Philippe Mayaux | Joint Research Centre (original) (raw)

Papers by Philippe Mayaux

Research paper thumbnail of State and evolution of the African rainforests between 1990 and 2010

Philosophical Transactions of the Royal Society B: Biological Sciences, 2013

This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution ... more This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images—imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr −1 for the period 1990–2000 and 0.14% yr −1 for the period 2000–2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-contro...

Research paper thumbnail of Mapping Congo Basin forest types from 300 m and 1km multi-sensor time series for carbon stocks and forest areas estimation

Biogeosciences Discussions, 2012

This study aimed to contribute to the understanding of the Congo Basin forests by delivering a de... more This study aimed to contribute to the understanding of the Congo Basin forests by delivering a detailed forest types map with an improved spatial discrimination and coherence for the whole Congo Basin region. A total of 20 land cover classes were described with the standardized Land Cover Classification System (LCCS) developed by the FAO. Based on a semi-automatic processing chain, the forest types map was produced by combining 19 months of observations from the ENVISAT MERIS full resolution products (300 m) and 8 yr of daily SPOT VEGETATION (VGT) reflectances (1 km). Four zones (north, south and two central) were delineated and processed separately according to their seasonal and cloud cover specificities. The discrimination between different vegetation types (e.g. forest and savannas) was significantly improved thanks to the MERIS sharp spatial resolution. This work achieved a better discrimination in cloudy areas by taking advantage of the temporal consistency of the SPOT VGT observations. This resulted in a precise delineation of the spatial extent of the rural complex in the countries situated along the Atlantic coast. Based on this new map, more accurate estimates of the surface areas of forest types were produced for each country of the Congo Basin. The impact of two forest definitions was then assessed in the framework of the reducing emissions from deforestation and degradation (REDD) initiative and carbon stocks were evaluated. Furthermore, the phenology of the different vegetation types was illustrated systematically with EVI temporal profiles. This Congo Basin forest types map reached a satisfactory overall accuracy of 71.5 % and even 78.9 % when the two savanna classes are aggregated. 1 Introduction Central Africa contains the second largest and the least degraded area of contiguous moist tropical forest of the world (de Wasseige et al., 2009). It provides huge ecosystem services from the local scale to the global one, in various economic, social and 7500 BGD 9, 7499-7553, 2012 Mapping Congo Basin forest types from 300 m and 1 km multi-sensor time A. Verhegghen et al.

Research paper thumbnail of Estimating the world's potentially available cropland using a bottom-up approach

Global Environmental Change, 2013

Research paper thumbnail of Comment on “Determination of Deforestation Rates of the World’s Humid Tropical Forests”

Achard et al. (2002) estimated tropical deforestation and atmospheric carbon emissions from 1990-... more Achard et al. (2002) estimated tropical deforestation and atmospheric carbon emissions from 1990-1997 and concluded that both were substantially lower than found in previous studies. However, we assert that they markedly underestimated carbon emissions, by omitting key factors and making some invalid assumptions. The net effect is a potentially large underestimate of the impact of tropical deforestation on global warming. Achard et al. (1) estimated tropical deforestation and atmospheric carbon (C) emissions from 1990-1997 and concluded that both were substantially lower than found in previous studies. However, we believe that the evidence favors higher estimates, particularly for C emissions. First, they confined their study to "humid tropical forests," excluding extensive drier forest types that were incorporated in earlier studies of tropical forests worldwide (2) and Brazilian Amazonia (3). As a result, deforestation estimates were reduced by 16.6% in Brazilian Amazonia (3) and by even greater amounts in tropical regions that include large expanses of seasonal forest.

Research paper thumbnail of A vegetation map of Central Africa derived from satellite imagery

Journal of Biogeography, 1999

Aim This paper presents the Joint Research Centre's TREES Project satellite derived Vegetation Ma... more Aim This paper presents the Joint Research Centre's TREES Project satellite derived Vegetation Map of Central Africa, at 1:5,000,000 scale, with a detailed description of the vegetation classes and their distribution. The information content of the map is compared with other conventional and satellite derived maps of the region for validation and evaluation purposes.Location The map focuses on the Guineo-Congolian ecological domain and covers the following countries: Cameroon, Central African Republic, Republic of Congo, Equatorial Guinea, Gabon and the Democratic Republic of Congo.Methods Using coarse resolution satellite imagery a map of vegetation cover has been produced based upon the spectral response of the vegetation cover. Digital image processing and geographical information systems techniques were employed, together with local knowledge, high resolution imagery and expert consultation, to compile a cartographic map product.Results The TREES Vegetation Map of Central Africa has been shown to be strongly correlated with the FAO Forest Resources Assessment for 1990. Comparison with other map sources indicates that the map contains greater spatial detail and is more consistent than conventionally compiled maps. The conventional maps however, contain more thematic information content relating to vegetation type.Main conclusions The map improves our state of knowledge of the vegetation cover of Central Africa and presents the most consistent and spatially detailed view yet published at this scale. Thematic information content on forest type is limited but should be improved in the near future with the inclusion of data from new satellite sensors. This first version of the map and future planned updates should provide an important input for regional stratification and planning purposes for forest resources, biodiversity and climate studies.

Research paper thumbnail of J.(2009). Monitoring Forest cover at global scale: The JRC approach

Research paper thumbnail of Harmonisation, mosaicing and production of the Global Land Cover 2000 database (Beta Version)

Research paper thumbnail of Global land cover mapping for the year 2000—Project status November 2002, European Commission, Joint Research Centre

Research paper thumbnail of A near-real time forest-cover map of Madagascar derived from SPOT-4 VEGETATION data

Using SPOT-4 VEGETATION data for near-real time mapping is new. In this Letter, a robust techniqu... more Using SPOT-4 VEGETATION data for near-real time mapping is new. In this Letter, a robust technique for cloud decontamination of the ten-day composites is presented. A forest-cover map of Madagascar is derived from monthly images from October 1998 to September 1999 with a user's accuracy of 87.8%.

Research paper thumbnail of Pan-tropical monitoring of deforestation

Abstract. This paper reviews the technical capabilities for monitoring deforestation from a pan-t... more Abstract. This paper reviews the technical capabilities for monitoring deforestation from a pan-tropical perspective in response to the United Nations Framework Convention on Climate Change (UNFCCC) process, which is studying the technical issues surrounding the ability to reduce greenhouse gas emissions from deforestation in developing countries.

Research paper thumbnail of Cartographie et évolution du couvert forestier en Afrique centrale

Research paper thumbnail of Some challenges in global land cover mapping: An assessment of agreement and accuracy in existing 1 km datasets

Many investigators need and use global land cover maps for a wide variety of purposes. Ironically... more Many investigators need and use global land cover maps for a wide variety of purposes. Ironically, after many years of very limited availability, there are now multiple global land cover maps and it is not readily apparent (1) which is most useful for particular applications or (2) how to combine the different maps to provide an improved dataset. The existing global land cover maps at 1 km spatial resolution have arisen from different initiatives and are based on different remote sensing data and employed different methodologies.

Research paper thumbnail of Between land and sea: livelihoods and environmental changes in mangrove ecosystems of Senegal

Unlike the global trend, the area of mangrove forest increased in the estuaries of Low Casamance ... more Unlike the global trend, the area of mangrove forest increased in the estuaries of Low Casamance and Sine-Saloum, Senegal, between 1986 and 2006. We collected multisource data (social and spatial) and applied a mix of qualitative and quantitative analytical methods to investigate the human–mangrove interactions during this period and to understand the causes of the observed increase.

Research paper thumbnail of New perspectives on global ecosystems from wide-area radar mosaics: flooded forest mapping in the tropics

Large floodplains in the tropics, like the Congo river basin in Central Africa, are interesting e... more Large floodplains in the tropics, like the Congo river basin in Central Africa, are interesting ecosystems that function as water storage and faunistic and florensis habitat. Moreover, they host a series of bio-chemical processes, such as methane emission, which have a significance in global change issues. Characterization of these complex ecosystems can be tackled from different view points, such as bio-chemistry, geology, climatology, hydrology, geomorphology, floristics and forest structure.

Research paper thumbnail of Multi-Sensor Monitoring System for Forest Cover Change Assessment in Central Africa

Abstract Forest monitoring from earth observation is crucial over tropical regions to assess fore... more Abstract Forest monitoring from earth observation is crucial over tropical regions to assess forest extent and provide up-to-date estimates of deforestation rates. Based on a systematic sample of 20x20 km size sites, a processing chain has been developed at the European Commission's Joint Research Centre (JRC) for producing deforestation estimates between years 1990, 2000 and 2005.

Research paper thumbnail of Wither radar Global mapping of the tropical forest: New avenues from the TREES ERS-1 Central Africa Mosaic

Résumé/Abstract The TREES ERS-I Central Africa Mosaic Project CAMP has opened an entirely new per... more Résumé/Abstract The TREES ERS-I Central Africa Mosaic Project CAMP has opened an entirely new perspective in radar remote sensing for the study of the earth ecosystem at large scale using radar remote sensing. The project was started in 1995 by the MTV unit (Monitoring Tropical Vegetation) of the DG JRC Space Applications Institute and consists of the assemblage of more than 450 ERS-I images covering the whole Central African tropical region.

Research paper thumbnail of Evolution du couvert forestier du bassin du Congo mesurée par télédétection spatiale= Remote sensing to measure changes in forest cover in the Congo Basin= Evolucion de la cubierta forestal de la cuenca del Congo medida por teledeteccion espacial

Depuis une décennie, les cartes de végétation d'Afrique centrale sont principalement dérivées d'i... more Depuis une décennie, les cartes de végétation d'Afrique centrale sont principalement dérivées d'images satellitaires. L'étendue forestière du bassin du Congo, son accessibilité réduite et son évolution rapide localement justifient l'utilisation de la télédétection. La cartographie du couvert forestier d'Afrique centrale et l'analyse de son évolution constituent l'un des objectifs du projet Trees visés par le Centre commun de recherche.

Research paper thumbnail of The ERS-1 Central Africa Mosaic: a new role for radar remote sensing in global studies of the tropical ecosystem

Abstract The Central Africa Mosaic project-CAMP-is an attempt to bring spaceborne SAR remote sens... more Abstract The Central Africa Mosaic project-CAMP-is an attempt to bring spaceborne SAR remote sensing into an entirely new perspective for global studies of the tropical ecosystem. The new approach hinges around the concept of multi-resolution information extraction, whereby using a high resolution radar sensor one can obtain information both at large geographical scale and at fine spatial detail; the access point to the data hierarchy-or the level of detail needed-is driven by the thematic application.

Research paper thumbnail of Monitoring land cover changes in African protected areas in the 21st century

Abstract Africa is home to some of the most vulnerable natural ecosystems and species on the plan... more Abstract Africa is home to some of the most vulnerable natural ecosystems and species on the planet. Around 7000 protected areas seek to safeguard the continent's rich biodiversity, but many of them face increasing management challenges. Human disturbances permeating into the parks directly and indirectly affect the ecological functioning and integrity of protected areas.

Research paper thumbnail of Calibration of tropical forest area estimates at coarse spatial resolution with fine resolution data

Abstract The interaction between the proportional errors produced by spatial aggregation and the ... more Abstract The interaction between the proportional errors produced by spatial aggregation and the spatial pattern of cover types has been modelled in an operational way at a broad spatial scale. A correction function has been calibrated on the basis of tropical forest maps derived from AVHRR 1 km data for the entire intertropical belt and a non-random sample of-thirteen Landsat TM scenes well-distributed among the main tropical forest regions.

Research paper thumbnail of State and evolution of the African rainforests between 1990 and 2010

Philosophical Transactions of the Royal Society B: Biological Sciences, 2013

This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution ... more This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images—imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr −1 for the period 1990–2000 and 0.14% yr −1 for the period 2000–2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-contro...

Research paper thumbnail of Mapping Congo Basin forest types from 300 m and 1km multi-sensor time series for carbon stocks and forest areas estimation

Biogeosciences Discussions, 2012

This study aimed to contribute to the understanding of the Congo Basin forests by delivering a de... more This study aimed to contribute to the understanding of the Congo Basin forests by delivering a detailed forest types map with an improved spatial discrimination and coherence for the whole Congo Basin region. A total of 20 land cover classes were described with the standardized Land Cover Classification System (LCCS) developed by the FAO. Based on a semi-automatic processing chain, the forest types map was produced by combining 19 months of observations from the ENVISAT MERIS full resolution products (300 m) and 8 yr of daily SPOT VEGETATION (VGT) reflectances (1 km). Four zones (north, south and two central) were delineated and processed separately according to their seasonal and cloud cover specificities. The discrimination between different vegetation types (e.g. forest and savannas) was significantly improved thanks to the MERIS sharp spatial resolution. This work achieved a better discrimination in cloudy areas by taking advantage of the temporal consistency of the SPOT VGT observations. This resulted in a precise delineation of the spatial extent of the rural complex in the countries situated along the Atlantic coast. Based on this new map, more accurate estimates of the surface areas of forest types were produced for each country of the Congo Basin. The impact of two forest definitions was then assessed in the framework of the reducing emissions from deforestation and degradation (REDD) initiative and carbon stocks were evaluated. Furthermore, the phenology of the different vegetation types was illustrated systematically with EVI temporal profiles. This Congo Basin forest types map reached a satisfactory overall accuracy of 71.5 % and even 78.9 % when the two savanna classes are aggregated. 1 Introduction Central Africa contains the second largest and the least degraded area of contiguous moist tropical forest of the world (de Wasseige et al., 2009). It provides huge ecosystem services from the local scale to the global one, in various economic, social and 7500 BGD 9, 7499-7553, 2012 Mapping Congo Basin forest types from 300 m and 1 km multi-sensor time A. Verhegghen et al.

Research paper thumbnail of Estimating the world's potentially available cropland using a bottom-up approach

Global Environmental Change, 2013

Research paper thumbnail of Comment on “Determination of Deforestation Rates of the World’s Humid Tropical Forests”

Achard et al. (2002) estimated tropical deforestation and atmospheric carbon emissions from 1990-... more Achard et al. (2002) estimated tropical deforestation and atmospheric carbon emissions from 1990-1997 and concluded that both were substantially lower than found in previous studies. However, we assert that they markedly underestimated carbon emissions, by omitting key factors and making some invalid assumptions. The net effect is a potentially large underestimate of the impact of tropical deforestation on global warming. Achard et al. (1) estimated tropical deforestation and atmospheric carbon (C) emissions from 1990-1997 and concluded that both were substantially lower than found in previous studies. However, we believe that the evidence favors higher estimates, particularly for C emissions. First, they confined their study to "humid tropical forests," excluding extensive drier forest types that were incorporated in earlier studies of tropical forests worldwide (2) and Brazilian Amazonia (3). As a result, deforestation estimates were reduced by 16.6% in Brazilian Amazonia (3) and by even greater amounts in tropical regions that include large expanses of seasonal forest.

Research paper thumbnail of A vegetation map of Central Africa derived from satellite imagery

Journal of Biogeography, 1999

Aim This paper presents the Joint Research Centre's TREES Project satellite derived Vegetation Ma... more Aim This paper presents the Joint Research Centre's TREES Project satellite derived Vegetation Map of Central Africa, at 1:5,000,000 scale, with a detailed description of the vegetation classes and their distribution. The information content of the map is compared with other conventional and satellite derived maps of the region for validation and evaluation purposes.Location The map focuses on the Guineo-Congolian ecological domain and covers the following countries: Cameroon, Central African Republic, Republic of Congo, Equatorial Guinea, Gabon and the Democratic Republic of Congo.Methods Using coarse resolution satellite imagery a map of vegetation cover has been produced based upon the spectral response of the vegetation cover. Digital image processing and geographical information systems techniques were employed, together with local knowledge, high resolution imagery and expert consultation, to compile a cartographic map product.Results The TREES Vegetation Map of Central Africa has been shown to be strongly correlated with the FAO Forest Resources Assessment for 1990. Comparison with other map sources indicates that the map contains greater spatial detail and is more consistent than conventionally compiled maps. The conventional maps however, contain more thematic information content relating to vegetation type.Main conclusions The map improves our state of knowledge of the vegetation cover of Central Africa and presents the most consistent and spatially detailed view yet published at this scale. Thematic information content on forest type is limited but should be improved in the near future with the inclusion of data from new satellite sensors. This first version of the map and future planned updates should provide an important input for regional stratification and planning purposes for forest resources, biodiversity and climate studies.

Research paper thumbnail of J.(2009). Monitoring Forest cover at global scale: The JRC approach

Research paper thumbnail of Harmonisation, mosaicing and production of the Global Land Cover 2000 database (Beta Version)

Research paper thumbnail of Global land cover mapping for the year 2000—Project status November 2002, European Commission, Joint Research Centre

Research paper thumbnail of A near-real time forest-cover map of Madagascar derived from SPOT-4 VEGETATION data

Using SPOT-4 VEGETATION data for near-real time mapping is new. In this Letter, a robust techniqu... more Using SPOT-4 VEGETATION data for near-real time mapping is new. In this Letter, a robust technique for cloud decontamination of the ten-day composites is presented. A forest-cover map of Madagascar is derived from monthly images from October 1998 to September 1999 with a user's accuracy of 87.8%.

Research paper thumbnail of Pan-tropical monitoring of deforestation

Abstract. This paper reviews the technical capabilities for monitoring deforestation from a pan-t... more Abstract. This paper reviews the technical capabilities for monitoring deforestation from a pan-tropical perspective in response to the United Nations Framework Convention on Climate Change (UNFCCC) process, which is studying the technical issues surrounding the ability to reduce greenhouse gas emissions from deforestation in developing countries.

Research paper thumbnail of Cartographie et évolution du couvert forestier en Afrique centrale

Research paper thumbnail of Some challenges in global land cover mapping: An assessment of agreement and accuracy in existing 1 km datasets

Many investigators need and use global land cover maps for a wide variety of purposes. Ironically... more Many investigators need and use global land cover maps for a wide variety of purposes. Ironically, after many years of very limited availability, there are now multiple global land cover maps and it is not readily apparent (1) which is most useful for particular applications or (2) how to combine the different maps to provide an improved dataset. The existing global land cover maps at 1 km spatial resolution have arisen from different initiatives and are based on different remote sensing data and employed different methodologies.

Research paper thumbnail of Between land and sea: livelihoods and environmental changes in mangrove ecosystems of Senegal

Unlike the global trend, the area of mangrove forest increased in the estuaries of Low Casamance ... more Unlike the global trend, the area of mangrove forest increased in the estuaries of Low Casamance and Sine-Saloum, Senegal, between 1986 and 2006. We collected multisource data (social and spatial) and applied a mix of qualitative and quantitative analytical methods to investigate the human–mangrove interactions during this period and to understand the causes of the observed increase.

Research paper thumbnail of New perspectives on global ecosystems from wide-area radar mosaics: flooded forest mapping in the tropics

Large floodplains in the tropics, like the Congo river basin in Central Africa, are interesting e... more Large floodplains in the tropics, like the Congo river basin in Central Africa, are interesting ecosystems that function as water storage and faunistic and florensis habitat. Moreover, they host a series of bio-chemical processes, such as methane emission, which have a significance in global change issues. Characterization of these complex ecosystems can be tackled from different view points, such as bio-chemistry, geology, climatology, hydrology, geomorphology, floristics and forest structure.

Research paper thumbnail of Multi-Sensor Monitoring System for Forest Cover Change Assessment in Central Africa

Abstract Forest monitoring from earth observation is crucial over tropical regions to assess fore... more Abstract Forest monitoring from earth observation is crucial over tropical regions to assess forest extent and provide up-to-date estimates of deforestation rates. Based on a systematic sample of 20x20 km size sites, a processing chain has been developed at the European Commission's Joint Research Centre (JRC) for producing deforestation estimates between years 1990, 2000 and 2005.

Research paper thumbnail of Wither radar Global mapping of the tropical forest: New avenues from the TREES ERS-1 Central Africa Mosaic

Résumé/Abstract The TREES ERS-I Central Africa Mosaic Project CAMP has opened an entirely new per... more Résumé/Abstract The TREES ERS-I Central Africa Mosaic Project CAMP has opened an entirely new perspective in radar remote sensing for the study of the earth ecosystem at large scale using radar remote sensing. The project was started in 1995 by the MTV unit (Monitoring Tropical Vegetation) of the DG JRC Space Applications Institute and consists of the assemblage of more than 450 ERS-I images covering the whole Central African tropical region.

Research paper thumbnail of Evolution du couvert forestier du bassin du Congo mesurée par télédétection spatiale= Remote sensing to measure changes in forest cover in the Congo Basin= Evolucion de la cubierta forestal de la cuenca del Congo medida por teledeteccion espacial

Depuis une décennie, les cartes de végétation d'Afrique centrale sont principalement dérivées d'i... more Depuis une décennie, les cartes de végétation d'Afrique centrale sont principalement dérivées d'images satellitaires. L'étendue forestière du bassin du Congo, son accessibilité réduite et son évolution rapide localement justifient l'utilisation de la télédétection. La cartographie du couvert forestier d'Afrique centrale et l'analyse de son évolution constituent l'un des objectifs du projet Trees visés par le Centre commun de recherche.

Research paper thumbnail of The ERS-1 Central Africa Mosaic: a new role for radar remote sensing in global studies of the tropical ecosystem

Abstract The Central Africa Mosaic project-CAMP-is an attempt to bring spaceborne SAR remote sens... more Abstract The Central Africa Mosaic project-CAMP-is an attempt to bring spaceborne SAR remote sensing into an entirely new perspective for global studies of the tropical ecosystem. The new approach hinges around the concept of multi-resolution information extraction, whereby using a high resolution radar sensor one can obtain information both at large geographical scale and at fine spatial detail; the access point to the data hierarchy-or the level of detail needed-is driven by the thematic application.

Research paper thumbnail of Monitoring land cover changes in African protected areas in the 21st century

Abstract Africa is home to some of the most vulnerable natural ecosystems and species on the plan... more Abstract Africa is home to some of the most vulnerable natural ecosystems and species on the planet. Around 7000 protected areas seek to safeguard the continent's rich biodiversity, but many of them face increasing management challenges. Human disturbances permeating into the parks directly and indirectly affect the ecological functioning and integrity of protected areas.

Research paper thumbnail of Calibration of tropical forest area estimates at coarse spatial resolution with fine resolution data

Abstract The interaction between the proportional errors produced by spatial aggregation and the ... more Abstract The interaction between the proportional errors produced by spatial aggregation and the spatial pattern of cover types has been modelled in an operational way at a broad spatial scale. A correction function has been calibrated on the basis of tropical forest maps derived from AVHRR 1 km data for the entire intertropical belt and a non-random sample of-thirteen Landsat TM scenes well-distributed among the main tropical forest regions.