Drought conditions in Amazonia are associated with increased fire incidence, enhancing aerosol emissions with degradation in air quality. Quantifying the synergic influence of climate and ...human-driven environmental changes on human health is, therefore, critical for identifying climate change adaptation pathways for this vulnerable region. Here we show a significant increase (1.2%-267%) in hospitalisations for respiratory diseases in children under-five in municipalities highly exposed to drought. Aerosol was the primary driver of hospitalisations in drought affected municipalities during 2005, while human development conditions mitigated the impacts in 2010. Our results demonstrated that drought events deteriorated children's respiratory health particularly during 2005 when the drought was more geographically concentrated. This indicates that if governments act on curbing fire usage and effectively plan public health provision, as a climate change adaptation procedure, health quality would improve and public expenditure for treatment would decrease in the region during future drought events.
Quantifying the impact of habitat disturbance on ecosystem function is critical to understanding and predicting the future of tropical forests. Many studies have examined post‐disturbance changes in ...animal traits related to mutualistic interactions with plants, but the effect of disturbance on plant traits in diverse forests has received much less attention.
Focusing on two study regions in the eastern Brazilian Amazon, we used a trait‐based approach to examine how seed dispersal functionality within tropical plant communities changes across a landscape‐scale gradient of human modification, including both regenerating secondary forests and primary forests disturbed by burning and selective logging.
Surveys of 230 forest plots recorded 26,533 live stems from 846 tree species. Using herbarium material and literature, we compiled trait information for each tree species, focusing on dispersal mode and seed size.
Disturbance reduced tree diversity and increased the proportion of lower wood density and small‐seeded tree species in study plots. Disturbance also increased the proportion of stems with seeds that are ingested by animals and reduced those dispersed by other mechanisms (e.g. wind). Older secondary forests had functionally similar plant communities to the most heavily disturbed primary forests. Mean seed size and wood density per plot were positively correlated for plant species with seeds ingested by animals.
Synthesis. Anthropogenic disturbance has major effects on the seed traits of tree communities, with implications for mutualistic interactions with animals. The important role of animal‐mediated seed dispersal in disturbed and recovering forests highlights the need to avoid defaunation or promote faunal recovery. The changes in mean seed width suggest larger vertebrates hold especially important functional roles in these human‐modified forests. Monitoring fruit and seed traits can provide a valuable indicator of ecosystem condition, emphasizing the importance of developing a comprehensive plant traits database for the Amazon and other biomes.
Sumário
Para melhor entender e prever o futuro das florestas tropicais é crítico quantificar o impacto de distúrbios antrópicos sobre as funções ecossistêmicas. Muitos estudos já avaliaram, após eventos de distúrbios, mudanças nas características funcionais da fauna relacionadas com interações mutualísticas com a flora. Porém, o efeito de distúrbios antrópicos nas características funcionais da comunidade arbórea de florestas megadiversas é ainda pouco estudado.
Este estudo focou em duas regiões distintas da Amazônia oriental brasileira, e utilizou um método baseado em características funcionais para entender como a dispersão de sementes, dentro de comunidades arbóreas, pode ser modificada ao longo de um gradiente de distúrbio antrópico, incluindo florestas secundárias e florestas primárias afetadas por fogo e corte seletivo.
Foram conduzidos inventários florestais em 230 parcelas de estudo, amostrando um total de 26.533 indivíduos vivos pertencentes a 846 espécies arbóreas. A partir de material depositado em herbários e informações da literatura, as características funcionais, para cada espécie arbórea, foram compiladas, focando no tipo de dispersão e no tamanho da semente.
Os distúrbios antrópicos reduziram a diversidade arbórea e aumentaram a proporção tanto de espécies com baixa densidade de madeira, como de espécies com sementes pequenas. Os distúrbios antrópicos também aumentaram a proporção de árvores com sementes que são ingeridas por animais e diminuíram àquelas dispersas por outros mecanismos, como o vento. Florestas secundárias em estágios mais avançados de sucessão apresentaram comunidades arbóreas funcionalmente semelhantes àquelas de florestas primárias com maior grau de distúrbios antrópicos. A nível de parcela, o tamanho médio das sementes e a densidade da madeira foram positivamente correlacionados para plantas com sementes dispersas por animais.
Síntese: Os distúrbios antrópicos influenciaram amplamente as características funcionais de sementes das comunidades arbóreas, com implicações diretas para as relações mutualísticas com a fauna. A elevada importância de animais na dispersão de sementes tanto em florestas primárias que sofreram distúrbios antrópicos assim como em florestas secundárias ressalta a importância de se evitar a defaunação e de promover a recuperação da fauna. As mudanças no tamanho médio da largura da semente sugerem que grandes vertebrados tem um papel funcional especialmente importante em florestas antropizadas. O monitoramento de características funcionais de frutos e sementes pode prover um valioso indicador das condições de ecossistemas, enfatizando a importância da criação de uma base de dados compreensiva para a Amazônia e para outros biomas contendo características funcionais da vegetação.
Anthropogenic disturbance has major effects on the seed traits of tree communities, with implications for mutualistic interactions with animals. The important role of animal‐mediated seed dispersal in disturbed and recovering forests highlights the need to avoid defaunation or promote faunal recovery. The changes in mean seed width suggest larger vertebrates hold especially important functional roles in these human‐modified forests. Monitoring fruit and seed traits can provide a valuable indicator of ecosystem condition, emphasizing the importance of developing a comprehensive plant traits database for the Amazon and other biomes.
Human activities pose a major threat to tropical forest biodiversity and ecosystem services. Although the impacts of deforestation are well studied, multiple land-use and land-cover transitions ...(LULCTs) occur in tropical landscapes, and we do not know how LULCTs differ in their rates or impacts on key ecosystem components. Here, we quantified the impacts of 18 LULCTs on three ecosystem components (biodiversity, carbon, and soil), based on 18 variables collected from 310 sites in the Brazilian Amazon. Across all LULCTs, biodiversity was the most affected ecosystem component, followed by carbon stocks, but the magnitude of change differed widely among LULCTs and individual variables. Forest clearance for pasture was the most prevalent and high-impact transition, but we also identified other LULCTs with high impact but lower prevalence (e.g., forest to agriculture). Our study demonstrates the importance of considering multiple ecosystem components and LULCTs to understand the consequences of human activities in tropical landscapes.
Consider both water and land
When designing terrestrial reserves, it is common to consider the needs of species and systems from a terrestrial perspective, with an assumption that any freshwater ...systems will benefit as well. Leal
et al.
tested this assumption by analyzing data from two locations in the Brazilian Amazon and found that it is far from accurate: Terrestrial systems confer little benefit to freshwater systems (see the Perspective by Abell and Harrison). However, the authors also found that integrating the needs of freshwater species into overall reserve planning increased freshwater benefits by 600% while only decreasing terrestrial outcomes by 1%. They argue that reserve planning must take freshwater systems into account if they are to protect across both realms.
Science
, this issue p.
117
; see also p.
38
A study of terrestrial and freshwater species in the Amazon suggests that the conservation needs of freshwater species need to be actively considered.
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.
The restoration and reforestation of 12 million hectares of forests by 2030 are amongst the leading mitigation strategies for reducing carbon emissions within the Brazilian Nationally Determined ...Contribution targets assumed under the Paris Agreement. Understanding the dynamics of forest cover, which steeply decreased between 1985 and 2018 throughout Brazil, is essential for estimating the global carbon balance and quantifying the provision of ecosystem services. To know the long-term increment, extent, and age of secondary forests is crucial; however, these variables are yet poorly quantified. Here we developed a 30-m spatial resolution dataset of the annual increment, extent, and age of secondary forests for Brazil over the 1986-2018 period. Land-use and land-cover maps from MapBiomas Project (Collection 4.1) were used as input data for our algorithm, implemented in the Google Earth Engine platform. This dataset provides critical spatially explicit information for supporting carbon emissions reduction, biodiversity, and restoration policies, enabling environmental science applications, territorial planning, and subsidizing environmental law enforcement.
We analysed the flora of 46 forest inventory plots (25 m x 100 m) in old growth forests from the Amazonian region to identify the role of environmental (topographic) and spatial variables (obtained ...using PCNM, Principal Coordinates of Neighbourhood Matrix analysis) for common and rare species. For the analyses, we used multiple partial regression to partition the specific effects of the topographic and spatial variables on the univariate data (standardised richness, total abundance and total biomass) and partial RDA (Redundancy Analysis) to partition these effects on composition (multivariate data) based on incidence, abundance and biomass. The different attributes (richness, abundance, biomass and composition based on incidence, abundance and biomass) used to study this metacommunity responded differently to environmental and spatial processes. Considering standardised richness, total abundance (univariate) and composition based on biomass, the results for common species differed from those obtained for all species. On the other hand, for total biomass (univariate) and for compositions based on incidence and abundance, there was a correspondence between the data obtained for the total community and for common species. Our data also show that in general, environmental and/or spatial components are important to explain the variability in tree communities for total and common species. However, with the exception of the total abundance, the environmental and spatial variables measured were insufficient to explain the attributes of the communities of rare species. These results indicate that predicting the attributes of rare tree species communities based on environmental and spatial variables is a substantial challenge. As the spatial component was relevant for several community attributes, our results demonstrate the importance of using a metacommunities approach when attempting to understand the main ecological processes underlying the diversity of tropical forest communities.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary
Soil nutrient availability can strongly affect root traits. In tropical forests, phosphorus (P) is often considered the main limiting nutrient for plants. However, support for the P paradigm ...is limited, and N and cations might also control tropical forests functioning.
We used a large‐scale experiment to determine how the factorial addition of nitrogen (N), P and cations affected root productivity and traits related to nutrient acquisition strategies (morphological traits, phosphatase activity, arbuscular mycorrhizal colonisation and nutrient contents) in a primary rainforest growing on low‐fertility soils in Central Amazonia after 1 yr of fertilisation.
Multiple root traits and productivity were affected. Phosphorus additions increased annual root productivity and root diameter, but decreased root phosphatase activity. Cation additions increased root productivity at certain times of year, also increasing root diameter and mycorrhizal colonisation. P and cation additions increased their element concentrations in root tissues. No responses were detected with N addition.
Here we showed that rock‐derived nutrients determined root functioning in low‐fertility Amazonian soils, demonstrating not only the hypothesised importance of P, but also highlighting the role of cations. The changes in fine root traits and productivity indicated that even slow‐growing tropical rainforests can respond rapidly to changes in resource availability.
Smoke pollution's impacts in Amazonia de Oliveira, Gabriel; Chen, Jing M; Stark, Scott C ...
Science (American Association for the Advancement of Science),
08/2020, Letnik:
369, Številka:
6504
Journal Article
Mapping plant species at the regional scale to provide information for ecologists and forest managers is a challenge for the remote sensing community. Here, we use a deep learning algorithm called ...U-net and very high-resolution multispectral images (0.5 m) from GeoEye satellite to identify, segment and map canopy palms over ∼3000 km 2 of Amazonian forest. The map was used to analyse the spatial distribution of canopy palm trees and its relation to human disturbance and edaphic conditions. The overall accuracy of the map was 95.5% and the F1-score was 0.7. Canopy palm trees covered 6.4% of the forest canopy and were distributed in more than two million patches that can represent one or more individuals. The density of canopy palms is affected by human disturbance. The post-disturbance density in secondary forests seems to be related to the type of disturbance, being higher in abandoned pasture areas and lower in forests that have been cut once and abandoned. Additionally, analysis of palm trees’ distribution shows that their abundance is controlled naturally by local soil water content, avoiding both flooded and waterlogged areas near rivers and dry areas on the top of the hills. They show two preferential habitats, in the low elevation above the large rivers, and in the slope directly below the hill tops. Overall, their distribution over the region indicates a relatively pristine landscape, albeit within a forest that is critically endangered because of its location between two deforestation fronts and because of illegal cutting. New tree species distribution data, such as the map of all adult canopy palms produced in this work, are urgently needed to support Amazon species inventory and to understand their distribution and diversity.
Wildfires produce substantial CO2 emissions in the humid tropics during El Niño-mediated extreme droughts, and these emissions are expected to increase in coming decades. Immediate carbon emissions ...from uncontrolled wildfires in human-modified tropical forests can be considerable owing to high necromass fuel loads. Yet, data on necromass combustion during wildfires are severely lacking. Here, we evaluated necromass carbon stocks before and after the 2015–2016 El Niño in Amazonian forests distributed along a gradient of prior human disturbance. We then used Landsat-derived burn scars to extrapolate regional immediate wildfire CO2 emissions during the 2015–2016 El Niño. Before the El Niño, necromass stocks varied significantly with respect to prior disturbance and were largest in undisturbed primary forests (30.2 ± 2.1 Mg ha−1, mean ± s.e.) and smallest in secondary forests (15.6 ± 3.0 Mg ha−1). However, neither prior disturbance nor our proxy of fire intensity (median char height) explained necromass losses due to wildfires. In our 6.5 million hectare (6.5 Mha) study region, almost 1 Mha of primary (disturbed and undisturbed) and 20 000 ha of secondary forest burned during the 2015–2016 El Niño. Covering less than 0.2% of Brazilian Amazonia, these wildfires resulted in expected immediate CO2 emissions of approximately 30 Tg, three to four times greater than comparable estimates from global fire emissions databases. Uncontrolled understorey wildfires in humid tropical forests during extreme droughts are a large and poorly quantified source of CO2 emissions.
This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.
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