Linking the macroclimatic niche of native lithophytic ferns and their prevalence in urban environments.

PREMISE: Vertical surfaces in urban environments represent a potential expansion of niche space for lithophytic fern species. There are, however, few records of differential success rates of fern species in urban environments. METHODS: The occurrence rates of 16 lithophytic fern species native to the northeastern USA in 14 biomes, including four urban environments differentiated by percentage of impervious surfaces, were evaluated. In addition, the natural macroclimatic ranges of these species were analyzed to test whether significant differences existed in climatic tolerance between species that occur in urban environments and species that do not. RESULTS: Three species appear to preferentially occur in urban environments, two species may facultatively occur in urban environments, and the remaining 11 species preferentially occur in nondeveloped rural environments. The natural range of fern species that occur in urban environments had higher summer temperatures than the range of species that do not, whereas other macroclimatic variables, notably winter temperatures and precipitation, were less important or insignificant. CONCLUSIONS: Vertical surfaces in urban environments may represent novel niche space for some native lithophytic fern species in northeastern USA. However, success in this environment depends, in part, on tolerance of the urban heat island effect, especially heating of impervious surfaces in summer.

Designing cities for everyday nature.

The motivations for incorporating nature into the design of cities have never been more compelling. Creating experiences with nature that occur every day (everyday nature) in cities could help reverse the fate of many threatened species and connect people with nature and living cultural traditions. However, this requires more than just urban greening; it involves ensuring daily doses of nature in a way that also supports nonhuman organisms. A major shift in the way nature is conceived of and is made part of the design of cities is required. Principles include reconsidering nature as a development opportunity rather than a constraint and eliminating offsetting of biodiversity site values. Processes include using biodiversity-sensitive design frameworks and establishing meaningful professional engagement among ecologists, planners, and designers. Challenges include design obstacles, conflicts between nature and people (e.g., safety, disease, and noise) that require careful management, and socioeconomic and political considerations (e.g., Global North vs. Global South). Research to interrogate the multiple benefits of nature in cities can complement experimental interventions, ultimately supporting better urban design and creating much more resiliently built environments for people and nature.

Diseño de ciudades para la naturaleza cotidiana Resumen Los motivos para incorporar a la naturaleza dentro del diseño urbano jamás habían sido tan convincentes. La creación en las ciudades de experiencias con la naturaleza que ocurren a diario (naturaleza cotidiana) podría ayudar a cambiar el destino de muchas especies amenazadas y conectar a las personas con la naturaleza y las tradiciones culturales vivientes. Lo anterior requiere más que reverdecimiento urbano ya que involucra dosis diarias de naturaleza de manera que también mantengan a los organismos no humanos. Se necesita de un cambio mayor en la manera en la que se concibe a la naturaleza y cómo se le hace parte del diseño urbano. Los principios incluyen reconsiderar a la naturaleza como una oportunidad de desarrollo en lugar de una limitación y eliminar la compensación del valor de los sitios de biodiversidad. Los procesos incluyen el uso de marcos de diseños sensibles con la biodiversidad y el establecimiento de una participación profesional significativa entre los ecologistas, los planeadores y los diseñadores. Los retos incluyen los obstáculos del diseño, conflictos entre la naturaleza y las personas (seguridad, enfermedades y ruido) que requieren de un manejo cuidadoso y consideraciones políticas (Norte Global versus Sur Global). La investigación para interrogar los múltiples beneficios de la naturaleza en las ciudades puede complementar a las intervenciones, a la larga respaldando un mejor diseño urbano y creando ambientes para las personas y la naturaleza construidos con mayor resiliencia.

High-Resolution Modeling of Summertime Biogenic Isoprene Emissions in New York City.

As cities strive for ambitious increases in tree canopy cover and reductions in anthropogenic volatile organic compound (AVOC) emissions, accurate assessments of the impacts of biogenic VOCs (BVOCs) on air quality become more important. In this study, we aim to quantify the impact of future urban greening on ozone production. BVOC emissions in dense urban areas are often coarsely represented in regional models. We set up a high-resolution (30 m) MEGAN (The Model of Emissions of Gases and Aerosols from Nature version 3.2) to estimate summertime biogenic isoprene emissions in the New York City metro area (NYC-MEGAN). Coupling an observation-constrained box model with NYC-MEGAN isoprene emissions successfully reproduced the observed isoprene concentrations in the city core. We then estimated future isoprene emissions from likely urban greening scenarios and evaluated the potential impact on future ozone production. NYC-MEGAN predicts up to twice as much isoprene emissions in NYC as the coarse-resolution (1.33 km) Biogenic Emission Inventory System version 3.61 (BEIS) on hot summer days. We find that BVOCs drive ozone production on hot summer days, even in the city core, despite large AVOC emissions. If high isoprene emitting species (e.g., oak trees) are planted, future isoprene emissions could increase by 1.4-2.2 times in the city core, which would result in 8-19 ppbv increases in peak ozone on ozone exceedance days with current NOx concentrations. We recommend planting non- or low-isoprene emitting trees in cities with high NOx concentrations to avoid an increase in the frequency and severity of future ozone exceedance events.

Increasing tree cover and high-albedo surfaces reduces heat-related ER visits in Los Angeles, CA.

There is an urgent need for strategies to reduce the negative impacts of a warming climate on human health. Cooling urban neighborhoods by planting trees and vegetation and increasing albedo of roofs, pavements, and walls can mitigate urban heat. We used synoptic climatology to examine how different tree cover and albedo scenarios would affect heat-related morbidity in Los Angeles, CA, USA, as measured by emergency room (ER) visits. We classified daily meteorological data for historical summer heat events into discrete air mass types. We analyzed those classifications against historical ER visit data to determine both heat-related and excess morbidity. We used the Weather Research and Forecasting model to examine the impacts of varied tree cover and albedo scenarios on meteorological outcomes and used these results with standardized morbidity data algorithms to estimate potential reductions in ER visits. We tested three urban modification scenarios of low, medium, and high increases of tree cover and albedo and compared these against baseline conditions. We found that avoiding 25% to 50% of ER visits during heat events would be a common outcome if the urban environment had more tree cover and higher albedo, with the greatest benefits occurring under heat events that are moderate and those that are particularly hot and dry. We conducted these analyses at the county level and compared results to a heat-vulnerable, working-class Los Angeles community with a high concentration of people of color, and found that reductions in the rate of ER visits would be even greater at the community level compared to the county.

Associations between violent crime inside and outside, air temperature, urban heat island magnitude and urban green space.

There are more incidents of violence in summer and on hot days, a trend likely to be exacerbated by climate change. Urban areas experience additional temperature modulation due to the urban form, however, to date, no studies have considered the effect of the urban heat island (UHI) or green space with respect to the temperature-violence relationship. This study modelled the relationship between the number of daily violent crime incidents that occurred inside or outside between July 2013 and June 2018, and the average surface UHI or percentage greencover (including grasses, shrubs and trees) within each local government area in Greater Sydney, Australia. Panelised negative binomial time series regression models indicated that the violent crime rate was associated with higher surface UHI for crimes committed outside (p = 0.006) but not inside (p = 0.072). Greater percentage of all vegetation was associated with significantly lower rates of violent crime committed outside (p = 0.011) but was not associated with violent crimes committed inside (p = 0.430). More socio-economic disadvantage was associated with higher rates of violent crime committed inside (p = 0.002) but not outside (p = 0.145). Greater temperature was non-linearly associated with higher rates of violent crime committed both inside and outside (p < 0.001). The findings of this study are important because both violence and heat exposure are critical health issues and will be stressed by urbanisation and climate change. The expansion of green space and/or reduction in UHI may mitigate these effects.

High-resolution emission inventory of biogenic volatile organic compounds for rapidly urbanizing areas: A case of Shenzhen megacity, China.

The effects of volatile organic compounds on urban air quality and the ozone have been widely acknowledged, and the contributions of relevant biogenic sources are currently receiving rising attentions. However, inventories of biogenic volatile organic compounds (BVOCs) are in fact limited for the environmental management of megacities. In this study, we provided an estimation of BVOC emissions and their spatial characteristics in a typical urbanized area, Shenzhen megacity, China, based on an in-depth vegetation investigation and using remote sensing data. The total BVOC emission in Shenzhen in 2019 was estimated to be 3.84 × 109 g C, of which isoprene contributed to about 24.4%, monoterpenes about 44.4%, sesquiterpenes about 1.9%, and other VOCs (OVOCs) about 29.3%. Metropolitan BVOC emissions exhibited a seasonal pattern with a peak in July and a decline in January. They were mainly derived from the less built-up areas (88.9% of BVOC emissions). Estimated BVOCs comprised around 5.2% of the total municipal VOC emissions in 2019. This percentage may increase as more green spaces emerge and anthropogenic emissions decrease in built-up areas. Furthermore, synergistic effects existed between BVOC emissions and relevant vegetation-based ecosystem services (e.g., air purification, carbon fixation). Greening during urban sprawl should be based on a trade-off between BVOC emissions and ecosystem benefits of urban green spaces. The results suggested that urban greening in Shenzhen, and like other cities as well, need to account for BVOC contributions to ozone. Meanwhile, greening cites should adopt proactive environmental management by using plant species with low BVOC emissions to maintain urban ecosystem services while avoid further degradation to ozone pollution.

Urban greening in Dhaka: Assessing rooftop agriculture suitability using GIS and MCDM techniques.

Dhaka ranks among the world's most densely populated cities, with built-up areas expanding to accommodate the demands of a growing population. The rapid urbanization has reduced green space and exacerbated urban heat and pollution in the city. In the quest for a greener and healthier urban environment, rooftop agriculture has emerged as a promising solution, offering opportunities for the restoration of the environment and safe food production. Despite its potential, limited studies have explored the viability of this alternative greening solution for Dhaka. Therefore, this study aims to assess the suitability of rooftops for agricultural activities employing Geographic Information System (GIS) and Multi-Criteria Decision Making (MCDM) techniques. First, seven criteria were selected based on the literature, such as building age, height, rooftop size, building utility, property value, sunlight, and water availability. Second, an expert opinion survey was conducted using the Best Worst Method (BWM) to calculate the criteria's weights. Finally, the suitability map for Dhaka was derived by combining the criteria layers and was subsequently validated. Rooftop area and property value were identified as the most and least important criteria. Approximately 9% (6.27 km2), 68% (46.59 km2), 22% (15.15 km2), and a negligible portion (0.1 km2) of Dhaka city has been classified as highly suitable, suitable, moderately suitable, and not suitable, respectively, for rooftop agriculture. By identifying and promoting the most suitable locations for rooftop agriculture and highlighting existing opportunities, this research will help to initiate and expand sustainable agriculture practices that can contribute to climate change adaptation and urban resilience.

Soil Black Carbon Increases Under Urban Trees with Road Density and Time: Opportunity Hotspots for Carbon Storage in Urban Ecosystems.

Black carbon (BC) can comprise a significant fraction of the soil carbon pool in cities. However, vegetation cover and human activity influence the spatial distribution of urban soil BC. We quantified soil total carbon (TC), soil organic carbon (SOC), BC, and total nitrogen (TN) in a medium-sized city in Dallas-Fort Worth, Texas. Soils were sampled to 20 cm depth from underneath 16 paired Quercus stellata (post oak) trees and open lawns. Effects of vegetation cover, road density, and building age (a proxy for time since development) on soil C and N were analyzed. Soil OC concentrations were higher under post oak trees (5.5%) compared to open lawns (3.6%) at 0-10 cm, but not at 10-20 cm depth. In contrast, soil BC and TN did not differ by vegetation cover. There were significant interaction effects between vegetation cover and road density and vegetation cover and building age on soil BC. At 0-10 cm, soil BC concentrations, stock, and BC/SOC ratios increased more with road density under trees than lawns, indicating enhanced atmospheric BC deposition to tree canopies. Black carbon in tree soils also increased with building age as compared to lawn soils, likely due to higher BC retention under trees, enhanced BC losses under lawns, or both. Our findings show that urban tree soils are localized opportunity hotspots for BC storage in areas with elevated emissions and longer time since development. Conserving and planting urban trees above permeable surfaces and soils could contribute to long-term carbon storage in urban ecosystems.

Demystifying normalized difference vegetation index (NDVI) for greenness exposure assessments and policy interventions in urban greening.

Most nature and health research use the normalized difference vegetation index (NDVI) for measuring greenness exposure. However, little is known about what NDVI measures in terms of vegetation types (e.g., canopy, grass coverage) within certain analysis zones (e.g., 500 m buffer). Additionally, exploration is needed to understand how to interpret changes in average NDVI (e.g., per 0.1 increments) exposure in relation to changes in vegetation amount and types. In this study, we aimed to explore what vegetation types and amounts best explain the average NDVI and how changes in average NDVI values indicate changes in different vegetation coverages. We used spatial modeling to sample mean NDVI and percentages of vegetation for sample locations within the Greater Manchester case study area. We fitted linear, nonlinear, and mixed multivariate and univariate generalized additive models (GAMs) for multiple spatial scales to identify the relationships between NDVI and vegetation amount and types. Our results showed that the relationships between NDVI and individual vegetation types mostly follow nonlinear trends. We found that canopy and shrubs coverage exhibited a greater influence on mean NDVI exposure values than grass coverage at 300 and 500 m indicating that NDVI values are sensitive to certain types and amounts of vegetation within various buffer zones. We also identified increment in mean NDVI exposure values at lower, mid, and high ranges might be associated with varying changes in total greenspace percentage and individual vegetation types. For instance, at 300 m buffer, an increment of mean NDVI in the lower range (e.g., from 0.2 to 0.3) is associated with an about 17% increase in greenspace percentage. Overall, interpreting changes in NDVI values for urban greening interventions would require careful evaluation of the relative changes in types and quantities of vegetation for different buffer zones.

Seasonal variations in the amount of black carbon particles deposited on the leaf surfaces of nine Japanese urban greening tree species and their related factors.

As black carbon (BC) particles can be deposited on the leaf surfaces, urban greening is considered to be effective in purifying urban air. However, little information on the seasonal variations in the amount of BC particles deposited on the leaf surfaces (BC amount on the leaves) is available in Japanese urban greening tree species. Therefore, we investigated seasonal variations in the BC amount on the leaves of evergreen (Quercus glauca, Quercus myrsinaefolia, Osmanthus fragrans and Ilex rotunda) and deciduous (Zelkova serrata, Styrax japonica, Magnolia kobus, Cornus kousa and Cornus florida) broad-leaved tree species. The BC amount on the leaves tended to increase from April for different periods, and then reached a saturated state in the tree species, excluding M. kobus. In the 4 evergreen broad-leaved trees, the seasonal variation was positively correlated with the atmospheric concentration of BC particle. In the 5 deciduous broad-leaved trees, the seasonal variation was negatively and positively correlated with the water-repellence (water droplet contact angle) and the amount of epicuticular wax on the leaf surface, respectively. Therefore, the BC amounts on the leaves of evergreen and deciduous broad-leaved urban tree species are considered to be mainly regulated by environmental factors and leaf surface characteristics, respectively.

This is the first paper that reports the seasonal variations in the amount of BC particles deposited on the leaves of Japanese urban greening tree species and their related factors such as environmental conditions and leaf surface characteristics. This study will provide the basic and novel information for the phytoremediation of urban air pollution induced by BC particles in Asia.

From Conservation to Connection: Exploring the Role of Nativeness in Shaping People's Relationships with Urban Trees.

Deciding whether to plant native or non-native trees in public urban green spaces is becoming complex and conflicted, and decisions purely based on biotic nativeness are likely to be hamstrung as climate change and rising urban heat push many native species beyond their natural ranges. Importantly, tree selection considerations by urban planners and environmental managers will have to move beyond a primary focus on securing conservation and ecological outcomes, to elucidate and engage with a growing interest in the socio-cultural values and services of urban trees. Building on emerging theoretical perspectives, this place-based study explores the role that perceptions of nativeness have in shaping people's relationships with native and non-native urban trees and landscapes in an Australian city. Nativeness was associated with a range of subjective meanings including cultural identity, political expression, nature connection, desirable and undesirable traits, and environmental and cultural compatibility. Our findings emphasise that the ways in which urban trees and green spaces are valued and experienced is likely mediated by people's perceptions of nativeness and its importance relative to other attributes. To provision and sustain green spaces that meet the diverse needs and preferences of urban publics, planners and managers need to elucidate and incorporate the nuanced, place-based and multifaceted subjective meanings of nativeness into urban greening decision-making and practice.

Characterization of Volatile Organic Compound Emissions and CO2 Uptake from Eco-roof Plants.

Vegetation plays an important role in biosphere-atmosphere exchange, including emission of biogenic volatile organic compounds (BVOCs) that influence the formation of secondary pollutants. Gaps exist in our knowledge of BVOC emissions from succulent plants, which are often selected for urban greening on building roofs and walls. In this study, we characterize the CO2 uptake and BVOC emission of eight succulents and one moss using proton transfer reaction - time of flight - mass spectrometry in controlled laboratory experiments. CO2 uptake ranged 0 to 0.16 µmol [g DW (leaf dry weight)]-1 s-1 and net BVOC emission ranges -0.10 to 3.11 µg [g DW]-1 h-1. Specific BVOCs emitted or removed varied across plants studied; methanol was the dominant BVOC emitted, and acetaldehyde had the largest removal. Isoprene and monoterpene emissions of studied plants were generally low compared to other urban trees and shrubs, ranging 0 to 0.092 µg [g DW]-1 h-1 and 0 to 0.44 µg [g DW]-1 h-1, respectively. Calculated ozone formation potentials (OFP) of the succulents and moss range 4×10-7 - 4×10-4 g O3 [g DW]-1 d-1. Results of this study can inform selection of plants used in urban greening. For example, on a per leaf mass basis, Phedimus takesimensis and Crassula ovata have OFP lower than many plants presently classified as low OFP and may be promising candidates for greening in urban areas with ozone exceedances.

Demographic and spatial variables associated with spending time in nature during COVID-19 lockdowns.

To stop the spread of SARS-CoV-2 coronavirus (COVID-19) governments around the world implemented lockdowns restricting public travel. In the Australian state of Victoria, this included limiting permitted reasons for leaving home and restricting movements to within a 5 km radius of one's home. In 2020, we conducted a state-wide survey (N = 1024) of Victorians that coincided with a lockdown. We asked respondents where they had spent time in nature and how they perceived lockdowns affected the amount of time they spent in nature. We then considered demographic and spatial predictors of spending more or less time in nature. Women, younger people, and those living in areas with higher socio-economic status were likely to report spending more time in nature. Closer proximity of residents to parks and waterways and higher proportional area of native vegetation within a 1-km radius were also associated with more time in nature. Understanding how different groups were affected by restrictions on access to nature can help improve government management of crises like pandemics, including through urban planning for green space, supporting improved individual and societal resilience. We discuss the implications of our findings for improving access to nature during lockdowns as well as opportunities for a post-pandemic relationship with nature, particularly in urban settings.

Designing "Tiny Forests" as a lesson for transdisciplinary urban ecology learning.

The sustainability and livability of urban areas call for the next generation of scientists, practitioners and policy makers to understand the benefits, implementation and management of urban greenspaces. We harnessed the concept of "Tiny Forests©" - a restoration strategy for small wooded areas (~100-400 m2) - to create a transdisciplinary and experiential project for university forestry students that follows an ecology-with-cities framework. We worked with 16 students and a local municipality in the Munich, Germany metropolitan region to survey a community about its needs and desires and then used this information alongside urban environmental features and data collected by students (e.g., about soil conditions) to design a Tiny Forest. In this article, we describe the teaching concept, learning outcomes and activities, methodological approach, and instructor preparation and materials needed to adapt this project. Designing Tiny Forests provides benefits to students by having them approach authentic tasks in urban greening while experiencing the challenges and benefits of transdisciplinary communication and engagement with community members. Supplementary Information: The online version contains supplementary material available at 10.1007/s11252-023-01371-7.

Is Urban Greening an Effective Solution to Enhance Environmental Comfort and Improve Air Quality?

Urban greening has often been proposed as a cost-effective solution to improve environmental comfort, but may also deteriorate air quality. Quantifying these two opposing effects of urban greening is necessary to develop successful environmental policies for specific mega-city clusters. In this study, a high-resolution regional climate and air quality model (WRF-Chem, v4.0.3) was employed to test three scenarios aimed at quantifying the impact of land-use change and biogenic emissions from urban greening on regional climate and air quality. It was found that urban greening could effectively decrease the near-surface temperature by up to 0.45 °C, but the increased biogenic volatile organic compound (BVOC) emissions offset some of this cooling effect (by up to 65%). Land-use change due to urban greening dominated the improvement in human comfort but worsened diffusion conditions to result in the convergence of fine particulate matter in specific areas. The selection of low-emission tree species may be imperative, although increased emissions from urban greening will not change the sensitivity of ozone to precursors under the current scenario of anthropogenic emissions. This is because BVOC emissions due to urban greening will become a more important source of pollution with the development of clean energy and the popularity of low-carbon lifestyles.

Increasing trees and high-albedo surfaces decreases heat impacts and mortality in Los Angeles, CA.

There is a pressing need for strategies to prevent the heat-health impacts of climate change. Cooling urban areas through adding trees and vegetation and increasing solar reflectance of roofs and pavements with higher albedo surface materials are recommended strategies for mitigating the urban heat island. We quantified how various tree cover and albedo scenarios would impact heat-related mortality, temperature, humidity, and oppressive air masses in Los Angeles, California, and quantified the number of years that climate change-induced warming could be delayed in Los Angeles if interventions were implemented. Using synoptic climatology, we used meteorological data for historical summer heat waves, classifying days into discrete air mass types. We analyzed those data against historical mortality data to determine excess heat-related mortality. We then used the Weather Research and Forecasting model to explore the effects that tree cover and albedo scenarios would have, correlating the resultant meteorological data with standardized mortality data algorithms to quantify potential reductions in mortality. We found that roughly one in four lives currently lost during heat waves could be saved. We also found that climate change-induced warming could be delayed approximately 40-70 years under business-as-usual and moderate mitigation scenarios, respectively.

Urban Greening Effect on Land Surface Temperature.

Urbanization has accelerated the conversion of vegetated land to built-up regions. The purpose of this study was to evaluate the effects of urban park configuration on the Land Surface Temperature of the park and adjacent areas. In urban parks, the study analyzed the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Built-up Index (NDBI), and the Land Surface Temperature (LST). The NDVI categorization process resulted in the development of a vegetation density distribution. The majority of Medan's urban areas were categorized as low density, as seen by their low NDVI values. The NDBI values were significantly higher in the majority of the area. This shows that the majority of places are experiencing a decline in vegetation cover. The density of vegetation varies according to the placement of park components such as trees, mixed plants, recreation, and sports areas. According to LST data, the temperature in the urban park was cooler than in the surrounding areas. Although the surrounding areas are densely populated, urban parks are dominated by trees. Additionally, there is a green space adjacent to the park, which is a green lane that runs alongside the main roadways.

Indicators for climate change-driven urban health impact assessment.

Climate change can cause multiply potential health issues in urban areas, which is the most susceptible environment in terms of the presently increasing climate volatility. Urban greening strategies make an important part of the adaptation strategies which can ameliorate the negative impacts of climate change. It was aimed to study the potential impacts of different kinds of greenings against the adverse effects of climate change, including waterborne, vector-borne diseases, heat-related mortality, and surface ozone concentration in a medium-sized Hungarian city. As greening strategies, large and pocket parks were considered, based on our novel location identifier algorithm for climate risk minimization. A method based on publicly available data sources including satellite pictures, climate scenarios and urban macrostructure has been developed to evaluate the health-related indicator patterns in cities. The modelled future- and current patterns of the indicators have been compared. The results can help the understanding of the possible future state of the studied indicators and the development of adequate greening strategies. Another outcome of the study is that it is not the type of health indicator but its climate sensitivity that determines the extent to which it responds to temperature rises and how effective greening strategies are in addressing the expected problem posed by the factor.

Costs and benefits of combined sewer overflow management strategies at the European scale.

Combined sewer overflows (CSOs) may represent a significant source of pollution, but they are difficult to quantify at a large scale (e.g. regional or national), due to a lack of accessible data. In the present study, we use a large scale, 6-parameter, lumped hydrological model to perform a screening level assessment of different CSO management scenarios for the European Union and United Kingdom, considering prevention and treatment strategies. For each scenario we quantify the potential reduction of CSO volumes and duration, and estimate costs and benefits. A comparison of scenarios shows that treating CSOs before discharge in the receiving water body (e.g. by constructed wetlands) is more cost-effective than preventing CSOs. Among prevention strategies, urban greening has a benefit/cost ratio one order of magnitude higher than grey solutions, due to the several additional benefits it entails. We also estimate that real time control may bring on average a CSO volume reduction of just above 20%. In general, the design of appropriate CSO management strategies requires consideration of context-specific conditions, and is best made in the context of an integrated urban water management plan taking into account factors such as other ongoing initiatives in urban greening, the possibility to disconnect impervious surfaces from combined drainage systems, and the availability of space for grey or nature-based solutions.

Historical Urban Tree Canopy Cover Change in Two Post-Industrial Cities.

Present-day spatial patterns of urban tree canopy (UTC) are created by complex interactions between various human and biophysical drivers; thus, urban forests represent legacies of past processes. Understanding these legacies can inform municipal tree planting and canopy cover goals while also addressing urban sustainability and inequity. We examined historical UTC cover patterns and the processes that formed them in the cities of Chelsea and Holyoke, Massachusetts using a mixed methods approach. Combining assessments of delineated UTC from aerial photos with historical archival data, we show how biophysical factors and cycles of governance and urban development and decay have influenced the spatiotemporal dynamics of UTC. The spatially explicit UTC layers generated from this research track historical geographic tree distribution and dynamic change over a 62-year period (1952-2014). An inverse relationship was found between UTC and economic prosperity: while canopy gains occurred in depressed economic periods, canopy losses occurred in strong economic periods. A sustainable increase of UTC is needed to offset ongoing losses and overcome historical legacies that have suppressed UTC across decades. These findings will inform future research on residential canopy formation and stability, but most importantly, they reveal how historical drivers can be used to inform multi-decadal UTC assessments and the creation of targeted, feasible UTC goals at neighborhood and city scales. Such analyses can help urban natural resource managers to better understand how to protect and expand their cities' UTC over time for the benefit of all who live in and among the shade of urban forests.