The global amphibian population is rapidly declining. Although many threats that affect amphibians are known, there are many contributing factors which are not fully understood. For adult amphibians, the largest part of the mortality comes from predation. We know of many predators which prey upon amphibians, but to what extent they affect the populations has not been subject to much investigation. Neither has the effects of specific taxa or species of predators. Birds are reputed amphibian-eaters, and they often occur in the same habitats. Both birds and amphibians often select for wetlands and other water bodies with high biodiversity, that often support a high diversity and/or density of birds as well as amphibians. The fact that a prey might flourish in an area that one of its strongest predators also inhabits might seem controversial. Especially when taking into account that it is often the density of predators that best explains the population growth of prey species. In this review, I investigate what effects large amounts of birds might have on amphibian populations as a result of their predation on adults. I consider how the effects might differ with high vs low densities of both prey and predator, and whether an eventual effect might impact the survival of a metapopulation differently depending on its size and spatial distribution. As an example of a habitat where both bird and amphibian species occur in large numbers, I use Trönninge ängar - a bird conservation area just outside the city of Halmstad, where populations of both amphibians and birds have been increasing over the last years. My results show that high densities of predatory birds in such communities could potentially cause declines in amphibian populations, but that this impact is softened when the population is more widely distributed in the area. There are also possibilities that birds do not only affect amphibians by predation, but also might facilitate their distribution by reducing other predators. Thus, bird predation in itself might not be a sufficient predictor for their effect on amphibian populations, as the relationship might be more complex than simple predator-prey interactions.

Many biological populations reside in increasingly fragmented landscapes, which arise from human activities and natural causes. Landscape characteristics may change abruptly in space and create sharp transitions (interfaces) in landscape quality. How patchy landscape affects ecosystem diversity and stability depends, among other things, on how individuals move through the landscape. Individuals adjust their movement behaviour to local habitat quality and show preferences for some habitat types over others. In this dissertation, we focus on how landscape composition and the movement behaviour at an interface between habitat patches of different quality affects the steady states of a single species and a predator-prey system. First, we consider a model for population dynamics in a habitat consisting of two homogeneous one-dimensional patches in a coupled ecological reaction-diffusion equation. Several recent publications by other authors explored how individual movement behaviour affects population-level dynamics in a framework of reaction-diffusion systems that are coupled through discontinuous boundary conditions. The movement between patches is incorporated into the interface conditions. While most of those works are based on linear analysis, we study positive steady states of the nonlinear equations. We establish the existence, uniqueness and global asymptotic stability of the steady state, and we classify their qualitative shape depending on movement behaviour. We clarify the role of nonrandom movement in this context, and we apply our analysis to a previous result where it was shown that a randomly diffusing population in a continuously varying habitat can exceed the carrying capacity at steady state. In particular, we apply our results to study the question of why and under which conditions the total population abundance at steady state may exceed the total carrying capacity of the landscape. Secondly, we model population dynamics with a predator-prey system in a coupled ecological reaction-diffusion equation in a heterogeneous landscape to study Turing patterns that emerge from diffusion-driven instability (DDI). We derive the DDI conditions, which consist of necessary and sufficient conditions for initiation of spatial patterns in a one-dimensional homogeneous landscape. We use a finite difference scheme method to numerically explore the general conditions using the May model, and we present numerical simulations to illustrate our results. Then we extend our studies on Turing-pattern formation by considering a predator-prey system on an infinite patchy periodic landscape. The movement between patches is incorporated into the interface conditions that link the reaction-diffusion equations between patches. We use a homogenization technique to obtain an analytically tractable approximate model and determine Turing-pattern formation conditions. We use numerical simulations to present our results from this approximation method for this model. With this tool, we then explore how differential movement and habitat preference of both species in this model (prey and predator) affect DDI.

This thesis is based on the premise that reproductive rights and environmental sustainability have synergistic interests: human population growth increases environmental impact and access to family planning triggers reduced fertility levels. Despite increasing scientific evidence indicating that the size of the global population matters for environmental sustainability, and by extension, that fulfilling reproductive rights may be beneficial for the latter, the linkages between reproductive rights and environmental sustainability have been largely understudied, ignored, and left out of environmental policy and reproductive rights agendas. Because of the complexity of this interdisciplinary field and its associated ethical questions, many researchers and policy makers have chosen to avoid this sensitive and polarizing issue altogether. However, capitalizing on these linkages could represent significant opportunity to advance the reproductive rights and environmental movements, and increase the prominence, legitimacy, and funding of global family planning services, in particular. This thesis uses an action research approach to explore the current framing of the reproductive rights and environmental sustainability linkage, study the perceptions of stakeholders of both the reproductive health and rights and environmental sustainability movements on this issue, and elaborate a strategic communication roadmap to promote its operationalisation.

Productivity of grey rhebok and mountain reedbuck was studied at Sterkfontein Dam Nature Reserve (eastern Free State) between September 1999 and May 2002. Within a study area of 550 ha, all herds of grey rhebok and all territorial male mountain reedbuck were identified, and general population dynamics were monitored. Lambs of both species were born seasonally between September and February, while most deaths occurred between June and November. Population levels appeared to be controlled in both species mainly by the eviction of young males, but the effects of extreme weather conditions were significant, being demonstrated by the deaths of 27 % and 51 % of the grey rhebok and mountain reedbuck populations respectively during heavy snow in September 2001. Disease and predation played no role in population control. Grey rhebok formed stable harem herds with home ranges varying between 23 ha and 104 ha (95 % MCP), with an average of 57.9 ha. Home ranges in areas with extensive steep slopes tended to be smaller than those in flatter areas. The ecological density was 1/15.7 ha. Territorial male mountain reedbuck were often solitary, and only accompanied by females when these moved into their territories. Home ranges of males varied between 7 ha and 21 ha (95 % MCP), with an average of 14.8 ha, and all had areas of steep slopes within. Females showed strong preference for steep slopes and used much greater areas than males. The ecological density was 1/8.7 ha. Grey rhebok rested less than mountain reedbuck, but did not feed for longer. Grey rhebok were active intermittently all day and night, but tended to be more active in the early morning and late afternoon than in the middle of the day. During the day, mountain reedbuck were most active in the late afternoon, rested for longer periods in the middle of the day, but were also very active at night. Body condition was investigated seasonally in mountain reedbuck at Sterkfontein and also Tussen die Riviere Nature Reserve. Kidney fat indices and leg fat percentages were lowest at the end of winter before the rains started and when the nutritive value of the veld was at its lowest. Endoparasites were investigated in both antelope species, but primarily in mountain reedbuck. Seventeen species of helminths, including fifteen nematodes, one trematode, and one cestode were recovered from mountain reedbuck at Sterkfontein and TdR. The most prevalent and abundant species were Cooperia yoshidai, Longistrongylus schrenki and Haemonchus contortus. Five nematode species were recovered from four grey rhebok at Sterkfontein. / Thesis (PhD (Veterinary Wildlife))--University of Pretoria, 2004. / Veterinary Tropical Diseases / unrestricted

Estimates of the brown trout (Salmo trutta) population were made in two areas of the Blacksmith Fork River, Cache County, Utah, from June 1972 to June 1973. Additional data were obtained on movement, growth, mortality, biomass, production, and yield. Population density was highly variable in the area where habitat alterations had occurred, but was relatively uniform where the habitat was undisturbed. The brown trout exhibited little movement except during spawning season. Instantaneous growth and mortality rates are provided for each age group. Mean annual biomass in the two areas was 12.0 and 10.2 grams per square meter and production was estimated at 9.2 and 7.7 grams per square meter per y ear in the two study areas. Gametes comprised approximately 5 percent of the annual production and angler harvest removed 39 percent of production.

Serpentine areas in the Czech Republic form minor but important islands in the landscape with specific chemical properties such as high content of magnesium and other heavy metals. Due to this, serpentine is toxic for most plants. Increased demands on the survival and occurrence of plants lead to the emergence of serpentine specialists obligatorily specialized in these extreme habitats. Currently, serpentine areas are threatened by gradual overgrowth of sites, insufficient or poor site management and fragmentation or shrinkage of sites due to anthropogenic activities. Along with the disappearing localities, the serpentine specialists, are becoming highly endangered. Minuartia smejkalii is highly endangered serpentine specialist with an endemic occurrence in the Czech Republic with great need of its conservation. The aim of the work was to collect data on population dynamics of the species and identify habitat and climatic factors affecting population growth. We studied dynamics in all existing 7 populations during the period from 2006 to 2020 were collected. We linked these data to information on population dynamics, habitat and climatic factors and analysed them using Integral projection models (IPM). The study presents the importance of individual habitat and climatic conditions on the dynamics...

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