How do people perceive urban trees? Assessing likes and dislikes in relation to the trees of a city

Cities are systems that include natural and human-created components. When a city grows without proper planning, it tends to have low environmental quality. If improving environmental quality is intended, people’s opinion should be taken into account for a better acceptance of urban management decisions. In this study, we assessed people’s perception of trees by conducting a survey with a controlled sample of citizens from the city of Morelia (west-central Mexico). Citizens liked both native and exotic tree species and rejected mainly exotic ones. Preference for trees were related to tree attributes; such as size. Trees that dropped leaves or tended to fall were not liked. The most-mentioned tree-related benefits were oxygen supply and shade; the most mentioned tree-related damages were accidents and infrastructure damage. The majority of respondents preferred trees near houses to increase tree density. Also, most respondents preferred trees in green areas as well as close to their houses, as they consider that trees provide oxygen. The majority of the respondents thought more trees were needed in the city. In general, our results show that although people perceive that trees in urban areas can cause damages, they often show more interest for the benefits related to trees and consider there should be more trees in cities. We strongly suggest the development of studies that broaden our knowledge of citizen preferences in relation to urban vegetation, and that further policy making takes their perception into account when considering creating new urban green areas, regardless of their type or size.     

Influences of landscape and lifestyle on home energy consumption

Rapid urbanization coupled with concerns about global climate change has renewed interest in energy conservation and carbon dioxide emissions reduction. Urban residential energy consumption is a valuable place to start reducing emissions, and urban tree planting programs have been both proposed and utilized as an energy conservation mechanism. Home energy savings associated with urban trees are often quantified using models because of the many complex interactions among variables that can influence home energy use. However, recent empirical analyses have found that energy savings associated with trees may be minimal relative to other important factors like building characteristics and human behaviors. We surveyed 176 residents from four neighborhoods in Raleigh, NC with varying socio-economic characteristics to assess relationships between summer energy usage, tree cover, homeowner behavior, and building characteristics. As hypothesized, we found that building characteristics, demographics, and human behaviors were all significant variables in describing the variability in summertime home energy usage. Although, total percent tree cover 18?m around the home did not affect summertime energy use, the number of trees in the NE and NW quadrants around each household did predict home energy use. These results indicate that planting trees may not be a successful strategy for reducing energy use from the residential sector in the heavily forested Southeast; rather efforts should target conservation and efficiency.     

The balance of planting and mortality in a street tree population

Street trees have aesthetic, environmental, human health, and economic benefits in urban ecosystems. Street tree populations are constructed by cycles of planting, growth, death, removal and replacement. The goals of this study were to understand how tree mortality and planting rates affect net population growth, evaluate the shape of the mortality curve, and assess selected risk factors for survival. We monitored a street tree population in West Oakland, CA for 5 years after an initial inventory (2006). We adapted the classic demographic balancing equation to quantify annual inputs and outputs to the system, tracking pools of live and standing dead trees. There was a 17.2 % net increase in live tree counts during the study period (995 in 2006, 1166 in 2011), with population growth observed each year. Of the live trees in 2006, 822 survived to 2011, for an annual mortality rate of 3.7 %. However, population growth was constrained by high mortality of young/small trees. Annual mortality was highest for small trees, and lower for mid-size and large trees; this represents a Type III mortality curve. We used multivariate logistic regression to evaluate the relationship between 2011 survival outcomes and inventory data from 2006. In the final model, significant associations were found for size class, foliage condition, planting location, and a multiplicative interaction term for size and foliage condition. Street tree populations are complex cultivated systems whose dynamics can be understood by a combination of longitudinal data and demographic analysis. Urban forest monitoring is important to understand the impact of tree planting programs.     

Comparing the relative abilities of tree species to cool the urban environment

Increasing urbanisation poses numerous challenges to human quality of life. Cities are particularly vulnerable to the urban heat-island effect, which will be amplified by climate change. Increasing tree cover may be one of the most cost-effective ways of moderating urban temperatures. Trees cool their surroundings by casting shade, reflecting solar radiation, transpiring, and intercepting rainfall that subsequently evaporates. However, the potential of trees to reduce the urban heat-island effect is underutilised. The aim of this study was to synthesise understanding of the relative abilities of different tree species to provide urban cooling in temperate regions of the world and thereby develop a pragmatic approach for choosing those trees that have greatest potential in that regard. Based on a literature review and semi-structured interviews with leading experts, we developed a series of scenarios to illustrate the impacts of a tree’s cooling mechanisms and tree species’ attributes on components of the surface-energy balance equation. This enabled us to select parameters and propose simple equations that can be used to compare the relative abilities of tree species in relation to each of the cooling mechanisms. The parameters selected were for: transpiration – crown diameter, Leaf Area Index (LAI), canopy aspect ratio, and stomatal conductance or growth rate; reflection – albedo, crown diameter and LAI; shading – canopy aspect ratio, crown diameter, LAI and tree height. The approach is intended for use by urban planners and managers who wish to make informed decisions about which tree species to select for planting to counter the urban heat-island effect.     

Quantifying urban forest structure,function, and value: the Chicago Urban Forest Climate Project

This paper is a review of research in Chicago that linked analyses of vegetation structure with forest functions and values. During 1991, the regions trees removed an estimated 5575 metric tons of air pollutants, providing air cleansing worth 9.2 million. Each year they sequester an estimated 315 800 metric tons of carbon. Increasing tree cover 10% or planting about three trees per building lot saves annual heating and cooling costs by an estimated 50 to 90 per dwelling unit because of increased shade, lower summertime air temperatures, and reduced neighborhood wind speeds once the trees mature. The net present value of the services trees provide is estimated as 402 per planted tree. The present value of long-term benefits is more than twice the present value of costs.     

Correlation between the geometrical characteristics of streets and morphological features of trees for the formation of tree lines in the urban design of the city of Orestiada,Greece

This paper classifies the streets of the city of Orestiada, Greece, and examines the correlation between the geometric characteristics of streets and the appropriate height of trees that form the street tree lines so that the microclimate in each street may be improved. The rows of trees improve the aesthetic quality of the urban spaces, and also strengthen the sense of enclosure through tree planting, especially in monotonous urban landscapes. Our main aim is to augment the vegetation in urban areas to achieve the greatest shading of streets in order to contribute to the improvement of the urban environment in terms of bioclimatic conditions. The methodology used in this paper aims to promote the use of trees in urban design, and to evaluate the effects of shading at the city scale with regard to microclimate and energy saving, and to develop tree selection and design guidelines for recommended planting programs. It is expected that the results of the study will be useful to Urban Planners, Urban Arboriculturists, Urban Foresters and Landscape Architects that are engaged in the design and construction of streetscapes in Mediterranean region.     

Urban forest structure,ecosystem services and change in Syracuse,NY

The tree population within the City of Syracuse was assessed using a random sampling of plots in 1999, 2001 and 2009 to determine how the population and the ecosystem services these trees provide have changed over time. Ecosystem services and values for carbon sequestration, air pollution removal and changes in building energy use were derived using the i-Tree Eco model. In addition, photo interpretation of aerial images was used to determine changes in tree cover between the mid-1990s and 2009. Between the mid-1990s and 2003, tree cover in Syracuse exhibited a decline from 27.5 to 25.9 %, but subsequently increased to 26.9 % by 2009. The total tree population exhibited a similar pattern, dropping from 881,000 trees in 1999 to 862,000 in 2001, and then increasing to 1,087,000 trees in 2009. Most of this increase in the urban tree population is due to invasive or pioneer trees species, particularly Rhamnus cathartica, which has more than tripled in population between 2001 and 2009. Insects such as gypsy moth and emerald ash borer pose a substantial risk to altering future urban forest composition. The annual ecosystem services provided by the urban forest in relation to carbon sequestration, air pollution removal and reduction in building energy use are estimated at about $2.4 million per year. An improved understanding of urban forests and how they are changing can facilitate better management plans to sustain ecosystem services and desired forest structure for future generations.     

Sustainable landscaping programs in the United States and their potential to encourage conservation and support ecosystem services

Sustainable landscaping programs are voluntary initiatives that recommend a set of practices to improve the environmental quality of urban ecosystems by providing landscaping materials, guidelines, and educational resources. Our goal was to examine the recommendations and outcomes of these programs in the United States and their value for encouraging conservation practices in residential ecosystems. We conducted a comprehensive web search and identified 193 sustainable landscaping programs in the United States. Programs aim to increase native species richness, affordably manage stormwater runoff, and offer residents meaningful experiences with nature. Sustainable landscaping programs present many opportunities to engage people with local ecological knowledge and conservation practices, provide accessible spaces for environmental education, cultivate interdisciplinary research collaborations, and advance inclusion in conservation. However, assessments of their ecological value are rare, leaving many questions surrounding the benefits to biodiversity and water quality afforded by participation. Many programs also require investments in landscaping materials and certification fees that might limit participation by some households. Future work should examine how recommended practices influence urban biodiversity, identify and address barriers to participation, and generate social-ecological knowledge that can inform future programs.

     

Modeling above-ground carbon storage: a remote sensing approach to derive individual tree species information in urban settings

Vegetation has gained importance in respective debates about climate change mitigation and adaptation in cities. Although recently developed remote sensing techniques provide necessary city-wide information, a sufficient and consistent city-wide information of relevant urban ecosystem services, such as carbon emissions offset, does not exist. This study uses city-wide, high-resolution, and remotely sensed data to derive individual tree species information and to estimate the above-ground carbon storage of urban forests in Berlin, Germany. The variance of tree biomass was estimated using allometric equations that contained different levels of detail regarding the tree species found in this study of 700 km², which had a tree canopy of 213 km². The average tree density was 65 trees/ha per unit of tree cover and a range from 10 to 40 trees/ha for densely urban land cover. City-wide estimates of the above-ground carbon storage ranged between 6.34 and 7.69 tC/ha per unit of land cover, depending on the level of tree species information used. Equations that did not use individually localized tree species information undervalued the total amount of urban forest carbon storage by up to 15 %. Equations using a generalized estimate of dominant tree species information provided rather precise city-wide carbon estimates. Concerning differences within a densely built area per unit of land cover approaches using individually localized tree species information prevented underestimation of mid-range carbon density areas (10–20 tC/ha), which were actually up to 8.4 % higher, and prevented overestimation of very low carbon density areas (0–5 tC/ha), which were actually up to 11.4 % lower. Park-like areas showed 10 to 30 tC/ha, whereas land cover of very high carbon density (40–80 tC/ha) mostly consisted of mixed peri-urban forest stands. Thus, this approach, which uses widely accessible and remotely sensed data, can help to improve the consistency of forest carbon estimates in cities.     

How to improve urban greenspace for woodland birds: site and local-scale determinants of bird species richness

Wooded habitats represent hotspots of urban biodiversity, however, urban development imposes pressure on biota in these refuges. Identification of the most influential habitat attributes and the role of local urban characteristics is crucial for proper decisions on management practices supporting biodiversity. We aimed to identify well manageable fine-scale habitat attributes to suggest specific, feasible and affordable management recommendations for green space in cities. We analysed species richness of woodland-associated bird communities and incidence of individual species at 290 sites in a wide variety of green areas scattered across the city of Prague, Czech Republic. Generalized linear mixed models (GLMM) and regression tree analyses were used to identify site-scale (100 m radius sampling sites) and local-scale (200 m and 500 m radius plots) habitat attributes shaping the bird communities at individual sites. Logistic regression was used to assess the responses of individual species to habitat characteristics. Our results imply that at the site scale, management practices should focus on maintenance and promoting species-diverse and older tree stands, with a mixture of coniferous and deciduous trees. Water-bodies and accompanying riparian habitats should be maintained and carefully managed to preserve high-quality remnants of natural vegetation. Presence of a few old trees (about 12 % of tree cover with DBH?>?50 cm) or small urban standing water and watercourses enrich the bird community by at least two species. Species richness of woodland avifauna at particular sites is further supported by the total amount of tree cover in the surroundings, including scattered greenery of public spaces and private gardens. We conclude that proper management at site scale has the potential to increase biodiversity of the urban environment.     

Determinants of urban tree canopy in residential neighborhoods: Household characteristics, urban form, and the geophysical landscape

The aesthetic, economic, and environmental benefits of urban trees are well recognized. Previous research has focused on understanding how a variety of social and environmental factors are related to urban vegetation. The aim is often to provide planners with information that will improve residential neighborhood design, or guide tree planting campaigns encouraging the cultivation of urban trees. In this paper we examine a broad range of factors we hypothesize are correlated to urban tree canopy heterogeneity in Salt Lake County, Utah. We use a multi-model inference approach to evaluate the relative contribution of these factors to observed heterogeneity in urban tree canopy cover, and discuss the implications of our analysis. An important contribution of this work is an explicit attempt to account for the confounding effect of neighborhood age in understanding the relationship between human and environmental factors, and urban tree canopy. We use regression analysis with interaction terms to assess the effects of 15 human and environmental variables on tree canopy abundance while holding neighborhood age constant. We demonstrate that neighborhood age is an influential covariate that affects how the human and environmental factors relate to the abundance of neighborhood tree canopy. For example, we demonstrate that in new neighborhoods a positive relationship exists between street density and residential tree canopy, but the relationship diminishes as the neighborhood ages. We conclude that to better understand the determinants of urban tree canopy in residential areas it is important to consider both human and environmental factors while accounting for neighborhood age.     

Photosynthetic CO<Subscript>2</Subscript> uptake and carbon sequestration potential of deciduous and evergreen tree species in an urban environment

Urban tree planting programmes are increasingly promoted as a way to reduce atmospheric carbon dioxide (CO₂) mixing ratios. However, few studies have investigated the photosynthetic CO₂ uptake potential of different urban tree species across seasons. In particular little is known about photosynthetic CO₂ uptake in cities with a subtropical, oceanic climate where evergreen species are dominant. We addressed this shortcoming by measuring net photosynthetic rates of ten native and exotic tree species during different seasons and times of the day in Auckland, New Zealand. We also assessed the potential of leaf nitrogen (N) concentration as a proxy for net photosynthetic capacities of urban trees, which is of particular importance to upscale leaf-level photosynthetic CO₂ uptake to local and regional scales. In addition, we compared measured net photosynthetic capacities (light-saturated net photosynthetic rates) with carbon (C) sequestration rates estimated using tree growth measurements and allometric equations. Mean net photosynthetic capacities ranged between 2.37 and 10.48 μmol m^?2 s^?1 across all seasons and were closely related to tree C sequestration rates, suggesting that increased photosynthesis enhances growth rates and therefore tree C sequestration rates. Given that winter net photosynthetic capacities remained high in evergreen species (3.38–13.96 μmol m^?2 s^?1), with almost 50% higher mean net photosynthetic capacity compared to summer across all species, we suggest that tree planting programmes for CO₂ mitigation should favour long living evergreen tree species with high basal area increments (BAI). Leaf N explained 43% and 57% of the variability of photosynthetic capacities across species in summer and winter, respectively. These results indicate that leaf N may be used as a proxy for net photosynthetic capacities of commonly planted urban trees in Auckland. However, further research is required to provide robust models that may be used to estimate photosynthetic CO₂ uptake at a local and urban scale.     

Habitat selection by an arboreal lizard in an urban parkland: not just any tree will do

The nocturnal, arboreal Marbled Gecko, Christinus marmoratus, is a common reptile in urban areas in southern Australia. This study compared the demographics and the distribution of geckos occupying different tree species in a modified urban park, the Adelaide Parklands, with those of a population occurring in Ferguson Conservation Park, a nearby native vegetation remnant surrounded by suburbia. The geckos in the modified urban and native remnant parks demonstrated different demographic characteristics. These differences were explained by tree circumference and the amount and type of bark cover on the tree trunk. In the Parkland, geckos were limited by the availability of thick exfoliating bark, its clearly preferred microhabitat as demonstrated by a laboratory choice experiment. The preference for trees with larger circumference, more cover, and thick bark were probably linked to thermoregulation, predator avoidance, and food resources. This study supports the premise that to support populations of urban animals, tree species selection needs careful consideration with regard to its microhabitat capabilities as well as food provision and other resource supports it can provide.     

Conflict and Conflict Resolution in Citizen Participation Programs:

Conflicts between governmental agencies and individuals are common in citizen participation programs. One source of these conflicts is barriers to full participation in decision-making. This paper identifies and examines these barriers. It also highlights how conflict may be reduced through the removal of these barriers in the case study of a community during a citizen participation program. The implications for program changes and community organizers are discussed.     

Ecosystem services from converted land: the importance of tree cover in Amazonian pastures

Deforestation is responsible for a substantial fraction of global carbon emissions and changes in surface energy budgets that affect climate. Deforestation losses include wildlife and human habitat, and myriad forest products on which rural and urban societies depend for food, fiber, fuel, fresh water, medicine, and recreation. Ecosystem services gained in the transition from forests to pasture and croplands, however, are often ignored in assessments of the impact of land cover change. The role of converted lands in tropical areas in terms of carbon uptake and storage is largely unknown. Pastures represent the fastest-growing form of converted land use in the tropics, even in some areas of rapid urban expansion. Tree biomass stored in these areas spans a broad range, depending on tree cover. Trees in pasture increase carbon storage, provide shade for cattle, and increase productivity of forage material. As a result, increasing fractional tree cover can provide benefits land managers as well as important ecosystem services such as reducing conversion pressure on forests adjacent to pastures. This study presents an estimation of fractional tree cover in pasture in a dynamic region on the verge of large-scale land use change. An appropriate sampling interval is established for similar studies, one that balances the need for independent samples of sufficient number to characterize a pasture in terms of fractional tree cover. This information represents a useful policy tool for government organizations and NGOs interested in encouraging ecosystem services on converted lands. Using high spatial resolution remotely sensed imagery, fractional tree cover in pasture is quantified for the municipality of Rio Branco, Brazil. A semivariogram and devolving spatial resolution are employed to determine the coarsest sampling interval that may be used, minimizing effects of spatial autocorrelation. The coarsest sampling interval that minimizes spatial dependence was about 22 m. The area-weighted fractional tree cover for the study area was 1.85 %, corrected for a slight bias associated with the coarser sampling resolution. The pastures sampled for fractional tree cover were divided between ‘high’ and ‘low’ tree cover, which may be the result of intentional incorporation of arboreal species in pasture. Further research involving those ranchers that have a higher fractional tree cover may indicate ways to promote the practice on a broader scale in the region.     

The role of local government bodies in European policy-making

Since the publication of the White Paper on European governance, COM (2001) 428, the Commission has stressed that ‘people increasingly distrust institutions and politics or are simply not interested in them’, registering the growing gap between the EU and European citizens. In this context, the European institutions have been promoting several initiatives with the aim of facilitating participation in the European decision-making process. The paper will focus on: (1) the relationship between local governance and participation in the European Union; in this frame, the European institutions tried to start a dialogue with local authorities (see the role of the CoR) and the actors of civil society (through both the European Economic and Social Committee and the Transparency Policy); (2) the consequences either in the theoretical field or in practice. On one hand, the initiatives carried out have created the basis for a new model of multi-level governance and ‘participative democracy’; on the other hand the demand for wider participation produces a continuous growth of lobbying by the actors of civil society, whose regulation appears rather difficult notwithstanding the important efforts made through the European Transparency Initiative.     

Faith-based evaluation: accountable to whom, for what?

Findings, issues, and lessons learned about program evaluation are examined from a national qualitative study of 15 faith-based human service programs targeting those in need in urban areas. Using a grounded theory design, five properties emerge as part of the evaluation network: (1) philosophy of accountability, (2) legitimacy, (3) evaluation design, (4) feedback loop, and (5) barriers to evaluation. While funders expect measurable outcomes to evaluate service effectiveness, respondents acknowledge other competing expectations of multiple constituents in religious and secular communities. What emerges is an excellent example of managing multiple program evaluation demands in programs that are particularly facile at process evaluation in the interest of quality service and relationship building. The article concludes with important lessons learned about the process of program evaluation.     

Participation in biodiversity conservation: Motivations and barriers of Australian landholders

Biodiversity conservation programs that appeal to landholders’ motivations and minimise their barriers to participation may result in both increased uptake rates and improved ecological outcomes. To understand their motivations and barriers to conserve biodiversity, qualitative interviews were conducted with 45 landholders who had participated in one of three different programs in Queensland, Australia. The results revealed that the landholders’ decisions to participate depended on the level of formal biodiversity protection offered by the program, potential changes to their property rights, personal benefits of participation, and the program objectives. Landholders’ motivations related to conservation, production, financial and experimental imperatives. Common barriers to participation were lost productivity, different interpretations of what constituted “conservation”, and limits to future development and land use options. Voluntary and economic policy instruments can be used to stimulate participation and overcome barriers, but must be applied with care to reduce the creation of perverse ecological outcomes, such as slippage and low additionality.     

Predicting tree species richness in urban forests

There has been an increasing interest in urban forests and the levels of biodiversity they contain. Currently there are no spatially explicit maps of tree species richness in urban areas. This research tests and identifies GIS and remote sensing metrics (climate, area, productivity, three-dimensional structure) hypothesized to be associated with species richness in native forests and identifies methods that can be applied to predict and map tree species richness in cities. We quantified tree species richness, floristic composition, and structure in 28 1-ha plots in the city of Los Angeles. Climate and remote sensing metrics from high-resolution aerial imagery (10 cm), QuickBird (60 cm), Landsat (30 m), MODIS (250 m), and airborne lidar (2 m) were collected for each plot. There were 1208 individual stems and 108 trees identified to species. Species richness ranged from 2 to 31 species per ha and averaged 17 species per ha. Tree canopy cover from QuickBird explained the highest portion of variance (54%) in tree species richness followed by NDVI from Landsat (42%). Tree species richness can be higher in residential urban forests than native forests in the United States. Spatially explicit species richness maps at 1 ha can be created and tested for cities in order to identify both hotspots and coldspots of tree species richness and changes in species richness over time.     

A small-scale response of urban bat activity to tree cover

Urban Ecosystems - Bats in urban areas depend on trees, and bat activity increases with tree cover. To effectively manage bat habitat in cities, it is important to know the distance to which tree...