Contrasting effects of urbanization on arboreal and ground-dwelling land snails: role of trophic interactions and habitat fragmentation

Urbanization generally reduces wildlife populations. Individual species responses, however, are often highly variable, and such variability can be explained by differences in species ecological traits. To examine this hypothesis, we focused on two co-occurring land snails, Ezohelix gainesi and Euhadra brandtii sapporo; the former is ground-dwelling and the latter is arboreal. We first estimated their population densities at nine sites distributed along an urbanization gradient: three were located in continuous natural forests, three at the edge of natural forests, and the rest in small isolated forests in urban areas. As a result, the ground-dwelling E. gainesi occurred at highest density in urban forests, followed by forest edges and continuous forests. By contrast, the arboreal E. b. sapporo occurred at highest density in continuous forests, but declined in forest edges and urban forests. We then conducted manipulative field experiments to quantify changes in predation pressure on these species. Ground-tethered E. gainesi and E. b. sapporo were repeatedly predated upon by forest-living mammals in continuous forests, but their survival rates increased in forest edges and urban forests. By contrast, canopy-tethered E. b. sapporo maintained high survival rates in all three forest types. The results indicate that a lack of mammalian predators enables ground-dwelling species to occur at high densities in urban forests, whereas the arboreal species was not affected by this predator relaxation effect. The combination of species-specific behavioural traits and changes in predator communities across an urbanization gradient has important effects on the biodiversity of urban ecosystems.

     

Educational Inequality

Abstract. This paper develops a theoretical model of the inequality in wages and salaries associated with differences in years of schooling (educational inequality, for short). Our model assumes that in the long run individual decisions to become more educated equalize the lifetime earnings of more educated workers and comparable less educated workers. Given this assumption, our model implies that innovations that increase the relative demand for more educated labor, and which cause short‐run increases in educational inequality, in the long run induce offsetting increases in the relative supply of more educated labor. But our model also has the novel implication that innovations that increase differences between the wages and salaries received by workers with the same years of education who are more or less able (ability premiums, for short) cause a smaller fraction of workers to choose to become more educated. Consequently, innovations that increase ability premiums in the long run also cause educational inequality to be larger than otherwise. In applying our theory to recent changes in educational inequality in the USA, we suggest that, to the extent that innovations that increase ability premiums are contributing to educational inequality, the increases in educational inequality during the 1980s and 1990s are unlikely to be reversed soon.     

Correction to: contrasting effects of urbanization on arboreal and ground-dwelling land snails: role of trophic interactions and habitat fragmentation

Urban Ecosystems - The original version of the article unfortunately contained mistakes in the legends of Fig. 3. The legends (1) Blue square: Euhadra brandtii sapporo, ground is changed...     

The Risk Screening for Indoor Air Pollution Chemicals in Japan

In recent years, public health problems caused by indoor air pollution have been drawing strong public concern in Japan. After conducting extensive exposure assessment, governmental agencies have taken effective measures to solve the problem; for instance, "Guidelines for indoor air quality (IAQ)" of 13 chemicals, for example, formaldehyde, toluene, and xylene, has been established. Thousands of chemicals have been identified in the indoor environment. Priority rating of those chemicals, however, was not based on the health risk level. We developed a risk-screening scheme for indoor air pollution chemicals and analyzed the current status of the risk levels of those chemicals in Japan. We researched scientific knowledge of health hazards and exposure surveys of indoor air pollution chemicals in Japan, and classified those chemicals based on the health risk level estimated from the scheme. The risk levels of 93 chemicals were characterized and six chemicals (formaldehyde, acrolein, 1,4-dichlorobenzene, benzene, tetrachloroethylene, and benzo(a)pyrene) were classified in the highest risk category.