating the organization of the cleaning service, such that an outsourced company would not be responsible for controlling all the cleaning services.     

Catalytic properties and polymorphism of serine endopeptidases from the midgut gland of the brown shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> (Decapoda,Caridea)

The brown shrimp Crangon crangon is a key species in the coastal areas of the North Sea. It constitutes a significant food source for fishes. Simultaneously, it is an important predator on a wide range of invertebrates. C. crangon shows a variety of digestive enzymes that allow to utilizing a wide range of food items. The initial step of alimentary protein digestion, that is the degradation into peptides, is facilitated by set of endopeptidases which are expressed by the midgut gland. In crustaceans, these endopeptidases are often dominated by serine proteinases. C. crangon, however, predominantly express cysteine proteinases, while only some specimens show a highly variable pattern of serine proteinases. The composition of these serine endopeptidases was investigated using liquid chromatography, substrate gel electrophoresis and inhibitor assays. Distinctly elevated activities were present only in about 10% of the samples. When activity was detected, two peaks, one with tryptic activity and the other one with chymotryptic activity, could be separated by anionic exchange chromatography. Moreover, specimens with elevated tryptic activities often showed highly polymorphic patterns of endopeptidases after electrophoretic separation. Overall, 30 different bands of endopeptidases were identified. There was no similarity between animals from the same sampling sites, neither between animals of similar size, weight or nutritive state. The polymorphism of proteinase from the midgut gland seems to reflect the high adaptive potential of this species to variable trophic conditions in a continuously changing environment.     

Genealogical Analysis of a Closed Herd of Black Hairless Iberian Pigs

Abstract: Livestock breeds are recognized as important components of world biodiversity. The Iberian pig is a swine breed well adapted to the Mediterranean forest ecosystem and provides cured products of high quality. The ancient population of Iberian pigs (  Sus scrofa meridionalis ) was differentiated in several local types, the black hairless pigs representing the fattest genetic type. The conservation program of the Guadyerbas strain has maintained this germplasm isolated since 1945 as a closed population in an experimental herd. The complete pedigree, with 1000 breeding animals descending from 24 founders, has been used to measure along the successive cohorts of breeding animals the effective number of founders, effective number of nonfounders, founder genome equivalents, and expected number of founders' surviving alleles. For the last cohort, the values were 10.34, 1.42, 1.25, and 4.06, respectively. The evolution of inbreeding and coancestry and its components attributable to each founder were also studied. The rate of increase in inbreeding and coancestry was 2.21% per cohort, or 0.906% per year. Finally, the effect of family structure and mating tactics on the evolution of coancestry was also analyzed. The greatest rates of coancestry per cohort were attributable to unbalanced family sizes, and the use of minimum coancestry matings effectively delayed the increase in inbreeding.     

Spatial Heterogeneity of Water Quality in a Highly Degraded Tropical Freshwater Ecosystem

Awareness of environmental heterogeneity in ecosystems is critical for management and conservation. We used the Xochimilco freshwater system to describe the relationship between heterogeneity and human activities. This tropical aquatic ecosystem south of Mexico City is comprised of a network of interconnected canals and lakes that are influenced by agricultural and urban activities. Environmental heterogeneity was characterized by spatially extensive surveys within four regions of Xochimilco during rainy and dry seasons over 2 years. These surveys revealed a heterogeneous system that was shallow (1.1 m, SD = 0.4 ), warm (17°C, SD = 2.9), well oxygenated (5.0 mg l⁻¹, SD = 3), turbid (45.7 NTU SD = 26.96), and extremely nutrient-rich (NO₃–N = 15.9 mg l⁻¹, SD=13.7; NH₄–N = 2.88 mg l⁻¹, SD = 4.24; and PO₄–P =  8.3 mg l⁻¹, SD = 2.4). Most of the variables were not significantly different between years, but did differ between seasons, suggesting a dynamic system within a span of a year but with a high resilience over longer periods of time. Maps were produced using interpolations to describe distributions of all variables. There was no correlation between individual variables and land use. Consequently, we searched for relationships using all variables together by generating a combined water quality index. Significant differences in the index were apparent among the four regions. Index values also differed within individual region and individual water bodies (e.g., within canals), indicating that Xochimilco has high local heterogeneity. Using this index on a map helped to relate water quality to human activities and provides a simple and clear tool for managers and policymakers.     

An evaluation of the estimation of road traffic emission factors from tracer studies

Road traffic emission factors (EFs) are one of the main sources of uncertainties in emission inventories; it is necessary to develop methods to reduce these uncertainties to manage air quality more efficiently. Recently an alternative method has been proposed to estimate the EFs. In that work the emission factors were estimated from a long term tracer study developed in Ho Chi Minh City (HCMC) Vietnam. A passive tracer was continuously emitted from a finite line source placed in one side of an urban street canyon. Simultaneously, the resulting tracer concentrations were monitored at the other side of the street. The results of this experiment were used to calculate the dispersion factors and afterwards, these dispersion factors were used to estimate the EFs. In this paper we use the Computational Fluids Dynamics (CFD) model WinMISKAM to critically evaluate the proposed methodology.In a first step, we use the results of the tracer study to validate the CFD model. Results show that the model is able to simulate quite well the tracer dispersion in most of the cases. The model is then used to evaluate the effect of varying the source configuration and to correct the EFs. A comparison with available studies shows that the corrected EFs are within the range of the EFs reported in other studies. Finally, the CFD model is used to find a source configuration that better represents the vehicle emissions and that may be used in future studies to estimate the EFs more accurately. Results show that a 200 m line placed in the center of the street would represent very well the vehicle emissions. This work shows that it is possible to accurately estimate the EFs from tracer studies.