Satisfaction with urban trees associates with tree canopy cover and tree visibility around the home.

Many world cities want to expand the number of urban trees. How this expansion occurs should consider what people expect from trees based on how they experience and perceive these trees. Therefore, we need a better understanding of how people perceptually respond to urban tree abundance. This research examined whether people's satisfaction with urban trees and satisfaction with the management of those trees were related to objective measures of greenery such as the Normalized Difference Vegetation Index (NDVI), percent tree canopy cover, and the Viewshed Greenness Visibility Index (VGVI) for trees. We used a demographically and geographically representative survey of 223 residents in Toronto, Canada, and calculated NDVI, canopy cover, and VGVI at three neighbourhood sizes. We analysed the data using generalized linear regression. We found that canopy cover and VGVI had a positive association with satisfaction with urban trees. The associations were comparatively stronger at larger neighbourhood scales than at smaller scales. There were no statistically significant associations with NDVI or satisfaction with the management of urban trees.

Resident Knowledge of and Engagement with Green Infrastructure in Toronto and Philadelphia.

Green infrastructure (GI) initiatives, including programs to plant trees and install bioswales, have been adopted by a growing number of local government and non-governmental organizations. While the details of these programs vary, a common characteristic of most Canadian and US GI initiatives is a distributed approach that includes both public and private land. To date, little research has explored residents' knowledge of GI or their engagement with related initiatives even though residents' installation of GI is often key to creating distributed GI networks. In this study, we (1) assess residents' knowledge of the term GI, (2) identify residents' level of engagement with GI initiatives, and (3) examine whether factors like level of concern about local environmental issues can predict GI knowledge or level of engagement with GI initiatives. We explored these objectives through a survey of residents in Toronto (Ontario, Canada) and Philadelphia (Pennsylvania, US). We found that about a quarter of survey respondents in both cities had previously heard the term "green infrastructure". Neither knowledge of GI nor level of engagement with GI initiatives could be predicted by the level of concern about local environmental issues, but residents' interest in using their outdoor space for nature activities (e.g., gardening) predicted GI knowledge in both cities and level of initiative engagement in Philadelphia. Our results suggest the need for widespread education campaigns that clearly define GI so that residents can be participants in policy discussions, link it with their needs, and identify ways to manage GI to create desired benefits.

Beyond 'trees are good': Disservices, management costs, and tradeoffs in urban forestry.

The provision of ecosystem services is a prominent rationale for urban greening, and there is a prevailing mantra that 'trees are good'. However, understanding how urban trees contribute to sustainability must also consider disservices. In this perspective article, we discuss recent research on ecosystem disservices of urban trees, including infrastructure conflicts, health and safety impacts, aesthetic issues, and environmentally detrimental consequences, as well as management costs related to ecological disturbances and risk management. We also discuss tradeoffs regarding species selection and local conservation concerns, as well as the central role of human perception in the interpretation of ecosystem services and disservices, particularly the uncritical assertion that 'everybody loves trees'. Urban forestry decision-making that fails to account for disservices can have unintended negative consequences for communities. Further research is needed regarding life cycle assessments, stakeholder decision-making, return-on-investment, and framings of services and disservices in urban forestry.

Vulnerability of Common Urban Forest Species to Projected Climate Change and Practitioners Perceptions and Responses.

While urban forests are often identified as part of climate change adaptation and mitigation strategies, less attention has been given to vulnerabilities urban trees may have to a changing climate and practitioners' response to those vulnerabilities. Yet, current planting and management decisions will impact how urban forests fare under future climatic conditions. We explore a case study of Mississauga (Ontario, Canada) to examine (1) if common urban forest species are vulnerable to two scenarios of projected climate change, (2) the experiences and responses of urban forestry practitioners to climate change, and (3) whether urban forestry practitioners' experience and practice are aligned with the vulnerability assessment. Vulnerabilities of 27 common species were examined based on 2071-2100 regional climate projections. Interviews were then conducted with practitioners working in the public and private sectors. The results suggest that the majority of examined species will be vulnerable to multiple conditions associated with projected climate. Practitioners all perceive recent changes in climate and extreme weather patterns, but do not prioritize future climate conditions in their species selection decisions. Moreover, they expressed uncertainty about how to make species selection decisions in light of climate change. Given the predicted vulnerabilities, alternative species need to be considered or more management resources (e.g., for watering) will be required to maintain the current composition. However, the lack of focus on future conditions by practitioners raises concerns, while also highlighting the need for more information about appropriate management strategies.

Residential Knowledge of Native Tree Species: A Case Study of Residents in Four Southern Ontario Municipalities.

In the past decade, municipalities across North America have increased investment in their urban forests in an effort to maintain and enhance the numerous benefits provided by them. Some municipalities have now drafted long-term urban forest management plans that emphasize the planting of native trees, to improve ecological integrity, and participation of residents, since the majority of urban trees are typically located on residential property. Yet it is unclear if residents are familiar with native trees or municipalities' urban forest management goals. Through a case study of southern Ontario municipalities, we administered a survey exploring residents' ability to correctly label common tree species as native or non-native, as well as their knowledge of urban forest management plans to test four hypotheses: 1) residents in municipalities with an urban forest management plans will be more knowledgeable about the native status of common street trees; 2) residents who have lived in the area longer will have greater knowledge; 3) knowledge level will be correlated with education level, ethnicity, and income; and 4) residents' knowledge will be related to having planted trees on their property. Our results indicate that residents are better able to identify common native trees than correctly determine which trees are non-native, although knowledge levels are generally low. Knowledge was significantly related to length of residency and tree planting experience, supporting hypotheses 2 and 4. These results highlight the importance of experience and local knowledge acquisition in relation to basic knowledge about urban trees, and also point to the failures of resident outreach within the case study municipalities.

Impervious surface as an indicator of pH and specific conductance in the urbanizing coastal zone of New Jersey, USA.

Impervious surface is often used as an indicator of non-point source pollution in urban areas due to the strong relationship between percent impervious surface cover and water-quality impacts. In many cases, a threshold effect exists where water quality rapidly degrades above a given percent cover, but the exact threshold level appears to vary across regions. This study explores the relationship between pH, specific conductance, and percent impervious surface cover in the urbanizing coastal zone of New Jersey (USA) to determine the nature of the relationship in the region. The results of the analysis suggest the system is very sensitive to impervious surface, with a threshold potentially existing between 2.4% and 5.1% impervious surface cover. An examination of future conditions suggests that by 2020 water quality in more than 50% of the catchments in the study area will be negatively impacted by non-point source pollution associated with impervious surface.

Modeling the ecological consequences of land-use policies in an urbanizing region.

Insight into future land use and effective ways to control land-use change is crucial to addressing environmental change. A variety of growth-control policies have been adopted by municipal and regional governments within the United States to try to minimize the ecological impact of continued urbanization, but it is often unclear if those policies can meet the stated ecological goals. Land-use-change models provide a way to generate predictions of future change, while exploring the impact of different land-use policies before irreversible transformations occur. In this article, an approach to modeling land-use policies that focuses on their ecological consequences is described. The policy simulation approach was used to predict future land use in the Barnegat Bay and Mullica River watersheds, in southeastern New Jersey, USA. Four commonly used policies were considered: down-zoning, cluster development, wetlands/water buffers, and open space protection. The results of the analysis suggest that none of the policies modeled were able to alter future land-use patterns, raising questions about the effectiveness of commonly adopted land-use policies. However, the policy modeling approach used in this study proved to be a useful way to determine if adoption of a given policy could improve the likelihood of meeting ecological goals.