Critical evaluation of the nursery role hypothesis for seagrass meadows

The vast majority of published papers concerning seagrass meadows contain statements to the effect that seagrass beds serve as important nurseries for many species. We reviewed more than 200 papers that were relevant to the nursery role hypothesis. We used both vote counting and meta-analytic techniques to evaluate whether the body of previous studies that report seagrass meadows to be nursery grounds actually contain data that support this proposition. We restricted our analyses to papers that compared seagrass beds to other habitats, and examined data on a variety of well-studied species concerning their density, growth, survival and migration to adult habitat. Within this group of papers, we considered potential factors that could influence the nursery function (e.g. location, or laboratory vs field studies). We also evaluated case histories of well-documented large-scale seagrass losses on the nursery function. Major results were consistent with the expectations that abundance, growth and survival were greater in seagrass than in unstructured habitats. Abundance data also suggested that seagrass beds in the Northern Hemisphere might be more important as nursery areas than those in the Southern Hemisphere. Surprisingly, few significant differences existed in abundance, growth or survival when seagrass meadows were compared to other structured habitats, such as oyster or cobble reefs, or macroalgal beds. Nor were there decreases in harvests of commercially important species that could clearly be attributed to significant seagrass declines in 3 well-studied areas. However, there were decreased abundances of juveniles of commercially important species in these areas, suggesting a strong link between seagrass abundance and those of juvenile finfish and shellfish. One important implication of these results is that structure per se, rather than the type of structure, appears to be an important determinant of nursery value. Clearly, more rigorous studies that test all aspects of the nursery role hypothesis are clearly needed for seagrass meadows as well as other structured habitats. The results of such studies will allow better decisions to be made concerning the conservation and restoration of marine habitats.

Itinerant foreign harvest workers in Australia: the impact of precarious employment on occupational safety and health

Horticulture work in many high-income economies is increasingly performed by temporary migrant workers from low-wage economies. In Australia, such work is now performed predominantly by international backpackers – young well-educated workers with mostly sound English language skills. These workers are drawn to harvesting work by a government scheme which provides an incentive for completing a specified number of days work in horticulture. This article examines the health and safety experience of these workers, through focus groups, interviews and an online survey. Notwithstanding their distinctive backgrounds, the harvesting experience of these temporary migrant workers is similar to that of low-skilled migrants working in other high-income countries. Health and safety risks associated with work organisation and payment systems, and a lack of compliance with OHS legal requirements, are commonplace but potentially compounded by a sense of invincibility amongst these young travellers. Furthermore, a growing pool of undocumented workers is placing downward pressures on their employment conditions. The vulnerability associated with work and earnings uncertainty, and the harsh environment in which harvesting work occurs, remains a constant notwithstanding the background of these workers.