Vegetation mapping of protected areas is a cornerstone of conservation worldwide. Established in 1928 and covering over 1.4 million hectares, Hwange National Park (HNP) is the largest natural reserve in Zimbabwe. In 1993, the sole comprehensive map of its vegetation to date was produced and since then it has been used in numerous research and conservation endeavours. Over the last two decades, however, the park's vegetation changed, safari areas and forest reserves were created at its edge and high-positional accuracy data on a suite of species were collected. To tend to contemporary mapping needs, in this article, we present the 2013-2014 vegetation structure map of HNP and its surroundings. It was produced by supervised classification of Landsat-8 Operational Land Imager (OLI) images, indices derived from these and the Landsat Tree Cover Continuous Field product. Its accuracy was assessed statistically using samples collected from high-resolution satellite imagery and basic ancillary field data. Of its total pixels, 83.2% were correctly classified. Mean omission and commission error were, respectively, 0.82 (0.74-0.90) and 0.82 (0.72-0.89), and this similarity held on a per class basis, indicating reliable area estimates. It was produced using only freely available imagery and software. Conservation implications: In addition to providing researchers and conservationists working within and around HNP with an updated vegetation map, aiming at an even broader audience, we provide a step-by-step approach for using modern freely available imagery and software for cost-effectively mapping HNP in future or other protected savannas across Africa.

OBJECTIVES: To examine the prevalence of gang involvement, the risk and protective factors associated with gang involvement, and the association between gang involvement and exposure to multiple risk and protective factors among school-aged youth in Trinidad and Tobago. METHODS: A survey instrument was administered to 2 206 students enrolled in 22 high-risk, urban public schools, from March-June 2006. It measured 30 risk factors and 13 protective factors within four domains: community, school, family, and peer-individual, plus levels of alcohol/drug use and delinquency. RESULTS: About 7.7% of youth reported being a gang associate; 6.8%, a former gang member; and 6.2%, a current gang member. Gang involvement was associated with perceived availability of handguns, residential mobility, having parents who favor antisocial behavior, early initiation of antisocial behavior, intention to use drugs, having antisocial peers, and having peers who use drugs. Those with social skills, belief in moral order, and interactions with prosocial peers were significantly less likely to self-report gang membership. Additionally, the probability of gang involvement increased as the number of risk factors increased. CONCLUSIONS: Gang membership among public school youth is about as prevalent in Trinidad and Tobago as it is in the United States, Canada, and Western Europe, but further research is needed. Although risk factors associated with gang involvement were present in all four domains, peer-individual risk factors were disproportionately likely to be associated with gang status. The most effective gang prevention strategies might be those that focus on multiple risk factors, with an emphasis on peer-individual factors and promoting a "belief in moral order."

OBJETIVOS: Examinar la prevalencia de la participación en pandillas, los factores de riesgo y los factores protectores asociados con la participación en pandillas, y la asociación entre la participación en pandillas y la exposición a diversos factores de riesgo y protectores en los adolescentes en edad escolar en Trinidad y Tabago. MÉTODOS: Entre marzo y junio del 2006 se administró un instrumento de encuesta a 2 206 estudiantes matriculados en 22 escuelas públicas urbanas de alto riesgo. La encuesta medía 30 factores de riesgo y 13 factores protectores en cuatro ámbitos diferentes: la comunidad, la escuela, la familia y los compañeros individuales, además de los niveles de consumo de alcohol o drogas y la delincuencia. RESULTADOS: Cerca de 7,7% de los adolescentes informaron que pertenecían a una pandilla, 6,8%, habían sido miembros de una pandilla y 6,2% lo eran en la actualidad. La participación en una pandilla se asociaba con la percepción de disponibilidad de pistolas, la movilidad residencial, tener padres que aprobaran la conducta antisocial, el inicio temprano de comportamientos antisociales, la intención de consumir drogas, tener compañeros antisociales y tener compañeros consumidores de drogas. Los adolescentes dotados de habilidades sociales, los que creían en un orden moral y los que se relacionaban con compañeros prosociales presentaban de forma significativa menos probabilidades de participación en una pandilla. Además, la probabilidad de participación en una pandilla se incrementaba si aumentaba el número de factores de riesgo. CONCLUSIONES: La prevalencia de la participación en pandillas en los adolescentes de las escuelas públicas de Trinidad y Tabago es aproximadamente la misma que la observada en Estados Unidos, Canadá y Europa occidental, pero es necesario ampliar la investigación. Aunque los factores de riesgo asociados con la participación en pandillas estaban presentes en los cuatro dominios, la probabilidad de que los factores de riesgo relacionados con los compañeros individuales se asociaran con la participación en una pandilla era desproporcionadamente alta. Las estrategias más eficaces para prevenir la participación en pandillas tal vez sean aquellas que se centran en múltiples factores de riesgo y hacen hincapié en los factores relacionados con los compañeros individuales.