Changes in the community structure of urban and rural forest patches in Baltimore from 1998 to 2015

Urban forests are often highly fragmented with many exotic species. Altered disturbance regimes and environmental pollutants influence urban forest vegetation. One of the best ways to understand the impacts of land-use on forest composition is through long-term research. In 1998, the Baltimore Ecosystem Study established eight forest plots to investigate the impacts of urbanization on natural ecosystems. Four plots were located in urban forest patches and four were located in rural forests. In 2015, I revisited these plots to measure abundances and quantify change in forest composition, diversity, and structure. Sapling, shrub, and seedling abundance were reduced in the rural plots. Alpha diversity and turnover was lower in the rural plots. Beta diversity was reduced in the rural plots. The structure of the urban plots was mostly unchanged, except for a highly reduced sapling layer. Beta diversity in the urban plots was consistent across surveys due to high species turnover.

Urbanization impacts on mammals across urban-forest edges and a predictive model of edge effects

With accelerating rates of urbanization worldwide, a better understanding of ecological processes at the wildland-urban interface is critical to conserve biodiversity. We explored the effects of high and low-density housing developments on forest-dwelling mammals. Based on habitat characteristics, we expected a gradual decline in species abundance across forest-urban edges and an increased decline rate in higher contrast edges. We surveyed arboreal mammals in sites of high and low housing density along 600 m transects that spanned urban areas and areas turn on adjacent native forest. We also surveyed forest controls to test whether edge effects extended beyond our edge transects. We fitted models describing richness, total abundance and individual species abundance. Low-density housing developments provided suitable habitat for most arboreal mammals. In contrast, high-density housing developments had lower species richness, total abundance and individual species abundance, but supported the highest abundances of an urban adapter (Trichosurus vulpecula). We did not find the predicted gradual decline in species abundance. Of four species analysed, three exhibited no response to the proximity of urban boundaries, but spilled over into adjacent urban habitat to differing extents. One species (Petaurus australis) had an extended negative response to urban boundaries, suggesting that urban development has impacts beyond 300 m into adjacent forest. Our empirical work demonstrates that high-density housing developments have negative effects on both community and species level responses, except for one urban adapter. We developed a new predictive model of edge effects based on our results and the literature. To predict animal responses across edges, our framework integrates for first time: (1) habitat quality/preference, (2) species response with the proximity to the adjacent habitat, and (3) spillover extent/sensitivity to adjacent habitat boundaries. This framework will allow scientists, managers and planners better understand and predict both species responses across edges and impacts of development in mosaic landscapes.

Citizen science program shows urban areas have lower occurrence of frog species, but not accelerated declines

Understanding the influence of landscape change on animal populations is critical to inform biodiversity conservation efforts. A particularly important goal is to understand how urban density affects the persistence of animal populations through time, and how these impacts can be mediated by habitat provision; but data on this question are limited for some taxa. Here, we use data from a citizen science monitoring program to investigate the effect of urbanization on patterns of frog species richness and occurrence over 13 years. Sites surrounded by a high proportion of bare ground (a proxy for urbanization) had consistently lower frog occurrence, but we found no evidence that declines were restricted to urban areas. Instead, several frog species showed declines in rural wetlands with low-quality habitat. Our analysis shows that urban wetlands had low but stable species richness; but also that population trajectories are strongly influenced by vegetation provision in both the riparian zone and the wider landscape. Future increases in the extent of urban environments in our study area are likely to negatively impact populations of several frog species. However, existing urban areas are unlikely to lose further frog species in the medium term. We recommend that landscape planning and management focus on the conservation and restoration of rural wetlands to arrest current declines, and the revegetation of urban wetlands to facilitate the re-expansion of urban-sensitive species.

Compact development minimizes the impacts of urban growth on native mammals

Unprecedented global human population growth and rapid urbanization of rural and natural lands highlight the urgent need to integrate biodiversity conservation into planning for urban growth. A challenging question for applied ecologists to answer is: What pattern of urban growth meets future housing demand whilst minimizing impacts on biodiversity? We quantified the consequences for mammals of meeting future housing demand under different patterns of compact and dispersed urban growth in an urbanizing forested landscape in south-eastern Australia. Using empirical data, we predicted impacts on mammals of urban growth scenarios that varied in housing density (compact versus dispersed) and location of development for four target numbers of new dwellings. We predicted that compact developments (i.e. high-density housing) reduced up to 6% of the area of occupancy or abundance of five of the six mammal species examined. In contrast, dispersed developments (i.e. low-density housing) led to increased mammal abundance overall, although results varied between species: as dwellings increased, the abundance or occurrence of two species increased (up to ∼100%), one species showed no change, and three species declined (up to ∼39%). Two ground-dwelling mammal species (Antechinus stuartii and Rattus fuscipes) and a tree-dwelling species (Petaurus australis) were predicted to decline considerably under dispersed rather than compact development. The strongest negative effect of dispersed development was for Petaurus australis (a species more abundant in forested interiors) which exhibited up to a 39% reduction in abundance due to forest loss and an extended negative edge effect from urban settlements into adjacent forests. Synthesis and applications. Our findings demonstrate that, when aiming to meet demand for housing, any form of compact development (i.e. high-density housing) has fewer detrimental impacts on forest-dwelling mammals than dispersed development (i.e. low-density housing). This is because compact development concentrates the negative effects of housing into a small area whilst at the same time preserving large expanses of forests and the fauna they sustain. Landscape planning and urban growth policies must consider the trade-off between the intensity of the threat and area of sprawl when aiming to reduce urbanization impacts.

Air pollution levels measured at traffic hot spots : Brisbane urban corridor study

Air pollution levels were monitored continuously over a period of 4 weeks at four sampling sites along a busy urban corridor in Brisbane. The selected sites were representative of industrial and residential types of urban environment affected by vehicular traffic emissions. The concentration levels of submicrometer particle number, PM2.5, PM10, CO, and NOx were measured 5-10 meters from the road. Meteorological parameters and traffic flow rates were also monitored. The data were analysed in terms of the relationship between monitored pollutants and existing ambient air quality standards. The results indicate that the concentration levels of all pollutants exceeded the ambient air background levels, in certain cases by up to an order of magnitude. While the 24-hr average concentration levels did not exceed the standard, estimates for the annual averages were close to, or even higher than the annual standard levels.

How can land and urban development make houses healthier?

Traditionally, the main focus of the professional community involved with indoor air quality has been indoor pollution sources, preventing or reducing their emissions, as well as lowering the impact of the sources by replacing the polluted indoor air with "fresh" outdoor air. However, urban outdoor air cannot often be considered "fresh", as it contains high concentrations of pollutants emitted from motor vehicles - the main outdoor pollution sources in cities. Evidence from epidemiological studies conducted worldwide demonstrates that outdoor air quality has considerable effects on human health, despite the fact that people spend the majority of their time indoors. This is because pollution from outdoors penetrates indoors and becomes a major constituent of indoor pollution. Urban land and transport development has significant impact on the overall air quality of the urban airshed as well as the pollution concentration in the vicinity of high-density traffic areas. Therefore, an overall improvement in indoor air quality would be achieved by lowering urban airshed pollution, as well as by lowering the impact of the hot spots on indoor air. This paper explores the elements of urban land and vehicle transport developments, their impact on global and local air quality, and how the science of outdoor pollution generation and transport in the air could be utilized in urban development towards lowering indoor air pollution.