One sixth of Amazonian tree diversity is dependent on river floodplains

Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.Naturali

Mapping density, diversity and species-richness of the Amazon tree flora

Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

Detecting emerging infectious diseases in the Torres Strait: a review of vector, host and disease studies

[Extract] The Torres Strait has long been recognised as a 'biological bridge' between Papua New Guinea and mainland Australia, where for millions of years species of plants and animals have moved between the two continents (Galloway and Loffler 1972). Currently, there is concern over the vulnerability of Torres Strait communities to emerging infectious diseases and the potential for disease movement across the islands to the mainland. This report addresses the emerging infectious disease threat to the Torres Strait Islands and mainland Australia. We review the past and current research into mosquito-borne vectors, and their role in past disease outbreaks. The threat of new vectors and diseases is examined and we describe the vector-disease dispersal models that have been developed for the region. Finally, we discuss the implications for continued vector management and surveillance in the region

Detecting emerging infectious diseases in the Torres Strait: a review of vector, host and disease studies

[Extract] The Torres Strait has long been recognised as a 'biological bridge' between Papua New Guinea and mainland Australia, where for millions of years species of plants and animals have moved between the two continents (Galloway and Loffler 1972). Currently, there is concern over the vulnerability of Torres Strait communities to emerging infectious diseases and the potential for disease movement across the islands to the mainland. This report addresses the emerging infectious disease threat to the Torres Strait Islands and mainland Australia. We review the past and current research into mosquito-borne vectors, and their role in past disease outbreaks. The threat of new vectors and diseases is examined and we describe the vector-disease dispersal models that have been developed for the region. Finally, we discuss the implications for continued vector management and surveillance in the region

Overcoming the challenges of mosquito (Diptera: Culicidae) sampling in remote localities: a comparison of CO2 attractants on mosquito communities in three tropical forest habitats

Emerging infectious diseases are on the rise with future outbreaks predicted to occur in frontier regions of tropical countries. Disease surveillance in these hotspots is challenging because sampling techniques often rely on vector attractants that are either unavailable in remote localities or difficult to transport. We examined whether a novel method for producing CO2 from yeast and sugar produces similar mosquito species captures compared with a standard attractant such as dry ice. Across three different vegetation communities, we found traps baited with dry ice frequently captured more mosquitoes than yeast-baited traps; however, there was little effect on mosquito community composition. Based on our preliminary experiments, we find that this method of producing CO2 is a realistic alternative to dry ice and would be highly suitable for remote field work

Invader from the dark side

[Extract] Environmental weeds typically invade open, disturbed areas or vegetation edges, and can have devastating ecological and economic consequences. The National Weeds List in Australia informs the public and land managers on weeds prioritized for management, but shade-tolerant weeds that can invade forest ecosystems are inadequately listed. Such weeds are now globally recognized for their ability to impact native vegetation. The Cherry Guava (Psidiumcattleianum) from Brazil, a shrub of the Myrtle family (Myrtaceae), is an exceptional exampl

Threats to environmentally sensitive areas from peri-urban expansion in Mauritius

Rapid population growth and economic change on the tropical islands of Mauritius have led to one of the highest rates of urban build-out in the world. Pressure on many of the island's natural features and resources increasingly risks further degradation to the environmental services that they provide to the country. Fourteen types of marine and terrestrial environmentally sensitive areas (ESAs) are critical to the nation's sustainable development. Twelve of these ESA types are currently at risk of degradation, owing to their spatial proximity to built-up areas (BUAs) and current use designation. There was a bimodal distribution in proximity; eight of the 12 ESA types analysed had an area-weighted modal peak < 500 m from the nearest BUA, and four ESAs had a modal peak 2–3 km from the nearest BUA. Six coastal and marine ESAs had limited protection from urban expansion and over-use. The Mauritian experience reflects trends that are emerging across many tropical developing countries, where the bulk of future global growth in urban area is expected to occur. The approach detailed in this case study is replicable and may be useful in assessing degradation risk as a result of urban expansion in other island countries