How fire interacts with habitat loss and fragmentation.

Biodiversity faces many threats and these can interact to produce outcomes that may not be predicted by considering their effects in isolation. Habitat loss and fragmentation (hereafter 'fragmentation') and altered fire regimes are important threats to biodiversity, but their interactions have not been systematically evaluated across the globe. In this comprehensive synthesis, including 162 papers which provided 274 cases, we offer a framework for understanding how fire interacts with fragmentation. Fire and fragmentation interact in three main ways: (i) fire influences fragmentation (59% of 274 cases), where fire either destroys and fragments habitat or creates and connects habitat; (ii) fragmentation influences fire (25% of cases) where, after habitat is reduced in area and fragmented, fire in the landscape is subsequently altered because people suppress or ignite fires, or there is increased edge flammability or increased obstruction to fire spread; and (iii) where the two do not influence each other, but fire interacts with fragmentation to affect responses like species richness, abundance and extinction risk (16% of cases). Where fire and fragmentation do influence each other, feedback loops are possible that can lead to ecosystem conversion (e.g. forest to grassland). This is a well-documented threat in the tropics but with potential also to be important elsewhere. Fire interacts with fragmentation through scale-specific mechanisms: fire creates edges and drives edge effects; fire alters patch quality; and fire alters landscape-scale connectivity. We found only 12 cases in which studies reported the four essential strata for testing a full interaction, which were fragmented and unfragmented landscapes that both span contrasting fire histories, such as recently burnt and long unburnt vegetation. Simulation and empirical studies show that fire and fragmentation can interact synergistically, multiplicatively, antagonistically or additively. These cases highlight a key reason why understanding interactions is so important: when fire and fragmentation act together they can cause local extinctions, even when their separate effects are neutral. Whether fire-fragmentation interactions benefit or disadvantage species is often determined by the species' preferred successional stage. Adding fire to landscapes generally benefits early-successional plant and animal species, whereas it is detrimental to late-successional species. However, when fire interacts with fragmentation, the direction of effect of fire on a species could be reversed from the effect expected by successional preferences. Adding fire to fragmented landscapes can be detrimental for species that would normally co-exist with fire, because species may no longer be able to disperse to their preferred successional stage. Further, animals may be attracted to particular successional stages leading to unexpected responses to fragmentation, such as higher abundance in more isolated unburnt patches. Growing human populations and increasing resource consumption suggest that fragmentation trends will worsen over coming years. Combined with increasing alteration of fire regimes due to climate change and human-caused ignitions, interactions of fire with fragmentation are likely to become more common. Our new framework paves the way for developing a better understanding of how fire interacts with fragmentation, and for conserving biodiversity in the face of these emerging challenges.

Prevalência de asma e rinite alérgica em escolares no município de Santo Ângelo/RS / Prevalence of asthma and allergic rhinitis among students from Santo Ângelo/RS

Introdução: A asma é uma doença inflamatória crônica, caracterizada por hiper-responsividade das vias aéreas inferiores que se manifesta por episódios recorrentes de sibilância, dispnéia, aperto no peito e tosse. Objetivo: Determinar a prevalência de asma e rinite alérgica em adolescentes do município de Santo Ângelo/RS. Metodologia: Foi realizado um estudo observacional, prospectivo e transversal; a amostra foi constituída por estudantes de 13 a 14 anos. Foram investigadas as variáveis: sexo, idade e interferência dos sintomas das doenças nas atividades diárias através da aplicação de um questionário epidemiológico padronizado do ISAAC (International Study of Asthma and Allergies in Childhood). Resultados: O número de questionários aplicados foi de 1.031, sendo considerados válidos 979 (94,9 por cento). A prevalência de asma nos adolescentes foi de 10,5 por cento, baseada na questão “já teve ou tem asma”. A prevalência de rinite alérgica foi de 34,6 por cento, baseada na questão “já teve ou tem rinite alérgica”. Quanto à polinose “alergia ao pólen na primavera” a prevalência foi de 30,4 por cento. Considerando-se o sub-diagnóstico das doenças, a prevalência de prováveis asmáticos foi de 12 por cento e a de adolescentes com provável rinite de 12 por cento. Conclusão: A prevalência de asma no presente estudo mostrou-se entre os valores médios mundiais e nacionais, já as prevalências de rinite alérgica e polinose mostraram-se elevadas de acordo com as médias de outros estudos. Estes dados apontam que em Santo Ângelo/RS essas doenças constituem um problema de saúde pública entre os adolescentes.

Introduction: Asthma is an inflammatory chronic disease, characterized as a hyperresponsivity of the lower airways that manifests itself through recurrent episodes of sibilance, dyspnea, chest pressure, and coughing. Aim: To determine the prevalence of asthma and allergic rhinitis in adolescents living in the municipality of Santo Ângelo/RS. Methods: An observational transversal, prospective study was performed, the sample comprising 13- and 14-year-old students. The variables sex, age, and interference of the symptoms of the disease in the daily activities were investigated through the administration of the standardized epidemiological questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC). Results: Of the 1,031 questionnaires responded, 979 (94.9 percent) were considered as valid. The prevalence of asthma among the adolescents was 10.5 percent, based on the question: “Have you ever had asthma?”. The prevalence of allergic rhinitis was 34.6 percent, based on the question “Have you ever had allergic rhinitis?. As for pollen allergy during the spring, the prevalence was 30.4 percent. Considering the underdiagnosis of the diseases, the prevalence of probable asthmatics was 12 percent and of adolescents with probable rhinitis was 12 percent. Conclusion: The prevalence of asthma in the present study was consistent with the reported mean world and national values, but the prevalences of allergic rhinitis and pollen allergies were high as compared to the means reported elsewhere. The data indicate that in Santo Ângelo, RS these conditions are a public health problem among adolescents.