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The performance of private forest governance systems, such as the standard and approach developed by the Forest Stewardship Council (FSC), is often assessed at the local level although they also have an indirect influence on public policies at the national level. Such spillover effects must be understood to assess the effectiveness of certification in contributing to improved forest governance. With this purpose, this article analyses the influences of the implementation of FSC standards on changes in forest governance in Cameroon, Congo and Gabon based on perceptions of 43 “knowledgeable” actors of FSC natural forest management. The information was collected through the use of semi-open and open interviews, and rankings. Findings show that perceived FSC influence on forest governance has followed two pathways: (a) a clear impact on stakeholder participation and timber traceability; and (b) a limited impact on improving national governance, as illustrated by the lack of global improvement in resource management practices or in biodiversity conservation. Moreover, interviewees agreed that struggles against corruption and transparency have not been impacted by the FSC certification in the Congo Basin. This mitigated influence of FSC on forest governance is first explained by a limited spillover effect of the virtuous practices of the seven FSC-certified companies on the national logging sector. Secondly, progress in FSC certification has been little taken up by public policies, which remain the main leverage for action on forest governance in producing countries.

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light-demanding long-lived pioneer species, usually fail to recover a stable number of large trees after exploitation. Several factors are known to affect tropical tree demographic processes, like tree growth, survival and recruitment. Tree growth has particularly been showed to depend on ecological conditions, tree genetics, and competition with surrounding vegetation, as well as tree size or ontogeny. Yet, due to the paucity of available data, the importance of such factors is unclear and usually ignored when estimating future timber yields. To fill this gap, we chose to evaluate the variability in growth of one African long-lived pioneer and commercially very important species: Triplochiton scleroxylon K. Schum, gathering a broad dataset composed of tree ring data recorded in one site in Cameroon and periodic field inventory data recorded in seven sites across central Africa. In total, we analyzed 13,225 records of annual tree diameter increments recorded over 920 trees from seven sites in Cameroon, Republic of the Congo and Central African Republic. We evaluated (i) to what extent the average growth of trees that reach harvestable dimensions differs from population average and (ii) to what extent past perturbations influence the growth of remaining trees. We found the diameter growth of T. scleroxylon to be remarkably variable and this study provided an unprecedented quantification of the magnitude of some key growth determinants. In unlogged forests, the diameter increment of T. scleroxylon ranged between 0.40 cm year−1 in Southern Cameroon and 0.83 cm year−1 in South-Eastern Cameroon. The diameter increment was weakly related to tree size but increased twofold from unlogged to logged forests. Perturbation caused by logging stimulates growth of T. scleroxylon for at least 10–15 years. Finally, harvestable timber stock of large-sized T. scleroxylon was found to be constituted by trees that grew in average twice faster than trees of the entire extant population. As more and more inventory data become available, quantifying these effects could be replicated for other timber species and in other sites, to improve the accuracy of future timber resource estimates and improve forest management guidelines.

International audience; Tropical forests harbor the greatest terrestrial biodiversity and provide various ecosystem services. The increase of human activities on these forests, among which logging, makes the conservation of biodiversity and associated services strongly dependent on the sustainability of these activities. However the indicators commonly used to assess the impact of forest exploitation, namely species richness and biomass, provide a limited understanding of their sustainability. Here, we assessed the sustainability of common forest exploitation in the Guiana Shield studying the recovery of two ecosystem services i.e. carbon storage and wood stock, and an ecosystem function i.e. seed dispersal by animals. Specifically, we compared total and commercial biomass, as well as functional composition in seed size of animal-dispersed species in replicated forest plots before and 27 years after exploitation. Species richness is also studied to allow comparison. While species richness was not affected by forest exploitation, total and commercial biomass as well as seed size of animal-dispersed species decreased 27 years after exploitation, similarly to forests affected by hunting. These results show that ecosystem services and function likely did not recover even at the lowest intensity of forest exploitation studied, questioning the sustainability of the most common rotation-cycle duration applied in the tropics.

There is increasing concern, to what extent production forests in the Neotropics are sustainably managed. The implementation of effective forest management strategies that are ecologically beneficial plays thus a central role to prevent forest degradation. However, to identify effective forest management strategies, there is a need for methods supporting the decision-making process. The main objective of our study is to analyze the mid- and long-term impacts of different management intensities, such as varying the minimum stem diameter of harvestable commercial trees, on the dynamic and structure of a species-rich tropical lowland forest of French Guiana. Therefore, we have applied the management module of a dynamic forest model and analyzed simulation experiments for undisturbed forest growth and selective logging. For the first time we were able to quantify the mean recovery times of multiple ecosystem functions and properties (biomass, gross primary production, leaf area index, Shanon diversity, timber volume) after selective logging. Accordingly, we validated simulation results (biomass, number of trees harvested) of selective logging with forest inventory data from the last 32 years. The forest model reliably reproduces the observed pre-logging biomass, tree-size distribution, and logging intensity (10 trees/ha, 39 m3/ha). In addition, it became clear how strongly management with higher logging intensities influences the forest in the long term: (1) the mean recovery times of the investigated ecosystem functions were significantly extended. With very intensive logging (116 m3/ha), the average recovery time of forest biomass was almost twice as long as in a moderate simulation scenario (tint 138 a, tmod 77 a). Similar patterns were observed for other ecosystem functions, e.g. timber volume (tint 158 a, tmod 62 a). (2) Additionally, the functional composition shifted, as up to 30% pioneer tree species in particular invaded the forest. This innovative use of forest growth models may help in the development of ecologically reasonable forest management strategies.

In tropical forests, selective logging generates a significant reduction of above-ground carbon stocks, due to direct removal of a few large merchantable individuals, and the death of smaller injured or smashed trees following harvesting. Several studies have shown a strong correlation between logging intensity and a reduction of biodiversity, wood production, and biomass stocks. However, little is known about the long-term effects of logging on the main forest carbon (C) stocks in above and below-ground tree biomass, deadwood, litter, and soil. In this study we quantified C stocks in 28 0.25-ha plots located in a mixed Dipterocarp forest, Borneo, Indonesia, logged 16 years ago at different intensities ranging from 0 to 57% of initial biomass removed. We investigated the effect of logging intensity, topography, and soil variables on each C stock using linear mixed models. Sixteen years after logging, total C stocks ranged from 218 to 554 Mg C ha−1 with an average of 314 ± 21 Mg C ha−1, of which more than 75% were found in live trees. Logging intensity was found to be the main factor explaining the variability in carbon stored in above- and below- ground biomass of tree DBH >20 cm and deadwood. Simultaneously, the proportion of deadwood increased with logging intensity reaching 13.5% of total C stocks in intensively logged plots (>20% removal of initial biomass). This study confirmed, therefore, the need to limit logging intensity to a threshold of 20% of initial biomass removal in order to limit the long-term accumulation of deadwood after logging, probably due to high post-logging mortality. With more than half of all Bornean forests already logged, accounting for total C post-logging is key to better assess the long-term carbon footprint of commercial logging in the region, and is a necessary step towards the development of C-oriented forest management in the tropics.

Tropical forests are major providers of natural resources and ecosystem services but their ecological functions are at threat, due to increasing human pressure linked to economic development. The identification of priority areas for conservation is crucial for land use planning to ensure the protection of biodiversity and ecological function. Intact Forest Landscapes (IFLs), as defined by Greenpeace and World Resources Institute (WRI), are areas of the forest ecosystems not subjected to human activities. They have been identified by mapping human disturbances through remote sensing. Contrary to similar global-scale concepts, IFLs have been integrated into the standards of the certification body Forest Stewardship Council (FSC) and therefore have practical implications for forest management policies. The Motion 65, approved in the general assembly of FSC in 2014, mandates the protection of IFLs located in FSC certified logging concessions. Until the implementation of national standards, forestry operations are banished from 80% of the IFL area within each forest management unit. To trace the history and evaluate the suitability of IFLs in the Central African context, we searched for documents related to the IFL method, and related approaches focusing on the identification of areas devoid of human disturbances. The IFL method is simple and cost-effective and allows for a global assessment of the influence of human infrastructures and industrial exploitation on forests. However, the method does not consider the situation below the canopy and those forest components not visible by satellites. For example, hunting, one of the main threats faced by wildlife in Central African forests today, cannot be detected with satellite imagery. On the other hand, other anthropogenic activities which remote sensing may detect may be compatible with forest ecosystem conservation. To better tailor the IFL approach to Central African forests, we recommend (i) the consideration of wildlife communities in the intactness analysis, (ii) a thorough evaluation of the impacts of human activities on forest ecosystems, and (iii) the integration of local stakeholders and governments in the design of land management strategies to respond to social, economic and environmental needs.

This viewpoint paper presents a reaction to the article by Brandt et al. (2016). It highlights the complexities inherent to the attribution of deforestation impacts to policy interventions when using remote-sensing data. This critique argues that in the context of the Congo a suite of factors (i.e., population density in particular) other than those considered by Brandt et al. (e.g., type of forest, distance from roads and markets) play essential roles in determining the fates of forests. It also contends that care is needed when making decisions regarding which units will be included in the comparison group so that contextual factors and on-the-ground information are properly considered (e.g., when logging operations are inactive or when a concession is used for 'conservation' purposes). Finally, it proposes that a focus on an analysis of deforestation rates for a given level of timber production might be a metric that more accurately represents one aspect of the consequences of forest management, which should also consider the appraisal of trade-offs associated with a larger set of social, financial and ecological objectives.

By 2010, about 25% (180 million ha) of The International Tropical Timber Organization (ITTO) producer countries’ permanent forest estate was being managed using an approved forest management plan (FMP). While the existence of a FMP is often used as evidence of sustainable forest management (SFM), State officials mandated to monitor and verify FMPs’ implementation often lack the technical knowledge and political incentives to assess the changes that have been introduced, notably in terms of harvested volumes and species. Among tropical timber producers, Cameroon is considered to be exemplary for its progressive forest regulatory framework. Here we aim to estimate for the first time in sub-Saharan Africa the causal impact of the implementation of FMPs on harvested volumes, species and carbon stocks. We do so by using a 12-year (1998–2009) unbalanced longitudinal data set of a detailed, official harvesting inventory of 81 concessions in Cameroon. Results provide evidence to the theoretical expectations that for many years many practitioners have had on the implementation of SFM, i.e. that FMPs show a substantial opportunity to reduce carbon emissions from forest while presenting logging companies with acceptable financial trade-offs. We explore the technical and political reasons for our findings and conclude that these analyses are important for countries that are underwriting carbon-related schemes in which they propose to reduce their emissions through the effective implementation of SFM. We also demonstrate that producer countries do record useful information that, when effectively used, can help them to inform their policies and improve their sustainable development strategies.

La proportion de tiges endommagées par l'exploitation est un paramètre clé de l'aménagement des forêts naturelles de production dans les trois continents tropicaux (Afrique, néotropiques, et Asie du sud-est). En s'appuyant sur une revue de la littérature et sur une méta-analyse des données publiées, nous avons estimé le taux de dégâts d'exploitation pour une exploitation conventionnelle, et l'avons comparé entre les trois continents. Des coefficients de conversion ont été estimés pour convertir le taux de dégâts et l'intensité d'exploitation d'une unité à l'autre. Les arbres abattus sont plus petits dans les néotropiques (61 cm dhp en moyenne) qu'en Afrique ou en Asie (92 cm dhp). Une équation pan-tropicale prédisant la proportion de tiges endommagées (a, sans dimension) en fonction de l'intensité d'exploitation (Nlog, en ha-1) a été ajustée : a = 1 - (1 + 0,09135Nlog)-0,70461. Un effet résiduel significatif du continent a été trouvé, lié à la taille des arbres exploités : à même intensité d'exploitation, le taux de dégâts est moins important dans les néotropiques qu'en Afrique ou en Asie. Le taux de dégâts varie selon la taille des arbres endommagés, et se répartit à parts égales entre arbres détruits et arbres blessés. Les arbres blessés subissent une mortalité trois fois plus importante pendant 5 à 10 ans. Prendre en compte au moins la dépendance du taux de dégâts vis-à-vis de l'intensité d'exploitation améliorerait les projections faites dans l'aménagement forestier.

In the Congo Basin where most timber species are light-demanding, the low logging intensities commonly implemented (1–2 trees harvested ha −1 ) do not provide sufficient canopy gaps to ensure species regeneration. The regeneration of light-demanding timber species may therefore benefit from more intensive logging, or from post-harvest treatments such as thinning by poison girdling that increases light penetration. Little is known of the impact of post-harvest treatments on the floristic composition of tropical moist forests. This study therefore aimed to assess the effects of low and high selective logging (≃2.33 and 4.73 trees harvested ha −1 , and ≃4.96 and 9.16 m 2 ha −1 of basal area removed (logging + damage), respectively) – followed or not by thinning (≃21.14 trees thinned ha −1 , and ≃6.57 m 2 ha −1 of basal area removed) – on the floristic composition of a tropical moist forest in the Central African Republic, from 7 to 23 years after logging. We analyzed abundance data for 110 tree genera recorded every year for 14 years in 25 one-hectare permanent subplots. We used multivariate analysis to detect floristic variations between treatments and we assessed changes in floristic composition throughout the period. We compared floristic composition recovery between thinned and unthinned subplots, using unlogged subplots as a reference characterizing the pre-logging floristic composition. Logging and thinning had little impact on the floristic composition of the subplots as quantified 7 to 23 years later, though they did increase the proportion of pioneer species. Surprisingly, additional thinning at both logging levels failed to further distance floristic composition from that of the unlogged subplots, though it did increase disturbance intensity. Floristic composition recovery appeared to be facilitated when thinning was associated with logging. Thinning seemed to favor the growth and survival of non-pioneer species, to the detriment of pioneer species. These non-pioneer species could either be non-pioneer light demanders or shade-bearers. One explanation for this is that thinning by tree-poison girdling increased light availability without causing major damage to the forest, and thus increased the growth and survival of advance regeneration. The resulting enhanced competition then reduced the survival of pioneer species.

Assessment of forest carbon (C) stock and sequestration and the influence of forest harvesting and climatic variations are important issues in global forest ecology. Quantitative studies of the C balance of tropical forests, such as those in Papua New Guinea (PNG), are also required for forest-based climate change mitigation initiatives. We develop a hierarchical Bayesian model (HBM) of aboveground forest C stock and sequestration in primary, selectively harvested, and El Niño SouthernOscillation (ENSO)- effected lowland tropical forest from 15 years of Permanent Sample Plot (PSP) census data for PNG consisting of 121 plots in selectively harvested forest, and 35 plots in primary forest. Model parameters indicated: C stock in aboveground live biomass (AGLB) of 137 ± 9 (95% confidence interval (CI)) MgC ha-1 in primary forest, compared with 62 ± 18 MgC ha-1 for selectively harvested forest (55% difference); C sequestration in primary forest of 0.23 ± 1.70 MgC ha-1 y-1, which was lower than in selectively harvested forest, 1.12 ± 3.41 MgC ha-1 y-1; ENSO-induced fire resulted in significant C emissions (-6.87 ± 3.94 MgC ha-1 y-1). High variability between PSPs in C stock and C sequestration rates necessitated random plot effects for both stock and sequestration. The HBM approach allowed inclusion of hierarchical autocorrelation, providing valid CIs on model parameters and efficient estimation. The HBM model has provided quantitative insights on the C balance of PNG's forests that can be used as inputs for climate change mitigation initiatives.

Large areas of African moist forests are being logged in the context of supposedly sustainable management plans. It remains however controversial whether harvesting a few trees per hectare can be maintained in the long term while preserving other forest services as well. We used a unique 24 year silvicultural experiment, encompassing 10 4 ha plots established in the Central African Republic, to assess the effect of disturbance linked to logging (two to nine trees ha −1 greater than or equal to 80 cm DBH) and thinning (11–41 trees ha −1 greater than or equal to 50 cm DBH) on the structure and dynamics of the forest. Before silvicultural treatments, above-ground biomass (AGB) and timber stock (i.e. the volume of commercial trees greater than or equal to 80 cm DBH) in the plots amounted 374.5 ± 58.2 Mg ha −1 and 79.7 ± 45.9 m 3 ha −1 , respectively. We found that (i) natural control forest was increasing in AGB (2.58 ± 1.73 Mg dry mass ha −1 yr −1 ) and decreasing in timber stock (−0.33 ± 1.57 m 3 ha −1 yr −1 ); (ii) the AGB recovered very quickly after logging and thinning, at a rate proportional to the disturbance intensity (mean recovery after 24 years: 144%). Compared with controls, the gain almost doubled in the logged plots (4.82 ± 1.22 Mg ha −1 yr −1 ) and tripled in the logged + thinned plots (8.03 ± 1.41 Mg ha −1 yr −1 ); (iii) the timber stock recovered slowly (mean recovery after 24 years: 41%), at a rate of 0.75 ± 0.51 m 3 ha −1 yr −1 in the logged plots, and 0.81 ± 0.74 m 3 ha −1 yr −1 in the logged + thinned plots. Although thinning significantly increased the gain in biomass, it had no effect on the gain in timber stock. However, thinning did foster the growth and survival of small- and medium-sized timber trees and should have a positive effect over the next felling cycle.