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BACKGROUND: REDD+ is being questioned by the particular status of High Forest/Low Deforestation countries. Indeed, the formulation of reference levels is made difficult by the confrontation of low historical deforestation records with the forest transition theory on the one hand. On the other hand, those countries might formulate incredibly high deforestation scenarios to ensure large payments even in case of inaction. RESULTS: Using a wide range of scenarios within the Guiana Shield, from methods involving basic assumptions made from past deforestation, to explicit modelling of deforestation using relevant socio-economic variables at the regional scale, we show that the most common methodologies predict huge increases in deforestation, unlikely to happen given the existing socio-economic situation. More importantly, it is unlikely that funds provided under most of these scenarios could compensate for the total cost of avoided deforestation in the region, including social and economic costs. CONCLUSION: This study suggests that a useful and efficient international mechanism should really focus on removing the underlying political and socio-economic forces of deforestation rather than on hypothetical result-based payments estimated from very questionable reference levels.

Background: REDD+ is being questioned by the particular status of High Forest/Low Deforestation countries. Indeed, the formulation of reference levels is made difficult by the confrontation of low historical deforestation records with the forest transition theory on the one hand. On the other hand, those countries might formulate incredibly high deforestation scenarios to ensure large payments even in case of inaction. Results: Using a wide range of scenarios within the Guiana Shield, from methods involving basic assumptions made from past deforestation, to explicit modelling of deforestation using relevant socio-economic variables at the regional scale, we show that the most common methodologies predict huge increases in deforestation, unlikely to happen given the existing socio-economic situation. More importantly, it is unlikely that funds provided under most of these scenarios could compensate for the total cost of avoided deforestation in the region, including social and economic costs. Conclusion: This study suggests that a useful and efficient international mechanism should really focus on removing the underlying political and socio-economic forces of deforestation rather than on hypothetical result-based payments estimated from very questionable reference levels.

Tropical forests of the Guiana Shield are the most affected by gold-mining in South America,experiencing an exponential increase in deforestation since the early 2000's.Using yearly deforestation data encompassing Guyana, Suriname, French Guiana and theBrazilian State of Amapá, we demonstrated a strong relationship between deforestation due togold-mining and gold-prices at the regional scale. In order to assess additional drivers ofdeforestation due to gold-mining, we focused on the national scale and highlighted theheterogeneity of the response to gold-prices under different political contexts. Deforestation dueto gold-mining over the Guiana Shield occurs mainly in Guyana and Suriname. On the contrary,past and current repressive policies in Amapá and French Guiana likely contribute to thedecorrelation of deforestation and gold prices. In this work, wefinally present a case studyfocusing on French Guiana and Suriname, two neighbouring countries with very different levelsof law enforcement against illegal gold-mining. We developed a modelling framework to estimatepotential deforestation leakages from French Guiana to Suriname in the border areas. Based onour assumptions, we estimated a decrease in deforestation due to gold-mining of approx. 4 300hectares in French Guiana and an increase of approx. 12 100 hectares in Suriname in response tothe active military repression of illegal gold-mining launched in French Guiana.Gold-mining in the Guiana Shield provides challenging questions regarding REDDþimplementation. These questions are discussed at the end of this study and are important topolicy makers who need to provide sustainable alternative employment to local populations inorder to ensure the effectiveness of environmental policies.

En Afrique tropicale, dans les plantations forestières, la majorité des espèces autochtones ont été délaissées au profit d'espèces exotiques à croissance initiale rapide. Cette tendance est encore plus marquée dans les zones soudanienne et soudano-guinéenne à longue saison sèche. Ainsi s'explique le manque de connaissances sur les potentialités et la sylviculture des espèces d'arbres autochtones ou " locales ". Pour contribuer à l'acquisition de ces connaissances indispensables, un arboretum de 2,56 ha a été installé en 1990 à proximité de Korhogo dans le nord de la Côte d'Ivoire. Sa particularité réside dans la mise en place de grandes parcelles de 1 596 m² avec 224 plants par espèce afin d'y mener une sylviculture qui conserverait de 10 à 16 arbres adultes de chaque espèce, exploitables notamment pour le bois d'oeuvre, au terme de la révolution. Par manque de maîtrise des techniques de pépinière pour certaines espèces, seules 12 espèces sur 22 ont été plantées avec les 224 plants prévus au départ. Les résultats sont présentés pour l'ensemble des espèces testées, aussi bien en pépinière qu'en plantation. Cet arboretum a été régulièrement suivi jusqu'en 1999 puis ne l'a plus été en raison des évènements politiques qui ont perturbé la bonne administration du pays. Une campagne de mesures a été diligentée en novembre 2019 qui a permis notamment de tirer des conclusions intéressantes sur l'aptitude de 15 espèces à croître en peuplements équiennes monospécifiques, dont deux (Pterocarpus erinaceus Poir. et Anogeissus leiocarpa (DC.) Guill. & Perr.) qui montrent une productivité remarquable. L'ensemble des données recueillies depuis la récolte des graines et tout au long de la vie de l'arboretum sont présentées ici et discutées dans l'espoir que les sylviculteurs de cette zone phytogéographique en tirent le meilleur profit. Les enseignements acquis doivent servir à la restauration des forêts et des paysages grâce aux reboisements auxquels les États se sont engagés pour lutter contre les variations climatiques, la perte de biodiversité et la dégradation des services écosystémiques aux populations.

Tropical deforestation drivers are complex and can change rapidly in periods of profound societal transformation, such as those during a pandemic. Evidence suggests that the COVID-19 pandemic has spurred illegal, opportunistic forest clearing in tropical countries, threatening forest ecosystems and their resident human communities. A total of 9583 km2 of deforestation alerts from Global Land Analysis & Discovery (GLAD) were detected across the global tropics during the first month following the implementation of confinement measures of local governments to reduce COVID-19 spread, which is nearly double that of 2019 (4732 km2). We present a conceptual framework linking tropical deforestation and the current pandemic. Zoonotic diseases, public health, economy, agriculture, and forests may all be reciprocally linked in complex positive and negative feedback loops with overarching consequences. We highlight the emerging threats to nature and society resulting from this complex reciprocal interplay and possible policy interventions that could minimize these threats.

As countries advance in greenhouse gas (GHG) accounting for climate change mitigation, consistent estimates of aboveground net biomass change (∆AGB) are needed. Countries with limited forest monitoring capabilities in the tropics and subtropics rely on IPCC 2006 default ∆AGB rates, which are values per ecological zone, per continent. Similarly, research into forest biomass change at a large scale also makes use of these rates. IPCC 2006 default rates come from a handful of studies, provide no uncertainty indications and do not distinguish between older secondary forests and old-growth forests. As part of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, we incorporate ∆AGB data available from 2006 onwards, comprising 176 chronosequences in secondary forests and 536 permanent plots in old-growth and managed/logged forests located in 42 countries in Africa, North and South America and Asia. We generated ∆AGB rate estimates for younger secondary forests (≤20 years), older secondary forests (>20 years and up to 100 years) and old-growth forests, and accounted for uncertainties in our estimates. In tropical rainforests, for which data availability was the highest, our ∆AGB rate estimates ranged from 3.4 (Asia) to 7.6 (Africa) Mg ha−1 year−1 in younger secondary forests, from 2.3 (North and South America) to 3.5 (Africa) Mg ha−1 year−1 in older secondary forests, and 0.7 (Asia) to 1.3 (Africa) Mg ha−1 year−1 in old-growth forests. We provide a rigorous and traceable refinement of the IPCC 2006 default rates in tropical and subtropical ecological zones, and identify which areas require more research on ∆AGB. In this respect, this study should be considered as an important step towards quantifying the role of tropical and subtropical forests as carbon sinks with higher accuracy; our new rates can be used for large-scale GHG accounting by governmental bodies, nongovernmental organizations and in scientific research.

The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US$166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.