Diego Rodrigues Macedo

Importance of environmental factors for the richness and distribution of benthic macroinvertebrates in tropical headwater streams

Abstract: An understanding of the interactions among local environmental factors (e.g., physical habitat and water quality) and aquatic assemblages is essential to conserve biodiversity in tropical and subtropical headwater streams. We evaluated the relative importance of multiple physical and chemical habitat variables that influence the richness of Ephemeroptera, Plecoptera, and Trichoptera (EPT) assemblages in wadeable Brazilian Cerrado (savanna) streams. We sampled macroinvertebrate assemblages and quantified physical and chemical habitat in 79 randomly selected sites in 2 Cerrado basins in southeastern Brazil. The environmental variables selected by multiple regression models (MLRs) via corrected Akaike Information Criteria (AICc) contributed significantly to variation in EPT taxon richness. The variance explained by physical-habitat variables was slightly greater in the Upper São Francisco Basin (adjusted R 2 = 0.53) than in the Upper Araguari Basin (adjusted R 2 = 0.46), and both were greater than the variance explained by a combined basin model (adjusted R 2 = 0.39). Physical-habitat variables were more important than water-quality variables in structuring EPT genera in streams with catchments dominated by agriculture or pasture land uses. Regional models can be improved by incorporating basin-specific information to refine biological assessments and to provide better understanding of the interactions that maintain biodiversity in stream networks.

Regionalisation is key to establishing reference conditions for neotropical savanna streams

Areas with minimal anthropogenic influences are frequently used as reference sites and represent the best ecological state available in a region. Streams in such conditions are necessary for evaluating the conservation status of aquatic ecosystems of a region and to monitor them, taking natural environmental variability into consideration. Therefore, the aim of the present study was to analyse whether hydrological units are reliable regional units for aggregating reference sites. To this end, reference sites were studied in three different landscape units of the same hydrological unit. The study tested the hypothesis that water quality, physical habitat structure and the composition and structure of macroinvertebrate assemblages will be more similar for sites in the same landscape unit than for sites located in different landscape units in the same hydrological unit. The study showed that taxonomic richness and composition of the macroinvertebrate assemblages were negatively affected by site slope and positively affected by the presence of leaf packs on the streambed. The three landscape units supported significantly different macroinvertebrate assemblages and indicator taxa. Therefore, a hydrological unit does not constitute a homogeneous entity in terms of environmental variables and biological composition if it incorporates high landscape heterogeneity. These results should improve and facilitate the selection of reference sites for biomonitoring programs and for managing tropical headwater streams.

Influence of environmental variables on stream fish fauna at multiple spatial scales

Effects of environmental variables at different spatial scales on freshwater fish assemblages are relatively unexplored in Neotropical ecosystems. However, those influences are important for developing management strategies to conserve fish diversity and water resources. We evaluated the influences of site- (in-stream) and catchment-scale (land use and cover) environmental variables on the abundance and occurrence of fish species in streams of the Upper Araguari River basin through use of variance partitioning with partial CCA. We sampled 38 1st to 3rd order stream sites in September 2009. We quantified site variables to calculate 11 physical habitat metrics and mapped catchment land use/cover. Site and catchment variables explained > 50% of the total variation in fish species. Site variables (fish abundance: 25.31%; occurrence: 24.51%) explained slightly more variation in fish species than catchment land use/cover (abundance: 22.69%; occurrence: 18.90%), indicating that factors at both scales are important. Because anthropogenic pressures at site and catchment scales both affect stream fish in the Upper Araguari River basin, both must be considered jointly to apply conservation strategies in an efficient manner.

Social perception in a urban stream restoration project in Belo Horizonte

RESUMO: A restauracao de cursos d’agua em areas urbanizadas e uma abordagem recente no Brasil, mas que e aplicada em paises desenvolvidos desde a decada de 1970. O Programa Drenurbs, efetivado em Belo Horizonte, e uma das primeiras iniciativas de restauracao de cursos d’agua urbanos no Brasil, mas que ja possui resultados praticos. Este artigo tem como objetivo levantar reflexoes sobre a efetividade das atuais iniciativas de restauracao de cursos d´agua urbanos em Belo Horizonte, com base na percepcao social dos resultados das intervencoes no Corrego Baleares, porcao norte da cidade. Para este fim, foi efetuado um survey, visando avaliar a articulacao entre os atores, a opiniao e a satisfacao social em relacao ao projeto. Os resultados mostraram que as intervencoes de restauracao foram bem aceitas pela populacao e, apesar da constatacao da baixa articulacao entre os atores, esses resultados trazem boas perspectivas em relacao a implantacao de projetos nestes moldes em outras bacias urbanas. Entretanto, os resultados tambem mostram que a preferencia pelo modelo tradicional de canalizacoes e vias sanitarias ainda e relevante. Dado o carater inovador das iniciativas de restauracao de cursos d´agua no Brasil, os resultados podem auxiliar futuros projetos e programas voltados a intervencoes em arterias hidrograficas urbanas. Palavras-chave: Percepcao social. Restauracao de cursos d’agua. Bacia hidrografica urbana. Drenurbs.

Development and validation of an environmental fragility index (EFI) for the neotropical savannah biome

Augmented production and transport of fine sediments resulting from increased human activities are major threats to freshwater ecosystems, including reservoirs and their ecosystem services. To support large scale assessment of the likelihood of soil erosion and reservoir sedimentation, we developed and validated an environmental fragility index (EFI) for the Brazilian neotropical savannah. The EFI was derived from measured geoclimatic controls on sediment production (rainfall, variation of elevation and slope, geology) and anthropogenic pressures (natural cover, road density, distance from roads and urban centers) in 111 catchments upstream of four large hydroelectric reservoirs. We evaluated the effectiveness of the EFI by regressing it against a relative bed stability index (LRBS) that assesses the degree to which stream sites draining into the reservoirs are affected by excess fine sediments. We developed the EFI on 111 of these sites and validated our model on the remaining 37 independent sites. We also compared the effectiveness of the EFI in predicting LRBS with that of a multiple linear regression model (via best-subset procedure) using 7 independent variables. The EFI was significantly correlated with the LRBS, with regression R2 values of 0.32 and 0.40, respectively, in development and validation sites. Although the EFI and multiple regression explained similar amounts of variability (R2 = 0.32 vs 0.36), the EFI had a higher F-ratio (51.6 vs 8.5) and better AICc value (333 vs 338). Because the sites were randomly selected and well-distributed across geoclimatic controlling factors, we were able to calculate spatially-explicit EFI values for all hydrologic units within the study area (~38,500 km2). This model-based inference showed that over 65% of those units had high or extreme fragility. This methodology has great potential for application in the management, recovery, and preservation of hydroelectric reservoirs and streams in tropical river basins.

Assessing the extent and relative risk of aquatic stressors on stream macroinvertebrate assemblages in the neotropical savanna

Abstract Freshwater ecosystems are among the most threatened by human activities, influencing losses of biodiversity. To efficiently address management practices to conserve and restore those ecosystems it is important to correctly identify and quantify the severity and magnitude of anthropogenic stressors degrading freshwater biota. In this study we assessed seven stressors describing poor water quality, physical habitat alteration, and land use by means of the relative risk (RR) and relative extent (RE) approach. The RR measures the co-occurrence probability of high stressor condition and poor biological condition. The RE measures the proportion of stream length in the region in high stressor condition. To obtain accurate estimations of RR and RE we used a probabilistic survey design to select a representative sample of perennial, wadeable and accessible streams within four hydrologic units in the neotropical savanna. Results were evaluated at two spatial scales: local – within each of the four hydrologic units, and regional – all four units combined. From 143 randomly selected sites we inferred our results to a target population of 9466 km of streams. Regionally, we found turbidity, % fine sediments and % agriculture as key stressors associated with poor biological condition. At the local scale, we also found that % pasture and total nitrogen were key stressors of biological condition, but their extent was relatively small. By evaluating both RR and RE we conclude that reducing excess sedimentation on streambeds should be the most effective means of improving biological condition over the region. That finding should guide decision makers and land managers to better focus their efforts and resources on improving biological condition of savanna streams.

Avaliação dos riscos para ocupação urbana: proposição metodológica baseada em geotecnologias

Esta pesquisa se insere na atual discussão do GT População e Meio Ambiente, recentemente renomeado para População, Espaço e Ambiente. O estudo desenvolveuse, até o momento, sob dois aspectos principais: como foco, os riscos e vulnerabilidades da ocupação urbana; como metodologia, a utilização de indicadores censitários e sua integração a Sistemas Informativos Geográficos. Neste contexto, o trabalho utiliza indicadores presentes no Censo Demográfico do IBGE, para a composição de um Índice de Vulnerabilidade da Ocupação Urbana – IVOU e sua espacialização, utilizando como unidade de análise os setores censitários. O objetivo deste índice é contrapô-lo às condições físicas naturais, identificadas por meio de modelagem cartográfica, afim de estabelecer áreas prioritárias para a intervenção do poder público. Neste sentido, a pesquisa tem um enfoque metodológico, propondo uma análise mais detalhada da questão dos perigos e riscos para a ocupação urbana em grandes centros. No Brasil, cada estação chuvosa constitui-se em novo ciclo de desastres – atingindo um expressivo contingente populacional –, que estão relacionados, sobretudo, a dois processos naturais potencializados pela ocupação urbana desordenada: deslizamentos de encostas e enchentes. Utilizou-se, como área-piloto, a microbacia do córrego da Abolição, localizada ao norte do município de Belo Horizonte, com uma área aproximada de 600.000m2 e um contingente populacional de cerca de 11.000 habitantes. Para o desenvolvimento dos trabalhos, consideram-se duas premissas básicas. A primeira refere-se ao meio físico, o qual engloba elementos formadores da paisagem que possuem fragilidades inerentes à ocorrência de processos naturais, colocando em perigo as populações locais. Nesta mesma linha de raciocínio, a segunda premissa considera que o risco se constitui na probabilidade de este perigo efetivamente atingir alguém. Assim, a metodologia desenvolvida segue estes dois pressupostos, contrapondo-se na análise final para buscar identificar as áreas prioritárias para a intervenção do poder público. Na proposta metodológica para avaliação da fragilidade do meio físico, utilizouse como técnica cartográfica a análise booleana para identificar a suscetibilidade aos eventos analisados na microbacia. A segunda etapa metodológica, de caráter mais demográfico, correspondeu à elaboração do IVOU, utilizando-se três indicadores básicos: renda, escolaridade e número e faixa etária dos habitantes. Com isso, elaborou-se um mapa mesclando as duas concepções estudadas. Em relação aos resultados do primeiro estudo, observaram-se dois problemas. O primeiro refere-se à forma como a metodologia de análise do meio físico foi concebida, apresentando dificuldade para replicá-la. Deve-se considerar que, em uma área maior, a diversidade de componentes do sistema tornará o modelo mais complexo, dificultando a interpretação das condicionantes do meio físico aos eventos estudados. Já o segundo diz respeito ao índice: foram utilizados poucos indicadores, além do fato de ser mais interessante compô-lo para todo o município de Belo Horizonte,