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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
621

Effects of translocation on kokako (Callaeas cinerea wilsoni) song and its application to management : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Palmerston North, New Zealand

Van Herpt, Sarah Michelle January 2009 (has links)
This thesis fills a research gap in our knowledge of kokako song by looking at how song evolves in multi-dialect areas. Kokako only exist in small remnant populations separated by large tracts of unsuitable land. Kokako are very poor flyers, only able to fly for approximately 100 metres at a time. In order to prevent inbreeding and a loss of genetic diversity in the remaining kokako populations, managers are carrying out translocations to establish new populations, maintain gene flow and prevent inbreeding. However, these translocations have the potential to be unsuccessful because kokako exhibit macrogeographic variation in their dialects, and tend not to breed with individuals who do not share the same dialect as them. If the purpose of the translocation is to enhance genetic diversity by having kokako from different areas breed then song is an important factor that must be dealt with. Song is extremely important to kokako for a number of reasons. Chiefly, it is hypothesised that song is their primary means of territory defence. A kokako gains all its resources from its territory, so it is imperative that they successfully defend it. Their duet song functions in territory defence, but also acts to form and maintain pair bonds. In order to try and address the problem that song causes in translocations I studied if and how song evolves in a multiple dialect area. I conducted research at Pukaha Mount Bruce, where there is a population of kokako originating from two different source populations, and thus two different dialects, Northern Mapara and Mangatutu. I looked at the Northern Mapara dialect, and recorded kokako belonging to three groups; kokako currently living in the source population, kokako that were translocated to Pukaha and kokako that were born at Pukaha. In order to determine how the song may be changing I looked at element repertoires, the levels of sharing between groups, the number of unique elements in repertoires and the syntactical and temporal characteristics of phrases. This study shows that translocation into multiple dialect areas can affect kokako song. Translocation did not affect the size of the kokako repertoire, but it seemed to affect the amount of sharing within and between different groups of kokako. Currently the level of sharing within the groups at Pukaha is lower than the level of sharing within the source Mapara population, indicating that the song may be diverging. There also seem to be more unique elements found at Pukaha, which in part explains the lack of sharing. There appears to be microgeographic variation at Pukaha, with birds clustered around the second (Mangatutu) dialect sharing less with the source population than do those kokako whose territories are lower down in the reserve. The phrases which are used are also evolving, with only one phrase truly shared among all groups. There are other phrases which show additions or deletions of elements, and so are evolving. The main change found in the phrases is the timing between elements, with six out of seven phrases examined showing changes. These results have repercussions for future kokako translocations, and the future of the Pukaha kokako. A low amount of phrase and element type sharing combined with changes of intra-phrase timing could lead to the Pukaha kokako’s inability to successfully defend their territories. This research shows how kokako song can give conservation managers information on the status of their populations in regards to interbreeding and raises questions which can be answered by further research, both at Pukaha and in other mixeddialect kokako populations.
622

Effects of translocation on kokako (Callaeas cinerea wilsoni) song and its application to management : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Palmerston North, New Zealand

Van Herpt, Sarah Michelle January 2009 (has links)
This thesis fills a research gap in our knowledge of kokako song by looking at how song evolves in multi-dialect areas. Kokako only exist in small remnant populations separated by large tracts of unsuitable land. Kokako are very poor flyers, only able to fly for approximately 100 metres at a time. In order to prevent inbreeding and a loss of genetic diversity in the remaining kokako populations, managers are carrying out translocations to establish new populations, maintain gene flow and prevent inbreeding. However, these translocations have the potential to be unsuccessful because kokako exhibit macrogeographic variation in their dialects, and tend not to breed with individuals who do not share the same dialect as them. If the purpose of the translocation is to enhance genetic diversity by having kokako from different areas breed then song is an important factor that must be dealt with. Song is extremely important to kokako for a number of reasons. Chiefly, it is hypothesised that song is their primary means of territory defence. A kokako gains all its resources from its territory, so it is imperative that they successfully defend it. Their duet song functions in territory defence, but also acts to form and maintain pair bonds. In order to try and address the problem that song causes in translocations I studied if and how song evolves in a multiple dialect area. I conducted research at Pukaha Mount Bruce, where there is a population of kokako originating from two different source populations, and thus two different dialects, Northern Mapara and Mangatutu. I looked at the Northern Mapara dialect, and recorded kokako belonging to three groups; kokako currently living in the source population, kokako that were translocated to Pukaha and kokako that were born at Pukaha. In order to determine how the song may be changing I looked at element repertoires, the levels of sharing between groups, the number of unique elements in repertoires and the syntactical and temporal characteristics of phrases. This study shows that translocation into multiple dialect areas can affect kokako song. Translocation did not affect the size of the kokako repertoire, but it seemed to affect the amount of sharing within and between different groups of kokako. Currently the level of sharing within the groups at Pukaha is lower than the level of sharing within the source Mapara population, indicating that the song may be diverging. There also seem to be more unique elements found at Pukaha, which in part explains the lack of sharing. There appears to be microgeographic variation at Pukaha, with birds clustered around the second (Mangatutu) dialect sharing less with the source population than do those kokako whose territories are lower down in the reserve. The phrases which are used are also evolving, with only one phrase truly shared among all groups. There are other phrases which show additions or deletions of elements, and so are evolving. The main change found in the phrases is the timing between elements, with six out of seven phrases examined showing changes. These results have repercussions for future kokako translocations, and the future of the Pukaha kokako. A low amount of phrase and element type sharing combined with changes of intra-phrase timing could lead to the Pukaha kokako’s inability to successfully defend their territories. This research shows how kokako song can give conservation managers information on the status of their populations in regards to interbreeding and raises questions which can be answered by further research, both at Pukaha and in other mixeddialect kokako populations.
623

Modélisation, étude mathématique et simulation des collisions

Baranger, Céline 17 June 2004 (has links) (PDF)
Dans ce travail, nous nous intéressons à des problèmes issus de la Mécanique des Fluides et plus particulièrement au cas des aérosols (ou sprays, c'est-à-dire un ensemble de particules en suspension dans un fluide environnant). Les phénomènes physiques mis en jeu sont modélisés par des équations aux dérivées partielles (EDP). La phase continue (fluide environnant) est décrite par des équations issues de la mécanique des milieux continus de type Navier-Stokes ou Euler. La phase dispersée est décrite par une équation cinétique de type Boltzmann.<br /><br />Le premier résultat que nous présentons est consacré à l'étude mathématique d'un couplage entre une équation cinétique de type Vlasov et les équations d'Euler isentropiques. Ces équations modélisent un spray fin. Nous démontrons l'existence en temps petit d'une solution régulière pour le couplage Vlasov-Euler isentropique.<br /><br />Ensuite, nous présentons les équations précises relatives à la modélisation des collisions, coalescences et fragmentations dans un spray.<br /><br />Nous décrivons par la suite la simulation numérique du couplage fluide-cinétique dans un code industriel (Commissariat à l'Énergie Atomique), en particulier l'ajout des phénomènes de collisions.<br /><br />Un deuxième modèle de fragmentation est également présenté. Ce modèle est plus pertinent dans les cas où les particules de la phase dispersée ont un grand nombre de Weber.<br /><br />Enfin, nous présentons un résultat concernant une estimation explicite de trou spectral pour l'opérateur de Boltzmann avec potentiels durs linéarisé, et pour l'opérateur de Landau avec potentiels durs linéarisé.
624

ETUDE SEDIMENTOLOGIQUE DU REMPLISSAGE<br />DE LA LAGUNE DE SIDI MOUSSA (CÔTE ATLANTIQUE MAROCAINE) CARACTERISATIONS GRANULOMETRIQUE, MINERALOGIQUE ET GEOCHIMIQUE

Maanan, Mohamed 24 October 2003 (has links) (PDF)
La lagune de Sidi Moussa (côte atlantique marocaine) est séparée de l'océan par un<br />cordon de dunes consolidées. Son bassin versant est constitué des terrains de crétacé et de<br />plioquaternaire. Le régime hydrologique se caractérise par une alimentation essentiellement<br />marine qui prédomine sur les apports continentaux. Le climat est de type méditerranéen sous<br />influence océanique.<br />L'approche morphologique de la lagune, basé d'une part, sur les photos d'interprétions<br />et d'autre part, par les observations in situ montre l'existence de quatre unités<br />morphologiques : 1- la zone de la passe principale et le delta interne de marée, 2- Chenal, la<br />zone intertidale et les schorres, 3- les marais salants et 4- le cordon littoral.<br />L'étude sédimentologique, minéralogique et géochimique de la couverture récente<br />montre l'existence de deux domaines :<br />- Un domaine à influence marine prépondérante, situé dans la zone aval de la lagune,<br />caractérisé par des faciès sableux pauvres en éléments métalliques et en matière organique et<br />riches en strontium et en carbonates d'origine biogénique.<br />- Un domaine typiquement lagunaire, situé dans la zone amont de la lagune, caractérisé par<br />des faciès silteux à silto-argileux riches en métaux lourds et en matière organique et pauvres<br />en strontium et en carbonates.<br />L'étude des caractères sédimentologiques, minéralogiques et géochimiques des<br />carottes permet de retrouver les deux ensembles précités superposés dans les carottes avec à<br />la base un faciès à dominance marine littorale qui caractérise un milieu ouvert et au sommet<br />un faciès typiquement lagunaire qui caractérise un milieu relativement fermé. Cette évolution<br />verticale des faciès tend vers un comblement lagunaire, ce qui est en accord avec le schéma<br />évolutif des lagunes proposées par Bird 1994.<br />Toute fois les teneurs en éléments métalliques des sédiments restent inférieures aux<br />teneurs observées dans d'autres systèmes lagunaires similaires au Maroc tel que Oualidia, la<br />lagune de Nador, ou en Europe (lagune de Venise, lagune d'Arcachon). Ces faibles teneurs<br />sont l'expression d'une pollution faible ou nulle de cet écosystème.
625

Samhällsekonomisk värdering vid potentiella katastrofer : Ekonomisk effektivitet i samband med den s.k. fågelinfluensan / Economic Appraisal for Potential Catastrophes : Economic Efficiency in the Context of an Avian Influenza

Solberger, Martin January 2006 (has links)
<p>Samhället är mer eller mindre konstant utsatt för risker. De flesta av dem är så små, och har kanske till och med så pass obetydande effekter för individen om de realiseras, att vi negligerar dem i våra dagliga beslut. Vid vissa tillfällen står vid dock inför beslut som är betydligt svårare, t.ex. i vilken mån vi ska handla kostsamma försäkringar för stora olyckor som högst osannolikt inträffar men skulle få katastrofala konsekvenser. Liknande situationer uppstår för centrala beslutsfattare där man fattar beslut att genomföra riskreducerande åtgärder i samband med potentiella katastrofer. Sådana åtgärder finansieras genom skattemedel och kanske kan man då kräva att myndigheter åtminstone försöker redovisa de förväntade kostnaderna och fördelarna som följs av besluten. För detta ändamål kan man använda kostnads-nyttoanalys, vilket vanligtvis rekommenderas för riskhantering inom t.ex. vägtrafik, eller i viss mån den mindre avancerade kostnads-effektanalysen. Riskanalysens utformning är bl.a. beroende av om man hanterar risk (man kan tilldela utfallen sannolikheter) eller osäkerhet (man känner till utfallen men kan inte tilldela dem sannolikheter) och begränsas vanligtvis av en mängd ovissheter, såsom värden för olika ingående parametrar (t.ex. värdet på ett statistiskt liv).</p><p>Detta arbete tar upp teori angående värdering ex ante av kostnader i samband med potentiella katastrofer och hur dessa värden kan användas under risk eller osäkerhet i en kvantitativ riskanalys. Med hjälp av det försöker jag beskriva i stora drag hur man skulle kunna värdera den ekonomiska nyttan av riskreducerande åtgärder i samband med den s.k. fågelinfluensan. Mina slutsatser är att en probabilistisk ansats och en kvantitativ riskanalys försvåras av bl.a. ett knapphändigt material för sannolikhetstolkningar, förekomsten av kollektiv risk och svårigheter i att värdera t.ex. statistiska liv. Socialstyrelsen är nationell samordnare av arbetet med förebyggande åtgärder i samband med potentiella pandemier men varken använder eller rekommenderar andra myndigheter att använda nyttobaserade beslutskriterier som en del av beslutsunderlaget i samband med den s.k. fågelinfluensan (i detta fall). Kanske borde det tillhöra deras uppgifter att se över möjligheterna att använda samhällsekonomiska utredningar vid sådana situationer. Istället använder de vad som liknar en försiktighetsprincip, vilket också kan försvaras under förutsättningen att riskerna är påtagliga. För stora och långsiktiga beslut borde man istället införa en snävare anti-katastrof-princip innefattande en prioriteringsordning för när man, baserat på om det är möjligt och utredningsekonomiskt motiverat, ska genomföra kostnads-nyttoanalyser och när man istället ska genomföra kostnads-effektanalyser. De kan sedan vara en del av ett större beslutsunderlag.</p> / <p>Our society is constantly exposed to risks. Most of them are so small, and maybe even have so little effect if they occur, that we disregard them in our daily decisions. Quite often, however, we face decisions that are harder for us to make, as whether or not to buy expensive insurance to cover for accidents that have only a small probability to occur but also catastrophic consequences. Similar situations appear for central decision makers when they decide whether or not to reduce a certain catastrophic risk for the society as a whole. Those actions are financed through taxes and therefore it might be fair to say that the authorities should at least try to account for the possible benefits and costs associated with a risk reducing programme. For this you may use Cost-Benefit Analysis (CBA), which is usually recommended for use in, for example, risk management for traffic risks, or the less advanced Cost-Effectiveness Analysis (CEA). The shape and form of the risk analysis is to a great deal dependent of whether you are dealing with risk (it’s possible to assign the predicted states probabilities) or uncertainty (it’s not possible to assign the predicted states probabilities) and is also usually limited by a number of other uncertainties, say in value parameters (e.g. the value of a statistical life, VSL).</p><p>This paper deals with theories regarding how to value (ex ante) the costs of potential catastrophes and how these values could be used in dealing with risk or uncertainty in a quantitative risk analysis. From there I try to describe how, possibly, you could value the benefits from programmes reducing risks of an avian influenza. My conclusions are that a probabilistic approach in a quantitative analysis is complicated by, among other things, the short amount of data necessary to compute objective probabilities, the existence of collective risks and for example difficulties in measuring VSL. The Swedish National Board of Health and Welfare (Socialstyrelsen) is the national coordinator for all work regarding risk reducing actions for potential pandemics, but the board neither uses nor recommends other authorities to use utility-based criteria as a part of their decision material when dealing with, in this case, the bird flue. Quite possibly it should be a part of their work to look into the possibilities of using economic evaluations in these situations. Instead they use what resembles a Precautionary Principle, which also can be used on justified grounds as long as the risks are highly present. What should be done for large and long term decision making, though, is to define a narrower Anti-Catastrophe Principle containing orders of priorities for when, based on if its possible and financially motivated, to use CBA and when to use CEA. Those analyses could then be used along with any other decision material.</p>
626

Effects of Great Cormorant Predation on Fish Populations and Fishery

Engström, Henri January 2001 (has links)
<p>The strong increase in number of Great cormorants <i>Phalacrocorax carbo</i> in Sweden in recent years has led to conflicts - particularly with fishery. This thesis focuses on the possible effects of cormorant predation on fish populations. In total, data from 15 lakes in South Sweden were included in this study while most studies were carried out in Lake Ymsen. The results suggest that the impact of cormorant predation on natural fish populations was small, and I observed no decline in fish mass after cormorants established. Cormorant predation on eel was difficult to evaluate because of several confounding factors.</p><p>Ruffe, roach and perch were the most important prey species to the cormorants and most fish taken were small. Cormorants do not seem to catch species and sizes in proportion to their occurrence in the fish community.</p><p>Total fish removal by cormorants varied considerably among lakes (0.2-15.0 kg/ha) and cormorant population sizes at the different lakes were significantly positively correlated with fishery catches, which in turn was significantly positively correlated with total phosphorous levels. Thus, cormorant densities in lakes, and perhaps elsewhere, seem to be governed chiefly by fish densities. The fact that cormorant predation appears not to reduce fish densities suggest cormorants to be regulated by other means than prey depletion. The mechanism behind population regulation could be a behavioural response of fish, making fish more difficult to catch for the cormorants.</p><p>In recent years, cormorant populations have been subjected to intensive legal and illegal actions with the aim to reduce cormorant numbers. However, the actions currently carried are well below the efforts needed to limit population sizes. To conclude, cormorants appear to compete little with fishery, with regards to free-living fish. The main problem is that cormorants sometimes damage and take away fish in fishing gears.</p>
627

Conditioning of unobserved period-specific abundances to improve estimation of dynamic populations

Dail, David (David Andrew) 28 February 2012 (has links)
Obtaining accurate estimates of animal abundance is made difficult by the fact that most animal species are detected imperfectly. Early attempts at building likelihood models that account for unknown detection probability impose a simplifying assumption unrealistic for many populations, however: no births, deaths, migration or emigration can occur in the population throughout the study (i.e., population closure). In this dissertation, I develop likelihood models that account for unknown detection and do not require assuming population closure. In fact, the proposed models yield a statistical test for population closure. The basic idea utilizes a procedure in three steps: (1) condition the probability of the observed data on the (unobserved) period- specific abundances; (2) multiply this conditional probability by the (prior) likelihood for the period abundances; and (3) remove (via summation) the period- specific abundances from the joint likelihood, leaving the marginal likelihood of the observed data. The utility of this procedure is two-fold: step (1) allows detection probability to be more accurately estimated, and step (2) allows population dynamics such as entering migration rate and survival probability to be modeled. The main difficulty of this procedure arises in the summation in step (3), although it is greatly simplified by assuming abundances in one period depend only the most previous period (i.e., abundances have the Markov property). I apply this procedure to form abundance and site occupancy rate estimators for both the setting where observed point counts are available and the setting where only the presence or absence of an animal species is ob- served. Although the two settings yield very different likelihood models and estimators, the basic procedure forming these estimators is constant in both. / Graduation date: 2012
628

Bird-vegetation relationships across ten years after thinning in young thinned and unthinned Douglas-fir forests

Yegorova, Svetlana 14 March 2012 (has links)
Bird-vegetation associations are a base for bird conservation and management, as well as for predictions of the effects of resource management and climate change on wildlife populations. A recent shift in forest management priorities from timber production to native species' habitat conservation on federal lands has emphasized the need to understand the mechanisms underlying the effects of vegetation management on wildlife. The assumption of strong bird-vegetation relationships is rarely tested for forest birds, especially at large temporal extents, which are more likely to reveal instabilities in bird-vegetation relationships than short-term studies. This study aimed to quantify bird-vegetation relationships and investigate their strength in young thinned and unthinned Douglas-fir forest stands over ten to years post thinning. Additionally, this study investigated whether disturbance associated with forest thinning decoupled bird-vegetation relationships in the thinned and unthinned stands. I used abundance or occurrence data for eight bird species collected at 58 point count surveys, conducted during six breeding seasons over ten years following forest thinning. I obtained detailed local-scale vegetation characteristics associated with bird sampling points and modeled bird occurrence or abundance as a function of vegetation characteristics. Vegetation characteristics explaining individual species occurrence or abundance varied among species and among years for any given species. Six out of eight species showed responses to examined vegetation characteristics. For three out of six species, the effects of vegetation characteristics on bird occurrence or abundance remained consistently positive or negative over time. For the other three species the absolute effect of vegetation decreased over time to that of not statistically different from zero. The estimates of vegetation effects on bird response varied in size among years, though they were not statistically different among years. Magnitude of vegetation effect on bird occurrence or abundance did not increase with time, nor was it related to species prevalence or abundance. I found evidence of a response threshold for one species, Swainson's thrush. I suggest that changing abundance of resources, associated with thinning disturbance, demographic stochasticity associated with small population sizes, as well as large-scale demographic processes and possibly life history traits of examined species, mediate the strength of local-level bird-vegetation associations. Variability of vegetation effects on bird occurrence or abundance over time suggests a greater uncertainty of results of vegetation-related wildlife management efforts than has previously been suggested by short-term studies. Therefore, incorporation of the uncertainty of bird-vegetation relationships into predictive models and continued long-term monitoring of species response to management may be crucial for future successful and effective management decisions. / Graduation date: 2012
629

Effects of Great Cormorant Predation on Fish Populations and Fishery

Engström, Henri January 2001 (has links)
The strong increase in number of Great cormorants Phalacrocorax carbo in Sweden in recent years has led to conflicts - particularly with fishery. This thesis focuses on the possible effects of cormorant predation on fish populations. In total, data from 15 lakes in South Sweden were included in this study while most studies were carried out in Lake Ymsen. The results suggest that the impact of cormorant predation on natural fish populations was small, and I observed no decline in fish mass after cormorants established. Cormorant predation on eel was difficult to evaluate because of several confounding factors. Ruffe, roach and perch were the most important prey species to the cormorants and most fish taken were small. Cormorants do not seem to catch species and sizes in proportion to their occurrence in the fish community. Total fish removal by cormorants varied considerably among lakes (0.2-15.0 kg/ha) and cormorant population sizes at the different lakes were significantly positively correlated with fishery catches, which in turn was significantly positively correlated with total phosphorous levels. Thus, cormorant densities in lakes, and perhaps elsewhere, seem to be governed chiefly by fish densities. The fact that cormorant predation appears not to reduce fish densities suggest cormorants to be regulated by other means than prey depletion. The mechanism behind population regulation could be a behavioural response of fish, making fish more difficult to catch for the cormorants. In recent years, cormorant populations have been subjected to intensive legal and illegal actions with the aim to reduce cormorant numbers. However, the actions currently carried are well below the efforts needed to limit population sizes. To conclude, cormorants appear to compete little with fishery, with regards to free-living fish. The main problem is that cormorants sometimes damage and take away fish in fishing gears.
630

Samhällsekonomisk värdering vid potentiella katastrofer : Ekonomisk effektivitet i samband med den s.k. fågelinfluensan / Economic Appraisal for Potential Catastrophes : Economic Efficiency in the Context of an Avian Influenza

Solberger, Martin January 2006 (has links)
Samhället är mer eller mindre konstant utsatt för risker. De flesta av dem är så små, och har kanske till och med så pass obetydande effekter för individen om de realiseras, att vi negligerar dem i våra dagliga beslut. Vid vissa tillfällen står vid dock inför beslut som är betydligt svårare, t.ex. i vilken mån vi ska handla kostsamma försäkringar för stora olyckor som högst osannolikt inträffar men skulle få katastrofala konsekvenser. Liknande situationer uppstår för centrala beslutsfattare där man fattar beslut att genomföra riskreducerande åtgärder i samband med potentiella katastrofer. Sådana åtgärder finansieras genom skattemedel och kanske kan man då kräva att myndigheter åtminstone försöker redovisa de förväntade kostnaderna och fördelarna som följs av besluten. För detta ändamål kan man använda kostnads-nyttoanalys, vilket vanligtvis rekommenderas för riskhantering inom t.ex. vägtrafik, eller i viss mån den mindre avancerade kostnads-effektanalysen. Riskanalysens utformning är bl.a. beroende av om man hanterar risk (man kan tilldela utfallen sannolikheter) eller osäkerhet (man känner till utfallen men kan inte tilldela dem sannolikheter) och begränsas vanligtvis av en mängd ovissheter, såsom värden för olika ingående parametrar (t.ex. värdet på ett statistiskt liv). Detta arbete tar upp teori angående värdering ex ante av kostnader i samband med potentiella katastrofer och hur dessa värden kan användas under risk eller osäkerhet i en kvantitativ riskanalys. Med hjälp av det försöker jag beskriva i stora drag hur man skulle kunna värdera den ekonomiska nyttan av riskreducerande åtgärder i samband med den s.k. fågelinfluensan. Mina slutsatser är att en probabilistisk ansats och en kvantitativ riskanalys försvåras av bl.a. ett knapphändigt material för sannolikhetstolkningar, förekomsten av kollektiv risk och svårigheter i att värdera t.ex. statistiska liv. Socialstyrelsen är nationell samordnare av arbetet med förebyggande åtgärder i samband med potentiella pandemier men varken använder eller rekommenderar andra myndigheter att använda nyttobaserade beslutskriterier som en del av beslutsunderlaget i samband med den s.k. fågelinfluensan (i detta fall). Kanske borde det tillhöra deras uppgifter att se över möjligheterna att använda samhällsekonomiska utredningar vid sådana situationer. Istället använder de vad som liknar en försiktighetsprincip, vilket också kan försvaras under förutsättningen att riskerna är påtagliga. För stora och långsiktiga beslut borde man istället införa en snävare anti-katastrof-princip innefattande en prioriteringsordning för när man, baserat på om det är möjligt och utredningsekonomiskt motiverat, ska genomföra kostnads-nyttoanalyser och när man istället ska genomföra kostnads-effektanalyser. De kan sedan vara en del av ett större beslutsunderlag. / Our society is constantly exposed to risks. Most of them are so small, and maybe even have so little effect if they occur, that we disregard them in our daily decisions. Quite often, however, we face decisions that are harder for us to make, as whether or not to buy expensive insurance to cover for accidents that have only a small probability to occur but also catastrophic consequences. Similar situations appear for central decision makers when they decide whether or not to reduce a certain catastrophic risk for the society as a whole. Those actions are financed through taxes and therefore it might be fair to say that the authorities should at least try to account for the possible benefits and costs associated with a risk reducing programme. For this you may use Cost-Benefit Analysis (CBA), which is usually recommended for use in, for example, risk management for traffic risks, or the less advanced Cost-Effectiveness Analysis (CEA). The shape and form of the risk analysis is to a great deal dependent of whether you are dealing with risk (it’s possible to assign the predicted states probabilities) or uncertainty (it’s not possible to assign the predicted states probabilities) and is also usually limited by a number of other uncertainties, say in value parameters (e.g. the value of a statistical life, VSL). This paper deals with theories regarding how to value (ex ante) the costs of potential catastrophes and how these values could be used in dealing with risk or uncertainty in a quantitative risk analysis. From there I try to describe how, possibly, you could value the benefits from programmes reducing risks of an avian influenza. My conclusions are that a probabilistic approach in a quantitative analysis is complicated by, among other things, the short amount of data necessary to compute objective probabilities, the existence of collective risks and for example difficulties in measuring VSL. The Swedish National Board of Health and Welfare (Socialstyrelsen) is the national coordinator for all work regarding risk reducing actions for potential pandemics, but the board neither uses nor recommends other authorities to use utility-based criteria as a part of their decision material when dealing with, in this case, the bird flue. Quite possibly it should be a part of their work to look into the possibilities of using economic evaluations in these situations. Instead they use what resembles a Precautionary Principle, which also can be used on justified grounds as long as the risks are highly present. What should be done for large and long term decision making, though, is to define a narrower Anti-Catastrophe Principle containing orders of priorities for when, based on if its possible and financially motivated, to use CBA and when to use CEA. Those analyses could then be used along with any other decision material.

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