Johan Oszwald's research while affiliated with Université de Rennes 2 and other places

Publications (105)

Article
While the scientific community documents environmental degradation and develops scenarios to identify the operational margins of system Earth, less attention is given to how decisions are made that steer the system in one direction or the other. We propose to use strategy games for this purpose, increasing the representation of human agency in scen...
Article
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• Global insect decline has recently become a cause for major concern, particularly in the tropics where the vast majority of species occurs. Deforestation is suggested as being a major driver of this decline, but how anthropogenic changes in landscape structure affect tropical insect communities has rarely been addressed. • We sampled Saturniidae...
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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. Thi...
Preprint
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While the scientific community has focused on documenting environmental degradation and developing scenarios that help identify the operational margins for system Earth, less attention has been given to the mental models of decision-makers that underpin environmental policies. We suggest that global efforts to stop deforestation and biodiversity lo...
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Along the edges of the Congo basin forest, where forest-savannah mosaics are the main ecological formation, it is important to determine how this mosaic has developed, particularly for forest protection. Have savannah lands resulted from deforestation or have forest patches expanded into them? Given the long-standing human occupation of this region...
Preprint
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Leclère et al.1 have outlined the possibility of a biodiversity transition for the 21st century, a line of thinking equivalent to the Forest Transition theory and what it says about forest cover globally2. The authors use a suite of global models to explore the impacts on global biodiversity of interventions on land-use, consumption and production...
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Assessing land use and land cover (LULC) change is essential for the sustainable 13 management of natural resources, biodiversity conservation, monitoring food security, and research 14 related to climate change and ecology. With increasingly rapid changes in LULC in response to 15 human population growth, a better assessment of land-use changes is...
Article
en Most landscape cover assessments for conservation programmes rely largely on remote sensing analyses. These analyses, however, neglect how people inhabiting protected zones perceive and structure land cover. Using socio‐ecological systems (SES) analysis in a forest‐savannah mosaic on the Congo Basin forest edge (Democratic Republic of Congo), we...
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Forests across the world stand at a crossroads where climate and land-use changes are shaping their future. Despite demonstrations of political will and global efforts, forest loss, fragmentation, and degradation continue unabated. No clear evidence exists to suggest that these initiatives are working. A key reason for this apparent ineffectiveness...
Article
Recently, there has been renewed interest in the ecosystem services of mangroves such as carbon sequestration or coastal protection, and consequently, the development of tools providing an effective and automatic monitoring of the dynamics of mangrove land coverage including rehabilitated or naturally regenerated forest stand is increasingly demand...
Preprint
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Forests across the world stand at the crossroad with climate and land use changes shaping their future. Despite the demonstration of political will and global efforts, forest loss, fragmentation and land degradation continue unabated. No clear evidence exists that these initiatives are working. Why are policies designed to halt deforestation and in...
Article
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Forest conservation in human-dominated tropical landscapes ensures provision of major ecosystem services. However, conservation goals are threatened by growing demands for agricultural products. As the expansion of agricultural frontiers continues to exert increasing pressure on forest cover, it is crucial to provide indicators on forest vulnerabil...
Article
Tropical forests in Central Africa host unique biodiversity threatened by human degradation of habitats and defaunation. Forests allocated to conservation, production and community management are expected to have different conservation values. Here, we aimed to identify the determinants of the conservation value of tropical forests in southeastern...
Article
In Central Africa, local populations are deeply dependent on tropical forests, which provide numerous ecosystem services (ES). For the first time in Central Africa, we assessed the perceptions of ES provided by tropical forests to local populations, considering three land allocation types: a protected area, a Forest Stewardship Council (FSC)-certif...
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D’une superficie de 225 000 ha, la Réserve de biosphère de Yangambi (République démocratique du Congo) est l’une des principales aires protégées menacées par l’anthropisation dans la région. Malgré son appartenance au réseau mondial des réserves de biosphère depuis les années 1970, les connaissances sur les dynamiques d’occupation du sol y sont enc...
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D’une superficie de 225 000 ha, la Réserve de Biosphère de Yangambi (République démocratique du Congo), est l’une des principales aires protégées menacées par l’anthropisation dans la région. Malgré son appartenance au réseau mondial des réserves de biosphère depuis les années 1970, les connaissances sur les dynamiques d’occupation du sol y...
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Approche critique de la cartographie de services écosystémiques. Quantifier et spatialiser les objets de nature : un enjeu toujours actuel. La carte, représentation partielle ou complète de la surface terrestre, sur un support plan, peut constituer un moyen de communication efficace. Elle peut, par exemple, faciliter le dialogue entre les chargés d...
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The issue of invasive plants in Togo (West Africa): contribution of landscape systemic analysis and remote sensing. Description of the subject. Invasive plants are a major threat to natural habitats, agriculture and health worldwide. Certain land uses are known to promote plant invasions. Despite the occurrence of rapid land-use mutations, particul...
Article
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Ecosystem Service (ES) mapping has become a key tool in scientific assessments of human-nature interactions and is being increasingly used in environmental planning and policy-making. However, the associated epistemic uncertainty underlying these maps often is not systematically considered. This paper proposes a basic procedure to present areas wit...
Presentation
Full-text available
Biological invasions and changes in land use are two components of global change affecting biodiversity worldwide. Both contemporary and historic land use may influence the spread of invasive plants by altering landscape patterns, soils, and biotic communities. Indeed, invasion within land uses is often associated with the historical legacy of chan...
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In the agricultural frontiers of Brazil, the distinction between forested and deforested lands traditionally used to map the state of the Amazon does not reflect the reality of the forest situation. A whole gradient exists for these forests, spanning from well conserved to severely degraded. For decision makers, there is an urgent need to better ch...
Article
Mapping ecosystem services (ES) over large scales is important for environmental monitoring but is often prohibitively expensive and difficult. We test a hybrid, low-cost method of mapping ES indicators over large scales in Pará State, Brazil. Four ES indicators (vegetation carbon stocks, biodiversity index, soil chemical quality index and rates of...
Article
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Quantifying and mapping ecosystem services (ES) is seen as one way to improve decision making and land management to better integrate environmental issues. This study aimed to characterize ES supply in deforestation context where an improvement of scientific knowledge should help develop more efficient environmental management. For three case studi...
Presentation
Tropical natural ecosystems host a very diverse flora and fauna and are key ecosystems for global climate and biogeochemical regulation. Unfortunately, in West African landscapes, large areas of savanna and forest have been progressively replaced or fragmented by crops. These dynamics promote the spread of many invasive plants representing on the o...
Article
Earthworms, as ecosystem engineers, help to mineralize soil organic matter, construct and maintain soil structure, and often stimulate plant growth and protect plants from pests. The aim of this study was (i) to determine the connection between earthworm traits and indicators of soil ecosystem services and (ii) to identify earthworm “response” trai...
Presentation
Landscapes of the Togodo Protected Area (TPA) in southeastern Togo and its periphery have been under increasing modifications for decades As for the dry savannah and forest ecosystems in West Africa, one of the main factors of this transformation in land cover/ use is the expansion of agricultural systems to meet the demand for food from a growing...
Article
Agrarian reform has become at highly topical issue in Brazil and is proceeding mainly along the Amazonian pioneer fronts, thus jeopardising the continuity of forest cover. Although it is sometimes accompanied by highly proactive policies for sustainable development, the results of these policies are extremely variable. In this article, we compare f...
Article
Full-text available
Le contexte actuel de changement climatique global souleve de nombreuses questions quant a l’evolution des climats aux echelles regionales et locales. La litterature scientifique, de plus en plus riche a ce sujet, merite d’etre approfondie. La methode des « Types de Climats Annuels » (TCA) a ete utilisee, selon la classification climatique de Koppe...
Article
Quantifying and mapping ecosystem services (ES), their indicators and their relationships is of crucial importance for environmental management. In this article, we analyze the spatial distribution of multiple-ES indicators at three locations on the pioneer fronts of the Brazilian Amazon. We identify trade-offs and synergies between six ES indicato...
Article
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The wide use of the concept of « Ecosystem services (ES) » imposes a cautious work for delimiting its scope, particularly regarding its effects on nature’s management strategies. The purpose of this paper is to discuss the advantages and limits of the concept when used as framework for hydrosystem management. Within a Foucauldian theoretical framew...
Article
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The forest transition framework describes the temporal changes of forest areas with economic development. A first phase of forest contraction is followed by a second phase of expansion once a turning point is reached. This framework does not differentiate forest types or ecosystem services, and describes forests regardless of their contribution to...
Data
Linear models of land-cover changes. (PDF)
Data
Results of the sub-watershed cluster analysis. (PDF)
Article
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The development of approaches to quantify and spatialize ecosystem services (ES) are greatly encouraged by the Millenium Ecosystem Assessment (MEA) and the REDD (Reducing Emissions from Deforestation and forest Degradation). Such approaches could allow the establishment of more appropriate and effective practices and policies for environmental mana...
Article
Full-text available
Agrarian reform has become at highly topical issue in Brazil and is proceeding mainly along the Amazonian pioneer fronts, thus jeopardising the continuity of forest cover. Although it is sometimes accompanied by highly proactive policies for sustainable development, the results of these policies are extremely variable. In this article, we compare f...
Article
Full-text available
Coastal marshlands may provide ecosystem services but their vegetation and related services may be impacted by environmental changes. Habitat mapping is a key step to monitor the spatio-temporal dynamics of vegetation and detect on-going changes. However, it is still a challenge to produce reliable vegetation maps at the regional scale. This study...
Conference Paper
Full-text available
Plant communities mapping is a major issue for environmental managers, by meeting the Habitat directive 92/43/EEC requirements on assessment of biodiversity and conservation status of semi-natural habitats. Thereafter, the French Ministry in charge of Ecology has launched the CarHab program which aims to map natural vegetation all over the national...
Article
Microtopography and, by extension, the water regime play a key role in the spatial distribution of vegetations in wetlands. This study aims to assess the interest of topographical LiDAR data for vegetation mapping in grasslands. Method is based on the Digital Terrain Model thresholding in respect with vegetation relevés distributed over a 35 ha sit...
Article
Full-text available
Microtopography and, by extension, the water regime play a key role in the spatial distribution of vegetations in wetlands. This study aims to assess the interest of topographical LiDAR data for vegetation mapping in grasslands. Method is based on the Digital Terrain Model thresholding in respect with vegetation relevés distributed over a 35 ha sit...
Article
Land use changes in the Amazon region strongly impact soil macroinvertebrate communities, which are recognized as major drivers of soil functions (Lavelle et al., 2006). To explore these relations, we tested the hypotheses that (i) soil macrofauna communities respond to landscape changes and (ii) soil macrofauna and ecosystem services are linked. W...
Article
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Landscape dynamics result from forestry and farming practices, both of which are expected to have diverse impacts on ecosystem services (ES). In this study, we investigated this general statement for regulating and supporting services via an assessment of ecosystem functions: climate regulation via carbon sequestration in soil and plant biomass, wa...
Article
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L'important corpus de recherches sur les changements d'utilisation des terres et de la couverture du sol en Amazonie brésilienne met généralement en évidence un effet significatif des systèmes de production paysanne. Cependant, l'influence des caractéristiques socio-économiques spécifiques des petits exploitants sur l'utilisation des terres et le c...