Drone remote sensing in urban forest management: A case study

We applied drone remote sensing to identify relationships between key forest health indicators collected in the field and four Vegetative Indices (VI) to improve conservation management of urban forests. Key indicators of urban forest health revealed several areas of conservation concern including a majority of overstory trees in moderate to severe decline, canopy gaps, anthropogenic dumping, vines overtaking the forest canopy, and invasion by non-native plant species. We found plot-level vegetation index (VI) values of NDVI, NDRE, GNDVI, and GRVI calculated from drone imagery are significantly related to the impact of several of these ecological concerns as well as metrics of forest composition and equitability. Despite the small number of plots, too few to provide a general predictive framework, these findings indicate a substantial potential for drone remote sensing as a low-cost, efficient tool for urban forest management. We discuss how our findings can advance urban forest management and discuss challenges and opportunities for future drone VI research in urban natural areas.     

Density,diversity and richness of woody plants in urban green spaces: A case study in Chennai metropolitan city

A tree diversity inventory was carried out in urban green spaces (UGSs) of Chennai metropolitan city, India. This inventory aims to study the diversity, density and richness of trees in UGSs of Chennai. A total of one hundred 10 m × 10 m (total 1 ha) plots were laid to reveal tree diversity and richness of UGSs. Trees with ≥10 cm girths at breast height (gbh) were inventoried. We recorded 45 species in 42 genera and 21 families. Caesalpiniaceae and Fabaceae each with 6 species dominated the study area followed by Arecaceae (3). Density and stand basal area of the present study were 500 stems ha^?1 and 64.16 m², respectively. Most of the inventoried trees were native (31 species) and deciduous (28 species). Fabaceae and Caesalpiniaceae dominated the present study area in terms of stand basal area and density. The Shannon diversity index and evenness of study area were 2.79 and 0.73, respectively. The most important species and families based on species important value index (IVI) and family important value index were Albizia saman, Polyalthia longifolia and Azadirachta indica; Fabaceae, Caesalpiniaceae and Annonaceae respectively. We find Chennai's urban forest is relatively superior to many urban forests of the world in terms of stand basal area and species richness. Results emphasize the importance of enhancement of urban green spaces in Chennai metropolitan city.     

Barriers to the effective planning and management of residential encroachment within urban forest edges: A Southern Ontario,Canada case study

Studies document degradation and loss of publicly owned urban woodland area following adjacent residential development due to residential encroachment. Residential encroachment is the negative impacts of housing land uses within both rural and urban green infrastructure networks. Prevailing planning, design and management approaches in Southern Ontario municipalities in Canada indicate planning and management tools have been developed to remove and impede encroachment impacts; however, many are infrequently implemented. This lack of implementation contributes to a high prevalence and spatial area of encroachment within Southern Ontario municipal woodland edges with adjacent housing. Long interviews were conducted with the planners, landscape architects, woodland managers and bylaw enforcement staff of six Southern Ontario municipalities to determine the barriers to implementation of municipal encroachment tools. Results indicate key barriers to policy implementation that reflect a lack of awareness of, and priority placed on addressing, residential encroachment impacts, and impacts following the point of development in general. Barriers include: (1) insufficient community and municipal access to information regarding residential encroachment and their significance relative to other development impacts; (2) lack of clarity of goals by municipalities and between departments; (3) insufficient municipal leadership and commitment to limiting encroachment; (4) lack of sufficient means within municipal departments to prevent and address encroachment; and (5) ineffectual dynamics of enforcement. Recommendations for overcoming barriers to the development and implementation of effective approaches for addressing encroachment are provided.     

Variations in municipal urban forestry policies: A case study of Toronto, Canada

Urban forest conditions are driven by a range of biophysical and social factors, including urban form, socioeconomic conditions, and municipal policy. However, relatively little attention has been paid to policies, particularly those aimed at private property. The purpose of this study was to identify the types of urban tree policies that exist in the Greater Toronto Area, begin to understand why those variations may occur, and determine if such variations lead to on-the-ground differences. To address these objectives, we conducted a survey to identify policies covering the planting and removal of privately owned trees, as well as publicly owned trees along roadways in 29 municipalities. The results of the survey were then compared to census and vegetation abundance data to determine the relationship between municipal characteristics, level of policy adoption, and on-the-ground differences. We found substantial variation in the type of policies in place, with regulations addressing tree protection on private property occurring only in larger municipalities. The existence of on-the-ground differences was less clear, possibly because of the relatively recent adoption of most policies. These results highlight the need to assist smaller municipalities in developing urban forestry policies and to monitor these policies’ influence over the long term to better understand their role in shaping the urban forest.     

Effect of different personal histories on valuation for forest ecosystem services in urban areas: A case study of Mt. Rokko,Kobe, Japan

This study investigated the effect of valuators’ personal history and beliefs on valuation of ecosystem services around Mt. Rokko, which is located near Kobe, a major city in Japan. Special attention was paid to how differences in lifestyle, access to nature, and experiences during childhood influence willingness to pay (WTP) for peri-urban ecosystem conservation. The estimated values (median: 1858 JPY) were relatively higher than in previous case studies including one on the World Heritage forest in the country, but the value was not outlier of the literature. From the simple model estimation, we focused on the effect of individual differences. The full model including information of personal experience with nature revealed differences in WTP among residents. The basic characteristics of age and income were found to have a significant effect. Interestingly, it was also found that certain experiences during childhood had a significant effect on increasing WTP for ecosystem and biodiversity conservation. These findings suggest the importance of considering the diversity of valuators in ecosystem valuation studies under urbanization processes, and it also warns the extinction of experience with nature under on going urbanization for urban ecosystem conservation.     

A gradient analysis of urban landscape pattern: a case study from the Phoenix metropolitan region,Arizona, USA

Landscape Ecology - Urbanization is arguably the most dramatic form of land transformation that profoundly influences biological diversity and human life. Quantifying landscape pattern and its...     

Decision making in urban forestry by using approval voting and multicriteria approval method (case study: Zvezdarska forest,Belgrade, Serbia)

This paper deals with a common urban forestry problem: selecting the most appropriate management policy for a forest situated within a city zone. In the presented case study, we analyzed this problem within the Zvezdarska forest in Belgrade, Serbia. The decision makers that took part in the decision making process represented the two main stakeholder groups – the public and the experts. The public group is divided into three different subgroups: local residents, tourists and environmentalists. The experts group is represented by local authorities and academic experts. The procedure implemented for evaluating and selecting the most desired management policy for the case study area combines approval voting and the multicriteria approval method, two social choice theory methods suitable for decision-making in forestry. The main reason for combining these techniques is to be sure that the selected policy will be accepted as the most desired option by both the public and the experts. The results and discussions with involved decision makers clearly show that the applied procedure possesses sufficient analyticity and full transparency in the decision-making process; hence it is applicable to problems in urban forest management as well as to natural resources in general.     

The effectiveness of schools-based National Arbor Week activities in greening of urban homesteads: A case study of Grahamstown, South Africa

Arbor Day, or Week, is a well-established greening initiative worldwide, focusing on tree planting and the benefits thereof. Frequently most effort is targeted at institutions such as schools and community groups. Yet there has been limited assessment of the success of Arbor Day, or Week, activities both at the schools, or the wider dissemination in neighbouring communities and suburbs. The objective of this study was to determine the influence of school-based Arbor Week activities on learners’ home-based practices regarding tree planting and urban forestry. Learners from three schools in Grahamstown South Africa, with good Arbor Week participation, were assessed on their tree planting knowledge. The learners’ parents were also interviewed to determine whether the information obtained by the learners at school was taken home. A control group consisting of people with no children or very young children was also assessed. This study found that Arbor Week activities were, for the most part, successfully taught in the case study schools, and most of the learners stated that their knowledge of trees and their benefits came from their school activities. However, many learners could not remember the activities in which their schools partook the previous year. Whilst most learners were aware of the importance of trees, few had encouraged tree planting at home. However, over one-fifth of adults claimed that their knowledge of the benefits of trees was as a consequence of Arbor Day activities when they were young. Numerous constraints to tree planting were provided by learners and both the adult groups, the two most frequent being limited space and falling leaves making their yards untidy. External organisations should become more actively involved and provide much needed support systems if greening initiatives are to reach the wider community.     

A method for locating potential tree-planting sites in urban areas: A case study of Los Angeles, USA

A GIS-based method for locating potential tree-planting sites based on land cover data is introduced. Criteria were developed to identify locations that are spatially available for potential tree planting based on land cover, sufficient distance from impervious surfaces, a minimum amount of pervious surface, and no crown overlap with other trees. In an ArcGIS environment, a computer program was developed to iteratively search, test, and locate potential tree-planting sites by virtually planting large, medium and small trees on plantable areas, with large trees given priority as more benefits are expected to accrue to them. A study in Los Angeles, USA found 2.2 million potential planting sites, approximately 109.3 km² of potential tree canopy cover.     

Pond area and distance from continuous forests affect amphibian egg distributions in urban green spaces: A case study in Sapporo,Japan

We examined factors that affect egg distributions of amphibians, which are currently declining globally, in urban areas. We counted the number of egg masses of two amphibian species (Hynobius retardatus and Rana pirica) in ponds in urban green spaces during two years (2011 and 2012) and investigated the effects of local and landscape factors on them. Forest area in green spaces and pond area had positive effects, and distance from continuous forests in the suburbs and the rate of pond shore protection had negative effects on the number of eggs. Among these factors, distance from continuous forests and pond area had strong effects on egg distributions. These results suggest the importance of water habitat size and the need for colonization by amphibians from surrounding continuous forests. To conserve urban amphibian assemblages, the preservation of ponds with sufficient area and continuous forests close to urban habitats would be important.     

Stress-resistant trees are more common in urban than rural forests: A case study of Cleveland,Ohio’s natural parks

Natural parks are comprised of preserved forested natural areas that are undergoing natural ecological processes. These areas can offer a refuge for local biodiversity and contribute substantially to ecosystem services in both rural areas with relatively low population densities, as well as high-density urban areas. Forested natural parks located in urban areas should experience more stressful environmental conditions than nearby rural areas, yet we know relatively little about how urbanization impacts tree communities within these important natural habitats. To better understand the impact of urbanization on forests, we investigated the species composition, abundance, and diversity of midstory and canopy trees as well as tree seedlings in urban and rural natural parks in and around Cleveland, Ohio. We found that both urban and rural natural parks have similar tree abundance, but midstory and canopy trees as well as tree seedling communities in the urban natural parks included higher abundances of stress-tolerant species compared to rural parks. In addition, this pattern was driven by changes in native tree species, as we observed low abundance of invasive species. More stress-resistant native species in urban areas include Quercus rubra and Prunus serotina, in contrast to rural natural parks which are dominated by Acer spp. and Fagus grandifolia. Lastly, we show that urban and rural natural parks have similar species diversity within plots, but we found higher variation in community composition among urban natural parks compared to among rural parks. Furthermore, Q. rubra and P. serotina were significantly larger in rural natural parks, indicating that both environmental stress and successional stage could drive compositional differences. Thus, we show that urbanization can have unexpected effects on plant community composition and diversity. Our study refutes the idea that these are degraded habitats, highlights the need to conserve them, and suggests that characterization of local variation in self-assembled urban tree communities will provide the most accurate picture of their management needs and potential ecosystem services.     

Refining the accessibility evaluation of urban green spaces with multiple sources of mobility data: A case study in Shenzhen,China

Urban green space (UGS) is an important component of urban resources which contributes to human physical and mental health. Studies on the accessibility of UGS under the two-step floating catchment (2SFCA) framework have recently received much attention. However, the effects of people’s actual mobility patterns have not been fully considered in current studies. Proposed in this study is an improved accessibility model called AM-Ga2SFCA, which refines the traditional Gaussian 2SFCA method with the actual mobility information extracted from mobile phone big data and online map. A new attractiveness index of UGS is implemented by combining the popularity evaluated by the PageRank algorithm and the actual utilisation based on buffer analysis. In addition, realistic travel time between each demand point and UGS is retrieved from the online map, which is further introduced into AM-Ga2SFCA as the travel cost. A case study is conducted in Shenzhen, China to validate the proposed model. Results show that the accessibility of UGS is strongly correlated with regional urbanization level, for example, higher accessibility generally occurred in the region with developed transportation and rich green resources. From the perspective of age groups and travel modes, we found that the environmental justice issue had already occurred in Shenzhen especially for the non-elderly: under the walk mode, nearly 80% of the non-elderly only shared 20% of UGS whilst approximately 80% of the elderly shared 30% of UGS. However, taxi or private vehicles can effectively alleviate the aforementioned phenomenon by reducing the Gini index to less than 0.5. The proposed model is expected to advance the understanding of UGS accessibility and facilitate effective planning to reduce environmental justice.     

Adapting and applying evidence gathering techniques for planning and investment in street trees: A case study from Brisbane,Australia

Trees along footpath zones (or verges) grow on the “front-line” of urban forest ecosystems, increasingly recognised as essential to the quality of human life in cities. Growing so close to where residents live, work and travel, these street trees require careful planning and active management in order to balance their benefits against risks, liabilities, impacts and costs. Securing support and investment for urban trees is tough and robust business cases begin with accurate information about the resource. Few studies have accounted for spatial heterogeneity within a single land-use type in analyses of structure and composition of street tree populations. Remotely sensed footpath tree canopy cover data was used as a basis for stratification of random sampling across residential suburbs in the study area of Brisbane, Australia. Analysis of field survey data collected in 2010 from 80 representative sample sites in 52 suburbs revealed street tree population (432,445 ± 26,293) and stocking level (78%) estimates with low (6.08%) sampling error. Results also suggest that this population was transitioning to low risk, small-medium sized species with unproven longevity that could limit the capacity of the Brisbane’s Neighbourhood Shadeways planting program to expand from 35% footpath tree canopy cover in 2010, to a target of a 50% by 2031. This study advances the use of contemporary techniques for sampling extensive, unevenly distributed urban tree populations and the value of accurate resource knowledge to inform evidence-based planning and investment for urban forests.