Tree Canopy Cover Research Articles

Local plant richness predicts bee abundance and diversity in a study of urban residential yards

Understanding the drivers of biodiversity in cities is a central goal of urban ecology. There is currently intense scientific and public interest in the factors that influence pollinator diversity in cities and their surroundings. Existing studies point to a variety of landscape and local factors as potentially important, including urbanization (often defined as impervious surface cover in the surrounding lands), tree canopy cover and the diversity and abundance of locally flowering plants. However, few studies have sought to weigh the relative importance of these predictors of bee community metrics. Using a set of 27 residential yards chosen to represent a gradient of both urbanization and tree canopy cover at a landscape scale, we used pan trapping and netting to assess the abundance and diversity of local bee communities across the City of Ottawa, Ontario, Canada. Surprisingly, the landscape factors (urbanization and tree cover) described only a tiny fraction (< 1%) of the total variance in bee abundance and diversity across sites. This was true regardless of the scale of analysis at which the landscape factors were measured. Instead, a yard's floral richness, and, to a somewhat lesser extent, its floral abundance, emerged as the most important predictors of a yard's bee community abundance and diversity. Our study offers an important counterpoint to a growing body of work emphasizing the impacts of landscape factors on bee communities. Instead, our research suggests that improving bee floral resources by increasing the plant species richness and abundance locally is a powerful tool to support bee conservation, regardless of the level of urbanization or tree cover in the surrounding landscape. Our work highlights that the practice of promoting ‘bee-friendly’ plantings in private yards, currently being undertaken by a number of non-profits around the world, can play an important role in restoring and maintaining urban pollinator communities.

Bats in the megafire: assessing species’ site use in a postfire landscape in the Sierra Nevada

Abstract Large high-severity fires are increasing in frequency in many parts of the world, including the coniferous forests of the Sierra Nevada mountains. These “megafires” alter vegetation and environmental conditions in forests, yet their impacts on native wildlife remain poorly understood. Bats play an important role in forest ecosystems, but their responses to megafires likewise are understudied. We investigated bat responses to the King Fire, a megafire that burned nearly 40,000 ha within the Eldorado National Forest in 2014, half of it at high severity. From June to September 2017, we used remote acoustic recorders to survey bats at 26 sites with varying fire severity (unburned, mixed, and high severity). We analyzed data with Royle–Nichols occupancy models to investigate how bat space use was influenced by megafires, and whether this response was driven by prey availability, fire severity, or fire-altered habitat conditions. We calculated prey species richness, biomass, and abundance, from moths sampled with blacklight surveys. Vegetation covariates included tree density, canopy cover, and shrub density, measured along vegetation transects. To capture general effects of fire, we also included fire severity and the percentage of dead trees as potential covariates on space use. Prey variables were highest in unburned forests, were the most common predictors of, and generally had positive effects on bat space use. Responses to tree density and canopy cover varied by species; the most common vegetation covariate, shrub density, had weak positive effects on bat space use. In spite of the varying prey and vegetation conditions across fire severity categories, most bats showed weak to no response in space use to fire severity and tree mortality. We attribute this to the highly mobile nature of bats, which reduces the impact of potentially negative local conditions.

Modeling the spatial distribution of the current and future ecosystem services of urban tree planting in Chicopee and Fall River, Massachusetts

Mature urban tree canopy cover disrupts the local effects of urban heat islands and provides important ecosystem services such as energy savings through evaporation and shading, pollution removal, storm runoff control, and carbon sequestration. Sustainable urban tree canopy relies on the planting of juvenile trees. Typically, tree planting programs are only evaluated by the number of trees planted and there is a lack of analysis of juvenile trees post-planting. This study examines the value and distribution of energy savings provided by juvenile trees and how that value changes considering predicted tree growth and mortality by 2050. Using i-Tree Eco software, this study models the current and future ecosystem services provided to residents based on a juvenile tree inventory of 2271 street and residential trees planted in Massachusetts (USA) from 2014 to 2015 by the Greening the Gateway Cities Program (GGCP) in Chicopee and Fall River, MA. Juvenile trees planted by the GGCP provided $776 and $1520 (2018) in annual savings from ecosystem service in Chicopee and Fall River while services modeled to mature tree 2050 conditions show increased total annual savings of $2911 and $5840 in Chicopee and Fall River (2050). The mean total savings per tree per household were $0.77 in 2018 and $13.60 in 2050, with the majority from cooling energy savings in the summer. Services were maximized in neighborhoods where large numbers of trees were planted or when tree planting location (distance and orientation to the house) was optimized for highest savings. Analysis of the distribution of benefits reveals different planting strategies in Chicopee and Fall River. Ecosystem services from juvenile trees are concentrated in US Census block groups with more pre-existing tree canopy cover and lower median income. A tree planting density of two to three trees per acre was able to achieve the largest energy savings. Results of this study reinforce the importance of tree survivorship on sustaining the urban tree canopy to provide ecosystem services.

Drivers of understory plant communities in Sierra Nevada mixed conifer forests with pyrodiversity

BackgroundFire suppression in western North America increased and homogenized overstory cover in conifer forests, which likely affected understory plant communities. We sought to characterize understory plant communities and their drivers using plot-based observations from two contemporary reference sites in the Sierra Nevada, USA. These sites had long-established natural fire programs, which have resulted in restored natural fire regimes. In this study, we investigated how pyrodiversity—the diversity of fire size, severity, season, and frequency—and other environment factors influenced species composition and cover of forest understory plant communities.ResultsUnderstory plant communities were influenced by a combination of environmental, plot-scale recent fire history, and plot-neighborhood pyrodiversity within 50 m. Canopy cover was inversely proportional to understory plant cover, Simpson’s diversity, and evenness. Species richness was strongly influenced by the interaction of plot-based fire experience and plot-neighborhood pyrodiversity within 50 m.ConclusionsPyrodiversity appears to contribute both directly and indirectly to diverse understory plant communities in Sierra Nevada mixed conifer forests. The indirect influence is mediated through variability in tree canopy cover, which is partially related to variation in fire severity, while direct influence is an interaction between local and neighborhood fire activity.

Blue-Green infrastructure determines the microclimate mitigation potential targeted for urban cooling

Urban Heat Island (UHI) exacerbated by global warming can increase the thermal load in cities, which leads to more extreme climate events. One of the strategies to mitigate the impact of extreme climates and UHI is through nature-based solutions such as the Blue-Green Infrastructure as it provides environmental and community benefits However, Blue-Green Infrastructure’s role in urban cooling in the tropics still needs to be further investigated. Therefore, this study examined the role of Blue-Green Infrastructure on microclimate modifications in an urban park. Microclimate measurements were made using systematic random sampling with random start (total of 64 sampling points) at a waterbody (Blue Infrastructure) and tree and grass (Green Infrastructure) areas during solar noon time (1200-1400). Blue-Green Infrastructure showed greater microclimate benefits compared to the open space with the reduction of air temperature by up 1.6°C. However, green infrastructure had greater cooling benefits compared to Blue Infrastructure especially trees with significantly lower air temperature and solar radiation interception (0.71°C and 250.3 W/m2, respectively) as well as higher relative humidity (12.17%). Moreover, stand characteristics determine the microclimate mitigation function. This study provides a useful indication of the role of blue and green spaces in urban cooling, where it further emphasizes the importance of Blue-Green Infrastructure utilization in urban landscapes. It further recommends that urban planners, managers and policymakers should consider these strategies for urban cooling purposes : 1) Utilising Blue and Green Infrastructures especially trees 2) Tree canopy cover and DBH should be set as priority traits.

Influence of trees on landscape temperature in semi-arid agro-ecosystems of East Africa

In the Dodoma region of Tanzania, overexploitation of natural resources has led to a severe land degradation and, consequently, to the need to restore local ecosystems. Within the possible strategies, the farmer managed natural regeneration agroforestry is strongly being promoted in the area. To validate the utilisation of this practise, this research aims (i) to assess the benefits of trees on microclimate studying the relationship between land surface temperature (LST) and tree canopy cover (TCC) in farmlands and (ii) to propose an operative tree density threshold to be set as objective by restoration activities in the area. Data collected with an unmanned aerial vehicle were integrated with Landsat 8 and Sentinel 2 satellite imagery. LST was retrieved through the practical single channel algorithm and TCC was calculated with a supervised classification. Pixel-based analyses at a resolution of 30 m and 10 m were performed, and the resulting data statistically analysed through the coefficient of determination, the Kruskal–Wallis test, and the Dunn test. Results showed that the TCC of the surveyed areas was 5.1%, and a significant decrease in LST of 1.32 °C (p < 0.01) was found in the areas with the highest TCC, during the late dry season. From these preliminary analyses, a threshold of 10% TCC is suggested for farmlands in this agroecological zone to bring beneficial microclimate changes in terms of temperature. Considering the average plant phenotype characteristic of the area, it corresponds to a tree density of 50 trees ha −1 . • LST decrease of 1.32 °C found in areas with high TCC in the late dry season. • 10% TCC threshold, or 50 trees ha −1 should be reached using restoration. • Integration of Landsat 8 with Sentinel 2 data gave improved analysis.

Bunker Oksigen Dan Karbon (Bok) Di Lingkungan Sekolah Sebagai Penyimpan Karbon, Manfaat, Dan Nilai Ekonominya

The impacts of pollution and climate change occurred in global and local communities, including at school environment. Uncomfortable school environment due to pollution and school damage due to sea-level rise interferes with learning processes and reduces students' academic performance. A new approach of a school greening programme called Bunkers of Oxygen and Carbon (BOCs) was developed in a public school (SMA Negeri 3 Merauke) in Merauke, Papua using a thematic approach to mitigate pollution and climate change. The research showed that carbon storage of BOCs is mean 74 Mg ha-1 . This is equal with carbon dioxide equivalent (CO2e) of mean 271 Mg CO2e ha-1. The capacity of BOCs as carbon storage can be optimized due to the age of vegetation in BOCs is only four years old, and below ground carbon stock was measured only up to 50 cm depth. The amount of carbon stock in BOCs was influenced by vegetation health (tree density and canopy coverage) and vegetation structure (tree diameter and height) in the BOCs (r2 = 0.56, p = 0.001). The mean economic value of carbon stocks in the BOCs was US $ 189 billion ha-1. This economic value may underestimate as many benefits and functions of the BOCs were excluded from the calculation. BOCs have ecological functions as a habitat for many wildlife species, various ecosystem services, recreational areas, aesthetic values, oxygen supply, and a place to improve creativity and as natural laboratories for practice and learning from nature. Therefore, the development of BOCs in the school environment across Indonesia is important as the functions and benefits are crucial to mitigate pollution and climate change, improve the learning process and the quality of national education.

Residential yard management and landscape cover affect urban bird community diversity across the continental USA.

Urbanization has a homogenizing effect on biodiversity and leads to communities with fewer native species and lower conservation value. However, few studies have explored whether or how land management by urban residents can ameliorate the deleterious effects of this homogenization on species composition. We tested the effects of local (land management) and neighborhood-scale (impervious surface and tree canopy cover) features on breeding bird diversity in six US metropolitan areas that differ in regional species pools and climate. We used a Bayesian multiregion community model to assess differences in species richness, functional guild richness, community turnover, population vulnerability, and public interest in each bird community in six land management types: two natural area park types (separate and adjacent to residential areas), two yard types with conservation features (wildlife-certified and water conservation) and two lawn-dominated yard types (high- and low-fertilizer application), and surrounding neighborhood-scale features. Species richness was higher in yards compared with parks; however, parks supported communities with high conservation scores while yards supported species of high public interest. Bird communities in all land management types were composed of primarily native species. Within yard types, species richness was strongly and positively associated with neighborhood-scale tree canopy cover and negatively associated with impervious surface. At a continental scale, community turnover between cities was lowest in yards and highest in parks. Within cities, however, turnover was lowest in high-fertilizer yards and highest in wildlife-certified yards and parks. Our results demonstrate that, across regions, preserving natural areas, minimizing impervious surfaces and increasing tree canopy are essential strategies to conserve regionally important species. However, yards, especially those managed for wildlife support diverse, heterogeneous bird communities with high public interest and potential to support species of conservation concern. Management approaches that include the preservation of protected parks, encourage wildlife-friendly yards and acknowledge how public interest in local birds can advance successful conservation in American residential landscapes.

Density management strategy for overstory and understory of urban woodland based on ecological size-density allometry

Urban woodland is a dominant landscape element in supporting sustainability of urban systems. The aesthetic, ecological and psychological benefits provided by urban woodland are closely related to characteristics of the overstory and understory. The distribution and dynamics of tree canopy cover has been well elucidated, however, few studies focused on functioning and structure of urban understory and the interaction between different vegetation layers. In this study, ecological size-density allometry obtained through linear, quadratic and piecewise linear models was employed to quantify the resource competition of understory vegetation and effects of overstory canopy cover on understory in Shanghai metropolitan area of China. We found that canopy cover shapes the size-density pattern rather than affecting biomass and density directly. Size-density allometric relationships from piecewise linear models provided the optimal planting density under different canopy cover levels. Considering the linkage between vegetation layers and resource competition, we proposed that middle canopy cover of overstory (60%–80%) and relative low density of understory herb (175 m−2) is an optimal management strategy for maintaining high ecosystem services and functioning of urban woodlands.

Street trees and crime: What characteristics of trees and streetscapes matter

The extent to which street trees affect crime is moderated by many characteristics of tree structure, streetscapes, and tree management. To effectively utilize urban greening interventions as crime preventing programs, it is necessary to distinguish tree-related characteristics that increase crime from those that cause crime to decline. This study derived a complete set of tree-related characteristics and crime attributes from a variety of sources. We then applied ordinary least squares and spatial Durbin regressions to reveal the associations between street trees and crime in New York City. Our results showed that street tree characteristics that were negatively associated with crime rates included tree canopy cover, species diversity, and streetscape greenery, while the opposite was observed for the proportion of small-sized trees. The characteristics of street trees that displayed a dual-feature with crime rates included tree health, proportion of harmful tree guards, and proportion of trees with trunk problems, while tree stewardship was not significantly associated with crime. In addition, our findings demonstrated that tree canopy cover and streetscape greenery were conducive to reduce crime severity. The mixed associations between street tree characteristics and crime could be potentially explained by the “broken window theory”, trees’ view-obstructing effect, the “eyes on the street”, and trees’ therapeutic effect. The revealed findings have important implications for the implementation of tree-planting programs in tackling the dual tasks of improving urban greening and reducing crime, and could help translate crime reduction into specific actions of streetscape design and tree management that can be taken by government and local stakeholders.

Riparian Land Cover, Water Temperature Variability, and Thermal Stress for Aquatic Species in Urban Streams

Thermal regime warming and increased variability can result in human developed watersheds due to runoff over impervious surfaces and influence of stormwater pipes. This study quantified relationships between tree canopy, impervious surface, and water temperature in stream sites with 4 to 62% impervious land cover in their “loggersheds” to predict water temperature metrics relevant to aquatic species thermal stress thresholds. This study identified significant (≥0.7, p &lt; 0.05) negative correlations between water temperature and percent tree canopy in the 5 m riparian area and positive correlations between water temperature and total length of stormwater pipe in the loggershed. Mixed-effects models predicted that tree canopy cover in the 5 m riparian area would reduce water temperatures 0.01 to 6 °C and total length of stormwater pipes in the loggershed would increase water temperatures 0.01 to 2.6 °C. To our knowledge, this is the first time that the relationship between stormwater pipes and water temperature metrics has been explored to better understand thermal dynamics in urban watersheds. The results highlight important aspects of thermal habitat quality and water temperature variability for aquatic species living in urban streams based on thermal thresholds relevant to species metabolism, growth, and life history.

Variation in characteristics and conservation values of plant communities on abandoned agricultural lands with and without fires

AbstractQuestionWhich plant community characteristics most consistently vary with prior land use?LocationOak Openings Preserve, Ohio, USA.MethodsIn 2020, we measured plant communities on 22 sites encompassing three prior land uses: (a) contemporary Quercus forests continuously forested since before the 1930s; (b) former agricultural lands, under cultivation in the 1930s and abandoned 70–80 years before our study and that were unburned; and (c) former agricultural lands also abandoned 70–80 years earlier and that were burned in 2013 prescribed fires. Among the three land uses, we compared 12 plant community variables, categorized into four groups characterizing different sets of community properties (structure, diversity, composition, and conservation values).ResultsA multivariate combination of the 12 community variables differed among all three land uses, each of the four categories of variables differed between at least two land uses, and eight of 12 individual variables differed between at least two land uses. Community structure displayed a gradient of decreasing tree canopy and understorey plant cover and increasing lichen–moss cover from continuously forested to unburned and burned formerly cultivated sites. Understorey plant species richness did not vary with land use, but species diversity was higher on cultivated sites, irrespective of fire history. While all three land uses now contain Quercus tree overstories, each land use exhibited unique understorey species composition. Only formerly cultivated sites contained state‐listed endangered species. Cultivated sites had a lower proportion of native species cover than did continuously forested sites, but native species still comprised over 90% of the plant cover on cultivated sites. Compared with continuous forests, the soil organic layer (O horizon) was five times thinner and loss on ignition in the 0–15 cm mineral soil 49% (unburned) and 66% (burned) lower on previously cultivated sites.ConclusionsCommunity characteristics varied in their sensitivity to land use history, with species composition among the most sensitive to prior land use. A dense sapling layer of Acer rubrum forming in long‐unburned Quercus forests across much of eastern North America was absent in our study on formerly cultivated sites, possibly due to dry, infertile soil. From a restoration and conservation standpoint of the study region's pre‐settlement, frequently burned and open savannas and woodlands, previously cultivated sites may be easier to keep open via prescribed fire. Moreover, perhaps precisely because much of the flora historically developed in open savannas and woodlands which previously cultivated sites on the contemporary landscape most closely mimicked, previously cultivated sites presently contain higher species diversity and more conservation priority species than do continuously forested sites.

Environmental service assessment of trees at Yogyakarta International Airport open space using CITYGreen 5.2

Urban development has many negative impacts in the form of an increase in the concentration of CO2 in the air. One of them is due to the increase in the volume of vehicles. CO2 causes an increase in global temperature (global warming) through the greenhouse effect. Yogyakarta International Airport has a green open space planted with trees to support the existence of the airport itself. Trees have contributed to efforts to reduce CO2 in the air through CO2 absorption. Control of the amount of CO2 emissions in the air is done by adding carbon stocks on land so that the CO2 concentration does not continue to increase, therefore this research is necessary. The purpose of this study is to analyze the ability of trees to absorb pollutants and store carbon and estimate the value of environmental services that will be contributed by the tree green system at Yogyakarta International Airport based on existing planting plans. The research method used is modeling using CITYGreen 5.2 software to determine the value of tree services in the ability to absorb air pollution, carbon storage capacity, and cost savings that can be done by tree canopies. The method used in this study consisted of preparation, data inventory, and data analysis. The results of this study show that the value of environmental services provided by 125,72 acres of tree canopy cover in absorbing air pollution in the airport area is $ 9.045,54 / year or equivalent to Rp 133.356.587,10 per year, the total concentration of pollutants that can be absorbed is 3.813,30 lbs/year or equivalent to 1.729,68 kg/year, and the capacity of carbon storage is 1.326,46 tons with a sequestration rate of around 29,9 tons/year.

Forest restoration after alluvial gold mining can recover vegetation structure. A case study in Colombia

Technical reclamation and spontaneous succession (passive restoration) are the two main approaches for restoring post-mining sites worldwide. Despite substantial differences between both approaches, little is known regarding how they differ in terms of ecological outcomes. We assessed and compared the vegetation structure and composition in one spontaneous succession forest that is 29 years old, two technically reclaimed forests that are 2 and 10 years old after alluvial gold mining, and one old-growth reference forest in northeastern Antioquia, Colombia. We sampled trees and saplings establishing three Modified-Whittaker Plots in each site. We measured tree basal area, canopy cover, vegetation height, tree density, and species richness. Vegetation structure and composition differed considerably among restoration approaches. Species richness was significantly greater in the spontaneous succession forest than at the other sites. Similarly, technical reclamation significantly increased the vegetation attributes after 10 years, reaching values similar to the reference forest. We underscore the importance of fast-growth planted species (Acacia mangium, Samanea saman, and Schizolobium parahyba) to revegetate mining degraded lands.

Multiscale effects of habitat loss and degradation on occurrence and landscape connectivity of a threatened subspecies

AbstractLand use change can result in complex environments of varying habitat quality and permeability that directly and indirectly influence the effectiveness of natural areas for wildlife conservation. To assess how isolation and degradation of protected natural areas may affect long‐term conservation efforts across the range of a sensitive subspecies, we used multiscale occupancy analysis, species distribution modeling, and circuit theory to identify hotspot areas of occurrence and potential landscape connectivity among areas of high quality habitat within and between protected natural areas. Big Cypress fox squirrels (Sciurus niger avicennia: BCFS) are state‐threatened subspecies of fox squirrel endemic to forested wetlands in southwest Florida, which have been highly altered by human activities. Probability of occupancy of BCFS among conservation areas varied widely due to differences in environmental features (Hedge's g = 1.4705, 95% CI: 1.074–1.763). Fine‐scale features indicative of habitat degradation, such as increasing midstory vegetation cover and decreasing bromeliad cover, negatively influenced BCFS occurrence. Home‐range‐level tree canopy cover differentially affected probability of occupancy dependent on proximity to urban areas. Additionally, home‐range‐level high summer temperature differentially affected probability of occupancy dependent on proximity to cypress domes. Habitat was distributed patchily both within and among conservation areas, separated by large areas of unsuitable vegetation communities and urbanized features that were barriers to movement. Considering the threat of increasing isolation of conservation areas due to continued development as well as current and impending degradation caused by land use and climate change within conservation area boundaries, we suggest a strong need for interagency coordination to improve, maintain, and acquire rights for protection of additional remaining habitat.

Predicting canopy cover of diverse forest types from individual tree measurements

Quantifying tree canopy cover is fundamental to applications in forestry and ecology, but estimates vary substantially depending on type of field measurement, imagery, or active sensing used. Our objective was to improve estimates of stand-level canopy cover from standard tree inventory measurements, using representative data collected across diverse forest plant association groups across Oregon, USA. Canopy cover was measured with line intercept sampling on 1706 inventory plots and compared to calculations from individually tallied trees. We investigated adjustments of tree crown area equations, adjustments of crown overlap factors, and modeling from climatic variables and standard forest measurements to estimate line intercept cover. Estimates based on simple crown width equations adjusted for tree social position and caps on maximum cover, had the lowest error (RMSE = 14% cover) of crown width approaches across all vegetation types. Random crown overlap applied to unadjusted crown area only performed well in drier forest types and was unable to match high line intercept cover levels (>90%) often found in productive forest types. Although statistical models had somewhat greater precision than the simpler crown-width summation approaches (RMSE of 12%), accuracy was comparable. The greater flexibility of crown width summation approaches could make them more useful in forestry applications and beyond our study area.

Assessing the performance and accuracy of invasive plant habitat suitability models in detecting new observations in Wisconsin

AbstractLand managers require tools that improve understanding of suitable habitat for invasive plants and that can be incorporated into survey efforts to improve efficiency. Habitat suitability models (HSMs) contain attributes that can meet these requirements, but it is not known how well they perform, as they are rarely field-tested for accuracy. We developed ensemble HSMs in the state of Wisconsin for 15 species using five algorithms (boosted regression trees, generalized linear models, multivariate regression splines, MaxEnt, and random forests), evaluated performance, determined variables that drive suitability, and tested accuracy. All models had good model performance during the development phase (Area Under the Curve [AUC] &gt; 0.7 and True Skills Statistic [TSS] &gt; 0.4). While variable importance and directionality was species specific, the most important predictor variables across all of the species’ models were mean winter minimum temperatures, total summer precipitation, and tree canopy cover. Post model development, we obtained 5,005 new occurrence records from community science observations for all 15 focal species to test the models’ abilities to accurately predict results. Using a correct classification rate of 80%, just 8 of the 15 species correctly predicted suitable habitat (α ≤ 0.05). Exploratory analyses found the number of reporters of these new data and the total number of new occurrences reported per species contributed to increasing correct classification. Results suggest that while some models perform well on evaluation metrics, relying on these metrics alone is not sufficient and can lead to errors when utilized for surveying. We recommend any model should be tested for accuracy in the field before use to avoid this potential issue.

Does tree canopy moderate the association between neighborhood walkability and street crime?

Creating walkable places and increasing urban vegetation in neighborhoods have emerged as important planning strategies to promote health, social, and environmental benefits. Although past studies have found that walkability and tree canopy are associated with crime, little research has comprehensively examined how neighborhood walkability and tree canopy are associated with street crime. The current study fills this gap by analyzing the relationship among walkable access to amenities measured by Walk Score, urban tree canopy, and the five-year violent and property street crime rates (2014–2018) across an entire city. This study used the case of Austin, Texas to investigate the association exists between 1) neighborhood walkability and street crime and 2) tree canopy and street crime. We also assessed whether the association between neighborhood walkability and street crime was moderated by tree canopy. The first set of models based on a negative binomial regression showed that neighborhood walkability was positively associated with both violent and property street crime rates while tree canopy was inversely associated with violent and property street crime rates. The second set of models revealed a nonlinear relationship between neighborhood walkability and the street crime rate. The final set of models showed that tree canopy cover can moderate the relationship between street crime and neighborhood walkability, suggesting that tree canopy can somewhat offset the negative influence of walkable neighborhoods, such as crowdedness and noise, in relation to street crime. The findings have implications for developing evidence-based planning, design, and policy strategies to create livable streets and prevent street crime by planting more trees in walking-friendly environments.

Association between Low Urban Neighborhood Greenness and Hypertensive Disorders of Pregnancy.

Urban neighborhood greenness is associated with greater cardiovascular health in the general population, and with better pregnancy and neonatal outcomes. Hypertension in pregnancy is a leading cause of maternal mortality and long-term cardiovascular morbidity and mortality in women. We sought to examine the association between greenness and hypertensive disorders of pregnancy. This study is a secondary analysis of a prospective cohort study of 1,943 women who received prenatal care from December 2013 to December 2016 at a single, urban, and tertiary academic medical center in Philadelphia, PA. Greenness measure was quantified via residential tree canopy cover within circumferential buffers of 100- and 500-meter radii around participants' homes. Associations between greenness and hypertensive disorders of pregnancy (defined as gestational hypertension or preeclampsia) were estimated by using multilevel logistic regression accounting for maternal sociodemographic information (race-ethnicity, insurance status, and age) medical history (diabetes, body mass index, smoking history, and parity), neighborhood deprivation index, and including 1,225 Philadelphia residents for whom key exposure and outcome data were available. At baseline, the participants' mean (SD) age was 27.5 (5.9) years, (range: 14-44 years). The majority of participants were non-Hispanic Black (857, 70.2%). Participants with less residential tree canopy cover were significantly more likely to have hypertensive disorders of pregnancy. The multivariable-adjusted odds ratio of hypertensive disorders of pregnancy among participants with less than 10% compared with those with greater than 30% tree canopy cover was 2.14 (95% confidence interval [CI]: 1.11-4.15) within 100-meter buffer. In our cohort, greenness was associated with lower hypertensive disorders of pregnancy odds. Our findings add to evidence that greenness may confer health benefits and warrant further investigations in identifying whether there is a causal pathway through which greenness may be protective against hypertensive disorders of pregnancy. · Low residential tree canopy is associated with increased risk of hypertensive disorders of pregnancy. · 100-meter buffers are most sensitive in identifying associations between tree canopy and HDP risk. · The role of greenness against hypertensive disorders of pregnancy should be further studied experimentally.

Changes in the vegetation of New Orleans from the disturbance impacts of Hurricane Katrina in 2005

The catastrophic flooding of New Orleans following landfall of Hurricane Katrina in August of 2005 left behind a unique urban environment for investigating disaster impacts on vegetation disturbance and recovery. The goal of this study was to analyze the changes in urban tree canopy cover (both live standing and downed) and the extent of vegetation as shrubs or herbaceous cover on blocks located within the most flood-impacted neighborhoods in 2005 of New Orleans, down to the scale of individual property lots. Remote sensing aircraft images from the U. S. Geological Survey's Digital Orthophoto Quadrangles (DOQs) imagery and the National Agriculture Imagery Program (NAIP) were used to generate high-resolution (1-m) vegetation cover maps for 2004, 2005 (post-Katrina), and 2019 for deeply flooded neighborhoods from 2005. Segmentation and object-based classification applied to all color infrared (CIR) imagery was used to generate and compare high-resolution maps of large tree canopies, shrubs, and herbaceous cover within property lots. Results showed that the Lower Ninth Ward and the Seventh Ward neighborhoods suffered the highest damage levels to canopy cover from the impacts of Hurricane Katrina, losing around 15% in overall tree cover, and sustaining severe damaged on as much as 75% of the neighborhoods' pre-2005 tree cover. Nevertheless, the Lower Ninth Ward has had the highest rate of regrowth of vegetation cover (as of 2019), mainly owing to unmaintained tall shrub cover that in 2019 commonly exceeded 2 m in height on many of the neighborhood's blocks. On a city-wide scale, New Orleans's urban forest is significantly more fragmented today into small tree canopies than it was in 2004.