1. Land-use change is the main driver of global biodiversity loss, but its relative impact on species turnover (β-diversity) across multiple spatial scales remains unclear. Plant communities in ...fragmented rain forests can undergo declines (floristic homogenization) or increases (floristic differentiation) in β-diversity. 2. We tested these alternative hypotheses analysing a large vegetation data base from a hierarchically nested sampling design (450 plots in 45 forest patches in 3 landscapes with different deforestation levels) at Los Tuxtlas rain forest, Mexico. Differences in β-diversity across spatial scales (i.e. among plots, among patches, and among landscapes) were analysed using multiplicative diversity decompositions of Hill numbers. 3. Plant β-diversity among plots within forest patches decreased in landscapes with higher deforestation levels, leading to floristic homogenization within patches. This homogenization process can be explained by the loss of rare and shade-tolerant plant species, and the recruitment and dominance of disturbance-adapted species, and can limit the accumulation of species (γ-diversity) in landscapes with higher deforestation. 4. Nevertheless, the landscape with the highest deforestation level showed the highest floristic differentiation among patches. This landscape showed the greatest isolation distances between patches; a landscape spatial pattern that can limit the interchange of seeds (and species) between patches. Because the study patches are undergoing secondary succession following disturbances (e.g. logging, edge effects), different disturbance regimes and increased distance among patches could lead to higher β-diversity. 5. Synthesis. These findings indicate that patterns of floristic homogenization and differentiation depend on the landscape configuration and on the spatial scale of analysis. At the landscape scale, our results suggest that, in accordance with non-equilibrium dynamics and the landscape-divergence hypothesis, patches located in landscapes with different forest cover and different connectivity can experience contrasting successional pathways due to increasing levels of compositional differentiation between patches. These novel findings add further uncertainties to the maintenance of biodiversity in severely deforested tropical landscapes and have key ecological implications for biodiversity conservation planning.
Chronic disturbances, such as selective logging, firewood extraction and extensive grazing, may lead to the taxonomic and phylogenetic impoverishment of remaining old-growth forest communities ...worldwide; however, the empirical evidence on this topic is limited. We tested this hypothesis in the Caatinga vegetation -a seasonally dry tropical forest restricted to northeast Brazil. We sampled 11,653 individuals (adults, saplings, and seedlings) from 51 species in 29 plots distributed along a gradient of chronic disturbance.The gradient was assessed using a chronic disturbance index (CDI) based on five recognized indicators of chronic disturbances: proximity to urban center, houses and roads and the density of both people and livestock. We used linear models to test if mean effective number of lineages, mean phylogenetic distance and phylogenetic dispersion decreased with CDI and if such relationships differed among ontogenetic stages. As expected, the mean effective number of lineages and the mean phylogenetic distance were negatively related to CDI, and such diversity losses occurred irrespective of ontogeny. Yet the increase in phylogenetic clustering in more disturbed plots was only evident in seedlings and saplings, mostly because clades with more descendent taxa than expected by chance (e.g., Euphorbiaceae) thrived in more disturbed plots. This novel study indicates that chronic human disturbances are promoting the phylogenetic impoverishment of the irreplaceable woody flora of the Brazilian Caatinga forest. The highest impoverishment was observed in seedlings and saplings, indicating that if current chronic disturbances remain, they will result in increasingly poorer phylogenetically forests. This loss of evolutionary history will potentially limit the capacity of this ecosystem to respond to human disturbances (i.e., lower ecological resilience) and particularly their ability to adapt to rapid climatic changes in the region.
Agriculture and development transform forest ecosystems to human‐modified landscapes. Decades of research in ecology have generated myriad concepts for the appropriate management of these landscapes. ...Yet, these concepts are often contradictory and apply at different spatial scales, making the design of biodiversity‐friendly landscapes challenging. Here, we combine concepts with empirical support to design optimal landscape scenarios for forest‐dwelling species. The supported concepts indicate that appropriately sized landscapes should contain ≥ 40% forest cover, although higher percentages are likely needed in the tropics. Forest cover should be configured with c. 10% in a very large forest patch, and the remaining 30% in many evenly dispersed smaller patches and semi‐natural treed elements (e.g. vegetation corridors). Importantly, the patches should be embedded in a high‐quality matrix. The proposed landscape scenarios represent an optimal compromise between delivery of goods and services to humans and preserving most forest wildlife, and can therefore guide forest preservation and restoration strategies.
We review key concepts on species responses to landscape disturbances to prioritize management strategies for conservation of forest wildlife. We design optimal landscape scenarios for preserving most forest wildlife and promoting the delivery of goods and services to humans. The proposed scenarios can therefore guide forest preservation and restoration strategies in human‐modified landscapes.
1. In addition to acute transformations of ecosystems caused by deforestation, old-growth forests world-wide are being increasingly altered by low-intensity but chronic human disturbance. Overgrazing ...and the continuous extraction of forest products are important drivers of chronic disturbance, which can lead to the gradual local extinction of species and the alteration of vegetation structure. 2. We tested this hypothesis in the Brazilian Caatinga vegetation, one of the most speciesrich and populated semi-arid regions of the world. Using a multimodel averaging approach, we examined the impact of five recognized indicators of chronic disturbance (i.e. proximity to urban centre, houses, roads, density of people and livestock) on the diversity, abundance and evenness of 30 woody plant communities. We separately tested the response of seedlings, saplings and adults to identify the ontogenetic stages that are most susceptible to chronic disturbance. 3. We recorded over 11 000 individuals belonging to 51 plant species. As expected, most indicators of chronic disturbance were negatively related to species diversity and stem abundance, with a variable effect on community evenness. The density of people and density of livestock were the main factors driving changes in plant communities, with a stronger negative impact on seedling and sapling diversities. Species composition also varied significantly with disturbance indicators, irrespective of ontogeny. 4. Our results show the potential negative impact that chronic disturbance can have on Caatinga plant assemblages and highlight the fact that disturbance resulting from an extractivism-based and subsistence economy are probably driving old-growth forest stands towards shrub-dominated secondary stands. 5. Synthesis and applications. These findings indicate that chronic disturbance should not continue to be neglected and we argue for: (i) research and rural programmes able to support better practices in terms of land use and sustainable exploitation of forest resources, (ii) improved governance and law enforcement to shift extractivism towards sustainable standards, and (iii) expanding the coverage and effective implementation of strictly protected areas.
1. Deforestation and forest fragmentation can drive species to local extinction, potentially changing the phylogenetic community structure and diversity of remaining assemblages. We tested this ...hypothesis analysing a large vegetation data set from a highly fragmented rain forest. 2. We assessed 9000 trees (both saplings and adults) from 268 species in 45 rain forest patches (ranging from < 1 to 700 ha) in three landscapes with different deforestation levels (4%, 11%, and 24% forest cover) in Los Tuxtlas, Mexico. We tested whether species density (i.e. number of species per unit area) and phylogenetic structure and diversity differed among landscapes, whether they were related to patch area, and whether the relationships differed among landscapes. 3. Overall, the observed differences in sapling and adult species densities across forest patches and landscapes (e.g. lower species densities in smaller patches) resulted in few and very weak changes in the phylogenetic community structure and diversity. Our results indicate that local extirpation of tree species may occur randomly or uniformly (but not in a clustered manner) throughout the phylogenetic tree, supporting the hypothesis of low phylogenetic conservatism of traits associated with vulnerability to forest fragmentation in the Neotropics. 4. Synthesis. This study indicates that in highly deforested and fragmented rain forests, the local extirpation of tree species does not occur across entire lineages. These novel and hopeful findings have direct implications for the ecology and conservation of fragmented rain forests. The maintenance of phylogenetic diversity in highly fragmented landscapes suggests that ecosystem function and stability may be maintained despite the loss of a number of tree species. We argue that in this unique Neotropical region, both large and small rain forest patches are critical for conserving regional tree evolutionary history.
Adolescence is characterized by continuing profound mental, physical, and social changes and entering into the labor market during this phase may have negative consequences on physical and mental ...health. Common mental disorders (CMD) are characterized as disorders of mental functions, including symptoms of depression and anxiety as well as various nonspecific and somatic complaints such as reduced ability to concentrate, tiredness, irritation, and forgetfulness. Despite its increasing prevalence, few studies have addressed CMD and its association with work, in adolescents. In the present study, we aimed to identify the main factors associated with CMD and evaluated its association with work, in school adolescents.
A cross-sectional study was conducted with 12 to 17-year-old adolescent students using a self-administered questionnaire with questions related to work. CMD was verified using the General Health Questionnaire of 12 items. In total, 3424 adolescents were studied.
The prevalence of CMD and work in the last year was 28.72% and 19.63%, respectively. After adjustment for potential confounding variables, multivariate analysis showed associations of CMD with female gender (OR=2.72) and work (OR=1.70).
In the present study, a high number of cases of CMD were observed among the studied adolescents. Female gender and work history in the last year were negatively and independently associated with the presence of CMD.
Climate emergency is a significant threat to biodiversity in the 21st century, but species will not be equally affected. In summing up the responses of different species at the local scale, we can ...assess changes in the species quantity and composition of biotic assemblages.
We used more than 420K curated occurrence records of 3060 plant species to model current and future patterns of plant species distribution in one of the world's largest tropical dry forests—the Caatinga. While allowing different model extrapolation scenarios, we estimated potential changes in the species richness and composition of dryland plant assemblages in response to projected climate change, and assessed how the ecological generalism and woodiness of plant assemblages can be impacted by the climate crisis.
More than 99% of plant assemblages were projected to lose species by 2060, with biotic homogenisation—the decrease in spatial beta diversity—forecasted in 40% of the Caatinga. The replacement of narrow‐range woody species by wide‐range non‐woody ones should impact at least 90% of Caatinga plant assemblages. The exacerbated species loss in the dryland plant assemblages was connected to the heterogenisation and homogenisation of biotic assemblages. Still, the magnitude of climate change impacts on ecological generalism and woodiness patterns of dryland plant assemblages differ according to the direction of the biotic change process.
Synthesis. The future increase in aridity will change the patterns of woodiness and ecological generalism of tropical dry forest plant assemblages by decreasing vegetation diversity and complexity. The projected biotic changes in dryland plant assemblages indicate the erosion of ecosystem services linked to biomass productivity and carbon storage. We highlight the importance of long‐term conservation planning for maintaining tropical dry forests.
The future increase in aridity will change the patterns of woodiness and ecological generalism of tropical dry forest plant assemblages by decreasing vegetation diversity and complexity. The projected biotic changes in dryland plant assemblages indicate the erosion of ecosystem services linked to biomass productivity and carbon storage. The authors highlight the importance of long‐term conservation planning for maintaining tropical dry forests.
The sinking of artificial structures has become increasingly common around the world, but whether the artificial structures favour or disfavour fish diversity remain under debate. Sinking may empty ...the nearby natural reefs locally and regionally by attracting their biota. Conversely, it may improve environmental conditions for species survival and reproduction, acting as source of diversity at the local and regional levels.
We tested these contrasting hypotheses by assessing the taxonomic, functional and phylogenetic diversity of 12 fish communities in Northeast Brazil: four ageing (>100‐year‐old) shipwrecks and eight surrounding natural reefs at comparable depths and distances. We partitioned the gamma diversity of artificial and natural reef communities into independent alpha and beta components, accounted for species’ abundance and assessed whether beta patterns were mostly driven by spatial turnover or nestedness.
We recorded 6,335 individuals distributed in 88 fish species and 38 families. While artificial and natural reefs shared 50 species (57%), 21 species (24%) were exclusive to the artificial reefs, suggesting that the nearby natural reefs—the most likely original source of these exclusive species—do not harbour them anymore. Alpha diversity of typical and dominant species did not significantly differ between the reef types, but alpha diversity of rare species was taxonomically, functionally and phylogenetically higher in artificial reefs, indicating positive effects of the structures at the local scale.
By contrast, regional beta diversity was higher in natural reefs in terms of taxonomic and functional diversity, regardless of species abundance. Pairwise beta diversity indicated that turnover had a large effect on the compositional dissimilarity in both reef types, whereas nestedness was almost irrelevant in artificial reefs.
Synthesis and applications. Artificial structures such as shipwrecks may promote the co‐occurrence of rare species, but they are unable to produce the beta diversity patterns that natural reefs do, even following many decades of colonization. Although artificial habitats host a significant portion of the regional reef fish diversity, they may have also contributed to the degradation of nearby natural reefs. We recommend the establishment of regulated diving spots, fishing grounds and no‐take areas as a strategy to conserve regional fish diversity.
Resumo
O afundamento de estruturas artificiais tem se tornado bastante comum em diversas partes do planeta, no entanto ainda tem sido muito debatido se essas estruturas favorecem ou desfavorecem a diversidade de peixes. O afundamento de novas estruturas pode acabar atraindo a biota dos recifes adjacentes, causando uma diminuição da diversidade local e regional desses recifes. Por outro lado, pode haver uma melhora nas condições ambientais, aumentando as taxas de sobrevivência e reprodução das espécies, e agindo como fonte de diversidade em escala local e regional.
Nós testamos essas diferentes hipóteses a partir da diversidade taxonômica, funcional e filogenética de 12 comunidades de peixes no Nordeste do Brasil: quatro naufrágios antigos (>100 anos de afundamento) e oito recifes naturais adjacentes com distâncias e profundidades similares. Nós particionamos a diversidade gama dos recifes artificias e naturais em seus componentes independentes alfa e beta, considerando a abundância das espécies, e analisamos se o padrão de diversidade beta encontrado era de aninhamento ou substituição.
Nós registramos 6,335 indivíduos pertencentes a 88 espécies e 38 famílias. Recifes artificiais e naturais compartilharam 50 espécies (57%), enquanto que 21 espécies (24%) foram exclusivas dos recifes artificiais, sugerindo que os recifes naturais adjacentes – o possível local de onde essas espécies exclusivas vieram – não abrigam mais as espécies exclusivas encontradas nos recifes artificiais. A diversidade alfa de espécies típicas e dominantes não foi diferiu significativamente entre os tipos de recifes, no entanto a diversidade alfa taxonômica, funcional e filogenética de espécies raras foi maior nos recifes artificiais, indicando efeitos positivos dessas estruturas em escala local.
Por outro lado, a diversidade beta taxonômica e funcional regional foi maior nos recifes naturais, independente da abundância. A diversidade beta par‐a‐par indicou que as taxas de substituição tiveram maior efeito na dissimilaridade da composição de espécies em ambos os tipos recifais, enquanto que as taxas de aninhamento foram praticamente irrelevantes nos recifes artificiais.
Síntese e aplicações. Estruturas artificiais como os naufrágios podem promover a co‐ocorrência de espécies raras, mas não conseguem produzir os padrões de diversidade beta encontrados nos recifes naturais, mesmo depois de muitas décadas de colonização. Embora os ambientes artificiais abriguem uma porção significativa da diversidade regional de peixes, esses mesmos ambientes podem também ter contribuído para a degradação dos recifes naturais adjacentes. Nós recomendamos a implementação de regulamentos definindo locais de mergulho, áreas de pesca e áreas em que essas atividades sejam proibidas como uma estratégia para conservar a diversidade regional de peixes.
Artificial structures such as shipwrecks may promote the co‐occurrence of rare species, but they are unable to produce the beta diversity patterns that natural reefs do, even following many decades of colonization. Although artificial habitats host a significant portion of the regional reef fish diversity, they may have also contributed to the degradation of nearby natural reefs. We recommend the establishment of regulated diving spots, fishing grounds and no‐take areas as a strategy to conserve regional fish diversity.
Tropical plant assemblages can be taxonomically and phylogenetically impoverished by chronic anthropogenic disturbance (CAD), such as firewood collection and extensive grazing. However, to what ...extent the functional dimension responds to CAD is still unclear. Such knowledge is urgently required for predicting, preventing or even reversing the impacts of CAD.
Chronic anthropogenic disturbance may operate as an ecological filter by selecting functional trait values (e.g. low wood density), thereby altering the functional composition and diversity of plant assemblages. We tested this hypothesis using 29 woody plant assemblages across three ontogenetic stages (seedlings, saplings and adults) in a 220‐km2 landscape of the Caatinga, northeast Brazil. We adopted a CAD index consisting of four indicators (proximity to urban centre and houses and the density of both people and livestock) and tested how well it explained the functional diversity and effect sizes (richness, evenness and dispersion) and composition (community‐weighted mean).
Chronic anthropogenic disturbance affected several functional metrics across the three ontogenetic stages. However, CAD effects were stronger in adult communities by negatively affecting functional richness, dispersion and their effect sizes. CAD also altered the functional composition of leaf mass per area, woody density and leaf area of adult assemblages. Sapling communities were affected in terms of functional composition (leaf area, leaf dry matter and wood density), with positive and negative effects, while seedling assemblages responded positively to CAD only in terms of functional evenness and its effect size. Some changes in functional metrics were influenced by dominant Euphorbiaceae species across ontogenetic stages, especially in terms of leaf area and woody density.
Synthesis. Chronic anthropogenic disturbance is an important driver of plant‐community functional organization across ontogenetic stages in the Caatinga. Adult assemblages are particularly sensitive and tend to lose functional niche space and support more acquisitive rather than conservative strategies as chronic anthropogenic disturbance increases. The proliferation of Euphorbiaceae disturbance‐adapted species can explain part of the community responses to chronic anthropogenic disturbance. Our findings highlight the ecological effects of chronic anthropogenic disturbance and show that it is a key influence on tropical biotas. Changes in plant functional traits associated with plant resource use are likely to affect ecosystem functioning and services provided by Caatinga.
Chronic anthropogenic disturbance (CAD) is an important driver of plant‐community functional organization across ontogenetic stages in the Caatinga. Adult assemblages are particularly sensitive and tend to lose functional niche space and support more acquisitive rather than conservative strategies as chronic anthropogenic disturbance increases. The proliferation of Euphorbiaceae disturbance‐adapted species can explain part of the community responses to chronic anthropogenic disturbance. Our findings highlight the ecological effects of chronic anthropogenic disturbance and show that it is a key influence on tropical biotas. Changes in plant functional traits associated with plant resource use are likely to affect ecosystem functioning and services provided by Caatinga.
In early September 2019, dense crude oil began to wash the beaches of Brazil's tropical coast. Four months after the first report, the oil has already been found along >3000 km of the Brazilian ...coastline on >980 beaches and was recently observed along the Amazon coast, making this oil spill the most extensive and severe environmental disaster ever recorded in Brazilian history, in the South Atlantic basin, and in tropical coastal regions worldwide. Four features of this oil-spill disaster make it unique: 1) the characteristics of the oil spill; 2) the characteristics of the affected region in tropical Brazil; 3) the significant number of protected areas (>55) and tropical ecosystems affected by the oil; and 4) the absence of measures and/or flaws in the measures taken by the federal government to address this environmental and social emergency. The affected species and poor human communities in Brazil should receive focused attention in the coming decades owing to the long-term impacts of the oil contamination. Environmental monitoring and response measures must be implemented to minimize the ecological, economic, and social effects of the spill. Biodiversity and climate regulation losses considering blue carbon environments should drive discussions regarding mining accidents and global consequences related to pre-salt oil exploitation, new spill events, and their global impacts. These measures are particularly relevant in areas with high tropical biodiversity and high social inequality, as in the present case, which represents one of the worst-case scenarios of an environmental and governmental disaster.
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•This oil spill disaster is unique owing to four main features.•The affected Brazilian tropical region is unique considering coral endemism.•The significant number of protected areas and tropical ecosystems affected by the oil.•The characteristics of the oil spill itself.•The absence of and/or flaws in the measures taken by the federal governmental to address this emergency.
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