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Tropical forests play a crucial role in climate regulation due to their high carbon sequestration capacity. However, degradation and disturbances in these forests may result in significant carbon losses. This study focuses on the impact of various biophysical, anthropogenic, and landscape factors on aboveground biomass (AGB) in heavily disturbed landscapes of Côte d'Ivoire (West Africa), a typical low-forest and high-deforestation country. AGB estimates from a National Forest Inventory dataset have been linked to five categories of variables (Climate, Soil, Topography, Landscape, and Human-related) through a random forest modeling approach that addressed collinearity among variables, selected key variables from each category, and used spatial cross-validation to evaluate model performance. The comprehensive model, combining landscape composition, physical soil properties, and climate variables, demonstrated strong performance with an R-squared of 0.62. Notably, the percentage of landscape occupied by forest within a radius of 1000 m (PLAND1000) had a highly significant impact on AGB, exhibiting a notable increase when PLAND1000 exceeded 80 % and a decrease when it felt below 25 %. Soil properties, both physical (Bulk Density and Coarse Fraction) and chemical (soil pH), significantly influenced AGB, too. Interestingly, climatic, topographic, and other anthropogenic variables had minimal relevance in predicting AGB, suggesting that their effects may have been captured by landscape and soil integrative variables. In order to enhance forest preservation and restoration initiatives in the face of deforestation and fragmentation challenges in the West African region, we recommend (i) evaluating the appropriate landscape scale of effect (a 1000 m radius circle being the most significant in this study); (ii) prioritizing the preservation or restoration of dense forest landscapes; and (iii) integrating landscape composition into forest management policies.

The vast peat deposits in the Peruvian Amazon are crucial to the global climate. Palm swamp, the most extensive regional peatland ecosystem faces different threats, including deforestation and degradation due to felling of the dominant palm Mauritia flexuosa for fruit harvesting. While these activities convert this natural C sink into a source, the distribution of degradation and deforestation in this ecosystem and related C emissions remain unstudied. We used remote sensing data from Landsat, ALOS-PALSAR, and NASA's GEDI spaceborne LiDAR-derived products to map palm swamp degradation and deforestation within a 28 Mha area of the lowland Peruvian Amazon in 1990–2007 and 2007–2018. We combined this information with a regional peat map, C stock density data and peat emission factors to determine (1) peatland C stocks of peat-forming ecosystems (palm swamp, herbaceous swamp, pole forest), and (2) areas of palm swamp peatland degradation and deforestation and associated C emissions. In the 6.9 ± 0.1 Mha of predicted peat-forming ecosystems within the larger 28 Mha study area, 73% overlaid peat (5.1 ± 0.9 Mha) and stored 3.88 ± 0.12 Pg C. Degradation and deforestation in palm swamp peatlands totaled 535,423 ± 8,419 ha over 1990–2018, with a pronounced dominance for degradation (85%). The degradation rate increased 15% from 15,400 ha y−1 (1990–2007) to 17,650 ha y−1 (2007–2018) and the deforestation rate more than doubled from 1,900 ha y−1 to 4,200 ha y−1. Over 1990–2018, emissions from degradation amounted to 26.3 ± 3.5 Tg C and emissions from deforestation were 12.9 ± 0.5 Tg C. The 2007–2018 emission rate from both biomass and peat loss of 1.9 Tg C yr−1 is four times the average biomass loss rate due to gross deforestation in 2010–2019 reported for the hydromorphic Peruvian Amazon. The magnitude of emissions calls for the country to account for deforestation and degradation of peatlands in national reporting.

Despite the documented increase in greenhouse gas (GHG) emissions from Southeast Asian peat swamp forest degradation and conversion to oil palm over recent decades, reliable estimates of emissions of nitrous oxide (N2O) and methane (CH4) are lacking. We measured soil fluxes of N2O and CH4 and their environmental controls along a peatland transition from primary forest (PF) to degraded drained forest (DF) to oil palm plantation (OP) over 18 months in Jambi, Sumatra, Indonesia. Sampling was conducted monthly at all sites and more intensively following two fertilization events in the OP. Mean annual emissions of N2O (kg N ha−1 yr−1) were 1.7 ± 0.2 for the PF, 2.3 ± 0.2 for the DF and for the OP 8.1 ± 0.8 without drainage canals (DC) and 7.7 ± 0.7 including DC. High N2O emissions in the OP were driven by peat decomposition, not by N fertilizer addition. Mean CH4 annual fluxes (kg C ha−1 yr−1) were 8.2 ± 1.9 for the PF, 1.9 ± 0.4 for the DF, and 1.6 ± 0.3 for the OP with DC and 1.1 ± 0.2 without. Considering their 20-year global warming potentials (GWP), the combined non-CO2 GHG emission (Mg CO2-equivalent ha−1 yr−1) was 3.3 ± 0.6 for the PF and 1.6 ± 0.2 for the DF. The emission in the OP (3.8 ± 0.3 with or without DC) was similar to the PF because reductions in CH4 emissions offset N2O increases. However, considering 100-year GWP, the combined non-CO2 GHG emission was larger in the OP (3.4 ± 0.3 with DC and 3.5 ± 0.3 without) compared to both the PF and the DF (1.5 ± 0.2 and 1.2 ± 0.1, respectively). The increase in peat N2O emissions associated with the land-use change transition from primary forest to oil palm plantation at our sites provides further evidence of the urgent need to protect tropical peat swamp forests from drainage and conversion.

Tropical peat swamp forests are major global carbon (C) stores highly vulnerable to human intervention. In Peruvian Amazonia, palm swamps, the prevalent peat ecosystem, have been severely degraded through recurrent cutting of Mauritia flexuosa palms for fruit harvesting. While this can transform these C sinks into significant sources, the magnitude of C fluxes in natural and disturbed conditions remains unknown. Here, we estimated emissions from degradation along a gradient comprising undegraded (Intact), moderately degraded (mDeg) and heavily degraded (hDeg) palm swamps. C stock changes above- and below-ground were calculated from biomass inventories and peat C budgets resulting from the balance of C outputs (heterotrophic soil respiration (Rh), dissolved C exports), C inputs (litterfall, root mortality) and soil CH4 emissions. Fluxes spatiotemporal dynamics were monitored (bi)monthly over 1–3 years. The peat budgets (Mg C ha−1 year−1) revealed that medium degradation reduced by 88% the soil sink capacity (from − 1.6 ± 1.3 to − 0.2 ± 0.8 at the Intact and mDeg sites) while high degradation turned the soil into a high source (6.2 ± 0.7 at the hDeg site). Differences stemmed from degradation-induced increased Rh (5.9 ± 0.3, 6.2 ± 0.3, and 9.0 ± 0.3 Mg C ha−1 year−1 at the Intact, mDeg, and hDeg sites) and decreased C inputs (8.3 ± 1.3, 7.1 ± 0.8, and 3.6 ± 0.7 Mg C ha−1 year−1 at the same sites). The large total loss rates (6.4 ± 3.8, 15.7 ± 3.8 Mg C ha−1 year−1 under medium and high degradation), originating predominantly from biomass changes call for sustainable management of these peatlands.

L'émergence de l'agroforesterie en Côte d'Ivoire est devenue une priorité nationale. Le secteur agricole du pays génère 70 % des recettes d'exportation, emploie les deux tiers de la population active et contribue à un tiers du PIB. Cependant, ces performances économiques remarquables reposent sur une agriculture de rente qui se développe au détriment des forêts naturelles, entraînant l'un des taux de déforestation les plus alarmants au monde. Pour faire face à cette situation, l'État ivoirien promeut l'agroforesterie comme solution, en particulier dans le secteur du cacao. Cependant, une analyse fine de l'origine des arbres présents dans les champs suggère que l'agroforesterie en Côte d'Ivoire peut être divisée en deux catégories : l'agroforesterie de reforestation, qui permet de reconstituer le couvert forestier en associant progressivement des arbres aux cacaoyers, et l'agroforesterie de déforestation, qui dégrade et appauvrit la couverture forestière en convertissant les forêts naturelles en systèmes agroforestiers. Il est crucial de distinguer ces deux formes d'agroforesterie afin de développer des politiques qui encouragent la reforestation plutôt que la déforestation. Il est également nécessaire de mettre en place des indicateurs dynamiques qui permettent d'évaluer les trajectoires agroforestières des champs dans le temps et, ainsi, de favoriser un engagement à long terme des agriculteurs dans l'augmentation de la couverture forestière.

The tropical forest carbon sink is known to be drought sensitive, but it is unclear which forests are the most vulnerable to extreme events. Forests with hotter and drier baseline conditions may be protected by prior adaptation, or more vulnerable because they operate closer to physiological limits. Here we report that forests in drier South American climates experienced the greatest impacts of the 2015–2016 El Niño, indicating greater vulnerability to extreme temperatures and drought. The long-term, ground-measured tree-by-tree responses of 123 forest plots across tropical South America show that the biomass carbon sink ceased during the event with carbon balance becoming indistinguishable from zero (−0.02 ± 0.37 Mg C ha−1 per year). However, intact tropical South American forests overall were no more sensitive to the extreme 2015–2016 El Niño than to previous less intense events, remaining a key defence against climate change as long as they are protected.

The consistent monitoring of trees both inside and outside of forests is key to sustainable land management. Current monitoring systems either ignore trees outside forests or are too expensive to be applied consistently across countries on a repeated basis. Here we use the PlanetScope nanosatellite constellation, which delivers global very high-resolution daily imagery, to map both forest and non-forest tree cover for continental Africa using images from a single year. Our prototype map of 2019 (RMSE = 9.57%, bias = −6.9%). demonstrates that a precise assessment of all tree-based ecosystems is possible at continental scale, and reveals that 29% of tree cover is found outside areas previously classified as tree cover in state-of-the-art maps, such as in croplands and grassland. Such accurate mapping of tree cover down to the level of individual trees and consistent among countries has the potential to redefine land use impacts in non-forest landscapes, move beyond the need for forest definitions, and build the basis for natural climate solutions and tree-related studies.

Much concern about tropical deforestation focuses on oil palm plantations, but their impacts remain poorly quantified. Using nation-wide interpretation of satellite imagery, and sample-based error calibration, we estimated the impact of large-scale (industrial) and smallholder oil palm plantations on natural old-growth (“primary”) forests from 2001 to 2019 in Indonesia, the world's largest palm oil producer. Over nineteen years, the area mapped under oil palm doubled, reaching 16.24 Mha in 2019 (64% industrial; 36% smallholder), more than the official estimates of 14.72 Mha. The forest area declined by 11% (9.79 Mha), including 32% (3.09 Mha) ultimately converted into oil palm, and 29% (2.85 Mha) cleared and converted in the same year. Industrial plantations replaced more forest than detected smallholder plantings (2.13 Mha vs 0.72 Mha). New plantations peaked in 2009 and 2012 and declined thereafter. Expansion of industrial plantations and forest loss were correlated with palm oil prices. A price decline of 1% was associated with a 1.08% decrease in new industrial plantations and with a 0.68% decrease of forest loss. Deforestation fell below pre-2004 levels in 2017–2019 providing an opportunity to focus on sustainable management. As the price of palm oil has doubled since the start of the COVID-19 pandemic, effective regulation is key to minimising future forest conversion.

On the outskirts of the city of Bangui, the capital of the Central African Republic, fuelwood production, slash-and-burn agriculture and artisanal timber exploitation are causing deforestation and forest ecosystem degradation. Within the framework of the REDD+ Component of the South-West Regional Development Project, the implementation of Assisted Natural Regeneration during weeding (ANRw) in the slash-and-burn system was proposed and set up by 23 volunteer farmers on 24 fields with an average area of 0.22 ha in two villages (Boteke and Salanga). The objective of the study was to characterise the floristic structure of the juvenile woody vegetation resulting from ANRw in these two villages. More specifically, it aimed to: 1) describe the methods used to inform and raise awareness amongst farmers who volunteer to practise ANRw; 2) identify the main species conserved by the farmers; 3) identify the reasons or factors that motivated farmers to choose these species; 4) identify the biological and ecological characteristics of these species; and 5) evaluate the height growth of young trees preserved by ANRw over a 14-month period. The third inventory of the 24 plots (volunteers' fields) gave 1,668 woody plants preserved by ANR on 5.35 ha (312 trees ha−1), divided into 42 genera, 47 species and 23 families. These results show that ANRw is a simple technique to implement and can help maintain trees in fields in areas where pressure on the forest is high. In the supported villages, communities have shown an interest in applying this technique to reintroduce trees in the fields. This technique should be popularised in other places to improve the sustainable management of anthropized forest landscapes. In addition, volunteers who have tested ANRw say they are willing to continue practicing it. However, despite this genuine initial enthusiasm, this restoration drive will need to be monitored and supported due to the current context of extreme poverty and economic, social and p

The phenology of tropical forests is tightly related to climate conditions. In the Amazon, the seasonal greening of forests is conditioned by solar radiation and rainfall. Yet, increasing anthropogenic pressures (e.g. logging and wildfires), raise concerns about the impacts of forest degradation on the functioning of forest ecosystems, especially in a climate change context. In this study, we relied on remote sensing data to assess the contribution of solar radiation and precipitation to forest greening in mature and fire degraded forests, with a focus on the 2015 drought event. Our results showed that forest greening is more dependent on water resources in degraded forests than in mature forests. As a consequence, the expected increase in drought episodes and associated fire occurrences under climate change could lead to a long-term drying of tropical forests.

Background and aims: Several studies have shown an increase in tree mortality in intact tropical forests in recent decades. However, most studies are based on networks of field plots whose representativeness is debated. We examine the potential of repeated Airborne LiDAR Scanning data to map forest structure change over large areas with high spatial resolution and to detect tree mortality patterns at landscape level. Methods: The study site is a complex forested landscape in French Guiana with varied topographic positions, vegetation structures and disturbance history. We computed a Gap Dynamics Index from Canopy Height Models derived from successive LiDAR data sets (2009, 2015 and 2019) that we compared to field-measured mortality rates (in stem number and basal area loss) obtained from regular monitoring of 74 1.56-ha permanent plots. Results: At the plot level, the relation between gap dynamics and absolute basal area loss rate (combining fallen and standing dead trees) was overall highly significant (R2 = 0.60) and especially tight for the 59 ha of unlogged forest (R2 = 0.72). Basal area loss rate was better predicted from gap dynamics than stem loss rate. In particular, in previously logged plots, intense self-thinning of small stems did not translate into detectable gaps, leading to poor predictability of stem mortality by LiDAR in those forests severely disturbed 30 years before. At the landscape scale, LiDAR data revealed spatial patterns of gap creation that persisted over the successive analysis periods. Those spatial patterns were related to local topography and canopy height. High canopy forests and bottomlands were more dynamic, with a higher fraction of canopy affected by gaps per unit time indicating higher basal area loss rates. Conclusion: Gap detection and mapping via multitemporal LiDAR data is poised to become instrumental in characterizing landscape-scale forest response to current global change. Meaningful comparison of gap dynamics across time

A Madagascar, le taux de déforestation est parmi le plus intense des régions tropicales. Pour la préservation des espaces forestiers, l'une des actions fortes des pouvoirs publics ces dernières décennies a été la mise en place d'espaces protégés. La connaissance des dynamiques d'occupation du sol avant et après la mise en place d'un parc permet d'estimer plus précisément l'efficience de ces dispositifs de protection. Dans cette optique, l'étude proposée cherche à évaluer les évolutions dans le parc national de Ranomafana et sa région, juste avant sa mise en place en 1991 jusqu'en 2013. Cet espace protégé, de plus de 400 km², classé au patrimoine mondiale de l'UNESCO en 2007, est totalement inscrit dans les forêts humides du SE de l'île. Dans cette étude, les évolutions paysagères forestières et agro-culturales sont analysées à partir de l'imagerie Landsat sur trois décennies depuis le début des années 1990. Si, sur la période étudiée, et sur l'ensemble de la région, la part de la couverture forestière montre une tendance générale à la baisse, l'évolution au sein du parc correspond clairement à des caractéristiques qui échappent à cette tendance régionale. Entre la création du parc et son impact sur une diminution de la déforestation, un décalage d'une décennie s'observe, mais son influence est tangible. On observe parfois des phases de reconquête forestière. Cependant, l'efficience de la protection liée à la mise en place du parc s'émousse en une décennie, et progressivement les dynamiques de déforestation observées antérieurement, ou régionalement, se réinstallent. A Madagascar, les parcs seuls ne peuvent probablement pas être suffisants pour enrayer la déforestation.

Quantifying ecological condition, notably the extent of forest degradation is important for understanding and designing measures to protect biodiversity and enhancing the capacity of forests to deliver ecosystem services. Conservation planning, particularly the prioritization of management interventions for forests, is often lacking spatial data on forest degradation, and it is often overlooked within decision-making processes. We develop a continuous metric termed Forest Condition (FC) which aims to measure the degree of forest degradation on a scale from 0 to 100, incorporating the temporal history of forest change over any spatial extent. We parameterize this metric based on estimated changes in above ground biomass in the context of forest fragmentation over time to estimate a continuous measure of forest degradation for Congo Basin countries. We estimate that just <70% of Congo Basin forests remain fully intact, a decrease from 78% in the year 2000. FC was validated by direct remote sensing measurements from Landsat imagery for DRC. Results showed that FC was significantly positively correlated with forest canopy cover, gap area per hectare, and magnitude of temporal change in Normalized Burn Ratio. We tested the ability of FC to distinguish primary and secondary degradation and deforestation and found significant differences in gap area and spectral anomalies to validate our theoretical model. We apply the IUCN Red List of Ecosystems criteria to demonstrate the integration of forest condition to assess the risk of ecosystem collapse. Based on this assessment, we found that without including FC in the assessment of biotic disruption, 12 ecosystems representing over 11% of forested area in 2015 would not have been assigned a threat status, and an additional 9 ecosystems would have a lower threat status. Our overall assessment of ecosystems found about half of all Congo Basin ecosystem types, accounting for 20% of all forest area are threatened to some degree, in

Beyond reducing deforestation, the control of forest degradation, the promotion of forest restoration, and the improvement of agricultural practices in the Brazilian Amazon are becoming increasingly important for sustainable development. To enable farmers and authorities to organize their landscapes and optimize both agricultural practices and the provision of ecosystem services, mapping land suitability is essential, but it is lacking in the region. In this paper, we present a method for mapping land suitability at a fine scale (30-m pixels), adapted to the needs of farmers and municipalities, to not only optimize agricultural production but also the ecosystem services provided by forests. We used topographic data from the Brazilian municipality of Paragominas to produce four maps, one each of soil texture, slope, floodplains, and hydrography, that we then combined into a single land suitability map. This map has been incorporated into a spatial database, which also contains information on land use, remoteness, and land tenure. We performed spatial analyses to measure the process of land use change, and to define indicators that enable local stakeholders to organize landscape restoration. We highlight an organic link between agricultural intensification and forest restoration, and provide a spatial tool for landscape design, assessment, and monitoring.

Accurate characterization of tropical moist forest changes is needed to support conservation policies and to quantify their contribution to global carbon fluxes more effectively. We document, at pantropical scale, the extent and changes (degradation, deforestation, and recovery) of these forests over the past three decades. We estimate that 17% of tropical moist forests have disappeared since 1990 with a remaining area of 1071 million hectares in 2019, from which 10% are degraded. Our study underlines the importance of the degradation process in these ecosystems, in particular, as a precursor of deforestation, and in the recent increase in tropical moist forest disturbances (natural and anthropogenic degradation or deforestation). Without a reduction of the present disturbance rates, undisturbed forests will disappear entirely in large tropical humid regions by 2050. Our study suggests that reinforcing actions are needed to prevent the initial degradation that leads to forest clearance in 45% of the cases.

The continued growth in demand for a relatively small number of agricultural and forest commodities in global trade has placed increasing pressures on forests across landscapes in the tropics and sub-tropics. These pressures are amplified by growing domestic demand in producing countries. Such trends have led to multiple environmental challenges linked to loss of forests and biodiversity and rising carbon emissions. They also create social challenges including threats to local food security, tenure rights and the livelihoods of indigenous peoples and local communities.Expansion of trade in forest-risk commodities over the past three decades has resulted in increased pressure from civil society organizations, consumers, international banks and shareholders of consumer goods companies to develop and implement a diverse array of instruments and tools to promote sustainable or deforestation-free sourcing, and as a way to reduce exposure to reputational, financial and regulatory risks. Multi-stakeholder platforms and commodity roundtables also emerged, in response to criticisms of government failures. The multiplication of sustainability initiatives has been driven by the growing complexity and diversity of conditions under which agri-food and timber supply chains operate. Private sector actors have increasingly defined and monitored their own sustainability performance by using certification standards or by developing their own procedures and criteria. More recently, a discernible shift toward landscape or jurisdictional approaches is seen as a way to meet sustainability goals. The growing complexity of policy regimes, inevitably, results in ambiguities and can lead to trade-offs between gains and losses. This review presents a synthesis of the multiple public, private and hybrid governance initiatives that aim to promote sustainable supplies of key forest-risk commodities. It aims to make it easier to understand a vast and rapidly expanding literature. By drawing on th

Définir les termes " forêt ", " déforestation " et " dégradation des forêts ", est un préalable incontournable dans la conception et la mise en oeuvre de toute stratégie visant à éliminer la déforestation importée. Cette définition doit s'adapter à la diversité des contextes écologiques rencontrés, et aux outils de suivi disponibles.

While forest degradation rates and extent exceed deforestation in the Brazilian Amazon, less attention is given to the factors controlling its spatial distribution. No quantified correlation exists between changes of forest structure due to anthropogenic disturbances and dynamics of land use and cover change occurring at broader spatial levels. This study examines the influence of multi-scale landscape structure factors (i.e. spatial composition, configuration and dynamic of land use/cover) on primary forest's aboveground biomass (AGB), spanning from low to highly degraded, in Paragominas municipality (Par ́a state). We used random forest models to identify the most important landscape predictors of degradation and clustering methods to analyze their distribution and interactions. We found that 58% of the variance of AGB could be explained by metrics reflecting land use practices and agricultural dynamics around primary forest patches and that their spatial patterns were not randomly distributed. Forest degradation is mainly driven by fragmentation effects resulting from old deforestation and colonization events linked with cropland expansion (e.g. soybean and maize) coupled with high accessibility to market. To a lesser extent, degradation is driven by recent and ongoing (1985–2015) deforestation and fragmentation in slash-and-burn agricultural areas, characterized by heterogeneous mosaics of pastures and fallow lands combined with high use of fire. Our findings highlight the potential of landscape-level framework and remotely sensed land cover data for a thorough understanding of the distribution of forest degradation across human-modified landscapes. Addressing these spatial determinants by looking at agricultural dynamics beyond forest cover is necessary to improve forest management which has major implications for biodiversity, carbon and other ecosystem services.

La dégradation des terres liée aux activités humaines est considérée comme la cause directe des problèmes de sécurité alimentaire et des migrations des populations, et constitue de ce fait un enjeu majeur à l'échelle mondiale. Le Mozambique, qui dispose encore d'une importante ressource forestière dominée par les formations forestières du Miombo, est particulièrement touché par ce phénomène, avec près d'un quart de ses terres qui seraient déjà dégradées. Ce pays, comme d'autres pays africains, s'est fixé des objectifs ambitieux avec la restauration d'1 million d'hectares de terres dégradées dans les dix prochaines années. Cependant, il existe très peu de données quantitatives et spatialisées sur l'état des terres et sur la capacité de résilience du Miombo. L'objectif de cette thèse est d'analyser les dynamiques, les caractéristiques et les déterminants de l'évolution des paysages forestiers afin d'alimenter les stratégies de restauration des terres dégradées au Mozambique. Cette étude s'est particulièrement intéressée à i) comprendre les facteurs de dégradation des terres à l'échelle nationale, ii) évaluer la résilience de l'écosystème du Miombo dans les systèmes d'agriculture sur brûlis dans la région centrale du pays (Zambézie), et iii) proposer une approche pour identifier les zones potentielles de restauration des paysages forestiers à partir des connaissances acquises dans les deux premiers points. Dans un premier temps, les analyses de séries temporelles satellitaires (indices de végétation et variables climatiques) ont permis de documenter l'état des terres à l'échelle nationale et quantifier les facteurs de dégradation et régénération des terres. Les résultats montrent que 25 % du pays ont subi une baisse significative de la productivité de la végétation et qu'une grande partie de ces changements (61 %) est directement attribuée aux activités humaines telles que la dégradation des forêts et la déforestation, principalement liée à l'agriculture sur brûlis. De

Forest conservation on privately owned lands is a cornerstone of the Brazilian environmental policy framework. Brazilian legislation requires that all farms in the country maintain and protect forest areas known as Legal Reserves. Since Legal Reserves have major implications for forest conservation and agricultural production, it is key that we understand landholders' perceptions towards Legal Reserves. We applied Q methodology to identify different perspectives of medium and large landholders on Legal Reserves and their relation to agricultural intensification in the municipality of Paragominas, eastern Amazon. We conducted 31 interviews in which landholders sorted 36 statements in a quasi-normal distribution array. Three groups of landholders were identified: 1) Land use planning enthusiasts (n = 16) were interested in zoning initiatives to explore alternative landscape designs and legislation that may deliver better conservation and production outcomes; 2) Agrochemical-based agriculture supporters (n = 7) held the most critical views against Legal Reserves and perceived their costs as higher than the potential environmental and life quality benefits; 3) Policy complacent-market responders (n = 4) showed no interest in Legal Reserves reforms and were the most market driven group.. While Paragominas has achieved notable successes in halting large-scale deforestation through a social “Green Municipality” pact, addressing persisting forest degradation and fragmentation in the region remains a key priority. Local governance initiatives that account for multi-stakeholder perceptions on forest conservation can foster dialogue and mutual understanding to effectively conserve and restore Legal Reserves. Insights on large landholders' perceptions on Legal Reserves can inform such governance processes to reconcile forest conservation and sustainable agricultural intensification in Paragominas.

The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality.

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.

Selective logging, fragmentation, and understory fires directly degrade forest structure and composition. However, studies addressing the effects of forest degradation on carbon, water, and energy cycles are scarce. Here, we integrate field observations and high‐resolution remote sensing from airborne lidar to provide realistic initial conditions to the Ecosystem Demography Model (ED‐2.2) and investigate how disturbances from forest degradation affect gross primary production (GPP), evapotranspiration (ET), and sensible heat flux (H). We used forest structural information retrieved from airborne lidar samples (13,500 ha) and calibrated with 817 inventory plots (0.25 ha) across precipitation and degradation gradients in the eastern Amazon as initial conditions to ED‐2.2 model. Our results show that the magnitude and seasonality of fluxes were modulated by changes in forest structure caused by degradation. During the dry season and under typical conditions, severely degraded forests (biomass loss ≥66%) experienced water stress with declines in ET (up to 34%) and GPP (up to 35%) and increases of H (up to 43%) and daily mean ground temperatures (up to 6.5°C) relative to intact forests. In contrast, the relative impact of forest degradation on energy, water, and carbon cycles markedly diminishes under extreme, multiyear droughts, as a consequence of severe stress experienced by intact forests. Our results highlight that the water and energy cycles in the Amazon are driven by not only climate and deforestation but also the past disturbance and changes of forest structure from degradation, suggesting a much broader influence of human land use activities on the tropical ecosystems.

The forests of Central Africa contain some of Earth's few remaining intact forests. These forests are increasingly threatened by infrastructure development, agriculture, and unsustainable extraction of natural resources (e.g. minerals, bushmeat, and timber), all of which is leading to deforestation and forest degradation, particularly defaunation, and hence causing declines in biodiversity and a significant increase in carbon emissions. Given the pervasive nature of these threats, the global importance of Central African forests for biodiversity conservation, and the limited resources for conservation and sustainable management, there is a need to identify where the most important areas are to orientate conservation efforts. We developed a novel approach for identifying spatial priorities where conservation efforts can maximize biodiversity benefits within Central Africa's most intact forest areas. We found that the Democratic Republic of Congo has the largest amount of priority areas in the region, containing more than half, followed by Gabon, the Republic of Congo and Cameroon. We compared our approach to one that solely prioritizes forest intactness and one that aims to achieve only biodiversity representation objectives. We found that when priorities are only based on forest intactness (without considering biodiversity representation), there are significantly fewer biodiversity benefits and vice versa. We therefore recommend multi-objective planning that includes biodiversity representation and forest intactness to ensure that both objectives are maximized. These results can inform various types of conservation strategies needed within the region, including land-use planning, jurisdictional REDD + initiatives, and performance related carbon payments, protected area expansion, community forest management, and forest concession plans.

Sub-national jurisdictions are promoted as strategic levels of governance for achieving reduced deforestation objectives. Jurisdictional approaches (JA) emerged as government-led, holistic approaches to forest and land use management across one or more legally defined territories. Despite increasing popularity amongst the science and practitioner communities, there is a lack of robust empirical data documenting their effectiveness in delivering environmental, social and economic outcomes. In this paper, we contend that further clarification of the JA concept would help its evaluation. More specifically, we suggest that current evaluation practices of JA would be strengthened if they were based on a theory of change clarifying the causal linkages between the interventions associated with a given JA and their effects. By integrating select empirical knowledge on JA with a selection of middle-range theories from the literature on collective environmental governance, we design a generic theory of change for JA, which is articulated around two intermediary outcomes, namely the emergence of collaboration and social learning. We also formulate hypotheses regarding the conditions that enable or hinder these collective intermediary outcomes of JAs. We acknowledge that another fundamental challenge for JAs is to remove or block the external contradicting signals that still fundamentally drive deforestation. Thus, JA interventions need to operate not only at the jurisdictional level, but also beyond.

Tropical forest degradation is a major source of greenhouse-gas emissions, but international forest and climate policies are yet to respond decisively to this. In some regions, as a result of population growth, climate change and forest degradation, the increased need for wood, whether for timber or fuelwood, will exceed the sustainable supply capacity of natural forests and plantations, potentially accelerating deforestation processes. As with the issue of food security, a problem of “wood supply security” is emerging in several developing countries. This issue is poorly understood by most international initiatives focused on climate or biodiversity, which want to conserve forests but neglect the importance of the productive role of forests to support this conservation through their sustainable use. Solutions exist, but a number of barriers, starting with unclear tenure rights and short-sighted policy choices, prevent the large-scale deployment of these ones. Putting investment back at the forefront of the international agenda and setting the right incentives for producers is necessary to overcome these barriers and create the conditions for achieving future results sought by the “results-based payments” schemes such as REDD+, currently favoured by donors. Beyond the production side, the role of the global demand and the consumers is critical, and trade policies should evolve significantly to favour sustainable and deforestation-free productions.

In the context of the global biodiversity crisis, human activities are the principal cause of natural habitat degradation, fragmentation, and destruction. Globally, the species extinction rate has reached an unprecedented level in human history and about one million species are nowadays threatened with extinction. Conservation biology is a multidisciplinary research area which attempts to address the current biodiversity crisis challenges. The development of practical approaches to promote conservation and reduce the research-implementation gap is one of its objectives. Last decades, systematic conservation planning (SCP) emerged in this direction as a framework relying on optimization and computer science research. Its main target is to provide decision support in the planning of conservation actions through the integration of ecological targets along with socio-economical constraints. In this PhD thesis, we introduced a formal approach for modelling and solving SCP problems based on constraint programming, a method from artificial intelligence based on automated reasoning. The main motivation of this approach was to provide more expressiveness into SCP (i.e. extend the breadth and variety of problems that users can represent and solve), notably through the integration of advanced spatial constraints and landscape indices. Formal approaches are often more demanding to implement and scale up than heuristic approaches. However, they provide satisfiability and optimality guarantees on the produced solutions. The insights offered by these guarantees can substantially improve the quality of decision support. We evaluated the methods developed in this thesis on real data from New Caledonian forests. As the smallest biodiversity hotspot in the world, New Caledonia has to struggle with many conservation challenges. Moreover, the developed, insular and low populated New Caledonian context allows high proximity between conservation stakeholders, which makes it an appropriate

The conservation of tropical forest cover is a key to ensuring sustainable provision of multiple ecosystem services. However, increasing demography, demand for agricultural products and changes in land uses are affecting forest sustainability through degradation processes. A first step to tailor effective forest management is to identify most vulnerable forests and to characterize their drivers. The objective of this thesis is to develop a multidimensional approach to assess forest degradation and the relations with the broader dynamics of land use/cover towards the evaluation of forest ecological vulnerability. The thesis was applied in Paragominas (Brazil) and Di Linh (Vietnam) where large-scale deforestation driven by commercial agriculture shaped the landscape into land use mosaics with increasing degradation pressures. In Paragominas, degradation is linked with selective logging and fire implying changes in forest structure. We estimated the potential of multisource remote sensing to map forest aboveground biomass from large-scale field assessment of carbon stock and investigated the consequences of degradation history on forest structures. We found that canopy textures correlated with forest structure variability and could be used as proxies to characterize degraded forests using very high resolution images. Based on environmental, geographical factors and landscape structure metrics, we demonstrated that 80% of forest degradation was mainly driven by accessibility, geomorphology, fire occurrence and fragmentation. The drivers of degradation acted together and in sequence. The combination of current forest state, landscape dynamics and information on degradation drivers would be at the basis of ecological vulnerability assessment. In Di Linh, degradation is driven by encroachment of coffee-based agriculture. Field inventory of the different forest types and other landscape elements combined with Sentinel-2 images allowed to map with high precision the current

La dégradation de la forêt est un changement de sa structure et de la composition floristique et faunistique, ce qui conduit à une perte de biodiversité, de production de biens et de services et à un accroissement de la vulnérabilité aux aléas climatiques et aux incendies. Elle concerne de vastes espaces en zone tropicale particulièrement dans les régions de fronts pionniers plus ou moins consolidés où la forêt primaire est soumise à l'extraction de bois, aux incendies et à la fragmentation. Pour évaluer son ampleur et son intensité, il est nécessaire de recourir à la télédétection. Mais les méthodologies disponibles restent encore insuffisantes. L'enjeu scientifique est de développer des méthodes adaptées à de grandes surfaces afin d'analyser l'effet de différentes perturbations sur les trajectoires suivies par le couvert forestier. Il s'agit également de distinguer différentes intensités de dégradation suite à l'accumulation de perturbations. C'est un préalable indispensable pour définir et mettre en oeuvre des plans de gestion adaptés. Le premier axe de ce travail a pour objectif de cartographier annuellement l'ampleur des perturbations, d'identifier les principaux types de perturbations et de caractériser la trajectoire de restauration de l'activité photosynthétique. Il est réalisé à partir de séries temporelles d'images Landsat traitées au moyen du progiciel CLASlite. L'agrégation des couvertures annuelles résultant des traitements avec CLASlite a également permis de constituer un indicateur de dégradation résultant du cumul de processus de perturbations sur plusieurs années. Le deuxième axe a pour objectif d'évaluer l'évolution de la sensibilité des forêts à la sécheresse en fonction de leur dégradation et de construire un indicateur de dégradation. L'approche utilise des images MODIS et des données de précipitations TRMM. Ce travail s'est déroulé dans la municipalité de Paragominas (état du Pará, Brésil) en Amazonie orientale.

The links between plantation expansion and deforestation in Borneo are debated. We used satellite imagery to map annual loss of old‐growth forests, expansion of industrial plantations (oil palm and pulpwood), and their overlap in Borneo from 2001 to 2017. In 17 years, forest area declined by 14% (6.04 Mha), including 3.06 Mha of forest ultimately converted into industrial plantations. Plantations expanded by 170% (6.20 Mha: 88% oil palm; 12% pulpwood). Most forests converted to plantations were cleared and planted in the same year (92%; 2.83 Mha). Annual forest loss generally increased before peaking in 2016 (0.61 Mha) and declining sharply in 2017 (0.25 Mha). After peaks in 2009 and 2012, plantation expansion and associated forest conversion have been declining in Indonesia and Malaysia. Annual plantation expansion is positively correlated with annual forest loss in both countries. The correlation vanishes when we consider plantation expansion versus forests that are cleared but not converted to plantations. The price of crude palm oil is positively correlated with plantation expansion in the following year in Indonesian (not Malaysian) Borneo. Low palm oil prices, wet conditions, and improved fire prevention all likely contributed to reduced 2017 deforestation. Oversight of company conduct requires transparent concession ownership.