Taxonomic and functional turnover of Amazonian stream fish assemblages is determined by deforestation history and environmental variables at multiple scales

High rates of deforestation, either in the past or the present, affect many of the ecological processes in streams. Integrating deforestation history and the current landscape structure enhances the evaluation of ecological effects of land-use change. This is especially true when contemporary landscape conditions are similar but the temporal path to those conditions differs. One approach that has shown promise for evaluating biodiversity responses over time and space is the β-diversity partitioning, which combines taxonomic and functional trait-based approaches. We tested hypotheses related to stream fish assemblages' turnover in watersheds with different environmental conditions and deforestation histories. We sampled fish from 75 watersheds in the Machado River basin, Brazil, and environmental factors were quantified at multiple scales. Taxonomic turnover was higher than expected by chance, whereas functional turnover was lower than expected by the observed taxonomic turnover, indicating that deterministic processes are structuring these assemblages. The turnover, and the environmental factors differed among watersheds with different deforestation histories. Besides being scale-dependent, turnover patterns are also likely dependent on land use dynamics and involve time-lags.(AU)

Altas taxas de desmatamento, seja no passado ou no presente, afetam muitos processos ecológicos em riachos. Integrar o histórico do desmatamento à estrutura atual da paisagem melhora a avaliação dos efeitos ecológicos da mudança do uso do solo. Isto é especialmente verdadeiro quando as condições da paisagem contemporânea são semelhantes, mas seguiram trajetórias distintas. Uma abordagem promissora para avaliar as respostas da biodiversidade ao longo do tempo e espaço é a partição da diversidade-β, que combina abordagens taxonômica e funcional. Testamos hipóteses relacionadas à substituição das assembleias de peixes de riachos em microbacias com diferentes condições ambientais e histórias de desmatamento. Amostramos 75 microbacias na bacia do rio Machado, fatores ambientais foram quantificados em múltiplas escalas. A substituição taxonômica foi maior do que esperada pelo acaso, enquanto a substituição funcional foi menor do que o esperado pela substituição taxonômica, indicando que as assembleias são estruturadas por processos determinísticos. As substituições e fatores ambientais diferiram entre microbacias com históricos de desmatamento distintos. Além de serem escala-dependentes, os padrões de substituição provavelmente são dependentes da dinâmica do uso do solo, envolvendo defasagem temporal.(AU)

Integrated terrestrial-freshwater planning doubles conservation of tropical aquatic species.

Conservation initiatives overwhelmingly focus on terrestrial biodiversity, and little is known about the freshwater cobenefits of terrestrial conservation actions. We sampled more than 1500 terrestrial and freshwater species in the Amazon and simulated conservation for species from both realms. Prioritizations based on terrestrial species yielded on average just 22% of the freshwater benefits achieved through freshwater-focused conservation. However, by using integrated cross-realm planning, freshwater benefits could be increased by up to 600% for a 1% reduction in terrestrial benefits. Where freshwater biodiversity data are unavailable but aquatic connectivity is accounted for, freshwater benefits could still be doubled for negligible losses of terrestrial coverage. Conservation actions are urgently needed to improve the status of freshwater species globally. Our results suggest that such gains can be achieved without compromising terrestrial conservation goals.

Second rate or a second chance? Assessing biomass and biodiversity recovery in regenerating Amazonian forests.

Secondary forests (SFs) regenerating on previously deforested land account for large, expanding areas of tropical forest cover. Given that tropical forests rank among Earth's most important reservoirs of carbon and biodiversity, SFs play an increasingly pivotal role in the carbon cycle and as potential habitat for forest biota. Nevertheless, their capacity to regain the biotic attributes of undisturbed primary forests (UPFs) remains poorly understood. Here, we provide a comprehensive assessment of SF recovery, using extensive tropical biodiversity, biomass, and environmental datasets. These data, collected in 59 naturally regenerating SFs and 30 co-located UPFs in the eastern Amazon, cover >1,600 large- and small-stemmed plant, bird, and dung beetles species and a suite of forest structure, landscape context, and topoedaphic predictors. After up to 40 years of regeneration, the SFs we surveyed showed a high degree of biodiversity resilience, recovering, on average among taxa, 88% and 85% mean UPF species richness and composition, respectively. Across the first 20 years of succession, the period for which we have accurate SF age data, biomass recovered at 1.2% per year, equivalent to a carbon uptake rate of 2.25 Mg/ha per year, while, on average, species richness and composition recovered at 2.6% and 2.3% per year, respectively. For all taxonomic groups, biomass was strongly associated with SF species distributions. However, other variables describing habitat complexity-canopy cover and understory stem density-were equally important occurrence predictors for most taxa. Species responses to biomass revealed a successional transition at approximately 75 Mg/ha, marking the influx of high-conservation-value forest species. Overall, our results show that naturally regenerating SFs can accumulate substantial amounts of carbon and support many forest species. However, given that the surveyed SFs failed to return to a typical UPF state, SFs are not substitutes for UPFs.

Disentangling the pathways of land use impacts on the functional structure of fish assemblages in Amazon streams.

Agricultural land use is a primary driver of environmental impacts on streams. However, the causal processes that shape these impacts operate through multiple pathways and at several spatial scales. This complexity undermines the development of more effective management approaches, and illustrates the need for more in-depth studies to assess the mechanisms that determine changes in stream biodiversity. Here we present results of the most comprehensive multi-scale assessment of the biological condition of streams in the Amazon to date, examining functional responses of fish assemblages to land use. We sampled fish assemblages from two large human-modified regions, and characterized stream conditions by physical habitat attributes and key landscape-change variables, including density of road crossings (i.e. riverscape fragmentation), deforestation, and agricultural intensification. Fish species were functionally characterized using ecomorphological traits describing feeding, locomotion, and habitat preferences, and these traits were used to derive indices that quantitatively describe the functional structure of the assemblages. Using structural equation modeling, we disentangled multiple drivers operating at different spatial scales, identifying causal pathways that significantly affect stream condition and the structure of the fish assemblages. Deforestation at catchment and riparian network scales altered the channel morphology and the stream bottom structure, changing the functional identity of assemblages. Local deforestation reduced the functional evenness of assemblages (i.e. increased dominance of specific trait combinations) mediated by expansion of aquatic vegetation cover. Riverscape fragmentation reduced functional richness, evenness and divergence, suggesting a trend toward functional homogenization and a reduced range of ecological niches within assemblages following the loss of regional connectivity. These results underscore the often-unrecognized importance of different land use changes, each of which can have marked effects on stream biodiversity. We draw on the relationships observed herein to suggest priorities for the improved management of stream systems in the multiple-use landscapes that predominate in human-modified tropical forests.

Is environmental legislation conserving tropical stream faunas? A large-scale assessment of local, riparian and catchment-scale influences on Amazonian fish.

Agricultural expansion and intensification are major threats to tropical biodiversity. In addition to the direct removal of native vegetation, agricultural expansion often elicits other human-induced disturbances, many of which are poorly addressed by existing environmental legislation and conservation programmes. This is particularly true for tropical freshwater systems, where there is considerable uncertainty about whether a legislative focus on protecting riparian vegetation is sufficient to conserve stream fauna.To assess the extent to which stream fish are being effectively conserved in agricultural landscapes, we examined the spatial distribution of assemblages in river basins to identify the relative importance of human impacts at instream, riparian and catchment scales, in shaping observed patterns. We used an extensive dataset on the ecological condition of 83 low-order streams distributed in three river basins in the eastern Brazilian Amazon.We collected and identified 24,420 individual fish from 134 species. Multiplicative diversity partitioning revealed high levels of compositional dissimilarity (DS) among stream sites (DS = 0.74 to 0.83) and river basins (DS = 0.82), due mainly to turnover (77.8% to 81.8%) rather than nestedness. The highly heterogeneous fish faunas in small Amazonian streams underscore the vital importance of enacting measures to protect forests on private lands outside of public protected areas.Instream habitat features explained more variability in fish assemblages (15%-19%) than riparian (2%-12%), catchment (4%-13%) or natural covariates (4%-11%). Although grouping species into functional guilds allowed us to explain up to 31% of their abundance (i.e. for nektonic herbivores), individual riparian - and catchment - scale predictor variables that are commonly a focus of environmental legislation explained very little of the observed variation (partial R2 values mostly <5%).Policy implications. Current rates of agricultural intensification and mechanization in tropical landscapes are unprecedented, yet the existing legislative frameworks focusing on protecting riparian vegetation seem insufficient to conserve stream environments and their fish assemblages. To safeguard the species-rich freshwater biota of small Amazonian streams, conservation actions must shift towards managing whole basins and drainage networks, as well as agricultural practices in already-cleared land.

Threshold responses of Amazonian stream fishes to timing and extent of deforestation.

Deforestation is a primary driver of biodiversity change through habitat loss and fragmentation. Stream biodiversity may not respond to deforestation in a simple linear relationship. Rather, threshold responses to extent and timing of deforestation may occur. Identification of critical deforestation thresholds is needed for effective conservation and management. We tested for threshold responses of fish species and functional groups to degree of watershed and riparian zone deforestation and time since impact in 75 streams in the western Brazilian Amazon. We used remote sensing to assess deforestation from 1984 to 2011. Fish assemblages were sampled with seines and dip nets in a standardized manner. Fish species (n = 84) were classified into 20 functional groups based on ecomorphological traits associated with habitat use, feeding, and locomotion. Threshold responses were quantified using threshold indicator taxa analysis. Negative threshold responses to deforestation were common and consistently occurred at very low levels of deforestation (<20%) and soon after impact (<10 years). Sensitive species were functionally unique and associated with complex habitats and structures of allochthonous origin found in forested watersheds. Positive threshold responses of species were less common and generally occurred at >70% deforestation and >10 years after impact. Findings were similar at the community level for both taxonomic and functional analyses. Because most negative threshold responses occurred at low levels of deforestation and soon after impact, even minimal change is expected to negatively affect biodiversity. Delayed positive threshold responses to extreme deforestation by a few species do not offset the loss of sensitive taxa and likely contribute to biotic homogenization.

Early ecological outcomes of natural regeneration and tree plantations for restoring agricultural landscapes.

Mixed tree plantings and natural regeneration are the main restoration approaches for recovering tropical forests worldwide. Despite substantial differences in implementation costs between these methods, little is known regarding how they differ in terms of ecological outcomes, which is key information for guiding decision making and cost-effective restoration planning. Here, we compared the early ecological outcomes of natural regeneration and tree plantations for restoring the Brazilian Atlantic Forest in agricultural landscapes. We assessed and compared vegetation structure and composition in young (7-20 yr old) mixed tree plantings (PL), second-growth tropical forests established on former pastures (SGp), on former Eucalyptus spp. plantations (SGe), and in old-growth reference forests (Ref). We sampled trees with diameter at breast height (DBH) 1-5 cm (saplings) and trees at DBH > 5 cm (trees) in a total of 32 20 × 45 m plots established in these landscapes. Overall, the ecological outcomes of natural regeneration and restoration plantations were markedly different. SGe forests showed higher abundance of large (DBH > 20 cm) nonnative species, of which 98% were resprouting Eucalyptus trees, than SGp and PL, and higher total aboveground biomass; however, aboveground biomass of native species was higher in PL than in SGe. PL forests had lower abundance of native saplings and lianas than both naturally established second-growth forests, and lower proportion of animal dispersed saplings than SGe, probably due to higher isolation from native forest remnants. Rarefied species richness of trees was lower in SGp, intermediate in SGe and Ref and higher in PL, whereas rarefied species richness of saplings was higher in SG than in Ref. Species composition differed considerably among regeneration types. Although these forests are inevitably bound to specific landscape contexts and may present varying outcomes as they develop through longer time frames, the ecological particularities of forests established through different restoration approaches indicate that naturally established forests may not show similar outcomes to mixed tree plantings. The results of this study underscore the importance that restoration decisions need to be based on more robust expectations of outcomes that allow for a better analysis of the cost-effectiveness of different restoration approaches before scaling-up forest restoration in the tropics.

Geographic information system and multilevel analysis: gingival status among 12-year-old schoolchildren in São Paulo, Brazil.

OBJECTIVE: To evaluate gingival and calculus status among schoolchildren 12 years of age using a geographic information system and multilevel analysis. METHODS: A total of 1 002 schoolchildren were selected from 18 municipal districts by means of cluster sampling, from among 25 public and private schools in Piracicaba, São Paulo, Brazil, in 2005. Examinations were carried out by a single calibrated examiner utilizing the criteria of the World Health Organization, as well as the Community Periodontal Index. Social, economic, and behavioral variables were recorded with the use of a questionnaire and were used in the individual analysis (first level). The variables "percentage of heads of families without income" and "percentage of illiterate heads of families" were used in the contextual analysis (second level). RESULTS: A geographic information system was constructed for mapping the distribution of gingival bleeding. The variables were visually distinguished in the maps and demonstrated a tendency toward better gingival health in the central areas of the city, which are recognized as more privileged. On the contextual level, only the "percentage of illiterate heads of families" was significantly associated to gingival bleeding. CONCLUSIONS: The study confirms better oral health status among schoolchildren from privileged families, but does not confirm the data regarding "income." The individuals from areas in which the heads of family did not have income were not associated to a higher prevalence of gingival problems. This suggests that these individuals are reasonably protected from the impact of social privation due to the actions of public health care services in the municipality.

Geographic information system and multilevel analysis: gingival status among 12-year-old schoolchildren in São Paulo, Brazil / Sistema de información geográfica y análisis de niveles múltiples: estado gingival en escolares de 12 años de edad en São Paulo, Brasil

OBJECTIVE: To evaluate gingival and calculus status among schoolchildren 12 years of age using a geographic information system and multilevel analysis. METHODS: A total of 1 002 schoolchildren were selected from 18 municipal districts by means of cluster sampling, from among 25 public and private schools in Piracicaba, São Paulo, Brazil, in 2005. Examinations were carried out by a single calibrated examiner utilizing the criteria of the World Health Organization, as well as the Community Periodontal Index. Social, economic, and behavioral variables were recorded with the use of a questionnaire and were used in the individual analysis (first level). The variables "percentage of heads of families without income" and "percentage of illiterate heads of families" were used in the contextual analysis (second level). RESULTS: A geographic information system was constructed for mapping the distribution of gingival bleeding. The variables were visually distinguished in the maps and demonstrated a tendency toward better gingival health in the central areas of the city, which are recognized as more privileged. On the contextual level, only the "percentage of illiterate heads of families" was significantly associated to gingival bleeding. CONCLUSIONS: The study confirms better oral health status among schoolchildren from privileged families, but does not confirm the data regarding "income." The individuals from areas in which the heads of family did not have income were not associated to a higher prevalence of gingival problems. This suggests that these individuals are reasonably protected from the impact of social privation due to the actions of public health care services in the municipality.

OBJETIVO: Evaluar el estado gingival y la presencia de sarro en escolares de 12 años de edad mediante el empleo de un sistema de información geográfica y análisis de niveles múltiples. MÉTODOS: En el año 2005, se seleccionó a un total de 1 002 escolares de 18 distritos municipales mediante muestreo por grupos, con la participación de 25 escuelas públicas y privadas de Piracicaba, en el estado de São Paulo, Brasil. Un único examinador calibrado, que utilizó los criterios de la Organización Mundial de la Salud, así como el Índice Periodontal Comunitario, llevó a cabo los exámenes. Mediante un cuestionario, se registraron las variables sociales, económicas y conductuales, y estas se emplearon en el análisis individual (primer nivel). En el análisis contextual (segundo nivel), se utilizaron las variables "porcentaje de cabezas de familia sin ingresos" y "porcentaje de cabezas de familia analfabetas". RESULTADOS: Se construyó un sistema de información geográfica para elaborar mapas de la distribución de la hemorragia gingival. Los mapas, donde se pueden distinguir visualmente las variables, demostraron una tendencia hacia una mejor salud gingival en las zonas del centro de la ciudad, consideradas como privilegiadas. En el nivel contextual, únicamente el "porcentaje de cabezas de familia analfabetas" se asoció significativamente con el sangrado gingival. CONCLUSIONES: El presente estudio confirma una mejor salud bucodental en los escolares pertenecientes a familias privilegiadas, pero no confirma los datos en cuanto a "ingresos". Las personas residentes en zonas donde las cabezas de familia no tenían ingresos no presentaron una mayor prevalencia de problemas gingivales. Esto indica que estas personas, como consecuencia de las actividades de los servicios de atención de salud pública del municipio, están razonablemente protegidas de la repercusión de la privación social.

Geographic information systems (GIS) in assessing dental health.

The present study investigated the distribution profile of dental caries and its association with areas of social deprivation at the individual and contextual level. The cluster sample consisted of 1,002 12-year-old schoolchildren from Piracicaba, SP, Brazil. The DMFT Index was used for dental caries and the Care Index was used to determine access to dental services. On the individual level, variables were associated with a better oral status. On the contextual level, areas were not associated with oral status. However, maps enabled determining that the central districts have better social and oral conditions than the deprived outlying districts.