Differential trends in the compression of mortality: Assessing the antecedents to current gaps in health expectancy in New Zealand

Health Expectancies (HEs) for New Zealand show significant differentials between Maori and non-Maori, but also by gender and period. These differentials correlate with findings from both generation and synthetic life-tables relating to New Zealand’s epidemiologic transition. At the beginning of that transition quartile 1 (Q(1)), and Median (Med) d(x) values were close and centred at young ages; during the transition the gap became very wide; at the transition’s end the gap again narrowed. Cohort and synthetic trends in d(x), l(x), M, Qs and Meds are reviewed and linked to recent HEs. Data point to epidemic polarisation. Cohort analysis allows the evaluation of the role of past experiences on the recent HEs, and thus point to possible strategies for reducing gaps in both d(x), and HEs

Missing men and unacknowledged women: Explaining gender disparities in New Zealand’s prime adult age groups 1986 – 2006

Questions concerning the widening disparity in numbers of males and females in the prime working age groups in New Zealand’s population have attracted attention from researchers and the media in recent years. This paper reviews some of the findings from research for a FRST-funded programme that has been investigating several inequalities based on gender and ethnicity in New Zealand’s population. The analysis here complements and extends that in our paper published in the New Zealand Population Review in May 2006. Our main finding is that a complex combination of issues related to the way our stock (census) and flow (arrival/departure) data are used to compile population estimates (the base for population projections), have contributed to exaggerating apparent gender disparities in the 20-49 year age groups at successive censuses. There is no single explanation for this, and the main new finding from our analysis is that gender disparities in the prime adult age groups in New Zealand’s population are as much a function of ‘unacknowledged women’ as of ‘missing men’

Apparent competition drives community-wide parasitism rates and changes in host abundance across ecosystem boundaries

Species have strong indirect effects on others, and predicting these effects is a central challenge in ecology. Prey species sharing an enemy (predator or parasitoid) can be linked by apparent competition, but it is unknown whether this process is strong enough to be a community-wide structuring mechanism that could be used to predict future states of diverse food webs. Whether species abundances are spatially coupled by enemy movement across different habitats is also untested. Here, using a field experiment, we show that predicted apparent competitive effects between species, mediated via shared parasitoids, can significantly explain future parasitism rates and herbivore abundances. These predictions are successful even across edges between natural and managed forests, following experimental reduction of herbivore densities by aerial spraying over 20ha. This result shows that trophic indirect effects propagate across networks and habitats in important, predictable ways, with implications for landscape planning, invasion biology and biological control

Changing sex ratios in New Zealand: Real change or a statistical problem?

In New Zealand, in all age groups under 20, and in key working age groups, historically there have been more men than women. Life table data suggest that, without migration, the number of males should remain greater than the number of females until around the age of 60 years. However, census data indicate that the number of New Zealand women residents relative to men in the broad 20-49 age group has been increasing since the 1980s. Given that birth ratios for New Zealand residents favour boys in common with international experience, the imbalance of women over men in the 20-49 age group has to come from four possible sources: 1) differential mortality; 2) more New Zealand born men leaving New Zealand; 3) a higher number of female immigrants; or 4) that statistical collections are undercounting men, and this undercounting has become progressively greater over the past 20 years. In this paper we focus on undercount and, through this investigation, raise some doubts about the validity of either a serious ‘man drought’ or a major 'surplus of women' in the population

Maori internal and international migration at the turn of the century: An Australasian perspective

At the beginning of the twenty-first century there were two major national clusters of Maori: New Zealand, the ancestral home for Maori, and Australia, home to a much smaller Maori population from the early years of the nineteenth century. In the 2001 censuses of New Zealand and Australia, the usually resident Maori populations were, respectively, 526,281 (ethnic group classification) and 72,956 (ancestry classification). In this paper we examine four dimensions of Maori population movement between 1996 and 2001 using the census data from New Zealand and Australia: 1) internal migration between rural and urban areas in New Zealand; 2) internal migration between rural and urban areas in Australia; 3) migration into New Zealand of Maori resident overseas in 1996; 4) migration into Australia of Maori resident overseas in 1996. There has never been a comprehensive assessment of Maori migration in an Australasian context before, but in the light of developments in population exchanges between New Zealand and Australia this sort of analysis is critical if one wishes to understand contemporary Maori population dynamics

Resilience of New Zealand indigenous forest fragments to impacts of livestock and pest mammals

A number of factors have combined to diminish ecosystem integrity in New Zealand indigenous lowland forest fragments surrounded by intensively grazed pasture. Livestock grazing, mammalian pests, adventive weeds and altered nutrient input regimes are important drivers compounding the changes in fragment structure and function due to historical deforestation and fragmentation. We used qualitative systems modelling and empirical data from Beilschmiedia tawa dominated lowland forest fragments in the Waikato Region to explore the relevance of two common resilience paradigms – engineering resilience and ecological resilience – for addressing the conservation management of forest fragments into the future. Grazing by livestock and foraging/predation by introduced mammalian pests both have direct detrimental impacts on key structural and functional attributes of forest fragments. Release from these perturbations through fencing and pest control leads to partial or full recovery of some key indicators (i.e. increased indigenous plant regeneration and cover, increased invertebrate populations and litter mass, decreased soil fertility and increased nesting success) relative to levels seen in larger forest systems over a range of timescales. These changes indicate that forest fragments do show resilience consistent with adopting an engineering resilience paradigm for conservation management, in the landscape context studied. The relevance of the ecological resilience paradigm in these ecosystems is obscured by limited data. We characterise forest fragment dynamics in terms of changes in indigenous species occupancy and functional dominance, and present a conceptual model for the management of forest fragment ecosystems

Daily survival and dispersal of adult Rhagonycha fulva (Coleoptera: Cantharidae) in a wooded agricultural landscape

Studies of insect population under field conditions to establish survival rates, longevity and dispersal rates are rare in the literature. These types of studies are important and can be used to inform studies of the effects of landscape composition and configuration on levels of biodiversity. Here the Cantharidae beetle, Rhagonycha fulva is studied under field conditions to derive estimates of daily survival rates for both males and females as well as local dispersal rates. Survival was studied at two sites, one in Wales and another in England, whilst dispersal was examined only at the Welsh site. Beetles were marked using different coloured enamel paints at the mid-point of a 200 m linear transect. The beetles were almost exclusively found (and marked) on common hogweed, Heracleum sphondylium. No difference in survival was found between males and females at both of the sites. The survival rates found at the two sites also did not differ. The overall daily survival rate was 0.771 equating with a median longevity of 4.37 days. Casual observations yielded a small number of marked individuals in excess of 400 m away from the point of marking. Movement of males along the transect differed from females. Marked females were never found far from the point of marking whilst males moved further away with time. This difference in behaviour is discussed in terms of hypothesized insect dispersal behaviour following emergence as mobile adults

Ecological and genetic effects of introduced species on their native competitors

Species introductions to new habitats can cause a decline in the population size of competing native species and consequently also in their genetic diversity. We are interested in why these adverse effects are weak in some cases whereas in others the native species declines to the point of extinction. While the introduction rate and the growth rate of the introduced species in the new environment clearly have a positive relationship with invasion success and impact, the influence of competition is poorly understood. Here, we investigate how the intensity of interspecific competition influences the persistence time of a native species in the face of repeated and ongoing introductions of the nonnative species. We analyze two stochastic models: a model for the population dynamics of both species and a model that additionally includes the population genetics of the native species at a locus involved in its adaptation to a changing environment. Counterintuitively, both models predict that the persistence time of the native species is lowest for an intermediate intensity of competition. This phenomenon results from the opposing effects of competition at different stages of the invasion process: With increasing competition intensity more introduction events are needed until a new species can establish, but increasing competition also speeds up the exclusion of the native species by an established nonnative competitor. By comparing the ecological and the eco-genetic model, we detect and quantify a synergistic feedback between ecological and genetic effects.Comment: version accepted at Theoretical Population Biolog

Sex, Migration And Aging: Demographic Overview Of A Dynamic Labour Market

This paper provides a broad overview of some of the demographic features of the work force in the context of the population as a whole. In this respect it differs from other papers in that it provides a background picture against which topics discussed elsewhere can be measured. The purpose is to provide context for discussion and a background to contextualise labour market research. The three key themes of sex, migration and change to identify the connection between the population and the policy drivers that impinge on the labour market

Re-Gendering Of The Workforce: Women And Men In “Non-Traditional” Occupations And Industries

Many occupations and industries have traditionally remained the preserve of either men or women. In recent years, a range of campaigns and policies have focussed on equity for women and equality of opportunity for both men and women in the work force. This paper looks at some of the background, ongoing discrimination and the forces acting for and against gender balance which has brought about some re-gendering of occupations