Amazonian tree species threatened by deforestation and climate change

Deforestation is currently the major threat to Amazonian tree species but climate change may surpass it in just a few decades. Here, we show that climate and deforestation combined could cause a decline of up to 58% in Amazon tree species richness, whilst deforestation alone may cause 19–36% and climate change 31–37% by 2050. Quantification is achieved by overlaying species distribution models for current and future climate change scenarios with historical and projected deforestation. Species may lose an average of 65% of their original environmentally suitable area, and a total of 53% may be threatened according to IUCN Red List criteria; however, Amazonian protected area networks reduce these impacts. The worst-case combined scenario—assuming no substantial climate or deforestation policy progress—suggests that by 2050 the Amazonian lowland rainforest may be cut into two blocks: one continuous block with 53% of the original area and another severely fragmented block. This outlook urges rapid progress to zero deforestation, which would help to mitigate climate change and foster biodiversity conservation

Ecological integrity of tropical secondary forests : concepts and indicators

Naturally regenerating forests or secondary forests (SFs) are a promising strategy for restoring large expanses of tropical forests at low cost and with high environmental benefits. This expectation is supported by the high resilience of tropical forests after natural disturbances, yet this resilience can be severely reduced by human impacts. Assessing the characteristics of SFs and their ecological integrity (EI) is essential to evaluating their role for conservation, restoration, and provisioning of ecosystem services. In this study, we aim to propose a concept and indicators that allow the assessment and classification of the EI of SFs. To this end, we review the literature to assess how EI has been addressed in different ecosystems and which indicators of EI are most commonly used for tropical forests. Building upon this knowledge we propose a modification of the concept of EI to embrace SFs and suggest indicators of EI that can be applied to different successional stages or stand ages. Additionally, we relate these indicators to ecosystem service provision in order to support the practical application of the theory. EI is generally defined as the ability of ecosystems to support and maintain composition, structure and function similar to the reference conditions of an undisturbed ecosystem. This definition does not consider the temporal dynamics of recovering ecosystems, such as SFs. Therefore, we suggest incorporation of an optimal successional trajectory as a reference in addition to the old-growth forest reference. The optimal successional trajectory represents the maximum EI that can be attained at each successional stage in a given region and enables the evaluation of EI at any given age class. We further suggest a list of indicators, the main ones being: compositional indicators (species diversity/richness and indicator species); structural indicators (basal area, heterogeneity of basal area and canopy cover); function indicators (tree growth and mortality); and landscape proxies (landscape heterogeneity, landscape connectivity). Finally, we discuss how this approach can assist in defining the value of SF patches to provide ecosystem services, restore forests and contribute to ecosystem conservation

Basin-wide variations in Amazon forest nitrogen-cycling characteristics as inferred from plant and soil 15N:14N measurements

Background: Patterns in tropical forest nitrogen cycling are poorly understood. In particular, the extent to which leguminous trees in these forests fix nitrogen is unclear.\ud \ud Aims: We aimed to determine factors that explain variation in foliar δ15N (δ15NF) for Amazon forest trees, and to evaluate the extent to which putatively N2-fixing Fabaceae acquire nitrogen from the atmosphere.\ud \ud Methods: Upper-canopy δ15NF values were determined for 1255 trees sampled across 65 Amazon forest plots. Along with plot inventory data, differences in δ15NF between nodule-forming Fabaceae and other trees were used to estimate the extent of N2 fixation.\ud \ud Results: δ15NF ranged from −12.1‰ to +9.3‰. Most of this variation was attributable to site-specific conditions, with extractable soil phosphorus and dry-season precipitation having strong influences, suggesting a restricted availability of nitrogen on both young and old soils and/or at low precipitation. Fabaceae constituted fewer than 10% of the sampled trees, and only 36% were expressed fixers. We estimated an average Amazon forest symbiotic fixation rate of 3 kg N ha−1 year−1. \ud \ud Conclusion: Plant δ15N indicate that low levels of nitrogen availability are only likely to influence Amazon forest function on immature or old weathered soils and/or where dry-season precipitation is low. Most Fabaceae species that are capable of nodulating do not fix nitrogen in Amazonia

Basin-wide variations in Amazon forest nitrogen-cycling characteristics as inferred from plant and soil ¹⁵N:¹⁴N measurements

<div><p> <b><i>Background:</i></b> Patterns in tropical forest nitrogen cycling are poorly understood. In particular, the extent to which leguminous trees in these forests fix nitrogen is unclear.</p> <p> <b><i>Aims:</i></b> We aimed to determine factors that explain variation in foliar δ¹⁵N (δ¹⁵N_F) for Amazon forest trees, and to evaluate the extent to which putatively N₂-fixing Fabaceae acquire nitrogen from the atmosphere.</p> <p> <b><i>Methods:</i></b> Upper-canopy δ¹⁵N_F values were determined for 1255 trees sampled across 65 Amazon forest plots. Along with plot inventory data, differences in δ¹⁵N_F between nodule-forming Fabaceae and other trees were used to estimate the extent of N₂ fixation.</p> <p> <b><i>Results:</i></b> δ¹⁵N_F ranged from −12.1‰ to +9.3‰. Most of this variation was attributable to site-specific conditions, with extractable soil phosphorus and dry-season precipitation having strong influences, suggesting a restricted availability of nitrogen on both young and old soils and/or at low precipitation. Fabaceae constituted fewer than 10% of the sampled trees, and only 36% were expressed fixers. We estimated an average Amazon forest symbiotic fixation rate of 3 kg N ha⁻¹ year⁻¹.</p> <p> <b><i>Conclusion:</i></b> Plant δ¹⁵N indicate that low levels of nitrogen availability are only likely to influence Amazon forest function on immature or old weathered soils and/or where dry-season precipitation is low. Most Fabaceae species that are capable of nodulating do not fix nitrogen in Amazonia.</p> </div

A framework for integrating biodiversity concerns into national REDD+ programmes

The UNFCCC mechanism for Reducing Emissions from Deforestation and Degradation in developing countries (REDD+) represents an unprecedented opportunity for the conservation of forest biodiversity. Nevertheless, there are widespread concerns surrounding the possibility of negative environmental outcomes if biodiversity is not given adequate consideration throughout the REDD+ process. We propose a general framework for incorporating biodiversity concerns into national REDD+ programmes based on well-established ecological principles and experiences. First, we identify how biodiversity distribution and threat data, together with data on biodiversity responses to forest change and management, can be readily incorporated into the strategic planning process for REDD+ in order to identify priority areas and activities for investment that will deliver returns for both carbon and biodiversity. Second, we propose that assessments of changes in biodiversity following REDD+ implementation could be greatly facilitated by paralleling, where possible, the existing IPCC architecture for assessing carbon emissions. A three-tiered approach is proposed for biodiversity assessment, where lower tiers can provide a realistic starting point for countries with fewer data and lower technical capacities. Planning and assessment of biodiversity safeguards for REDD+ need not overburden an already encumbered UNFCCC process. Immediate progress is already possible for a large number of developing countries, and a gradual, phased approach to implementation would minimise risks and facilitate the protection of additional biodiversity benefits from REDD+ activities. Greater levels of coordination between the UNFCCC and CBD, as well as other agencies and stakeholder groups interested in forest conservation are needed if biodiversity safeguards are to be fully adopted and implemented

Plot Data from "Diversity and carbon storage across the tropical forest biome."

Tropical forests are global centres of both biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest diversity-carbon relationship and this remains largely unexplored. Attempts to assess and understand this relationship in tropical forest ecosystems have been hindered by the scarcity of inventories where carbon storage in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of the relationship between carbon storage and tree diversity. We find strongly contrasting variation in diversity and carbon among continents. Thus, on average, African forests have high carbon storage but relatively low diversity, Amazonian forests have high diversity but less carbon, and Southeast Asian forests have both high diversity and high carbon storage. Carbon-diversity relationships among all plots across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). Within 1 ha plots a weak positive relationship is detectable, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to most conservation planning means that carbon-centred conservation strategies alone would miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both will require explicit consideration when optimising policies to manage tropical carbon and biodiversity