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Modeling urban distributions of host trees for invasive forest insects in the eastern and central USA: A three-step approach using field inventory data

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... Primarily, our analysis focuses on street trees, which are a subset of all urban trees that possess the richest data and most consistent management across communities (Box 1). Our fitting set (used as the basis for street tree distribution extrapolation) consisted of 653 street tree databases for US communities where street tree inventory data had been collected ( Figure S3, Koch et al., 2018). In two communities (Tinley Park and, IL and Fort Wayne, IN), preventive cutting for EAB was conducted prior to the most recent inventory and was therefore accounted for within our dataset. ...
... We modelled the total abundance of street trees in a community using boosted regression trees (BRT, gbm.step within R package dismo, Hijmans et al., 2017, Appendix S1) relating the logarithmically scaled total tree abundance within a DBH class to communityspecific predictors, employing environmental variables from WORLDCLIM (Fick & Hijmans, 2017) and community characteristics used in Koch et al. (2018), which were sourced largely from the National Land Cover Database (NLCD, Homer et al., 2015), the US Census and the American Community Survey (https://www.census. ...
... While previous analyses have indicated that urban trees are associated with the largest share of economic damages due to IAFIs (Aukema et al., 2011;Kovacs et al., 2010;Paap et al., 2017), until recently, data did not exist on the urban distribution of host trees (Koch et al., 2018), the spread of IAFIs (Hudgins et al., 2017(Hudgins et al., , 2020 or the mortality risk for hosts due to different IAFIs (Potter et al., 2019). With these new models, it is now possible to forecast where and when IAFIs will have the most damages across the US. ...
Article
Urban trees are important nature‐based solutions for future well‐being and liveability but are at high risk of mortality from insect pests. In the United States (US), 82% of the population live in urban settings and this number is growing, making urban tree mortality a matter of concern for most of its population. Until now, the magnitudes and spatial distributions of risks were unknown. Here, we combine new models of street tree populations in ~30,000 US communities, species‐specific spread predictions for 57 invasive insect species and estimates of tree death due to insect exposure for 48 host tree genera. We estimate that 1.4 million street trees will be killed by invasive insects from 2020 through 2050, costing an annualized average of US$ 30 M. However, these estimates hide substantial variation: 23% of urban centres will experience 95% of all insect‐induced mortality. Furthermore, 90% of all mortality will be due to emerald ash borer (Agrilus planipennis, EAB), which is expected to kill virtually all ash trees (Fraxinus spp.) in >6,000 communities. We define an EAB high‐impact zone spanning 902,500 km2, largely within the southern and central US, within which we predict the death of 98.8% of all ash trees. ‘Mortality hotspot cities’ include Milwaukee, WI; Chicago, IL; and New York, NY. We identify Asian wood borers of maple and oak trees as the highest risk future invaders, where a new establishment could cost US$ 4.9B over 30 years. Policy implications. To plan effective mitigation, forest pest managers must know which tree species in which communities will be at the greatest risk, as well as the highest risk species. We provide the first country‐wide, spatial forecast of urban tree mortality due to invasive insect pests. This framework identifies dominant pest insects and spatial impact hotspots, which can provide the basis for spatial prioritization of spread control efforts such as quarantines and biological control release sites. Our results highlight the need for emerald ash borer (EAB) early‐detection efforts as far from current infestations as Seattle, WA. Furthermore, these findings produce a list of biotic and spatiotemporal risk factors for future high‐impact US urban forest insect pests. To plan effective mitigation, forest pest managers must know which tree species in which communities will be at the greatest risk, as well as the highest‐risk species. We provide the first country‐wide, spatial forecast of urban tree mortality due to invasive insect pests. This framework identifies dominant pest insects and spatial impact hotspots, which can provide the basis for spatial prioritization of spread control efforts such as quarantines and biological control release sites. Our results highlight the need for emerald ash borer (EAB) early‐detection efforts as far from current infestations as Seattle, WA. Furthermore, these findings produce a list of biotic and spatiotemporal risk factors for future high‐impact US urban forest insect pests.
... This accords well with the widely-recognized importance of propagule pressure as a driver of biological invasions (Simberloff 2009). The availability and density of urban forests, which were not directly measured here but could be correlated with human population density, may play a more important role than our findings suggest (Colunga-Garcia et al. 2009Koch et al. 2018;Branco et al. 2019). ...
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The geographical distributions of non-native forest insects and pathogens (pests) result from a multitude of interacting abiotic and biotic factors. Following arrival, the presence of suitable host trees and environmental conditions are required for pests to establish and spread, but the role of forest biodiversity in this process is not well-understood. We analyzed county-level data for 22 non-native forest pests in the conterminous United States, developing species-specific models to investigate the effects of spatial contagion, human activities, and host and non-host tree biomass or richness on the occurrence of pest species. Species-specific models indicated that (i) the spatial contagion of invasions was the most common driver of invasion incidence, (ii) facilitation effects from host biomass and richness were present in approximately half of the invasions and almost entirely observed in invasions by sap-feeding insects or pathogens, and (iii) there was substantial variation in the direction and magnitude of the effects of non-host tree biomass and richness on invasion. Our analyses highlighted the prominent role of spatially derived propagule pressure in driving intracontinental invasions whereas effects of forest biodiversity were variable and precluded broad generalizations about facilitation and dilution effects as drivers of forest pest invasions at large spatial scales.
... Many previous studies have utilized tree inventory data to analyze the structure of municipally managed tree populations at specific points in time, both for an individual municipality (Richards 1983;Maco and McPherson 2003;Yang et al. 2012) and for groupings of multiple municipalities (Thomsen et al. 2016;Koch et al. 2018;Cowett and Bassuk 2020). Less common are studies that have utilized tree inventory data collected at multiple points in time to evaluate the change in the structure of these tree populations. ...
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Municipally managed urban trees provide environmental, social, and economic benefits. Continued provision of these benefits depends on the health and sustainability of these trees, which depends in turn on tree managers having the type of information usually found in a tree inventory. The city of Ithaca, New York, USA possesses 7 inventories of its street and park trees dating back to 1902. This paper uses the data contained in these inventories to assess the health and sustainability of the city’s street and park tree populations. Attention is given to the structure of these populations with emphasis placed on species and genera diversity and DBH size class distributions. Prior to 1987, the city’s municipal tree population was dominated by a few species, such as Norway maple (Acer platanoides), and genera such as maples (Acer) and elms (Ulmus), and the DBH size class distribution was skewed unsustainably towards older trees. From 1987 onwards, new plantings have significantly increased species and genera diversity, and the DBH size class distribution suggests sufficient younger trees to account for tree mortality and removals. These changes did not occur quickly due to the persistent legacy effect of past planting preferences and practices, but required a consistent effort by municipal tree managers over many years. As a result, based on an analysis of the most recent tree inventory conducted in 2019, the city’s street and park trees and the benefits they provide look to be on a more sustainable footing, although challenges still remain.
... Economic impact was featured eight times and the social aspect four times, while only one article referred to the cultural values of urban trees. Only five studies involved joint initiation with private actors [58,59,[76][77][78], which mirrors the fact that only eight studies [21,46,48,58,76,[79][80][81] included private tree owners. ...
Article
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Urban trees provide important ecosystem services, across ownership and governance structures, and tree inventories are an important tool enabling urban foresters and green space managers to monitor and perform the sustainable management of urban trees. For optimal management of urban trees, a better understanding is needed concerning how urban tree inventories can provide long-term monitoring overviews across administrative borders, and how inventory protocols should be adapted to address specific practitioner issues. In this review, 98 articles on urban tree inventories were examined, the primary focus being sampling design. A governance arrangement approach was applied to identify the policy-making arrangements behind the inventories. Stratification is commonly used in the sampling design, despite being problematic for long-term representativeness. Only 10% of the stratification sampling designs identified were considered as having long-term validity. The studies frequently relied on an individual sampling design aimed at a particular issue, as opposed to using an existing longitudinal sampling network. Although private trees can constitute over 50% of the urban tree population, 41% of the studies reviewed did not include private trees at all. Urban tree inventories focused primarily on tree data on a local scale. Users or private tree owners are commonly not included in these studies, and limited attention is paid to economic, cultural or social factors. A long-term validation of sampling methods in urban areas, and a multi-lateral approach to tree inventories, are needed to maintain long-term operational value for local managers in securing ecosystem service provisions for entire urban forests.
... However, its modelling is limited due to their variability in severity and extent (Dietze and Matthes 2014). In the context of urban trees, Koch et al. (2018) recently modeled urban distributions of host trees for invasive forest insects using field inventory data. However, studies at stand or landscape level are much more numerous. ...
... The finding that non-ash tree density facilitates spread may be attributable to preference of beetles to disperse into or across forested areas and/or increased risk of firewood movement between forested areas (e.g. campground to campground movement (Koch, Ambrose, Yemshanov, Wiseman, & Cowett, 2018), and future forecasts of EAB dynamics and other pests will likely be improved by their consideration. We note, however, that proximity to invaded areas is the main driver of this invasion (Table 1), and thus, despite the absence of rural ash, some counties in Colorado are at relatively high risk ( Figure 5). ...
Article
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Non‐native insects pose threats to forest health and often spread via stratified dispersal in which long‐distance jumps cause elevated rates of range expansion. Quantifying patterns and developing models of spread is central to understanding drivers of invasion and forecasting future invasions. We investigated the utility of models for characterizing and predicting spread of emerald ash borer (EAB), quantified temporal dynamics of spread, and identified correlates of county‐level invasion risk. We estimated rates and frequency of EAB spread and length of long‐distance jumps throughout the contiguous USA from 1997‐2018 and compared observed patterns with model predictions. A time‐to‐event model was then developed at the county‐level to assess the influence of habitat characteristics and propagule pressure on invasion risk. The final model was used to forecast invasion risk across the contiguous USA. Range expansion by EAB accorded well with model predictions. Following the initial establishment phase, range expansion rates were biphasic, shifting to a faster, linear pattern around 2002 and then declining from 2015 onwards. From 2003 onwards, EAB invaded 6 – 134 new counties per year, including a mean of 14 discrete jumps per year averaging 93 ± 7 SE km. Risk of spread was positively associated with proximity to previously invaded areas, human population density, and densities of ash and non‐ash forest trees but negatively associated with temperature. Synthesis and applications At the regional level, the invasion by emerald ash borer (EAB) appears to be entering the saturation phase, indicating that most high‐risk counties in the eastern USA have been invaded. Even though spread has recently slowed, counties in close proximity to invaded areas and that have high densities of humans and trees are at the greatest risk of becoming invaded. Taken together, our findings provide insight into historical and future dynamics of range expansion by EAB, which can be used to guide risk assessments for potential invaders capable of frequent long‐distance dispersal.
... In most cases, however, data are only available for street trees, whereas other urban trees (e.g., those in private backyards) are harder to identify because of limited accessibility (Nielsen et al. 2014). One solution here is to use regression models to extrapolate the general tree composition of an urban landscape based on street tree inventory data and geography (Koch et al. 2018). Despite the increasing research effort on automated tree identification techniques, their application is still limited, and few inventory data are available at the different relevant scales with sufficient coverage to constitute relevant FIAS DSS data input (Fig. 1). ...
Article
Biological invasions represent an increasing threat to ecosystems worldwide, with negative ecological and socio-economic impacts, while risk assessment and management remain challenging. The development of decision support systems (DSS) has the potential to help decision makers and managers mitigate invasive species, but few DSS exist for forest invasive alien species (FIAS). The use of DSS in forestry is not new but they represent an asset in decision making in times of increasing complexity of issues foresters have to face and factors they have to consider. Yet, few forest DSS address the problem of FIAS. In this review, we identify key elements of the FIAS risk assessment and management decision-making process, discuss these elements with a model-based DSS development perspective, and summarize outstanding challenges and opportunities for FIAS DSS development. FIAS DSS should not only estimate the probability of FIAS invasion but also consider forest vulnerability and quantify exposure (i.e., value at risk), while allowing different threat scenarios and possible solutions to be compared. Such a complete risk assessment and management calls for integrative modelling approaches that explicitly link different components of FIAS invasion, management and impact assessment into a DSS. Such integrative modelling is challenging and may require collaboration between experts of different domains. International collaboration is also needed to facilitate data exchange, as the lack of data appears as one of the main challenges here. In many cases, data and ecological knowledge of invasive species are too limited (in quantity or quality) to constitute useful input to DSS or their components (e.g., species distribution model). Another challenge is to better consider the multiple sources of uncertainties inherent to modelling invasions (e.g., host preferences and behavior, forest vulnerability, potential impacts and cost and benefits of mitigation actions) when assessing FIAS risk and communicating results from risk assessment. Communication with stakeholders and DSS end-users, in fact, appears as one of the keys to successful DSS development and appropriation, not only to ensure that they correspond to end-users’ needs but also to ensure ease of use, functionality and good visualization of DSS outputs.
... For each infested tree, we estimated the distance to the group of trees with the oldest recorded infestation. We also identified the locations of other non-infested ash trees from municipal tree inventories [57,58] and urban tree data for St. Paul used in Koch et al. [59]. We divided the area into a grid of 1×1 km sites, and for each site, estimated the proportion of infested ash trees. ...
Article
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Detections of invasive species outbreaks are often followed by the removal of susceptible host organisms in order to slow the spread of the invading pest population. We propose the acceptance sampling approach for detection and optional removal of susceptible host trees to manage an outbreak of the emerald ash borer (EAB), a highly destructive forest pest, in Winnipeg, Canada. We compare the strategy with two common delimiting survey techniques that do not consider follow-up management actions such as host removal. Our results show that the management objective influences the survey strategy. The survey-only strategies maximized the capacity to detect new infestations and prioritized sites with high likelihood of being invaded. Comparatively, the surveys with subsequent host removal actions allocated most of the budget to sites where complete host removal would minimize the pest's ability to spread to uninvaded locations. Uncertainty about the pest's spread causes the host removal measures to cover a larger area in a uniform spatial pattern and extend to farther distances from already infested sites. If a decision maker is ambiguity-averse and strives to avoid the worst-case damages from the invasion, the optimal strategy is to survey more sites with high host densities and remove trees from sites at farther distances, where EAB arrivals may be uncertain, but could cause significant damage if not detected quickly. Accounting for the uncertainty about spread helps develop a more robust pest management strategy. The approach is generalizable and can support management programs for new pest incursions.
... For each infested tree, we estimated the distance from the tree to the known centre of the Twin Cities infestation, which was assumed to be the group of trees with the oldest infestations. We estimated the locations of other non-infested ash trees from municipal tree inventories (City of Minneapolis, 2017;TreeKeeper, 2018) and an urban tree database for St. Paul (used in Koch et al., 2018). We then divided the known-infested area into a grid of 1 × 1 km sites, and for each site, counted the number of infested and uninfested ash trees. ...
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We develop an acceptance sampling approach for surveillance of the emerald ash borer (EAB), a harmful forest pest, in Winnipeg, Canada. We compare sampling strategies computed with two different management objectives. The first objective maximizes the expected area with detected infestations and the second objective minimizes the expected number of undetected infested trees in sites that were not inspected or where inspection did not find an infestation. The choice of the management objective influences the survey strategy: achieving the first objective involves selecting sites with high infestation rates proximal to the infested area, whereas the second objective requires inspecting sites with both high infestation rates and high host densities. Adding uncertainty prescribes inspecting a larger area with lower sampling rates and extending the surveys to farther distances from the infested locations. If a decision maker wants to minimize the worst-case damage from failed detections, the optimal strategy is to survey more sites with high host densities at farther distances, where EAB arrivals could cause significant damage if not detected quickly. Accounting for the uncertainty addresses possible variation in infestation rates and helps develop a more diversified survey strategy. The approach is generalizable and can support survey programmes for new pest incursions.
... For each infested tree, we estimated the distance from the tree to the known centre of the Twin Cities infestation, which was assumed to be the group of trees with the oldest infestations. We estimated the locations of other non-infested ash trees from municipal tree inventories (City of Minneapolis, 2017;TreeKeeper, 2018) and an urban tree database for St. Paul (used in Koch et al., 2018). We then divided the known-infested area into a grid of 1 × 1 km sites, and for each site, counted the number of infested and uninfested ash trees. ...
Article
Full-text available
We develop an acceptance sampling approach for surveillance of the emerald ash borer (EAB), a harmful forest pest, in Winnipeg, Canada. We compare sampling strategies computed with two different management objectives. The first objective maximizes the expected area with detected infestations and the second objective minimizes the expected number of undetected infested trees in sites that were not inspected or where inspection did not find an infestation. The choice of the management objective influences the survey strategy: achieving the first objective involves selecting sites with high infestation rates proximal to the infested area, whereas the second objective requires inspecting sites with both high infestation rates and high host densities. Adding uncertainty prescribes inspecting a larger area with lower sampling rates and extending the surveys to farther distances from the infested locations. If a decision maker wants to minimize the worst-case damage from failed detections, the optimal strategy is to survey more sites with high host densities at farther distances, where EAB arrivals could cause significant damage if not detected quickly. Accounting for the uncertainty addresses possible variation in infestation rates and helps develop a more diversified survey strategy. The approach is generalizable and can support survey programmes for new pest incursions.
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Environmental quality and the citizens' well-being largely depend on the urban forests. But managing this natural capital is challenging for its biological complexity and interactions with other environmental, social, and economic aspects of the cities. In line with the current digital revolution with the rise of Smart Cities, the use of Artificial Intelligence (AI) is becoming more common, including in urban forestry. In this systematic review, we evaluated 67 studies on the interplay between AI and urban forestry surveyed on Science Direct and Scopus to provide an overview of the state of the art and identify new research avenues. The sample includes studies in 23 countries and 85 cities, including 5 megacities, comprising the remote assessment of canopy cover and species distribution; ecosystem services assessment; management practices; and socioeconomic aspects of urban forestry. Most studies focused on extant urban forests, with few examples evaluating temporal trends, and only one focused on future scenarios despite the predictive potential of AI. A total of 22 AI methods were employed in these studies. Only half of them point to clear advantages of the chosen methods, such as robustness against missing data, overfitting, collinearity, non-linearity, non-normality, the combination of discrete and continuous variables, and higher accuracy. The choice of these methods depends on the various combinations of aim, timescale, data type, and data source. The application of AI in urban forestry is in full growth and will support decision making to improve livability in the cities.
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1. Multi-day survey campaigns are critical for timely detection of biological invasions. We propose a new modelling approach that helps allocate survey inspections in a multi-day campaign aimed at detecting the presence of an invasive organism. 2. We adopt a team orienteering problem to plan daily inspections and use an acceptance sampling approach to find an optimal surveillance strategy for emerald ash borer in Winnipeg, Manitoba, Canada. The manager's problem is to select daily routes and determine the optimal number of host trees to inspect with a particular inspection method in each survey location, subject to upper bounds on the survey budget, daily inspection time, and total survey time span. 3. We compare optimal survey strategies computed with two different management objectives. The first problem minimizes the expected number of survey sites (or area) with undetected infestations. The second problem minimizes slippage-the expected number of undetected infested trees in sites that were not surveyed or where the surveys did not find infestation. 4. We also explore the impact of uncertainty about site infestation rates and detection probabilities on the surveillance strategy. Accounting for uncertainty helps address temporal and spatial variation in infestation rates and yields a more robust surveillance strategy. The approach is generalizable and can support delimiting survey programs for biological invasions at various spatial scales.
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Street tree diversity is widely viewed as a key component in the resilience of street tree populations to pests, diseases, and climate change. Assessment of street tree diversity is considered integral to sustainable street tree management and preservation of the ecosystem services and social benefits that street trees provide. This paper assesses street tree diversity in three northeastern U.S. states-New Jersey, New York, and Pennsylvania-by analyzing municipal street tree inventory data stratified by the 2012 USDA Plant Hardi-ness Zones. Despite the lesson learned from the historical devastation of overplanted American elms (Ulmus americana) by Dutch elm disease, and awareness of the contemporary threats posed to ashes (Fraxinus spp.) by the emerald ash borer (Agrilus planipennis) and to maples (Acer spp.), and other tree genera by the Asian longhorned beetle (Anoplophora glabripennis), results presented here indicate a current concentration of street trees among a relatively small number of species and genera, and in particular the dominance of maples as street trees. Results also show a positive relationship between street tree diversity and warmer average minimum winter temperatures. Consequently, there is a clear need in all three states for greater species and genus diversity in statewide and municipal street tree populations. However, meaningful impediments exist to increasing street tree diversity, especially in the short term.
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Urban forest monitoring data are essential to assess the impacts of tree planting campaigns and management programs. Local practitioners have monitoring projects that have not been well documented in the urban forestry literature. To learn more about practitioner-driven monitoring efforts, the authors surveyed 32 local urban forestry organizations across the United States about the goals, challenges, methods, and uses of their monitoring programs, using an e-mailed questionnaire. Non-profit organizations, municipal agencies, state agencies, and utilities participated. One-half of the organizations had six or fewer urban forestry staff. Common goals for monitoring included evaluating the success of tree planting and management, taking a proactive approach towards tree care, and engaging communities. The most commonly recorded data were species, condition rating, mortality status, and diameter at breast height. Challenges included limited staff and funding, difficulties with data management and technology, and field crew training. Programs used monitoring results to inform tree planting and maintenance practices, provide feedback to individuals responsible for tree care, and manage tree risk. Participants emphasized the importance of planning ahead: carefully considering what data to collect, setting clear goals, developing an appropriate database, and planning for funding and staff time. To improve the quality and consistency of monitoring data across cities, researchers can develop standardized protocols and be responsive to practitioner needs and organizational capacities.
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With a growing number of urban tree inventory methods and diversifying use of tree inventory data by city authorities and researchers, there is a need to evaluate, review, and critically assess the inventory methods available. This study reviewed studies using urban tree inventories at single-tree level as their data source. Based on this, a bibliographic overview was established and a typology of contemporary urban tree inventory methods was created and used as a framework for evaluation and discussion of the measurement type and accuracy achievable with different methods. The authors found that data from urban tree inventories are currently being employed in research with an increasing number of focuses across a geographical scope that spans all continents except Africa. Four main types of urban tree inventories were distinguished: satellite-supported methods, airplane-supported methods, on-the-ground scanning or digital photography, and field surveys. Compiling results across studies and evaluating the parameters collected by these inventory methods and their accuracy of measurement revealed that the technology itself and current data processing methods limit the reliability of the data obtained from all methods except field surveys. The study authors recommend further technological development and scientific testing before these methods can replace field surveys.
Book
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This is the first book on the history of trees in Britain’s towns and cities and the people who have planted and cared for them. It is a highly readable and authoritative account of the trees in our urban landscapes from the Romans to the present day, including public parks, private gardens, streets, cemeteries and many other open spaces. It charts how our appreciation of urban trees and woodland has evolved into our modern understanding of the many environmental, economic and social benefits of our urban forests. A description is also given of the various threats to these trees over the centuries, such as pollution damage during the Industrial Revolution and the recent ravages of Dutch elm disease. Central and local government initiatives are examined together with the contribution of civic and amenity societies. However, this historical account is not just a catalogue of significant events but gives a deeper analysis by exploring fundamental issues such as who owned those treed landscapes, why they were created and who had access to them. The book concludes with the fascinating story of how trees have contributed to efforts to improve urban conditions through various ‘visions of urban green’ such as the model villages, garden cities, garden suburbs and the new towns. Studies in garden and landscape history have often been preoccupied with those belonging to the rich and powerful. This book focuses particularly on working people and the extent to which they have been able to enjoy urban trees and greenspace. It will appeal to a general readership, especially those with an interest in garden history, heritage landscapes and the natural and built environment. Its meticulous referencing will also ensure it is much appreciated by students and academics pursuing further reading and research.
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A visually apparent but scientifically untested outcome of land-use change is homogenization across urban areas, where neighborhoods in different parts of the country have similar patterns of roads, residential lots, commercial areas, and aquatic features. We hypothesize that this homogenization extends to ecological structure and also to ecosystem functions such as carbon dynamics and microclimate, with continental-scale implications. Further, we suggest that understanding urban homogenization will provide the basis for understanding the impacts of urban land-use change from local to continental scales. Here, we show how multi-scale, multi-disciplinary datasets from six metropolitan areas that cover the major climatic regions of the US (Phoenix, AZ; Miami, FL; Baltimore, MD; Boston, MA; Minneapolis-St Paul, MN; and Los Angeles, CA) can be used to determine how household and neighborhood characteristics correlate with land-management practices, land-cover composition, and landscape structure and ecosystem functions at local, regional, and continental scales.
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We developed a neural network based approach to identify urban tree species at the individual tree level from lidar and hyperspectral imagery. This approach is capable of modeling the characteristics of multiple spectral signatures within each species using an internally unsupervised engine, and is able to catch spectral differences between species using an externally supervised system. To generate a species-level map for an urban forest with high spatial heterogeneity and species diversity, we conducted a treetop-based species identification. This can avoid the problems of double-sided illumination, shadow, and mixed pixels, encountered in the crown-based species classification. The study indicates lidar data in conjunction with hyperspectral imagery are not only capable of detecting individual trees and estimating their tree metrics, but also identifying their species types using the developed algorithm. The integration of these two data sources has great potential to take the place of traditional field surveys.
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The rapid urbanization of the world has significant ecological consequences that shape global biodiversity patterns. The plant communities now common in urban centers may represent new habitats with unique dynamics and the potential for highly modified ecological services. This study, joining extensive spatial and floristic data sets, examined current distribution patterns of non-native and native woody plant species in the New York metropolitan region, USA. We joined the New York Metropolitan Flora (NYMF) database of woody species with GIS data of urban land cover for 297 5 km by 5 km landscape blocks. We tested the relationship between urbanization and native and non-native species richness patterns, the extent of non-native species presence in the urban area, and the change in beta diversity across a gradient of urban land cover. We found that across the urban–rural gradient, native plant species richness decreased and non-native species richness increased with increasing urban land cover. Total richness does not change across the urban–rural gradient. Our analyses show that these patterns are highly correlated with urbanization, but vary across the New Jersey landscape. We also found an increase in beta diversity with urbanization; urban areas are not homogenized in plant species composition compared to rural areas. Here we show a species-rich flora dominated by non-native species which are differentiating the urban flora. These results can help guide appropriate conservation decisions for the maintenance of plant biodiversity in cities.
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AimGeographical variation in numbers of established non-native species provides clues to the underlying processes driving biological invasions. Specifically, this variation reflects landscape characteristics that drive non-native species arrival, establishment and spread. Here, we investigate spatial variation in damaging non-native forest insect and pathogen species to draw inferences about the dominant processes influencing their arrival, establishment and spread. LocationThe continental USA, including Alaska (Hawaii not included). Methods We assembled the current geographical ranges (county-level) of 79 species of damaging non-indigenous forest insect and pathogen species currently established in the continental USA. We explored statistical associations of numbers of species per county with habitat characteristics associated with propagule pressure and with variables reflecting habitat invasibility. We also analysed relationships between the geographical area occupied by each pest species and the time since introduction and habitat characteristics. ResultsThe geographical pattern of non-native forest pest species richness is highly focused, with vastly more species in the north-eastern USA. Geographical variation in species richness is associated with habitat factors related to both propagule pressure and invasibility. Ranges of the non-native species are related to historical spread; range areas are strongly correlated with time since establishment. The average (all species) radial rate of range expansion is 5.2 km yr−1, and surprisingly, this rate did not differ among foliage feeders, sap-feeders, wood borers and plant pathogens. Main conclusionsForest pest species are much more concentrated in the north-eastern region of the USA compared with other parts of the country. This pattern most likely reflects the combined effects of propagule pressure (pest arrival), habitat invasibility (pest establishment) and invasion spread. The similarity in historical spread among different types of organisms indicates the importance of anthropogenic movement in spread.
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While we know that urban vegetation is often distributed unequally, most studies have been undertaken in cities with relatively high levels of income inequality, using a single measure of distribution (usually tree cover) and in a single land use. This study explores predictors of both tree cover and species richness in gardens, streetscapes and parks in Ballarat, Australia. Spatial regression models found that education level was a more important predictor of tree cover than household income across all land uses in Ballarat which can be explained by some people with high incomes relative to education level choosing to live in new residential developments with disproportionately low levels of tree cover. Inequality in tree cover was greater in streetscapes than in residential gardens, suggesting that ‘top down’ political factors are more important than individual behaviours in determining tree cover in Ballarat. In contrast, physical rather than socioeconomic factors were better predictors of species richness across all land uses, highlighting that different measures of vegetation distribution are not necessarily correlated.
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The U.S. Department of Agriculture, Forest Service (USFS), together with state partners, developed methods to monitor urban forest structure, function, and health at a large statewide scale. Pilot studies have been established in five states using protocols based on USFS Forest Inventory and Analysis and Forest Health Monitoring program data collection standards. Variables and data analysis are described. Advantages of a large-scale monitoring study are discussed and examples of results from Wisconsin are presented. Studies in Indiana, Wisconsin, New Jersey, Tennessee, and Colorado, U.S., have shown that urban forest health monitoring data collection and analysis is feasible and can be implemented nationally.
Article
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Currently, slightly less than half the world's population lives in dense urban areas, principally cities. In Australia, nearly 85% of people live in towns with 1000 or more residents. Although individual species of urban flora and fauna have often been well studied, little is known of the long-term temporal patterns associated with changes in both the abiotic and biotic environments as urban systems expand. Using historical and current information, the changes in species richness (defined as the native and introduced vertebrates and vascular plants) in Adelaide, South Australia, are described from its founding in 1836 until 2002. Adelaide is an isolated city of over a million inhabitants, bordered by a range of hills and the South Australian coastline. With a Mediterranean climate, a culture that places high importance on private residential gardens, and the presence of extensive public parklands, the metropolitan area has a significant diversity of both native and introduced flora and fauna. Using only the presence or absence of a species, the changes to plant and vertebrate species richness were quantified by analyzing the observed patterns of change at a functional group level. Powerful correlative evidence is provided to explain the de- velopment and establishment of patterns in urban ecology. There has been a dramatic change in species composition, with an increase in total species numbers of ;30%. At least 132 native species of plants and animals have become locally extinct, and a minimum of 648 introduced species have arrived (mostly plants). The plants increased in species richness by 46%. Fifty percent of the native mammal species were lost, and overall, the birds declined by one species, representing 21 extinctions and 20 successful introductions. Amphibians and reptiles showed no net change. The herbaceous perennial and annual plant species richness showed a substantial increase. This temporal approach to urban ecology demonstrates new ways to identify individual species or groups at risk of extinction and provides some long-term management goals for large urban areas.
Article
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Scientists and managers often use urban forest canopy cover as an indicator of for- est health. Furthermore, canopy cover is often the measure communities use to set tree planting goals. Little is known, however, about factors that contribute to varia- tion in canopy cover. We describe canopy cover in 60 urban areas in Central Indi- ana. We then propose and test a model that treats canopy cover as a function of eco- logical and geographic factors, urban form, socioeconomic factors, and a policy index. Urban areas are more likely to have more canopy cover if they are in counties with more canopy cover, have higher proportions of their populations with college degrees, have older housing stock, have both more land and land with slopes greater than 15%, and have denser stream networks. Population density, median household income, and planning and zoning or status as a Tree City are not corre- lated with urban canopy cover.
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When organisms are moved from their natural range to new ecosystems, they are considered nonindigenous, invasive, or exotic species. Movement of exotic or native species may be international or from areas within Canada. Historically, Canada's forests have felt the effects of nonindigenous species introductions, as for example, Dutch elm disease, white pine blister rust, gypsy moth, and pine shoot beetle. With changes in global trade patterns, novel introductions will continue to occur. Although most of the research and regulatory efforts to control the movement of nonindigenous species has focused on insects, projects are underway to study fungal organisms and their association with insect vectors. International quarantine standards are being developed to minimize the risk associated with solid wood packing materials, a major entry pathway for nonindigenous organisms. Research needs include the development of enhanced detection capabilities, improved diagnostic tools, effective mitigation measures, as well as socio-economic impact assessments and basic biological information about nonindigenous species and their interactions with hosts.
Book
This book describes an array of power tools for data analysis that are based on nonparametric regression and smoothing techniques. These methods relax the linear assumption of many standard models and allow analysts to uncover structure in the data that might otherwise have been missed. While McCullagh and Nelder's Generalized Linear Models shows how to extend the usual linear methodology to cover analysis of a range of data types, Generalized Additive Models enhances this methodology even further by incorporating the flexibility of nonparametric regression. Clear prose, exercises in each chapter, and case studies enhance this popular text.
Article
AimWe propose and test a climate tolerance and trait choice hypothesis of urban macroecological variation in which strong filtering associated with low winter temperatures restricts urban biodiversity while weak filtering associated with warmer temperatures and irrigation allows dispersal of species from a global source pool, thereby increasing urban biodiversity. LocationTwenty cities across the USA and Canada. Methods We examined variation in tree community taxonomic diversity, origins and production of an aesthetic ecosystem service trait in a cross-section of urban field surveys. We correlated urban tree community composition indicators with a key climate restriction, namely mean minimum winter temperature, and evaluated alternative possible drivers: precipitation, summer maximum temperature, population size and the percentage of adults with a college education. ResultsSpecies accumulation curves differed substantially among cities, with observed richness varying from 22 to 122 species. Similarities in tree communities decreased exponentially with increases in climatic differences. Ordination of tree communities showed strong separation among cities with component axes correlated with minimum winter temperature and annual precipitation. Variation among urban tree communities in richness, origins and the provisioning of an aesthetic ecosystem service were all correlated with minimum winter temperature. Main conclusionsThe urban climate tolerance and trait choice hypothesis provides a coherent mechanism to explain the large variation among urban tree communities resulting from an interacting environment, species and human decisions. Reconciling the feedbacks between human decision making and biophysical limitations provides a foundation for an urban ecological theory that can better understand and predict the dynamics of other linked biotic communities, associated ecosystem dynamics and resulting services provided to urban residents.
Article
There is a need to understand how anthropogenic influences affect urban and periurban forest diversity at the regional scale. This study aims to compare urban and periurban tree composition along a geographic gradient, and test hypotheses about species composition and ecological homogeneity. We paired urban forest (UF) data from eight cities across the southeastern US with periurban forest (PF) data from the USDA Forest Service Forest Inventory and Analysis program. We found that tree diversity, as well as both observed and estimated species richness values were greater in UF versus PF. Community size structure analysis also indicated a greater proportion of large trees and greater numbers of non-native, invasive, and unclassified tree species in the UF versus the PF, regardless of location. Both forest type and ecological province had a significant effect on community species composition, with forests closer together in space being more similar to each other than those more distant. While land use change and management has been associated with ecological homogenization in human dominated landscapes, we found that species composition was more dissimilar along latitudinal lines than compared to between forest types, refuting this hypothesis, at least in terms of tree diversity.
Article
This study examines the financial impact of emerald ash borer (EAB, Agrilus planipennis Farimaire; Coleoptera: Buprestide) on municipal forestry budgets. Three distinct phases were evident: an initial time period of 0–4 years (little budget change), year 5–8 time period (rapid budget increase), and years 9–12 (rapid budget decrease) after EAB was confirmed in a state. The 5–8 year time period had increased spending as detected through the total forestry budget (p = 0.011), total municipal forestry budget (percent forestry budget) as a percentage of the total municipal budget (p < 0.001), and per capita spending (p < 0.001). A $1.58 per capita increase occurred in annual municipal forestry budgets in states in which EAB was confirmed (EAB+) compared to states without a confirmed EAB case (EAB−). This has a $280.5 (±79.9) million annual impact on municipal budgets. The percent forestry budget increased as the time since EAB was confirmed in a state increased. A mean 0.33% (0.03 SE, n = 82) percent forestry budget occurred during the initial 0–4 years after confirmation of EAB. This exponentially increased from 0.47% (0.05 SE, n = 43) in year 5–1.17% (0.12 SE, n = 38) at the peak in year 8, and rapidly declined back to 0.47% (0.05 SE, n = 51) in years 10–12 which was a level slightly higher than initial conditions. Federal, state, and local urban forestry managers can use these results to financially plan for the impacts of EAB on municipal forestry budgets.
Book
The first edition of this book has established itself as one of the leading references on generalized additive models (GAMs), and the only book on the topic to be introductory in nature with a wealth of practical examples and software implementation. It is self-contained, providing the necessary background in linear models, linear mixed models, and generalized linear models (GLMs), before presenting a balanced treatment of the theory and applications of GAMs and related models. The author bases his approach on a framework of penalized regression splines, and while firmly focused on the practical aspects of GAMs, discussions include fairly full explanations of the theory underlying the methods. Use of R software helps explain the theory and illustrates the practical application of the methodology. Each chapter contains an extensive set of exercises, with solutions in an appendix or in the book’s R data package gamair, to enable use as a course text or for self-study.
Article
Accurately measuring the biophysical dimensions of urban trees, such as crown diameter, stem diameter, height, and biomass, is essential for quantifying their collective benefits as an urban forest. However, the cost of directly measuring thousands or millions of individual trees through field surveys can be prohibitive. Supplementing field surveys with remotely sensed data can reduce costs if measurements derived from remotely sensed data are accurate. This study identifies and measures the errors incurred in estimating key tree dimensions from two types of remotely sensed data: high-resolution aerial imagery and LiDAR (Light Detection and Ranging). Using Sacramento, CA, as the study site, we obtained field-measured dimensions of 20 predominant species of street trees, including 30-60 randomly selected trees of each species. For each of the 802 trees crown diameter was estimated from the aerial photo and compared with the field-measured crown diameter. Three curve-fitting equations were tested using field measurements to derive diameter at breast height (DBH) (r2 = 0.883, RMSE = 10.32 cm) from the crown diameter. The accuracy of tree height extracted from the LiDAR-based surface model was compared with the field-measured height (RMSE = 1.64 m). We found that the DBH and tree height extracted from the remotely sensed data were lower than their respective field-measured values without adjustment. The magnitude of differences in these measures tended to be larger for smaller-stature trees than for larger stature species. Using DBH and tree height calculated from remotely sensed data, aboveground biomass (r2 = 0.881, RMSE = 799.2 kg) was calculated for individual tree and compared with results from field-measured DBH and height. We present guidelines for identifying potential errors in each step of data processing. These findings inform the development of procedures for monitoring tree growth with remote sensing and for calculating single tree level carbon storage using DBH from crown diameter and tree height in the urban forest.
Article
A survey of 586 community representatives with urban tree canopy responsibilities was conducted to provide data on ash density within four states in the Midwestern U.S., and to examine potential economic losses should emerald ash borer (EAB) become established in their communities. One hundred twenty-three responses were received from communities of various sizes. Data represented 10.5% of the population of Illinois, Indiana, Michigan, and Wisconsin, U.S., and 21% of all communities surveyed. Assuming the complete loss of ash due to EAB, losses in landscape value for ash trees within community boundaries were estimated to be between USD $7.7 (median-based) and $15 billion (mean-based). The cost to remove those trees is somewhat smaller and would be between $3 and $5.8 billion. Replacing trees lost to EAB with smaller 5 cm trees in street, park, and private plantings would cost between $2.7 and $5.2 billion. The total loss of ash for communities in the four states surveyed, including landscape losses, tree removals, and replacements are estimated to be between. $ 13.4 and $26 billion. The potential total costs per 1,000 residents in the four-state region is estimated to be between. $395,943 and $769,687. The rates per 1,000 residents estimates can be utilized by communities to begin developing contingency plans should EAB impact them.
Article
The accuracy and validity of urban forest resource data collected by trained volunteers were established, using an actual case study in Brookline, Massachusetts. Results indicate that the data collected by trained volunteers are valid, and the accuracy compares favorably with levels found among a control group of certified arborists. Indirect benefits associated with this type of volunteer effort include the development of a more informed urban forest constituency, increased environmental awareness, an increased political voice, and an improved quality of life for urban residents. The cost of utilizing community volunteers to conduct urban forest inventories is competitive with similar programs conducted by professional arborists.
Article
Auburn University (Auburn, Alabama, U.S.) was used as a site for a case study evaluating the standard plot sampling protocol for i-Tree Eco. A 100% tree inventory of the managed areas of campus was conducted in 2009-2010 and provided a complete data set for the evaluation. Air pollution removal, carbon storage, and carbon sequestration were the ecosystem services examined. Total tree population was also utilized for this assessment to provide a comparison to i-Tree Eco protocol. To achieve an estimate with a ±10% allowable error of the total campus value, 622 plots (0.04 ha each) with at least one tree present would need to be inventoried for air pollution removal, 870 plots for carbon storage, 483 plots for carbon sequestration, and 258 plots for number of trees, as opposed to the standard i-Tree Eco protocol of 200 plots. This study provides a first step in evaluating i-Tree Eco sampling protocol; however, efforts testing these results at sites throughout the southern United States are needed to provide the most accurate estimate of plot numbers necessary for predicting ecosystem services of urban forests.
Article
AimWe examined species composition of urban forests from local to global scales using occurrence and abundance information to determine how compositional similarity is defined across spatial scales. We predicted that urban forests have become more homogeneous world-wide, which should result in minimal scale dependence that is more pronounced for non-native species, especially when considering abundance information.LocationThirty-eight cities world-wide.Methods We estimated compositional dissimilarities of urban forests, including both spontaneous and cultivated trees, from local to global spatial scales using six dissimilarity metrics. We used redundancy analysis to determine how climate, geographic distance and anthropogenic factors are related to compositional dissimilarity among cities. These analyses were implemented for all species combined and for native and non-native species separately.ResultsThe 38 cities contained a median of 77 tree species, with a greater percentage of these classified as native (median = 58%). The similarity of urban forests was scale dependent, declining as the spatial scale increased – an outcome that did not differ when considering native and non-native species separately. Climate, geographic distance and city age were the main factors describing variation in tree species composition among cities. The addition of abundance information resulted in lower dissimilarity across spatial scales.Main conclusionsCompositional similarity of urban forests is a scale-dependent phenomenon that is not affected by the presence or absence of non-native species, suggesting a limited role for biotic interchange in promoting homogenization. However, compositional similarity across spatial scales increased uniformly with the addition of abundance information, suggesting that patterns of abundance may have greater biological relevance when homogenization trends among urban forests are considered.
Article
The emerald ash borer (EAB), a phloem-feeding beetle native to Asia, was discovered killing ash trees in southeastern Michigan and Windsor, Ontario, in 2002. Like several other invasive forest pests, the EAB likely was introduced and became established in a highly urbanized setting, facilitated by international trade and abundant hosts. Up to 15 million ash trees in urban and forested settings have been killed by the EAB. Quarantines in the United States and Canada restrict the movement of ash trees, logs, and firewood to prevent new introductions. Research studies are underway to assist managers leading eradication and containment efforts. Long-term efforts will be needed to protect ash in urban and forested settings across North America.
Article
Tree canopy cover is a fundamental component of the landscape, and the amount of cover influences fire behavior, air pollution mitigation, and carbon storage. As such, efforts to empirically model percent tree canopy cover across the United States are a critical area of research. The 2001 national-scale canopy cover modeling and mapping effort was completed in 2006, and here we present results from a pilot study for a 2011 product. We examined the influence of two different modeling techniques (random forests and beta regression), two different Landsat imagery normalization processes, and eight different sampling intensities across five different pilot areas. We found that random forest out-performed beta regression techniques and that there was little difference between models developed based on the two different normalization techniques. Based on these results we present a prototype study design which will test canopy cover modeling approaches across a broader spatial scale.
Article
Quantifying tree canopy cover in a spatially explicit fashion is important for broad-scale monitoring of ecosystems and for management of natural resources. Researchers have developed empirical models of tree canopy cover to produce geospatial products. For subpixel models, percent tree canopy cover estimates (derived from fi ne-scale imagery) serve as the response variable. The explanatory variables are developed from reflectance values and derivatives, elevation and derivatives, and other ancillary data. However, there is a lack of guidance in the literature regarding the use of leaf-on only imagery versus multi-season imagery for the explanatory variables. We compared models developed from leaf-on only Landsat imagery with models developed from multi-season imagery for a study area in Georgia. There was no statistical difference among models. We suggest that leaf-on imagery is adequate for the development of empirical models of percent tree canopy cover in the Piedmont of the Southeastern United States.
Article
Despite numerous ecosystem services provided by urban trees, they are continually threatened by combined natural disturbances, invasive species, development and negligent management practices. This research characterizes the amount and cause of tree loss in Worcester, Massachusetts, in the northeast United States, and neighbouring towns between 2008 and 2010 using multi-source remotely sensed imagery and historical land cover maps (1976–2009). Historical land-change analysis reveals that proportional forest cover loss in the Worcester County study area exceeds that of the state by 0.26% per year, 67% of which was driven by the expansion of low-density residential land use. Between 2008 and 2010, 2% of Worcester County’s tree canopy was lost to high- and low-density urban development (47% of the total loss), United States Department of Agriculture (USDA) tree removal for Asian longhorned beetle (ALB) eradication (25%), timber harvest (15%) and ice storm damage (6%). The use of multi-source geographic information system (GIS) data to characterize tree canopy loss makes it a flexible and replicable method to monitor urban tree health.
Article
A climatic moisture index (Im) used extensively by C. W. Thornthwaite and others is examined, and a modified version of the index is proposed. Arbitrary limits [−100 ≤ Im≤ 100 (∞− 1)], combined with its dimensionless property, make the original index difficult to interpret. Our refined version also is dimensionless, but the limits have been recast so that −1 ≤ Im≤ 1. Wet climates have positive values of Im while dry climates are negative, and the index is symmetric about zero. The spatial distribution of our modified annual-average moisture index over the world's continents is mapped and described.
Article
Generalized additive models have the form η(x) = α + σ fj(xj), where η might be the regression function in a multiple regression or the logistic transformation of the posterior probability Pr(y = 1 | x) in a logistic regression. In fact, these models generalize the whole family of generalized linear models η(x) = β′x, where η(x) = g(μ(x)) is some transformation of the regression function. We use the local scoring algorithm to estimate the functions fj(xj) nonparametrically, using a scatterplot smoother as a building block. We demonstrate the models in two different analyses: a nonparametric analysis of covariance and a logistic regression. The procedure can be used as a diagnostic tool for identifying parametric transformations of the covariates in a standard linear analysis. A variety of inferential tools have been developed to aid the analyst in assessing the relevance and significance of the estimated functions: these include confidence curves, degrees of freedom estimates, and approximate hypothesis tests.The local scoring algorithm is analogous to the iterative reweighted least squares algorithm for solving likelihood and nonlinear regression equations. At each iteration, an adjusted dependent variable is formed and an additive regression model is fit using the backfitting algorithm. The backfitting algorithm cycles through the variables and estimates each coordinated function by smoothing the partial residuals.
Article
This study demonstrates an approach to quantify the structure, benefits, and costs of street tree populations in resource-limited communities without tree inventories. Using the city of Davis, California, U.S., as a model, existing data on the benefits and costs of municipal trees were applied to the results of a sample inventory of the city's public and private street trees. Results indicate that Davis maintained nearly 24,000 public street trees that provided $1.2 million in net annual environmental and property value benefits, with a benefit-cost ratio of 3.8:1. The city can improve long-term stability of this resource by managing maintenance, new plantings, and stand rejuvenation on a city zone basis.
Article
Over the course of 150 years, a combination of cultural and natural processes drove Sacramento's transition from City of the Plains to the City of Trees. This paper describes how the many authors of Sacramento's treescape have affected the health, management, and public perception of the city's trees. Local government directed early street and park tree plantings and banned problem tree species by ordinance. During the first half of the 20th century, participation in street tree planting and preservation by groups such as the Chamber of Commerce, Boy Scouts, Science Teachers Association, and "tree enthusiasts" raised public awareness and civic pride. The large trees shading city streets became a community icon, frequently described as the "crowning jewel of Sacramento." More recently, concern about street tree health associated with declining funds for municipal tree care has spawned new partnerships that involve trained volunteers in Dutch elm disease control, residents in energy-conserving yard tree planting, and a public task force in developing policy recommendations to perpetuate Sacramento's legacy as the City of Trees.