Miguel Equihua

Fuzzy clustering of ecological data.

Many concepts in ecology are imprecise because ecosystems are large, loosely organized objects. Fuzzy-set theory provides a mathematical approach that is able to cope with imprecision. The aim of this paper is to demonstrate that fuzzy sets are a suitable description of ecological communities, using Calluna vulgaris moorland data from the North York Moors National Park as an example. (...)

Impact of carpets of the invasive moss Campylopus introflexus on Calluna vulgaris regeneration

The moss Campylopus introflexus is a Southern Hemisphere species in the process of expanding its distributional range. It was first found in Europe in 1941. Some of the potential impacts of the invasion of C. introflexus into moorland habitats are investigated. In particular, the effects that the moss carpets may have on germination and subsequent growth of Calluna vulgaris are assessed. A glasshouse experiment contrasted both the amount of germination of Calluna seeds and the performance of the seedlings on moss carpets and on bare ground. The effect of moisture availability was analysed, comparing normal daily watering with continuous water supply at the base of the pots. A significant depressive effect (60% reduction) of the moss carpet on the amount of germination was observed, irrespective of the form of water supply (...)

The desert vegetation of El Pinacate, Sonora, Mexico

The Pinacate region is part of the Gran Desierto, one of the driest deserts in North America. The presence-absence of perennial plant species, together with soil and landform characteristics, were registered in 110 sampling sites within this region. A classification and ordination of plant communities showed soil and landform units to be good predictors of plant variation. Plant distribution and species richness were also strongly related to altitude and rockiness. A Generalised Linear Model was used to fit the response curves of individual species. The environmental factors related with plant distribution are indicators of the water regime within a given site. Plant communities repeat along topographic gradients the large-scale biogeographic variation of the Sonoran Desert. Microphyllous shrubs colonise the drier bajada slopes, while more diverse communities, dominated by cacti and drought-deciduous trees, grow on the wetter pediments and in pockets within rocky soils.

Urban expansion and the environmental effects of informal settlements on the outskirts of Xalapa city, Veracruz, Mexico

This paper analyzes the dynamics of population growth and urban expansion in the city of Xalapa, Mexico. It focuses on the establishment of informal settlements, which are one of the many threats to forest and farmland conservation (although these settlements are not the only source of the problem). Spatial analysis of growth data (using Geographical Information Systems (GIS) and statistical modelling) showed that by 2007, 90 per cent of the land area in the municipality of Xalapa had already been altered by human activity. Furthermore, informal settlements occupied around 54 per cent of the urban area. The cover of cloud forest, the region’s original ecosystem that is of immense ecological importance and biological wealth, was calculated at only 7.6 per cent (9.3 square kilometres) and this is being threatened by the continued expansion of informal settlements. It appears that, at the time when these informal settlements are being established, a certain environmental logic operates, which in turn makes possible the social logic that sets off the occupation of spaces that are, in principle, not suitable for urbanization. The inadequate income of much of the population and their need for housing, as well as the absence of genuine long-term urban planning and, most importantly, the lack of legally available contiguous land for building, are encouraging the occupation of land not suitable for urban development, including sites at high risk of landslides and flooding. This is also causing natural resource and farmland degradation as well as the deterioration of living conditions within the urban boundary, problems that threaten the city’s sustainability.

Establishment of Aedes aegypti (L.) in mountainous regions in Mexico: Increasing number of population at risk of mosquito-borne disease and future climate conditions.

The study was conducted in the central region of Veracruz Mexico, in the metropolitan area of Xalapa. It is a mountainous area where Aedes aegypti (L.) is not currently endemic. An entomological survey was done along an elevation gradient using the Ae. aegypti occurrences at different life cycle stages. Seven sites were sampled and a total of 24 mosquito species were recorded: 9 species were found in urban areas, 18 in non-urban areas with remnant vegetation, and 3 occurred in both environments. Ae. aegypti was found only in the urban areas, usually below 1200m a.s.l., but in this study was recorded for the first time at 1420m a.s.l. These occurrences, together with additional distribution data in the state of Veracruz were used to developed species distribution models using Maxlike software in R to identify the current projected suitable areas for the establishment of this vector and the human populations that might be affected by dengue transmission at higher elevations. Its emergence in previously unsuitable places appears to be driven by both habitat destruction and biodiversity loss associated with biotic homogenization. A border study using data from the edges of the vectors distribution might allow sensitive monitoring to detect any changes in this mosquitos distribution pattern, and any changes in the anthropic drivers or climate that could increase transmission risk.

Analysis of finite mixture of distributions: a statistical tool for biological classification problems

A microcomputer program to analyze finite mixtures of normal, binomial, Poisson or exponential distributions by a maximum likelihood estimation procedure is described. The program is coded in Turbo Pascal. Some theoretical and practical aspects of the compound distributions are discussed, mainly mathematical characteristics, fitting procedures and tests of hypotheses. The statistical tool, which is a cluster analysis technique, is presented in a general context for applications in biology. In particular an ecological example is briefly described: the age class structure resolution of a white-tailed deer population. To improve the usefulness for classification purposes, the link with discriminant analysis is examined. For a successful analysis of finite mixture of distributions the need for a large sample size is emphasized.

Using Four Capitals to Assess Watershed Sustainability

The La Antigua watershed drains into the Gulf of Mexico and can be considered as one of the most important areas in Mexico because of its high productivity, history, and biodiversity, although poverty remains high in the area in spite of these positive attributes. In this study, we performed an integrated assessment of the watershed to recommend a better direction toward a sustainable management in which the four capitals (natural, human, social, and built) are balanced. We contrasted these four capitals in the municipalities of the upper, middle and lower watershed and found that natural capital (natural ecosystems and ecosystem services) was higher in the upper and middle watershed, while human and social capitals (literacy, health, education and income) were generally higher downstream. Overall, Human Development Index was negatively correlated with the percentage of natural ecosystems in the watershed, especially in the upper and lower watershed regions. Our results indicate that natural capital must be fully considered in projections for increasing human development, so that natural resources can be preserved and managed adequately while sustaining intergenerational well-being.

Visual programming languages as a tool to identify and communicate the effects of a development project evaluated by means of an environmental impact assessment

Abstract One of the most important requisites in environmental impact assessments (EIAs) is that the evaluation and communication of impacts must be done with objectivity and transparency. Traditional methods as checklists, matrices, geographic information systems (GISs), and cause–effect diagrams fail to reach this objective because, in general, it is difficult to follow the assumptions and rationale behind the evaluation process. In this paper, we show how the use of visual programming languages (VPLs) is a useful tool that can enhances the quality of these studies. The pros and cons of this approach are evaluated based on a study case of a thermoelectric generation plant.

Data documenting the potential distribution of Aedes aegypti in the center of Veracruz, Mexico

The data presented in this article are related to the research article entitled “Establishment of Aedes aegypti (L.) in mountainous regions in Mexico: Increasing number of population at risk of mosquito-borne disease and future climate conditions” (M. Equihua, S. Ibáñez-Bernal, G. Benítez, I. Estrada-Contreras, C.A. Sandoval-Ruiz, F.S. Mendoza-Palmero, 2016) [1]. This article provides presence records in shapefile format used to generate maps of potential distribution of Aedes aegypti with different climate change scenarios as well as each of the maps obtained in raster format. In addition, tables with values of potential distribution of the vector as well as the average values of probability of presence including data of the mosquito incidence along the altitudinal range.