Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Spatial Cohesion – An indicator for regional assessment of biodiversity in SENSOR
    Mücher, C.A. ; Eupen, M. van; Vos, C.C. ; Kiers, M.A. ; Renetzeder, C. ; Wrbka, T. - \ 2009
    Zalf : SENSOR (SENSOR report series 2009/01) - 207
    biodiversiteit - fragmentatie - landgebruiksplanning - biodiversity - fragmentation - land use planning
    Habitat fragmentation is in Europe a serious threat for biodiversity caused by intensive land use practices of our population. Spatial cohesion is a sustainability indicator to determine whether the size and connectivity of ecosystem networks is sufficient for sustainable biodiversity protection. This report presents the model LARCH-SCAN that calculates spatial cohesion of forest ecosystems for specific species groups that function on different spatial scales
    'Verbind Europese natuur'
    Vos, C.C. - \ 2009
    Kennis Online 6 (2009)mei. - p. 12 - 12.
    eu regelingen - klimaatverandering - fragmentatie - natuurbescherming - habitats - ecologische hoofdstructuur - habitatfragmentatie - eu regulations - climatic change - fragmentation - nature conservation - habitats - ecological network - habitat fragmentation
    Klimaatverandering is slecht nieuws voor honkvaste diersoorten. Om ze toch een kans te geven is een Europees netwerk van natuurgebieden noodzakelijk, vindt Alterra-onderzoeker Claire Vos. Nederland zal daarin een kruispunt zijn voor moerasnatuur
    Open grenzen voor natuur
    Jongman, R.H.G. - \ 2009
    Kennis Online 6 (2009)mei. - p. 4 - 5.
    eu regelingen - europa - fragmentatie - ecologische hoofdstructuur - natuurbeleid - natuurontwikkeling - eu regulations - europe - fragmentation - ecological network - nature conservation policy - nature development
    Om de biodiversiteit te versterken moeten dieren en planten kunnen gaan en staan waar ze willen. Natuurgebieden moeten daarom op Europees niveau op elkaar aansluiten. Onderzoekers van Wageningen UR maakten een eerste kaart van zo’n ecologisch netwerk. De praktische uitwerking vraagt nog veel afstemming tussen lidstaten
    Climate change and habitat fragmentation : range shifts for Dutch butterfly species
    Cormont, A. - \ 2009
    papilionidae - habitats - klimaatverandering - verplaatsing - fragmentatie - papilionidae - habitats - climatic change - displacement - fragmentation
    Poster over klimaatverandering bekeken aan de hand van Nederlandse vlindersoorten en fragmentatie en verschuiving van hun leefgebieden
    Application of GIS-BIOLOCO for design and assessment if biomass delivery chains
    Geijzendorffer, I.R. ; Annevelink, E. ; Elbersen, B.S. ; Smidt, R.A. ; Mol, R.M. de - \ 2008
    geografische informatiesystemen - deterministische modellen - fragmentatie - biomassa - ruimtelijke modellen - modelleren - biobased economy - geographical information systems - deterministic models - fragmentation - biomass - spatial models - modeling - biobased economy
    Poster about the application of the model GIS-BIOLOCO for design and assessment of biomass delivery chains
    Dispersie in gefragmenteerde landschappen
    Ozinga, W.A. - \ 2008
    Landschap : tijdschrift voor landschapsecologie en milieukunde 25 (2008)3. - ISSN 0169-6300 - p. 132 - 133.
    plantengemeenschappen - dispersie - migratie - fragmentatie - biodiversiteit - herstel - plant communities - dispersion - migration - fragmentation - biodiversity - rehabilitation
    Planten zijn voor het transport van hun zaden afhankelijk van wind, water en dieren. Deze externe transportmiddelen vormen in het landschap een complexe dispersie-infrastructuur voor zaden. Een sterke aantasting hiervan heeft geleid tot een vervlakking van de plantendiversiteit in Nederlandse landschappen
    Robuuste ecologische verbindingen tussen de Veluwe en het Ketelwald
    Groot Bruinderink, G.W.T.A. - \ 2006
    Natuurhistorisch Maandblad 95 (2006)5. - ISSN 0028-1107 - p. 111 - 115.
    wild - migratie - landschap - fragmentatie - duitsland - ecologische hoofdstructuur - gelderland - limburg - wildlife - migration - landscape - fragmentation - germany - ecological network - gelderland - limburg
    In het Ketelwald ontmoeten twee robuuste ecologische verbindingszones elkaar: namelijk de tracés Oostvaardersplassen - Veluwe - Duitsland en die van Schinveld - Mook. Samen vormen ze een noord-zuid verbinding van 200 km, die bij Schinveld maar enkele tientallen kilometers verwijderd is van de Eifel en de Ardennen. Het onderdeel Veluwe - Ketelwald heeft het ambitieniveau "Edelhert", maar de hele route zal ook voor andere dieren kunnen functioneren
    Uit de bodem- en natuurprogramma's : Effecten van zware metalen op de Das. Interactie tussen versnippering en vergiftiging
    Klok, T.C. - \ 2004
    Wageningen : Alterra (Informatieblad 384/396.01) - 2
    zware metalen - dassen (zoogdieren) - aardwormen - wegen - bodemverontreiniging - fragmentatie - habitats - verontreiniging - habitatfragmentatie - ecotoxicologie - heavy metals - badgers - earthworms - roads - soil pollution - fragmentation - habitats - pollution - habitat fragmentation - ecotoxicology
    In dit infoblad wordt de invloed van bodemvervuiling door cadmium en koper op de Das besproken. Deze effecten worden gerelateerd aan de effecten van versnippering. Uit deze studie komt naar voren dat in leefgebieden met een lage kwaliteit als gevolg van vervuiling het aannemelijk is dat dassen langer moeten foerageren en grotere afstanden afleggen om in hun dagelijkse voedselbehoefte te voorzien. Dit omdat een verlies van voedingsstoffen door nierschade moet worden gecompenseerd door langer te foerageren terwijl een lagere dichtheid aan regenwormen gecompenseerd kan worden door meer gebieden te bezoeken. Hierdoor zal in een leefgebied dat wordt doorsneden door wegen de verkeerssterfte kunnen toenemen
    Beleidsevaluatie ecologische hoofdstructuur en ganzenbeleid; achtergronddocument bij Natuurbalans 2004
    Sanders, M.E. ; Geertsema, W. ; Broekmeijer, M.E.A. ; Dam, R.I. van; Greft-van Rossum, J.G.M. van der; Blitterswijk, H. van - \ 2004
    Wageningen : Natuurplanbureau (Planbureaurapporten 11) - 118
    natuurbescherming - overheidsbeleid - evaluatie - ganzen - ruimtelijke ordening - fragmentatie - regionale planning - nederland - ecologische hoofdstructuur - nature conservation - government policy - evaluation - geese - physical planning - fragmentation - regional planning - netherlands - ecological network
    Het Milieu- en Natuurplanbureau volgt jaarlijks de voortgang van de Ecologische Hoofdstructuur (EHS) en rapporteert daarover in de Natuurbalans. De onderwerpen van deze beleidsevaluatie die in dit rapport aan de orde komen zijn: planologische veiligstelling bij provincies en gemeenten, de ruimtelijke samenhang van de EHS, gebiedsgerichte samenwerking en de mate van realisatie in het veld. Een tweede onderwerp is het ganzenbeleid omdat er dit jaar overgeschakeld wordt van schadevergoedingen naar structurele opvang. De resultaten zijn gebaseerd op literatuurstudie, interviews met sleutelpersonen van belanghebbende organisaties en GIS-analysen van de natuurdoelenkaart. Trefwoorden: planologische veiligstelling, natuurbeleid, gemeenten, bestemmingsplannen, streekplannen, provincies, Nota Ruimte, Ecologische Hoofdstructuur (EHS), biodiversiteit, ruimtelijke samenhang, versnippering, ganzenopvang, natuurdoelen, gebiedsgerichte samenwerking.
    Natuurverbinding Naardermeer-Ankeveense Plassen; advies voor inrichtingsmaatregelen rond de N236 en 's-Gravelandse Vaart
    Grift, E.A. van der - \ 2004
    Wageningen : Alterra (Alterra-rapport 1033) - 76
    natuurreservaten - meren - landinrichting - fragmentatie - ontwerp - wildpassages - nature reserves - lakes - land development - fragmentation - design - wildlife passages
    In opdracht van de Provincie Noord-Holland is een advies opgesteld ten behoeve van de realisering van een robuuste natuurverbinding tussen het Naardermeer en de Ankeveense Plassen. Het advies richt zich op nut en noodzaak van de natuurverbinding, ontsnipperende maatregelen bij de provinciale weg N236 en ¿s-Gravelandse Vaart en natuurontwikkeling in de Hilversumse Bovenmeent.
    Landscape linkages and biodiversity in European landscapes
    Jongman, R.H.G. - \ 2004
    In: The new dimensions of the European landscape. - Dordrecht : Springer - ISBN 9781402029097 - p. 179 - 189.
    landschap - biodiversiteit - soorten - verspreiding - homogenisatie - fragmentatie - europa - landscape - biodiversity - species - dispersal - homogenization - fragmentation - europe
    Linear features are structuring landscape elements. We change our landscapes and rebuild them into new linkages, and landscapes are even constructed around these linkages. Landscape linkages are important for species migration and dispersal on a large scale and a small scale: storks, bats and badgers. There is, however also diversity within landscapes and landscape elements: plants species, insects and breeding birds. History and land-use development hampered both biodiversity at the European level and at the landscape level. As landscapes are dynamic, cultural landscapes are not only historic, but they will be constructed and reconstructed. History has had an impact on the regional diversity. Reconstructing European linkages should take into account large-scale structures and ecosystems such as mountain ranges, wetlands, forests and rivers and small-scale structures such as hedgerows, ponds, stonewalls and small forests. Landscape construction is not a simple making of landscape elements. The reconstruction of biodiversity is much more complex as it does not seem to return so easily. We can learn from European experiences and exchanges that it is important to exchange and share experiences and disseminate results. To link the different aspects of landscape planning and the conservation of landscape diversity requires interdisciplinary research programmes.
    Ecological corridors on a European scale: a typology and identification of target species
    Bouwma, I.M. ; Foppen, R.P.B. ; Opstal, A.J.F.M. van - \ 2004
    In: Ecological networks and greenways; concept, desing, implementation / Jongman, R.H.G., Pungetti, G., Cambridge : Cambridge University Press (Studies in landscape ecology ) - ISBN 9780521535021 - p. 94 - 106.
    landschapsecologie - landschap - fragmentatie - populatiedynamica - landscape ecology - landscape - fragmentation - population dynamics
    Meerjarenprogramma Ontsnippering : knelpuntenanalyse
    Grift, E.A. van der; Pouwels, R. ; Reijnen, R. - \ 2003
    Wageningen : Alterra (Alterra-rapport 768) - 168
    natuurbescherming - fragmentatie - wegen - infrastructuur - spoorwegen - waterwegen - nederland - ecologische hoofdstructuur - netwerken - habitatfragmentatie - nature conservation - fragmentation - roads - infrastructure - railways - waterways - netherlands - ecological network - networks - habitat fragmentation
    De natuur in Nederland raakt steeds meer versnipperd. Infrastructuur is op veel plaatsen mede verantwoordelijk voor deze versnippering. Om een overzicht te krijgen van de locaties waar zich knelpunten voordoen tussen de natuur en infrastructuur is eenlandsdekkende knelpuntenanalyse uitgevoerd. De knelpuntenanalyse richt zich wat natuur betreft op de ecologische hoofdstructuur (EHS), gestelde natuurdoelen buiten de EHS en de robuuste verbindingen. Wat betreft infrastructuur beperkt deze studie zich tot rijkswegen, provinciale wegen, spoorwegen en vaarwegen. Een significante vermindering van de levensvatbaarheid van dierpopulaties als gevolg van de aanwezigheid van infrastructuur is bij het achterhalen van de knelpunten als graadmeter gebruikt. Deze analyse is uitgevoerd met het expertsysteem LARCH. Hierbij zijn tien soortgroepen, zogenaamde ecoprofielen, doorgerekend. Deze soortgroepen zijn representatief voor circa driekwart van het Nederlandse (droge) natuurareaal. In totaal zijn 126 knelpunten vastgesteld, exclusief de knelpunten binnen robuuste verbindingen. Per knelpunt is de ecologische winst berekend wanneer het desbetreffende knelpunt zou zijn opgelost. Op basis van deze ecologische winst zijn de knelpunten geprioriteerd. Tevens is aangeduid wanneer knelpunten samenhang met elkaar hebben; dit betekent dat het oplossen van het ene alleen zinvol is wanneer ook het andere knelpunt wordt aangepakt.
    Dealing with Central European land fragmentation : a critical assessment on the use of Western European instruments
    Dijk, T. van - \ 2003
    Delft University of Technology. Promotor(en): Adri van den Brink. - Delft : Uitgeverij Eburon - ISBN 9789051669961 - 219
    landbouwgrond - fragmentatie - centraal-europa - instrumentatie - beoordeling - landgebruiksplanning - ruilverkaveling - agricultural land - land use planning - land consolidation - fragmentation - central europe - instrumentation - assessment
    Ecologisch rendement van ontsnippering: de casestudie edelhert en wild zwijn Veluwe
    Pouwels, R. ; Groot Bruinderink, G.W.T.A. ; Kuipers, H. - \ 2002
    Wageningen : Alterra (Alterra-rapport 533) - 55
    sus scrofa - cervus elaphus - fragmentatie - verspreiding - natuurbescherming - evaluatie - ecologie - beleid - nederland - veluwe - ecologische hoofdstructuur - habitatfragmentatie - fauna - landschapsecologie - ontsnippering - versnippering - zoogdieren - Gelderland - sus scrofa - cervus elaphus - fragmentation - dispersal - nature conservation - evaluation - ecology - policy - netherlands - ecological network - veluwe - habitat fragmentation - fauna
    Inrichtingsplannen worden vaak op meerdere functies beoordeeld. Om deze verschillende functies met elkaar te kunnen vergelijken, zullen eenvoudige graadmeters gebruikt moeten worden. Binnen deze studie zijn de effecten van inrichtingsscenario's voor de Veluwe op aspecten van ecologie en economie beoordeeld. In dit rapport wordt ingegaan op de ecologische beoordeling. De scenario's zijn gericht op ontsnipperende maatregelen voor grote zoogdieren. Dit rapport beschrijft de methode en resultaten van de ecologische beoordeling. Het blijkt dat met name het weghalen van de grofwildrasters resulteert in ecologische winst.
    The Dutch Planning Experience
    Valk, A.J.J. van der - \ 2002
    Landscape and Urban Planning 58 (2002)2/4. - ISSN 0169-2046 - p. 201 - 210.
    ruimtelijke ordening - landgebruiksplanning - landschap - nederland - fragmentatie - physical planning - land use planning - landscape - fragmentation - netherlands
    The Netherlands is densely populated and highly urbanised. Growth management and spatial planning have a long-standing tradition. This article reveals driving forces and new trends in planning. The intricacies of the planning system are interpreted in an institutional and political framework. Decision making by consensus is the dominant planning style in The Netherlands. Notwithstanding, a strict adherence to the compact cities policy and a restrictive building policy for open areas, the western southern and central parts of the country are developing into an urban field. Fear for suburban sprawl and fragmentation of land is a stimulus for the development of new concepts for efficient land use. Multiple land use is an eye-opener for Dutch planners at the start of the new era.
    Fragmentation and land use planning : an introduction
    Carsjens, G.J. ; Lier, H.N. van - \ 2002
    Landscape and Urban Planning 58 (2002). - ISSN 0169-2046 - p. 79 - 82.
    fragmentatie - landgebruiksplanning - territorium - nadelige gevolgen - ruimtelijke ordening - habitatfragmentatie - fragmentation - land use planning - territory - adverse effects - physical planning - habitat fragmentation
    Ecoprofielen voor soortanalyses van ruimtelijke samenhang met LARCH
    Pouwels, R. ; Reijnen, M.J.S.M. ; Kalkhoven, J.T.R. ; Dirksen, J. - \ 2002
    Wageningen : Alterra (Alterra-rapport 493) - 54
    biodiversiteit - biologische indicatoren - indicatorsoorten - ecologie - populaties - natuurbescherming - fragmentatie - modellen - informatiesystemen - nederland - landschapsecologie - natuurbehoud - populatiebiologie - versnippering - biodiversity - biological indicators - indicator species - ecology - populations - nature conservation - fragmentation - models - information systems - netherlands
    Voor het Ministerie van LNV wordt het kennissysteem LARCH ontwikkeld. Het wordt met name gebruikt bij verkennende studies. Hierbij wordt voor enkele indicatorsoorten de ruimtelijke samenhang van een landschap in beeld gebracht. De keuze voor deze indicatorsoorten wordt vaak gedaan vanuit praktisch oogpunt en levert veel discussie op. Door soorten te koppelen aan een ecoprofiel worden de analyses met LARCH gestandaardiseerd en daardoor beter inzichtelijk. In dit rapport wordt ingegaan op de indeling van ecoprofielen en het koppelen van soorten aan een ecoprofiel. Het betreft de soorten die voor de Natuurverkenningen 2 geanalyseerd zijn.
    Homogenisation and fragmentation of the European landscape: ecological consequences and solutions
    Jongman, R.H.G. - \ 2002
    Landscape and Urban Planning 58 (2002)2-4. - ISSN 0169-2046 - p. 211 - 221.
    landschapsecologie - ruimtelijke ordening - biodiversiteit - fragmentatie - cultuurlandschap - landgebruik - landinrichting - versnippering - Europa - landscape ecology - physical planning - biodiversity - fragmentation
    The rural landscapes of Europe are in both a homogenisation and a fragmentations process. Regional differences are disappearing due to the dominating equalising impact of the worldwide market. If regional differences are not maintained and protected then the cultural landscapes of Europe and their biological diversity will decline and only remnants will remain. Models on agricultural management and data on landscape changes from all Europe confirm this. Regional differences have to be maintained through conscious environmental and ecological planning. Concepts for this have been developed in all countries in Europe, such as the ecostabilisation concept and the concept of ecological networks. Nature management by farmers is more and more accepted. Landscape planners should be aware of their changing role from designer towards negotiator with the actors in the landscape with different landscape functions and planning tasks in mind.
    Striking the metapopulation balance : mathematical models & methods meet metapopulation management
    Etienne, R.S. - \ 2002
    Wageningen University. Promotor(en): J.A.P. Heesterbeek; J. Grasman. - S.l. : S.n. - ISBN 9789058085986 - 205
    wiskunde - wiskundige modellen - populaties - natuurbescherming - ecologie - fragmentatie - populatiedynamica - netwerken - mathematics - mathematical models - populations - nature conservation - ecology - fragmentation - population dynamics - networks

    There are two buzz words in nature management: fragmentation and connectivity. Not only (rail) roads, but also agricultural, residential and industrial areas fragment previously connected (or even continuous) habitat. Common sense tells us that the answer to habitat fragmentation is defragmentation and hence much effort is put into building corridors, of which fauna crossings are just one example. Corridors are conduits connecting two pieces of habitat through an environment of hostile non-habitat. As such, the use of corridors need not be restricted to the animal kingdom; plants can also use them as stepping-stones for their seeds, enabling them to colonize distant habitat. Although corridors may not only act as conduits but also as habitat, filters or even as barriers, in most cases they are constructed primarily for their conduit function. Connectivity is nowadays taken to its extreme in the "Ecologische Hoofdstructuur" (Ecological Main Structure) in The Netherlands. This is a plan in operation to create an extensive ecological structure by connecting a substantial part of the remaining "natural" habitat, which includes conduits of decommissioned farmland bought by the government. Similar plans exist in other parts of the world.

    Needless to say, there are good reasons for building corridors and plans involving them. Yet, there are some valid arguments against connecting everything. The risk of spreading of infectious diseases through these corridors is one of the most prominent arguments. The spread of the effects of (natural) catastrophes such as fire is another. But even when dismissing such negative effects of connectivity, there may be other mitigating measures which are much more efficient (and less expensive) than building corridors. The question whether this is the case and how alternatives should be compared stimulated the work for this thesis.

    A theory that is well suited for predicting the effects of fragmentation is metapopulation theory. As almost every text on metapopulations will tell you, this theory was conceived by Richard Levins in 1969-1970, although its roots may be found in earlier work. The core of the theory is the following observation. Populations are assumed to live in distinct habitat fragments, called patches. These local populations can go extinct relatively quickly, but immigration from other patches can lead to recolonization of empty patches. Thus, the whole population of populations, the metapopulation, can potentially persist if these recolonizations outweigh the extinctions of local populations. In a sense, the population spreads the risk of extinction by spatial separation. The basic model of the theory captures these processes in a simple ordinary differential equation.

    This thesis consists of eight chapters and is divided into four parts. Part I, containing only one chapter, can be regarded as a review of fundamental metapopulation processes, set in the context of a persistent problem in conservation science, the SLOSS problem. This problem, of which the acronym stands for Single Large Or Several Small, raises the question whether the optimal design of a habitat network consists of a single large nature reserve or several small reserves. Although this question was initially concerned with biodiversity (which design can contain the largest number of species?), it can be equally well applied to a single species living in a metapopulation for which the question becomes: which design optimizes the persistence of the species?

    Defined thus, it represents a fine example of opposing processes requiring mathematical modelling. On the one hand, patches must be as large as possible to minimize the risk of local extinction; on the other hand, there must be as many patches as possible to maximize the probability of recolonization and to minimize the risk of simultaneous extinction. Precise mathematical formulation of these thoughts can in principle lead to a solution of the problem. Sometimes the mathematical formulation requires that the question be expressed differently or more clearly. In chapter 1 SLOSS is replaced by the more neutral FLOMS, short for Few Large Or Many Small, because in the chosen framework a single large patch is not really possible (it exists only in a limit).

    Which design is optimal turns out, not completely surprisingly, to depend upon the measure one employs for metapopulation persistence. Two measures are introduced: the metapopulation extinction time and the colonization potential, which is a type of basic reproduction number (the number of patches colonized by a local population during its lifetime in an environment where all other patches are empty). These measures return in subsequent chapters.

    Which design is optimal also depends on how designs with different size and number of patches are compared. In chapter 1 this is done such that the amount of habitat per unit area is constant. This implies that few large patches have larger interpatch distances than many small patches.

    The two measures are functions of the extinction and colonization rates of the metapopulation. Several mechanisms for the extinction and colonization processes are formulated from which the dependence of these rates on patch size is calculated. It turns out that the metapopulation extinction time generally increases with patch size for all mechanisms, which supports the preference of few large patches. However, the colonization potential supports this preference only in the case of some special, rather unrealistic, mechanisms. In many other, more realistic, cases an intermediate patch size exists for which metapopulation persistence measured by the colonization potential is optimal.

    Part II concentrates on the Levins model. Models are often considered inadequate because the underlying assumptions are thought to be unrealistic. Yet, these assumptions can be formulated in a way that is stronger than necessary for the development of the mathematical model. Therefore, they need to be subjected to careful scrutiny, such that all superfluous elements are eliminated. If the model is still discarded, at least it is so for the right reasons.

    In chapter 2 the assumptions of the Levins model are examined. One of the assumptions as it often appears in the literature proves to be too strong: After colonization, the newly born population need not grow to the carrying capacity. It is sufficient if local dynamics are fast enough for a steady population size distribution to be established. It follows that patches need not all have the same extinction and colonization rates, but merely that these form a steady distribution depending on the population size distribution. The extinction and colonization rates in the Levins model are weighted averages over these distributions. Although this does not make the model much more realistic, it does remove restrictions on more realistic extensions of the Levins model. Three such extensions are studied: two extensions in chapter 2, involving the rescue effect and the patch preference effect, and one in chapter 3, dealing with the Allee effect. The first and third are attempts at a more careful and more mechanistic formulation of already existing models. Although the conclusions remain basically the same in these new formulations, they provide more insight in the responsible processes and are scientifically and aesthetically more satisfactory.

    The second extension of the Levins model in chapter 2 incorporates preference for occupied or empty patches in the Levins model. Preference for occupied patches may arise because of conspecific attraction; preference for empty patches seems plausible for territorial species. Preference for empty patches is shown to increase patch occupancy; preference for occupied patches lowers patch occupancy. Chapter 2 briefly studies patch preference and the rescue effect simultaneously as well, because it is not a priori evident how the rescue effect interferes with patch preference. On the one hand, empty patches should be preferred because colonization of empty patches is the only way in which the metapopulation can reproduce. On the other hand, additional colonization of occupied patches prolongs survival of the local population due to the rescue effect. It turns out that the effects are almost additive as far as patch occupancy is concerned. This could, however, be quite different if the metapopulation extinction time is taken as a measure of metapopulation persistence.

    Most metapopulation models, particularly Levins-type models, are only used to study equilibria. The last chapter of part II, chapter 4, deals with non-equilibria and their consequences for metapopulation management, using both the Levins model and its stochastic counterpart. These non-equilibria are created by imposing sudden changes in patch number and the colonization and extinction parameters on systems in equilibrium. One of the most striking results is that if we want to counteract the effects of habitat loss or increased dispersal resistance, the optimal conservation strategy is not to restore the original situation (that is, to create habitat or decrease resistance against dispersal), but rather to improve the quality of the remaining habitat in order to decrease local extinction rate. Optimality here pertains to metapopulation extinction time computed using the stochastic model. Chapter 4 also tells us that using the relaxation time of the deterministic Levins model as a surrogate for the metapopulation extinction time is not always warranted, which is not totally surprising, yet still somewhat disappointing, because the metapopulation extinction time is often hard to compute.

    Chapter 4 forms a bridge between part II and III: it introduces the stochastic approach used in the chapters following it and it already provides us with a rule of thumb for metapopulation conservation as we stated above. In part III rules of thumb that can guide management of metapopulations play a central role. First, in chapter 5, rules of thumb are derived on the abstract level of colonization and extinction probabilities. Then, in chapter 6, some of these rules are tested on the less abstract level of two landscape characteristics which often mainly determine the probabilities of colonization and extinction, viz. patch size and interpatch distance.

    The rules of thumb generated in chapter 5 can be summarized as: to optimize metapopulation extinction time, decreasing the risk of local extinction is preferable over increasing colonization probability and this should generally be done in the least extinction-prone patches; if changing local extinction risk is impossible, then increasing the colonization probability between the two least extinction-prone patches is most preferable. When extinction and colonization are related to patch size and interpatch distance in chapter 6 by mechanistic submodels of the corresponding processes, the last two of these rules transform into: the preferred strategies to optimize the metapopulation extinction time and the basic reproduction number are, firstly, increasing the size of the largest patch (which is least extinction-prone) and, secondly, decreasing the effective interpatch distance between the two largest patches. These rules are less strongly supported than those of chapter 5, and the first is even reversed if absolute (instead of relative) increases in patch size are considered. The reason for this is that in the mechanistic submodel for local extinction a large patch requires a large increase in size to substantially alter its local extinction probability. Since it is not a priori clear whether increases in patch sizes must be compared on an absolute or a relative basis, final conclusions cannot be drawn. Thus, chapters 5 and 6 are two parts of a trilogy which would be completed by a socio-politico-economic chapter taking into account e.g. the costs of habitat creation in relation to the size of the patch to which habitat is added. That is, it would then be almost completed, because there should also be an additional section on the important biological question how ecoducts and the like change the effective interpatch distance; this is usually merely hidden in the parameters. Although the trilogy is not complete, at least more light has been shed on the range of possible final conclusions and, more importantly, the conditions under which they are valid.

    Whereas the first three parts of this thesis deal with general models of hypothetical metapopulations, and are somewhat academic, part IV concentrates on (statistical) methodology assisting in making model predictions, illustrated by two real case studies. Chapter 7 shows how the (relative) impact of human interventions can be predicted despite data of poor quality, for two amphibian species threatened by the reinstatement of an old railway track, using uncertainty analysis. Again, the measure employed, in this case metapopulation extinction time and the occupancy of each local population, plays a crucial role in deciding which scenario of human interventions is most preferable. It is also noted that the optimal scenario may differ for different species which aggravates the decision making process, because species must then be assigned a certain quantity representing their importance. Furthermore, the most important source of uncertainty is not the uncertainty in the effects of the railway track on extinction and colonization, as one might expect, but the uncertainty due to the inherent stochastic nature of the model combined with the uncertainty about the default parameter settings.

    Chapter 8 demonstrates how Bayesian inference using Monte Carlo Markov Chain simulations can help in obtaining (estimates of posterior) probability distributions of meta- population model parameters based on a dataset, typical in metapopulation studies: a few years of data of occupancy (presence or absence) of the tree frog in 202 patches with many missing data. Parameter estimation methods were available before for such datasets (and surely formed a source of inspiration for this new method), but none of them could use all information in the dataset as well as provide a joint probability distribution of the parameters rather than a point estimate. Such a joint probability distribution is necessary for model predictions that take into account the uncertainties about the model parameters. It does take some time to compute, however, so much that it would not have been possible within a reasonable time until recently. Therefore, the appendix of chapter 8 also supplies an efficient algorithm.

    What does this thesis contribute to metapopulation theory and to metapopulation management? Being aware of the fact that I may not be the right person to answer this question, I will endeavor to provide an answer, at the risk of being pretentious.

    As far as metapopulation theory is concerned, I hope to have drawn attention to some underexposed aspects (the necessity of a careful definition of the SLOSS problem and the constant realization that different measures may yield different conclusions). Furthermore, I hope to have shown how existing models may be adjusted to a more satisfactory form that can be more easily extended (by incorporating the rescue and Allee effects into the Levins model). I also hope to have built more solid foundations and intermodel connections (by formulating more precise assumptions of the Levins model and examining the extensions which result when one of these assumptions is violated, by comparing the stochastic and deterministic versions of the Levins model, and by studying different modifications of the discrete-time stochastic model) and to have made some fairly original additions to the theory (patch preference, non-equilibria).

    As far as metapopulation management is concerned, I would be content if due to my work those responsible for metapopulation management thought twice before they decided upon, for example, building an ecoduct. At the same time, I would be disappointed if they followed the rules of thumb mindlessly. Along with many skeptical scientists, particularly biologists, I do not believe that there are rules of thumb upon which can be relied unconditionally. Yet, far from disposing of them altogether, I think they are very important; their value lies in summarizing a large part of our knowledge, the importance of which evidently increases with the robustness of the rules, and in provoking discussions. These discussions already commence in chapters 5 and 6, and are hopefully taken up by others. The discussions should deal with the many assumptions underlying the rules of thumb, when these assumptions are (approximately) valid and when they are clearly violated, and the extent to which such violations entail a change in the rules of thumb.

    Furthermore, I would be pleased if uncertainty analysis of metapopulation model predictions became standard, especially in situations where expert judgment is the most significant source to parameterize a model. I hope that chapter 7 makes clear that there are sophisticated yet easily understandable and implementable techniques. Likewise, I would be satisfied if our Bayesian parameterization method were in vogue, in cases where data are available. With the example of a non-standard incidence function model, I hope to have demonstrated its generality.

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