Modeling spatial decisions with graph theory: logging roads and forest fragmentation in the Brazilian Amazon.

This article addresses the spatial decision-making of loggers and implications for forest fragmentation in the Amazon basin. It provides a behavioral explanation for fragmentation by modeling how loggers build road networks, typically abandoned upon removal of hardwoods. Logging road networks provide access to land, and the settlers who take advantage of them clear fields and pastures that accentuate their spatial signatures. In shaping agricultural activities, these networks organize emergent patterns of forest fragmentation, even though the loggers move elsewhere. The goal of the article is to explicate how loggers shape their road networks, in order to theoretically explain an important type of forest fragmentation found in the Amazon basin, particularly in Brazil. This is accomplished by adapting graph theory to represent the spatial decision-making of loggers, and by implementing computational algorithms that build graphs interpretable as logging road networks. The economic behavior of loggers is conceptualized as a profit maximization problem, and translated into spatial decision-making by establishing a formal correspondence between mathematical graphs and road networks. New computational approaches, adapted from operations research, are used to construct graphs and simulate spatial decision-making as a function of discount rates, land tenure, and topographic constraints. The algorithms employed bracket a range of behavioral settings appropriate for areas of terras de volutas, public lands that have not been set aside for environmental protection, indigenous peoples, or colonization. The simulation target sites are located in or near so-called Terra do Meio, once a major logging frontier in the lower Amazon Basin. Simulation networks are compared to empirical ones identified by remote sensing and then used to draw inferences about factors influencing the spatial behavior of loggers. Results overall suggest that Amazonia's logging road networks induce more fragmentation than necessary to access fixed quantities of wood. The paper concludes by considering implications of the approach and findings for Brazil's move to a system of concession logging.

Protecting the Amazon with protected areas.

This article addresses climate-tipping points in the Amazon Basin resulting from deforestation. It applies a regional climate model to assess whether the system of protected areas in Brazil is able to avoid such tipping points, with massive conversion to semiarid vegetation, particularly along the south and southeastern margins of the basin. The regional climate model produces spatially distributed annual rainfall under a variety of external forcing conditions, assuming that all land outside protected areas is deforested. It translates these results into dry season impacts on resident ecosystems and shows that Amazonian dry ecosystems in the southern and southeastern basin do not desiccate appreciably and that extensive areas experience an increase in precipitation. Nor do the moist forests dry out to an excessive amount. Evidently, Brazilian environmental policy has created a sustainable core of protected areas in the Amazon that buffers against potential climate-tipping points and protects the drier ecosystems of the basin. Thus, all efforts should be made to manage them effectively.

Tenacidad en estudiantes universitarios chilenos: Un estudio inicial de su estructura y red nomológica / Grit in Chilean university students: An initial study of its structure and nomological network

En los últimos años ha surgido un creciente interés por indagar el rol de las habilidades no cognitivas, como la tenacidad, en el desempeño académico. Si bien la investigación sobre tenacidad no ha generado aún conclusiones definitivas, debe considerarse que ella no ha incluido a poblaciones latinoamericanas. Ante este panorama, este estudio inicial se propuso examinar en estudiantes universitarios chilenos de pedagogía en matemáticas: (1) la estructura interna de la tenacidad y (2) su posición en una red nomológica integrada por desempeño académico, sexo, edad y años en el programa educativo. Un total de 153 estudiantes de la Universidad de La Frontera, una institución estatal chilena, respondió la Escala Corta de Tenacidad y un cuestionario sociodemográfico. Análisis factoriales exploratorios revelaron que la tenacidad adquiere una configuración unidimensional que posee una adecuada consistencia interna. Además, adoptando una relación no lineal semejante a una curva hiperbólica, niveles altos de tenacidad se vincularon con desempeño académico alto, en tanto que niveles bajos o moderados se vincularon con desempeño bajo. Finalmente, la tenacidad apareció asociada con sexo (las mujeres mostraron más tenacidad que los hombres) y, en una relación directa, con los años en el programa. Tenacidad no correlacionó significativamente con edad. Este conjunto de hallazgos, que discrepan mayormente de aquellos reportados en la literatura, son discutidos principalmente en términos del dominio disciplinar previo de los participantes y/o de la dificultad del programa educativo. Se proponen explicaciones para estos hallazgos a fin de que sean evaluadas en estudios futuros, empleando un enfoque confirmatorio.

Traditionally, academic performance has been linked to intelligence and some other student´s cognitive abilities. However, in recent 4 years we have witnessed a growing interest in expanding this view by investigating the role that other non-cognitive skills, such as tenacity, may play in academic achievement. Grit can conceptually be conceived as perseverance and passion aimed at achieving long-term goals. A review of the literature shows that grit does not appear to be configured, as some authors claim, as a hierarchical structure with a general second-order construct and two first-order facets (perseverance of effort and consistency of interest). The literature also points out that grit is only a modest predictor of academic performance and that it presents a slightly positive correlation with age and a very weak one with sex and the students' number of years in an academic program. While research on grit has not yet generated any definitive conclusions, it must be considered that it has not included Latin American populations. Given this scenario, this initial study aimed to examine in mathematics teacher Chilean students (1) the internal structure of grit and (2) their position in a nomological network integrated by academic achievement, sex, age and years enrolled in the program. Participants consisted in the total population (n = 153) of students enrolled in a mathematics teacher program at Universidad de La Frontera, a public institution located in the Central-South area from Chile. The program was selected because it presents a high level of difficulty to its students and because it includes highly formalized tasks, as part of its disciplinary courses. Participants responded the Short Grit Scale (Grit-S) and a demographic questionnaire. In this study, Grit-Swas previously translated and adapted into Spanish from the original English version. Grit-Scontains eight items intended to measure the two facets of grit. Exploratory factorial analysis revealed that, after excluding two items due to low factor loadings (items No. 1 and 2), grit presented a one-dimensional configuration, with an adequate internal consistency (ordinal Alpha: .80). A positive linear correlation, although marginally significant, was obtained between grit and academic achievement, r(143)= .12, p =.069, d = .24. However, a planned contrast revealed that a nonlinear relationship, similar to a hyperbolic curve, better explains the link between these two variables. Specifically, this analysis showed that students in the upper grit quintile obtained a significantly higher grade point average than the combined grade point average of the remaining grit quintiles, t(138) =1.87, p = .032, d = .32. This result suggests that academic achievement remains reduced when grit level is low or moderate and only increases when grit level is high. A multiple regression analysis indicated that sex, age and number of years in the program account for 12.6% of grit variance, F(3, 149) = 7.15, p < .001, d = .76. Sex significantly contributed to the prediction (β =.198, p = .011, d = .38) with women, (M = 3.77,dt = .61) reporting higher levels of grit than men (M = 3.53, dt = .69). Whereas age did not significantly contribute to the prediction (β =.102, p = .206), the number of years in the program showed a significant direct association with grit (β = .261, p = .001, d = .60. Due to the originality of these findings, most differing from those reported in the literature, this study offers tentative explanations that future research could use to formulate and empirically test new hypotheses using, hopefully, a confirmatory approach. These possible explanations mainly refer to the participants' previous level of mathematic mastery and/or the level of difficulty demanded by the educational program.