Biotic interactions are an unexpected yet critical control on the complexity of an abiotically driven polar ecosystem.

Abiotic and biotic factors control ecosystem biodiversity, but their relative contributions remain unclear. The ultraoligotrophic ecosystem of the Antarctic Dry Valleys, a simple yet highly heterogeneous ecosystem, is a natural laboratory well-suited for resolving the abiotic and biotic controls of community structure. We undertook a multidisciplinary investigation to capture ecologically relevant biotic and abiotic attributes of more than 500 sites in the Dry Valleys, encompassing observed landscape heterogeneities across more than 200 km2. Using richness of autotrophic and heterotrophic taxa as a proxy for functional complexity, we linked measured variables in a parsimonious yet comprehensive structural equation model that explained significant variations in biological complexity and identified landscape-scale and fine-scale abiotic factors as the primary drivers of diversity. However, the inclusion of linkages among functional groups was essential for constructing the best-fitting model. Our findings support the notion that biotic interactions make crucial contributions even in an extremely simple ecosystem.

Have urban/rural inequalities in suicide in New Zealand grown during the period 1980-2001?

Previous studies have noted that in many countries there has been a disproportionate increase in suicide in rural areas, contributing to greater urban/rural inequalities in health. This paper evaluates whether this trend was also apparent in New Zealand during the 1980s and 1990s, a period of rapid social and economic change. Using suicide incidence data for the period 1980-2001, we investigate whether urban/rural status had an effect upon rates of suicide independently of socioeconomic deprivation. While both male and female suicide rates were significantly higher in urban than rural areas in 1980-1982, by the end of the 1990s, urban/rural differences in suicide rates were not significant. The narrowing of urban/rural differences was, to some extent, a result of the growth in suicide rates in more isolated rural communities and small rural service centres. Recent geographical variations in suicide in New Zealand are therefore to a large extent similar to trends observed elsewhere, but are less marked. Potential explanations are offered for the fluctuating urban/rural inequalities in suicide including compositional arguments, rural restructuring and economic decline, social isolation and health service utilisation.

Did geographical inequalities in suicide among men aged 15-44 in New Zealand increase during the period 1980-2001?

OBJECTIVE: It has previously been reported that rates of suicide among men aged 15-44 increased rapidly during the 1980s and 1990s. The present study examines whether geographical inequalities in suicide rates among men in this age group rose during the period 1980-2001 in New Zealand. METHODS: Age-standardized rates of suicide for men aged 15-44 were calculated for District Health Boards (DHBs) and in deprivation quintiles (using the 2001 New Zealand deprivation score) for the periods 1980-1982, 1985-1987, 1990-1992, 1995-1997 and 1999-2001. Geographical inequality was measured by calculating the ratio of the suicide rate deprivation quintile 5 to quintile 1. RESULTS: Age-standardized rates of suicide among men aged 15-44 increased in all but two DHBs between 1980 and 2001. The ratio of inequality in suicide between the least deprived and most deprived areas of New Zealand rose from 1.68 in 1980-1982 to a high of 1.94 in 1990-1992, followed by a small reduction to 1.86 by the end of the study period. CONCLUSIONS: Geographical inequalities in suicide among men aged 15-44 grew during the period 1980-2001 and remain at high levels. The greatest increase in inequality was during the late 1980s and early 1990s, a period of rapid social and economic change to New Zealand society.