Laurent Kergoat

Laurent Kergoat
French National Centre for Scientific Research | CNRS · Observatoire Midi-Pyrénées Toulouse

PhD

About

209
Publications
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Publications

Publications (209)
Article
Abstract Woody plants play a major role for the resilience of drylands and in peoples' livelihoods. However, due to their scattered distribution, quantifying and monitoring woody cover over space and time is challenging. We develop a phenology driven model and train/validate MODIS (MCD43A4, 500 m) derived metrics with 178 ground observations from N...
Article
Full-text available
The potential of the short-wave infrared (SWIR) bands to detect dry-season vegetation mass and cover fraction is investigated with ground radiometry and MODIS data, confronted to vegetation data collected in rangeland and cropland sites in the Sahel (Senegal, Niger, Mali). The ratio of the 1.6 and 2.1 μm bands (called STI) acquired with a ground ra...
Article
Desertification of the Sahel region has been debated for decades, while the concept of a “re-greening” Sahel appeared with satellite remote sensing data that allowed vegetation monitoring across wide regions and over increasingly long series of years (nowadays 30 years with the GIMMS-3g dataset). However, the scarcity of long-term field observation...
Article
Full-text available
Optimum daily light-use efficiency (LUE) and normalized canopy photosynthesis (GEE*) rate, a proxy for LUE, have been derived from eddy covariance CO2 flux measurements obtained at a range of sites located in the mid to high latitudes. These two variables were analyzed with respect to environmental conditions, plant functional types (PFT) and leaf...
Article
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The paradigm of Sahelian desertification, whose roots lie in the colonial period, increased in popularity following the droughts of the 1970s and 1980s. This “desertification narrative” was shaped in the international arena by organizations working in the fields of international cooperation, human rights, regional development, economic regulation a...
Article
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Study Region: Middle Niger River Basin (MNRB), Ansongo to Niamey, Sahel, West Africa. Study Focus: Although MNRB hydrology and the red flood phenomena have been addressed in the past literature, water quality parameters and suspended particulate matter (SPM) dynamics remain poorly known. SPM impacts dam silting, exacerbating flooding, and microbial...
Article
Although a recovery of woody vegetation has been observed throughout the Sahel, western Niger has not followed the overall satellite-derived greening trend. While satellite imagery can be used to study overall patterns and trends, only field observations can provide insights in the dynamics of woody plant populations. Here we used field data from 2...
Article
Full-text available
ContextWind erosion plays a major role in land degradation in semi-arid areas, especially in the Sahel. There, wind erosion is as sensitive to land use and land management as to climate factors. Future land use intensification may increase wind erosion and induce regional land degradation.Objective We aimed to estimate wind erosion responses to cha...
Article
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In 2017, diarrheal diseases were responsible for 606 024 deaths in Sub-Saharan Africa. This situation is due to domestic and recreational use of polluted surface waters, deficits in hygiene, access to healthcare and drinking water, and to weak environmental and health monitoring infrastructures. Escherichia coli ( E . coli ) is an indicator for the...
Preprint
Full-text available
In 2017, diarrheal diseases were responsible for 606 024 deaths in Sub-Saharan Africa. This situation is due to domestic and recreational use of polluted surface waters, deficits in hygiene, access to healthcare and drinking water, and to weak environmental and health monitoring infrastructures. Escherichia coli ( E. coli ) is an indicator for the...
Article
Full-text available
Dryland ecosystems are a major source of land cover, account for about 40% of Earth's terrestrial surface and net primary productivity, and house more than 30 % of the human population. These ecosystems are subject to climate extremes (e.g. large-scale droughts and extreme floods) that are projected to increase in frequency and severity under most...
Book
Le climat exerce une influence très forte sur l'agriculture, qui est considérée comme l'activité humaine sans doute la plus dépendante des variations climatiques. Les impacts du changement climatique sur l'agriculture affecteront tout particulièrement les pays en développement des latitudes tropicales, qui connaissent déjà une grande variabilité cl...
Article
Full-text available
A large proportion of dryland trees and shrubs (hereafter referred to collectively as trees) grow in isolation, without canopy closure. These non-forest trees have a crucial role in biodiversity, and provide ecosystem services such as carbon storage, food resources and shelter for humans and animals1,2. However, most public interest relating to tre...
Article
Full-text available
Sahel rangelands degradation is prone to many controversies. In Sahel, rangeland forage resources availability is characterized by large spatial heterogeneity and wide seasonal and interannual variations. Pastoral livestock systems adapt to these patchy and variation resources by herd mobility and some supplement feeding that only partially overcom...
Article
Sahel rangelands degradation is prone to many controversies. In Sahel, rangeland forage resources availability is characterized by large spatial heterogeneity and wide seasonal and interannual variations. Pastoral livestock farming systems adapt to these patchy and variation resources by herd mobility and some supplement feeding that only partially...
Preprint
Full-text available
Dryland ecosystems form a major land cover, accounting for about 40 % of Earth's terrestrial surface and net primary productivity, and housing more than 30 % of the human population. These ecosystems are subject to climate extremes (e.g. large-scale droughts) that are projected to increase in frequency and severity under most future climate scenari...
Article
Full-text available
Because total suspended sediments (TSS) influence the penetration of light into the water column and are likely to carry pollutants and nutrients, their study is essential for understanding the functioning of African river ecosystems. If the estimation of solid transport is important in the context of hydro-agricultural developments, its quantifica...
Article
Full-text available
The Sahel (semi-arid fringe south of the Sahara) experienced a long and prolonged drought from the 1970s to the mid-1990s, with a few extremely severe episodes that strongly affected ecosystems and societies. Long-term observations showed that surface runoff has increased during this period, despite the rainfall deficit. This paradox stems from the...
Article
Full-text available
Dryland ecosystems comprise a balance between woody and herbaceous vegetation. Climate change impacts rainfall timing, which may alter the respective contributions of woody and herbaceous plants on the total vegetation production. Here, we apply 30 years of field-measured woody foliage and herbaceous mass from Senegal and document a faster increase...
Conference Paper
Full-text available
The West African Sahel experienced a long drought from the 1970s to the 1990s during which runoff has paradoxically increased, as a response to human and climate-induced changes in surface conditions. Despite the vegetation recovery (re-greening) observed at regional scale over the past 30 years, surface runoff is still increasing, suggesting that...
Article
Full-text available
Echinochloa stagnina (Retz) P. Beauv., a widespread semi-aquatic perennial grass, is a key species for the sustainability of many African wetlands. In an effort to assess interactions between hydrological regimes and management strategies targeting conservation, this study focuses on characterizing the growth of a typical East African wet grassland...
Conference Paper
Full-text available
The Sahel witnessed a climatic drought from the 1970s to the 2000s. During this period, vegetation cover decreased and surface runoff increased in many places. While annual rainfall has partly recovered since the begining of this century, runoff has not reacted accordingly. The state of the ecohydrological system changed, and it responds in a new w...
Poster
Full-text available
The semi-arid Sahelian region is particularly prone to wind erosion due to low and variable annual precipitation producing low vegetation cover with a high interannual variability. Surfaces traditionally devoted to livestock grazing are used as croplands, increasing the proportion of bare surface unprotected from wind erosion. Wind erosion could si...
Poster
Full-text available
The role of the land surface on dust variability over West Africa is still debated. Early studies have identified a correlation between dust optical depth over the Atlantic and previous year Sahelian precipitation and NDVI. Recent studies, however, point to a modest role of vegetation on dust emission variability, either with model attribution stud...
Article
This study (i) presents a coupled vegetation-soil model adapted to perennial C4 seasonally flooded semi-arid grasslands; and (ii) applies the model to evaluate changes in the annual productivity of the grasslands of the Tana River Delta, Kenya, under changing flooding conditions. Main plant growth processes are modelled within coupled plant carbon...
Article
Full-text available
West Africa is a region in fast transition from climate, demography, and land use perspectives. In this context, the African Monsoon Multidisciplinary Analysis (AMMA)–Couplage de l’Atmosphère Tropicale et du Cycle eco-Hydrologique (CATCH) long-term regional observatory was developed to monitor the impacts of global change on the critical zone of We...
Article
Full-text available
In the West African Sahel, two paradoxical hydrological behaviors have occurred during the last five decades. The first paradox was observed during the 1968–1990s ‘Great Drought’ period, during which runoff significantly increased. The second paradox appeared during the subsequent period of rainfall recovery (i.e., since the 1990s), during which th...
Article
Full-text available
Woody vegetation in farmland acts as a carbon sink and provides ecosystem services for local people, but no macroscale assessments of the impact of management and climate on woody cover exist for drylands. Here we make use of very high spatial resolution satellite imagery to derive wall-to-wall woody cover patterns in tropical West African drylands...
Article
Full-text available
West Africa is a region in fast transition from climate, demography, and land use perspectives. In this context, the African Monsoon Multidisciplinary Analysis (AMMA)-Couplage de l'Atmosphere Tropicale et du Cycle eco-Hydrologique (CATCH) long-term regional observatory was developed to monitor the impacts of global change on the critical zone of We...
Article
Full-text available
The Sahelian region is characterized by significant variations in precipitation, impacting water quantity and quality. Suspended particulate matter (SPM) dynamics has a significant impact on inland water ecology and water resource management. In-situ data in this region are scarce and, consequently, the environmental factors triggering SPM variabil...
Article
Full-text available
In most state-of-the-art climate models, systematic errors persist in the representation of the rainfall seasonality, near surface air temperature, and surface energy budget over West Africa, even during the dry season. Most biases are related to an incorrect latitudinal position of the monsoon structures. To disentangle the role of the large-scale...
Article
Full-text available
In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as the Sahelian paradox, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain th...
Article
In the Sahel, climate change and demographic growth are raising major concerns about the ability of crop yields to support the local population. Agro-pastoral management affects wind erosion (e.g. through crop residue management and tillage practices, which modify surface characteristics), which itself substantially affects the soil fertility, and...
Conference Paper
Full-text available
In the last decades the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as "the Sahelian paradox", is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain...
Article
The drivers of dust emission inter-annual variability in North Africa, the largest dust source on earth, are still debated. Early studies outlined the role of previous-season rainfall and vegetation growth, while some recent studies emphasize the role of wind variability. Here, we use a newly-developed estimation of dry-season nonphotosynthetic veg...
Preprint
Woody vegetation in farmland acts as a carbon sink and provides ecosystem services for local people, but no macro-scale assessments of the impact of management and climate on woody cover exists for drylands. Here we make use of very high spatial resolution satellite imagery to derive wall-to-wall woody cover patterns in tropical West African drylan...
Article
Full-text available
It has been shown that vegetation growth in semi-arid regions is important to the global terrestrial CO2 sink, which indicates the strong need for improved understanding and spatially explicit estimates of CO2 uptake (gross primary production; GPP) in semi-arid ecosystems. This study has three aims: (1) to evaluate the MOD17A2H GPP (collection 6) p...
Article
Full-text available
Land surface processes play an important role in the West African monsoon variability. In addition, the evolution of hydrological systems in this region, and particularly the increase of surface water and runoff coefficients observed since the 1950s, has had a strong impact on water resources and on the occurrence of floods events. This study addre...