Jan De Leeuw
World Agroforestry Centre, East African Team, Faculty Member
- Agricultural Impact on Environment, Environmental Sustainability, Impact assessment of agricultural technology uptake, Environment and natural resources conservation, Mainstreaming of gender and environmental issues in rural development programs, Sustainable Development, and 9 morePoverty, Biology, Ecology, Conservation Biology, Biodiversity, Botany, Landscape Ecology, Environmental Education, and Science Communicationedit
- Jan de Leeuw has worked in higher education and research in environmental science in a wide variety of environments a... moreJan de Leeuw has worked in higher education and research in environmental science in a wide variety of environments around the world. He is now research team leader at ILRI in Nairobi, leading research on vulnerability in pastoral systems.
The research of Jan de Leeuw, which initially focussed on plant ecology, eco-hydrology and vegetation monitoring, broadened over the years to long term ecological research and environmental assessment and the application of earth observation in mapping and monitoring of environmental change. Later he developed interest in the contribution of geo-informatics and earth observation to support environmental policies.
The current work at ILRI builds on this, while studying pastoral livelihood systems and the impact of policies and drought relief and mitigating interventions in reducing vulnerabilities in these systems.edit
The provision of food to breeding and migrating waterfowl is one of the major functions of submerged aquatic vegetation in shallow lakes. Vallisneria spiralis L. is a submerged aquatic plant species widely distributed within Jiangxi... more
The provision of food to breeding and migrating waterfowl is one of the major functions of submerged aquatic vegetation in shallow lakes. Vallisneria spiralis L. is a submerged aquatic plant species widely distributed within Jiangxi Poyang Lake National Nature Reserve, China. More than 95% of the world population of the endangered Siberian crane as well as significant numbers of Bewick's swan and swan goose over winter in this area, while foraging on the tubers of Vallisneria.
ABSTRACT The wetlands of the Volga River delta have been designated wetlands of international importance and include the protected areas of the Astrakhanskiy Biosphere Reserve (Zapovednik (. Space photographs help document the effects of... more
ABSTRACT The wetlands of the Volga River delta have been designated wetlands of international importance and include the protected areas of the Astrakhanskiy Biosphere Reserve (Zapovednik (. Space photographs help document the effects of sea-level change in the Caspian Sea on the vegetation of the delta and on habitat suitability for waterbirds and mammals. The dramatic increase in vegetation that accompanied the most recent regression (until 1978l attracted great flocks of birds that nested and/or wintered in the area.
Page 1. 1 Do termites enhance the invasion of southern African savannas by alien plants? Mhosisi Masocha; Andrew. K. Skidmore; Herbert HT Prins; Milena Holmgren; & Jan de Leeuw Page 2. 2 A plant community becomes more prone to alien plant... more
Page 1. 1 Do termites enhance the invasion of southern African savannas by alien plants? Mhosisi Masocha; Andrew. K. Skidmore; Herbert HT Prins; Milena Holmgren; & Jan de Leeuw Page 2. 2 A plant community becomes more prone to alien plant invasions if the amount of unused resources increases Davis, MA, Grime, JP, & Thompson, K. 2000. Journal of Ecology, 88, 528-534. Page 3.
Abstract Livestock is considered a pathway out of poverty for poor small holder farmers in the developing world. Livestock production systems deliver benefits that have an effect on human wellbeing, by interacting with different... more
Abstract Livestock is considered a pathway out of poverty for poor small holder farmers in the developing world. Livestock production systems deliver benefits that have an effect on human wellbeing, by interacting with different ecosystems and their components. While generating these benefits to people, livestock produce negative environmental externalities.
Ericksen, P., Leeuw, J. de and Herrero, M. 2011. Harnessing livestock resources for food security in the pastoral areas of Eastern and Central Africa. Paper prepared for the 1st ASARECA General Assembly, Entebbe, Uganda, 14-16 December... more
Ericksen, P., Leeuw, J. de and Herrero, M. 2011. Harnessing livestock resources for food security in the pastoral areas of Eastern and Central Africa. Paper prepared for the 1st ASARECA General Assembly, Entebbe, Uganda, 14-16 December 2011. Entebbe, Uganda: ASARECA.
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Information on the spatial distribution of grass communities in wetland is increasingly recognized as important for effective wetland management and biological conservation. Remote sensing techniques has been proved to be an effective... more
Information on the spatial distribution of grass communities in wetland is increasingly recognized as important for effective wetland management and biological conservation. Remote sensing techniques has been proved to be an effective alternative to intensive and costly ground surveys for mapping grass community. However, the mapping accuracy of grass communities in wetland is still not preferable. The aim of this paper is to develop an effective method to map grass communities in Poyang Lake Natural Reserve.
Coping with drought and climate change in the pastoral sector in Sub-Saharan Africa: Policy considerations.
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There is a generally held perception that roads have negative environmental impacts (Clevenger et al. 2003; Forman 2003; Roedenbeck et al. 2007). Ironically, this paradigm stems from regions where fences and regulations restrict vehicles... more
There is a generally held perception that roads have negative environmental impacts (Clevenger et al. 2003; Forman 2003; Roedenbeck et al. 2007). Ironically, this paradigm stems from regions where fences and regulations restrict vehicles to paved roads. The situation is different in sparsely populated rural areas in the developing world, where the scarcity of paved roads forces drivers to create their own tracks, often with considerable environmental degradation as a result.
(1) In 1972, 11 ha of woodland, heathland and previously manured pasture was fenced in for a sheep-grazing experiment. The different grazing intensities in the grassland area were quantified, since it is considered a prerequisite for the... more
(1) In 1972, 11 ha of woodland, heathland and previously manured pasture was fenced in for a sheep-grazing experiment. The different grazing intensities in the grassland area were quantified, since it is considered a prerequisite for the establishment of heterogeneous vegetation patterns, ie closely grazed areas, roughness and shrub.(2) Grazing intensity, implying associated effects of treading and dunging (occupancy), can be estimated by dunging intensity.
1 The relationships between soil development, vertical vegetation zonation, vegetation succession and herbivory by Brent geese, Branta bernicla, were studied in a coastal salt marsh. We were able to analyse up to 100 years of salt marsh... more
1 The relationships between soil development, vertical vegetation zonation, vegetation succession and herbivory by Brent geese, Branta bernicla, were studied in a coastal salt marsh. We were able to analyse up to 100 years of salt marsh development by comparing sites where vegetation succession had progressed for various periods of time. These data were related to a continuous daily record of high water levels measured since 1824.
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A microbial assay and in-source pyrolysis mass spectrometry were used to demonstrate a shift in the characteristics of sestonic particulate organic matter after tidal inundation of a coastal salt marsh in the southwest Netherlands.... more
A microbial assay and in-source pyrolysis mass spectrometry were used to demonstrate a shift in the characteristics of sestonic particulate organic matter after tidal inundation of a coastal salt marsh in the southwest Netherlands. Analysis of seston samples collected from the main tidal creek of the marsh during a series of tidal cycles showed that an increase in microbial degradability accompanied a more pronounced lipid character of the seston after inundation.
This article describes an exercise to portray, quantify and map ecosystem services in the arid and semi-arid lands of Northern Kenya. We used a framework that distinguished intermediate services, final services and benefits to classify... more
This article describes an exercise to portray, quantify and map ecosystem services in the arid and semi-arid lands of Northern Kenya. We used a framework that distinguished intermediate services, final services and benefits to classify ecosystem services. The intermediate services were water and forage, key inputs into the final benefits of livestock production, wildlife tourism and cropping.
Abstract Directional reflectance factors that spanned the entire exitance hemisphere were collected on the ground throughout the morning period for common cover types in Tunisia, Africa. NOAA 7/8 AVHRR bands 1 (0.58–0.68 μm) and 2... more
Abstract Directional reflectance factors that spanned the entire exitance hemisphere were collected on the ground throughout the morning period for common cover types in Tunisia, Africa. NOAA 7/8 AVHRR bands 1 (0.58–0.68 μm) and 2 (0.73–1.1 μm) were used in data collection. The cover types reported were a plowed field, annual grassland, steppe grassland, hard wheat, salt plain, and irrigated wheat.
Net aerial primary production (NAPP) of marsh macrophytes is usually estimated either by destructive sampling techniques or by phenometric techniques. Destructive methods, however, are thought to be inaccurate while phenometric techniques... more
Net aerial primary production (NAPP) of marsh macrophytes is usually estimated either by destructive sampling techniques or by phenometric techniques. Destructive methods, however, are thought to be inaccurate while phenometric techniques are very labour intensive. In this study a new method is presented which allows an accurate and more efficient estimation of NAPP.
Abstract Animal distribution is usually predicted from the spatial variation in food biomass, whereas foraging theory commonly uses net energy intake rate as the currency to be maximized. We tested whether net energy intake rate better... more
Abstract Animal distribution is usually predicted from the spatial variation in food biomass, whereas foraging theory commonly uses net energy intake rate as the currency to be maximized. We tested whether net energy intake rate better predicted the distribution and abundance of tundra swans than food biomass. In a shallow lake, we mapped the density of sago pondweed tubers during 2 years, and calculated the foraging benefits and costs to tundra swans. Swan residence was expressed in bird-days, ie the sum of daily counts.
Leeuw, J. de, Kifugo, S., Msiyuni, Z., Said, S. and Peden, D. 2011. Impact of abstractions upstream on the benefits of riverine water discharge into the Lorian swamps, Kenya. Presented at the International Congress on Water 2011... more
Leeuw, J. de, Kifugo, S., Msiyuni, Z., Said, S. and Peden, D. 2011. Impact of abstractions upstream on the benefits of riverine water discharge into the Lorian swamps, Kenya. Presented at the International Congress on Water 2011 Integrated Water Resources Management in Tropical and Subtropical Drylands, Mekelle, Ethiopia, 19-26 September 2011. Nairobi, Kenya: ILRI.
Abstract There is consensus that pastoral mobility is beneficial for both pastoralists and the environment. However, rapid change arising from multiple factors, including landscape fragmentation, sedentarization, and demographic drivers... more
Abstract There is consensus that pastoral mobility is beneficial for both pastoralists and the environment. However, rapid change arising from multiple factors, including landscape fragmentation, sedentarization, and demographic drivers might affect the effectiveness of this pastoral coping strategy in times of drought. We investigate livestock mortality rates following the 2005 drought in four areas in Maasailand: the Maasai Mara, the Kitengela plains, the Amboseli, and the Simanjiro plains.
1. Abstract This paper analyses the historic changes in the populations of Kenyan large herbivore species and presents data on the encroachment of agriculture into the Kenyan ASAL zone during the period 1970's-1990's. It further... more
1. Abstract This paper analyses the historic changes in the populations of Kenyan large herbivore species and presents data on the encroachment of agriculture into the Kenyan ASAL zone during the period 1970's-1990's. It further investigates the change in the ratio of people to livestock.
Abstract Research and practice are increasingly demonstrating the environmental benefits of pastoralism and the opportunity for sustainable development of pastoral communities through a combination of livestock and biodiversity-related... more
Abstract Research and practice are increasingly demonstrating the environmental benefits of pastoralism and the opportunity for sustainable development of pastoral communities through a combination of livestock and biodiversity-related business. To take full advantage of the potential biodiversity-pastoral synergies, it will be crucial to put in place supporting policies. They need to be embedded in the context of overall pastoral development.
ABSTRACT The paper presents the first results of Dutch-Russian joint research project which aimed at application of GIS-techniques for the management of Astrakhankiy Biosphere Reserve (Russia). The reserve is located in Volga delta and... more
ABSTRACT The paper presents the first results of Dutch-Russian joint research project which aimed at application of GIS-techniques for the management of Astrakhankiy Biosphere Reserve (Russia). The reserve is located in Volga delta and highly depend upon fluctuations both of Volga river flow and Caspian sea level. Since 1977 the sea level increases rapidly. It strongly affects the structure and functioning of ecosystems.
Abstract: Use and retention of river water in African highlands deprive communities in arid lowlands of their benefits. This paper reviews information on water use in the Ewaso Ng'iro catchment, Kenya, to evaluate the effects of upstream... more
Abstract: Use and retention of river water in African highlands deprive communities in arid lowlands of their benefits. This paper reviews information on water use in the Ewaso Ng'iro catchment, Kenya, to evaluate the effects of upstream abstraction on the Lorian Swamp, a wetland used by pastoralists downstream. We first assess the abstractions and demands for water upstream and the river water supplies at the upper and the lower end of the Lorian Swamp.
In August 2010, the Food and Agriculture Organization (FAO) sub-Regional Emergency Office for Eastern and Central Africa (REOA) contracted the International Livestock Research Institute (ILRI) to develop a proto-type “Livestock Drought... more
In August 2010, the Food and Agriculture Organization (FAO) sub-Regional Emergency Office for Eastern and Central Africa (REOA) contracted the International Livestock Research Institute (ILRI) to develop a proto-type “Livestock Drought Management”(LDM) decision support tool for use by a range of emergency and relief planners and practitioners throughout the region.
Livestock are considered a pathway out of poverty for poor smallholder farmers in the developing world (Thornton and Herrero 2001). Consequently many development interventions aim at enhancing the income from livestock, such as through... more
Livestock are considered a pathway out of poverty for poor smallholder farmers in the developing world (Thornton and Herrero 2001). Consequently many development interventions aim at enhancing the income from livestock, such as through improved market access, development of value chains and intensification of livestock production (Herrero et al. 2010).
ABSTRACT: Significant numbers of grass eating geese migrate in east Asia as far south as the Yangtze. Geese prefer young and high quality vegetation, a resource difficult to find in central China in autumn and winter when vegetation turns... more
ABSTRACT: Significant numbers of grass eating geese migrate in east Asia as far south as the Yangtze. Geese prefer young and high quality vegetation, a resource difficult to find in central China in autumn and winter when vegetation turns senescent. Cool season grasses and Carices develop in autumn in flood recessional grasslands along the Yangtze and geese forage in this biotope, attracted by the availability of young tissue of high quality in autumn and winter.
abstract In this study, we monitored the quality of fresh tea leaves as raw materials of tea products by hyperspectral technology, as a way to explore the potential of hyperspectral remote sensing to detect the taste-related chemical... more
abstract In this study, we monitored the quality of fresh tea leaves as raw materials of tea products by hyperspectral technology, as a way to explore the potential of hyperspectral remote sensing to detect the taste-related chemical components with low concentration in living plants. At leaf scale, empirical models have been established to find the relationships between quality-related chemicals in fresh tea leaves and foliar spectral data.
Abstract This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do... more
Abstract This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do so tree patterns were quantified for African savannas from historical aerial photographs applying frequently used landscape metrics. Also, additional data for these areas were collected to quantify the processes taking place at these locations.
Abstract Poyang Lake is the largest freshwater lake in China covering 3800 km2 during the summer wet season. It drains into the Changjiang (Yangtze River) at its northern end through a narrow outlet. During the last half of the twentieth... more
Abstract Poyang Lake is the largest freshwater lake in China covering 3800 km2 during the summer wet season. It drains into the Changjiang (Yangtze River) at its northern end through a narrow outlet. During the last half of the twentieth century (1949–1999) average annual maximum stage and number of severe flood events in China's Poyang Lake region increased significantly. There are two primary causes for this trend. One was increasing Changjiang stage, which is the most important determinant of Poyang Lake stage.
Abstract Biodiversity in rangelands is decreasing, due to intense utilization for livestock production and conversion of rangeland into cropland; yet the outlook of rangeland biodiversity has not been considered in view of future global... more
Abstract Biodiversity in rangelands is decreasing, due to intense utilization for livestock production and conversion of rangeland into cropland; yet the outlook of rangeland biodiversity has not been considered in view of future global demand for food. Here we assess the impact of future livestock production on the global rangelands area and their biodiversity.
ABSTRACT Wildlife management requires reliable and consistent information on the abundance, distribution of species and their habitats as well as threats. This article reviews the application of remote sensing and CIS techniques in... more
ABSTRACT Wildlife management requires reliable and consistent information on the abundance, distribution of species and their habitats as well as threats. This article reviews the application of remote sensing and CIS techniques in wildlife distribution and habitat mapping and modelling.
Abstract Decline of seagrasses has been documented in many parts of the world. Reduction in water clarity, through increased turbidity and increased nutrient concentrations, is considered to be the primary cause of seagrass loss. Recent... more
Abstract Decline of seagrasses has been documented in many parts of the world. Reduction in water clarity, through increased turbidity and increased nutrient concentrations, is considered to be the primary cause of seagrass loss. Recent studies have indicated the need for new methods that will enable early detection of decline in seagrass extent and productivity, over large areas.
The Ewaso Ng'iro catchment is a landscape comprised of communal and trust lands, cattle ranches and private wildlife conservancies managed by both by pastoralist communities and commercial enterprises, as well as agricultural plots... more
The Ewaso Ng'iro catchment is a landscape comprised of communal and trust lands, cattle ranches and private wildlife conservancies managed by both by pastoralist communities and commercial enterprises, as well as agricultural plots managed by agribusinesses and smallholder farmers. Although parks and protected areas cover less than 10% of the catchment it is home to the greatest diversity and density of wild ungulates in East Africa outside of the Serengeti-Mara park system (Georgiadis et al.
An initially uniform Holcus lanatus-dominated sward came partly under hay-making and partly under sheep-grazing. Preferential grazing by sheep resulted in grazing at different intensities giving rise to a macro-pattern of various plant... more
An initially uniform Holcus lanatus-dominated sward came partly under hay-making and partly under sheep-grazing. Preferential grazing by sheep resulted in grazing at different intensities giving rise to a macro-pattern of various plant communities. Besides this macro-pattern a micro-pattern developed in the grazed area, which was absent under hay-making. In the micro-pattern short, heavily grazed areas alternated with taller, lightly grazed patches, both having the same species composition.