W. Ligtvoet - Academia.edu (original) (raw)

Papers by W. Ligtvoet

In this chapter a review is given of the recent changes in the fish communities of Lake Victoria.... more In this chapter a review is given of the recent changes in the fish communities of Lake Victoria. The abundance and spatial distribution of the currently most important commercial fish species Nile perch (Lates), dagaa (Rastrineobola argentea) and Nile tilapia (Oreochromis niloticus) is described and information is presented about the different types of fishery associated with them. Finally a description of types of landing sites in the Tanzanian part of Lake Victoria is given.

standardised evaluative measurement of nature impacts:

EWaS3 2018, 2018

The United Nations Food and Agriculture Organization (FAO) has established the Water-Energy-Food ... more The United Nations Food and Agriculture Organization (FAO) has established the Water-Energy-Food Nexus, implying that the three commodities are inextricably linked forming a complex system of interrelations. Perceiving water, energy and food as a system variable with dependencies rather than a singularity suggests an approach of a more holistic view that can offer a sustainable plan for managing resources. In this article, the already established three-way Nexus is expanded to include two more dimensions, namely land use and climate and a framework for modelling the interlinkages among these dimensions is presented.

Rijn-Schelde Delta: gedeelde langetermijnvisie noodzakelijk voor goed afgestemde investeringsbesl... more Rijn-Schelde Delta: gedeelde langetermijnvisie noodzakelijk voor goed afgestemde investeringsbeslissingen Welke economische perspectieven zijn er binnen de Rijn-Schelde Delta? Is de A4 te beschouwen als een economische ontwikkelingszone voor de Delta of alleen als transportas? Hoe om te gaan met veiligheid en met zoet- en zoutwater in de Delta? Is een (gedeeltelijk) herstel van natuurlijke dynamiek mogelijk? Hoe ontwikkelen de havens zich en hoe is de steeds intensievere scheepvaart te accommoderen? Is in de toekomst steeds weer natuurcompensatie langs de Westerschelde noodzakelijk of zijn er alternatieven? Hoe passen de strategische keuzes op verschillende schaalniveaus bij elkaar? Een gezamenlijke visie voor de langetermijnontwikkeling van de Rijn-Schelde Delta is van groot belang om tot samenhangende beslissingen te komen. Dit stelden de betrokken Directeuren-Generaal vast op een door het PBL georganiseerde themabijeenkomst. Aan de orde was of integraal werken ook – of juist – bi...

De Balans van de Leefomgeving geeft parlement, kabinet en samenleving een feitelijk onderbouwd in... more De Balans van de Leefomgeving geeft parlement, kabinet en samenleving een feitelijk onderbouwd inzicht in de huidige kwaliteit van de fysieke leefomgeving. De Balans is de tweejaarlijkse peilstok van het PBL die aangeeft in hoeverre de door de politiek zelf ten doel gestelde leefomgevingskwaliteit tijdig wordt bereikt. De Balans van de Leefomgeving 2014 heeft als motto meegekregen: de toekomst is nu.

Technical notes document the research or analytical methodology underpinning a publication, inter... more Technical notes document the research or analytical methodology underpinning a publication, interactive application, or tool.

Although climate change is expected to continue, its negative impacts for the Netherlands appear ... more Although climate change is expected to continue, its negative impacts for the Netherlands appear manageable. Here, most climatic changes will take place more gradual than in many other regions, thus enabling citizens, companies and authorities to adapt. Furthermore, current policies focus attention on important aspects of climate change, such as the risk of flooding, drought and precipitation extremes.

Annales Zoologici Fennici, 1996

Size distributions of cohorts of pikeperch and perch originating from three lakes in the Netherla... more Size distributions of cohorts of pikeperch and perch originating from three lakes in the Netherlands were compared to test the hypothesis that skewness or bimodality within cohorts of pikeperch and perch develops especially in environments with a discontinuous size distribution of their potential food items. In older, more eutrophic lake ecosystems like Tjeukemeer and IJsselmeer, where macro-invertebrates occur in low densities, 0-group pikeperch generally exhibit differential growth of fast-growing piscivores and slow-growing zooplanktivores. The size distributions of such cohorts become positively skewed during their first summer and often become bimodal at the end of the growing season with modes at ca. 10-15 cm and 6-8 cm, respectively. The size attained by zooplanktivorous 0-group perch in these systems is relatively small (6-9 cm) and is positively related to summer temperature. Cohorts of perch in these systems shift to piscivory, partially or totally, in their second or third summer. The differential growth of zooplanktivorous and piscivorous perch of the same cohort can cause a broadening and a positive skewness in the cohort size distribution, but never results in a bimodal size distribution. In the recently freshened, mesotrophic Volkerak ecosystem, the initial high availability of the macro-invertebrate Neomysis integer, in the first couple of years enabled 0-group pikeperch and perch to reach similar large sizes of 12-14 cm and to both switch to piscivory in their second summer. After ca. 5 years Volkerak became more eutrophic, the stock biomass of cyprinids increased, the size distribution of 0group pikeperch became bimodal and the 0-group perch stayed small (< 10 cm), as in the older, more eutrophic systems. It is postulated that more productive systems with a higher fish biomass, but with lower biomasses of macro-invertebrates and less largesized zooplankton probably have stronger selection mechanisms for recruiting percids.

Future population growth is expected to concentrate in urban agglomerations that are already expo... more Future population growth is expected to concentrate in urban agglomerations that are already exposed to numerous natural hazards. It is difficult, however, to assess this increase in risk as natural hazards are often concentrated in space and population growth scenarios tend to be defined at much coarser scales. By combining recently released high-resolution spatial data on land use, population density and natural hazards with a novel, computationally effective simulation approach we analyse global increases in local exposure to two important natural hazards: flood risk and landslides. We develop global spatially explicitp rojections of population change and urban expansion using a land-use and population allocation model. The model is developed in the Geo Data and Model Server (GeoDMS) modelling framework, that also underlies Land Use Scanner and several other operational models of land-use change developed for individual countries, larger river catchment areas and the territory of...

Α novel methodology for addressing policy inconsistencies and knowledge gaps that hinder the tran... more Α novel methodology for addressing policy inconsistencies and knowledge gaps that hinder the transition to a greater resource efficiency Europe is proposed. We focus on the integration of all different sectors that interact and influence each other, namely the “water- energy- food- land use- climate nexus” and we develop tools for identifying and quantifying their complex interlinkages under the influence of climate change. In order to achieve this, we employ a series of sophisticated models (referred to as “thematic models”), each of which addresses a different nexus dimension, or a combination of a few, while none addresses all nexus dimensions in an integrative manner. We use dynamic systems modeling and other complexity science techniques in order to “merge” different thematic model outputs in a single coherent result, which is presented to the user in an easyto-comprehend Serious Game environment. This way, the effect of policies that are designed to affect one field (nexus dim...

On March 8, 1989, Technical Meeting 46 of the TNO Committee on Hydrological Research (CHO-TNO) wa... more On March 8, 1989, Technical Meeting 46 of the TNO Committee on Hydrological Research (CHO-TNO) was held on the theme: "Hydroecological relations in the Delta Waters of the South-West Netherlands'. The results of this meeting are published in Proceedings and Information CHO-TNO No. 41. On June 4, 1992, Technical Meeting 50 of CHO-TNO took place. During this meeting the results have been presented of an evaluation of the water management of Lake Volkerak/Zoom - a new freshwater system in the Delta. This publication contains the papers presented at this meeting, which was organized in co-operation with Rijkswaterstaat, Directorate Zeeland. These papers consider the key questions, whether water management has been able to deal with the changes in Lake Volkerak/Zoom and whether the management policy targets will be achieved.

International Journal of Disaster Risk Reduction

Abstract The Dutch National Risk Assessment (NRA) is a methodology to assess the impact and likel... more Abstract The Dutch National Risk Assessment (NRA) is a methodology to assess the impact and likelihood of all possible threats and hazards that might hit the Netherlands, including a large-scale flood. This methodology addresses all the physical and social aspects that determine social disruption. The NRA has been applied to six European floods in Central and Western Europe. The results show that the NRA impact score for a flooding scenario can be interpreted as a measure for social disruption. Some comments can be made, however. The all hazards approach of the NRA is designed as a robust instrument that enables covering a wide array of threats and disasters. As a result, the NRA in its ‘original’ form offers little room for detailed differences in the consequences of different flooding scenarios. Tailor-made adjustments to the NRA are needed to insure that, for instance, differences in the number of casualties for different floods do not get lost in the bandwidth of the impact criteria. Socio-psychological factors significantly mark the impact of flooding. This offers opportunities to steer on avoiding or restricting social disruption by flooding by putting an adequate flood risk and crisis communication in place. The floods in Central Europe in 2002 and 2013 more or less present the lower and upper bounds of the impacts of recent large-scale river floods in Central and Western Europe. Compared with this bandwidth, the impact of a scenario of a worst-case river flood in the Netherlands is not unusual in a European context.

In this chapter a review is given of the recent changes in the fish communities of Lake Victoria.... more In this chapter a review is given of the recent changes in the fish communities of Lake Victoria. The abundance and spatial distribution of the currently most important commercial fish species Nile perch (Lates), dagaa (Rastrineobola argentea) and Nile tilapia (Oreochromis niloticus) is described and information is presented about the different types of fishery associated with them. Finally a description of types of landing sites in the Tanzanian part of Lake Victoria is given.

standardised evaluative measurement of nature impacts:

EWaS3 2018, 2018

The United Nations Food and Agriculture Organization (FAO) has established the Water-Energy-Food ... more The United Nations Food and Agriculture Organization (FAO) has established the Water-Energy-Food Nexus, implying that the three commodities are inextricably linked forming a complex system of interrelations. Perceiving water, energy and food as a system variable with dependencies rather than a singularity suggests an approach of a more holistic view that can offer a sustainable plan for managing resources. In this article, the already established three-way Nexus is expanded to include two more dimensions, namely land use and climate and a framework for modelling the interlinkages among these dimensions is presented.

Rijn-Schelde Delta: gedeelde langetermijnvisie noodzakelijk voor goed afgestemde investeringsbesl... more Rijn-Schelde Delta: gedeelde langetermijnvisie noodzakelijk voor goed afgestemde investeringsbeslissingen Welke economische perspectieven zijn er binnen de Rijn-Schelde Delta? Is de A4 te beschouwen als een economische ontwikkelingszone voor de Delta of alleen als transportas? Hoe om te gaan met veiligheid en met zoet- en zoutwater in de Delta? Is een (gedeeltelijk) herstel van natuurlijke dynamiek mogelijk? Hoe ontwikkelen de havens zich en hoe is de steeds intensievere scheepvaart te accommoderen? Is in de toekomst steeds weer natuurcompensatie langs de Westerschelde noodzakelijk of zijn er alternatieven? Hoe passen de strategische keuzes op verschillende schaalniveaus bij elkaar? Een gezamenlijke visie voor de langetermijnontwikkeling van de Rijn-Schelde Delta is van groot belang om tot samenhangende beslissingen te komen. Dit stelden de betrokken Directeuren-Generaal vast op een door het PBL georganiseerde themabijeenkomst. Aan de orde was of integraal werken ook – of juist – bi...

De Balans van de Leefomgeving geeft parlement, kabinet en samenleving een feitelijk onderbouwd in... more De Balans van de Leefomgeving geeft parlement, kabinet en samenleving een feitelijk onderbouwd inzicht in de huidige kwaliteit van de fysieke leefomgeving. De Balans is de tweejaarlijkse peilstok van het PBL die aangeeft in hoeverre de door de politiek zelf ten doel gestelde leefomgevingskwaliteit tijdig wordt bereikt. De Balans van de Leefomgeving 2014 heeft als motto meegekregen: de toekomst is nu.

Technical notes document the research or analytical methodology underpinning a publication, inter... more Technical notes document the research or analytical methodology underpinning a publication, interactive application, or tool.

Although climate change is expected to continue, its negative impacts for the Netherlands appear ... more Although climate change is expected to continue, its negative impacts for the Netherlands appear manageable. Here, most climatic changes will take place more gradual than in many other regions, thus enabling citizens, companies and authorities to adapt. Furthermore, current policies focus attention on important aspects of climate change, such as the risk of flooding, drought and precipitation extremes.

Annales Zoologici Fennici, 1996

Size distributions of cohorts of pikeperch and perch originating from three lakes in the Netherla... more Size distributions of cohorts of pikeperch and perch originating from three lakes in the Netherlands were compared to test the hypothesis that skewness or bimodality within cohorts of pikeperch and perch develops especially in environments with a discontinuous size distribution of their potential food items. In older, more eutrophic lake ecosystems like Tjeukemeer and IJsselmeer, where macro-invertebrates occur in low densities, 0-group pikeperch generally exhibit differential growth of fast-growing piscivores and slow-growing zooplanktivores. The size distributions of such cohorts become positively skewed during their first summer and often become bimodal at the end of the growing season with modes at ca. 10-15 cm and 6-8 cm, respectively. The size attained by zooplanktivorous 0-group perch in these systems is relatively small (6-9 cm) and is positively related to summer temperature. Cohorts of perch in these systems shift to piscivory, partially or totally, in their second or third summer. The differential growth of zooplanktivorous and piscivorous perch of the same cohort can cause a broadening and a positive skewness in the cohort size distribution, but never results in a bimodal size distribution. In the recently freshened, mesotrophic Volkerak ecosystem, the initial high availability of the macro-invertebrate Neomysis integer, in the first couple of years enabled 0-group pikeperch and perch to reach similar large sizes of 12-14 cm and to both switch to piscivory in their second summer. After ca. 5 years Volkerak became more eutrophic, the stock biomass of cyprinids increased, the size distribution of 0group pikeperch became bimodal and the 0-group perch stayed small (< 10 cm), as in the older, more eutrophic systems. It is postulated that more productive systems with a higher fish biomass, but with lower biomasses of macro-invertebrates and less largesized zooplankton probably have stronger selection mechanisms for recruiting percids.

Future population growth is expected to concentrate in urban agglomerations that are already expo... more Future population growth is expected to concentrate in urban agglomerations that are already exposed to numerous natural hazards. It is difficult, however, to assess this increase in risk as natural hazards are often concentrated in space and population growth scenarios tend to be defined at much coarser scales. By combining recently released high-resolution spatial data on land use, population density and natural hazards with a novel, computationally effective simulation approach we analyse global increases in local exposure to two important natural hazards: flood risk and landslides. We develop global spatially explicitp rojections of population change and urban expansion using a land-use and population allocation model. The model is developed in the Geo Data and Model Server (GeoDMS) modelling framework, that also underlies Land Use Scanner and several other operational models of land-use change developed for individual countries, larger river catchment areas and the territory of...

Α novel methodology for addressing policy inconsistencies and knowledge gaps that hinder the tran... more Α novel methodology for addressing policy inconsistencies and knowledge gaps that hinder the transition to a greater resource efficiency Europe is proposed. We focus on the integration of all different sectors that interact and influence each other, namely the “water- energy- food- land use- climate nexus” and we develop tools for identifying and quantifying their complex interlinkages under the influence of climate change. In order to achieve this, we employ a series of sophisticated models (referred to as “thematic models”), each of which addresses a different nexus dimension, or a combination of a few, while none addresses all nexus dimensions in an integrative manner. We use dynamic systems modeling and other complexity science techniques in order to “merge” different thematic model outputs in a single coherent result, which is presented to the user in an easyto-comprehend Serious Game environment. This way, the effect of policies that are designed to affect one field (nexus dim...

On March 8, 1989, Technical Meeting 46 of the TNO Committee on Hydrological Research (CHO-TNO) wa... more On March 8, 1989, Technical Meeting 46 of the TNO Committee on Hydrological Research (CHO-TNO) was held on the theme: "Hydroecological relations in the Delta Waters of the South-West Netherlands'. The results of this meeting are published in Proceedings and Information CHO-TNO No. 41. On June 4, 1992, Technical Meeting 50 of CHO-TNO took place. During this meeting the results have been presented of an evaluation of the water management of Lake Volkerak/Zoom - a new freshwater system in the Delta. This publication contains the papers presented at this meeting, which was organized in co-operation with Rijkswaterstaat, Directorate Zeeland. These papers consider the key questions, whether water management has been able to deal with the changes in Lake Volkerak/Zoom and whether the management policy targets will be achieved.

International Journal of Disaster Risk Reduction

Abstract The Dutch National Risk Assessment (NRA) is a methodology to assess the impact and likel... more Abstract The Dutch National Risk Assessment (NRA) is a methodology to assess the impact and likelihood of all possible threats and hazards that might hit the Netherlands, including a large-scale flood. This methodology addresses all the physical and social aspects that determine social disruption. The NRA has been applied to six European floods in Central and Western Europe. The results show that the NRA impact score for a flooding scenario can be interpreted as a measure for social disruption. Some comments can be made, however. The all hazards approach of the NRA is designed as a robust instrument that enables covering a wide array of threats and disasters. As a result, the NRA in its ‘original’ form offers little room for detailed differences in the consequences of different flooding scenarios. Tailor-made adjustments to the NRA are needed to insure that, for instance, differences in the number of casualties for different floods do not get lost in the bandwidth of the impact criteria. Socio-psychological factors significantly mark the impact of flooding. This offers opportunities to steer on avoiding or restricting social disruption by flooding by putting an adequate flood risk and crisis communication in place. The floods in Central Europe in 2002 and 2013 more or less present the lower and upper bounds of the impacts of recent large-scale river floods in Central and Western Europe. Compared with this bandwidth, the impact of a scenario of a worst-case river flood in the Netherlands is not unusual in a European context.