Better Forests, Better Cities

Chapter 2

Health and Well-Being

Integrating trees and forests into the urban landscape makes cities more vibrant and livable, and can generate a diverse suite of health benefits, from cooler temperatures to improved mental health to space for social interaction and community building. Outside cities, forests hold the blueprints to medicines, help provide cleaner water, and provide spaces to relax and recreate.

Minoru K/Shutterstock


Living in cities provides numerous benefits, including access to economic and educational opportunities, shorter commutes, public services, and intercultural exchange. But urban living can have negative impacts on the mental and physical health of residents. Exposure to air pollution, chronic stressors such as noise pollution, sedentary lifestyles, increased risk of communicable disease in crowded conditions, and extreme temperatures in the built environment can erode overall health and quality of life—and can sometimes be deadly (Bai et al. 2012; Kuddus et al. 2020). Climate change threatens to amplify impacts through higher temperatures, aberrant rainfall, and, for coastal cities, rising sea levels (Revi et al. 2014).

As they strive to create healthier cities, city leaders can embrace sustainably managed inner or “urban” forests as an NBS. When trees are integrated into the urban landscape in socially and ecologically appropriate ways, cities can become more livable and vibrant spaces. Evidence suggests that, unlike many issue-specific municipal investments, the “urban forest” can generate a diverse suite of benefits at the same time—from cooler temperatures and air quality improvement to improved health and space for social interaction.

How forests relate to human well-being

In 1984, a pioneering study found that patients whose windows looked out upon a group of trees healed from surgery faster and needed fewer painkillers than those whose windows had no view of nature (Ulrich 1984). Since then, a rapidly expanding and compelling body of evidence—spanning disciplines as diverse as epidemiology, psychology, forestry, and geography—suggests that forests and nature play an important role in human health. Evidence also indicates that forests in and around cities may contribute to social and economic well-being because benefits accrue to individuals using forests to support their livelihoods, to property owners whose parcels increase in value, and to entire regions as forests support tourism or other industries.

Why context matters

Cities are immensely diverse in climate, culture, politics, language, and environmental contexts. As such, considering the local cultural, political, climatic, environmental, and socioeconomic contexts is important for successfully integrating trees and forests into city planning. The benefits that forests in cities provide will vary from city to city around the world.

Inner forests (and related green infrastructure) may not always provide the intended benefits, and they can sometimes present unintended risks (Hartig et al. 2014; Lõhmus and Balbus 2015). By understanding these risks and deliberately incorporating how to address them into the planning and decision-making processes, the potential for unintended negative outcomes can be minimized and the many positive benefits realized (Lõhmus and Balbus 2015; Wolf 2017). And by empowering communities to guide urban greening initiatives and stewardship of the inner forest, these living elements of urban infrastructure can help to diminish—rather than exacerbate—inequities among groups.

About This Section

Forests near and far support human health and well-being—socially, economically, and ecologically. In the following sections, we summarize the ways that inner and nearby forests affect the quality of life of city residents. Local forests provide many direct and indirect health benefits. This section thus focuses on inner forests that provide unique opportunities for leaders seeking to create healthy and habitable cities. Nearby and faraway forests also provide health benefits via water access and treatment, climate change mitigation, and biodiversity, which are addressed in the respective sections.

To explore these benefits, we synthesized statements and goals shared by many city leaders around the world into eight specific goals related to health and well-being:

  1. Reducing extreme heat
  2. Enhancing urban air quality
  3. Promoting physical and mental health in city residents
  4. Creating walkable, safe streets
  5. Supporting community connections
  6. Reducing urban environmental inequity
  7. Ensuring provision of food, medicine, and raw materials
  8. Enhancing economic well-being

Goal 1: Reducing Extreme Heat


Cities suffer from the heat island effect. Most cities are dominated by buildings and pavement, with relatively little vegetation and green space, which contributes to “urban heat islands”—elevated temperatures in urban areas compared to their rural surroundings. Urban areas can be 2°C–4°C—and as much as 15°C—warmer than adjacent areas (Taha 1997; Heaviside et al. 2017; Mohajerani et al. 2017). The heat island effect presents a number of risks to human health and well-being, including the following:

  • Increased risk of heat-related mortality and morbidity, especially during heat waves; high temperatures can cause heat stroke, dehydration, exacerbate existing diseases, and even cause death (Luber and McGeehin 2008); stifling heat may also interfere with worker productivity (Zander et al. 2015) and with learning and educational achievement (Park et al. 2020)
  • Potential for negative effects on mental health, although more research is needed (Thompson et al. 2018)
  • Spikes in energy demand (Li et al. 2019)
  • Power outages due to high energy demand at midday, which can further affect resident safety, impair economic activity, and burden health and emergency services (WMO and WHO 2015)
  • Degradation of environmental quality, such as increased concentrations of urban smog (Akbari et al. 2001), increased ground-level ozone (Luber and McGeehin 2008; Jacob and Winner 2009), and decreased water quality (Phelan et al. 2015; Heaviside et al. 2017)

Climate change will exacerbate these risks. Since the advent of the Industrial Revolution, the average temperature near Earth’s surface has increased about 1°C (1.8°F; IPCC 2018). The urban heat island effect magnifies the effects of climate change for cities, leading to higher temperatures than rural areas and more extreme heat waves (Estrada et al. 2017). Already, extreme heat in cities has been responsible for thousands of excess mortalities in recent decades (Heaviside et al. 2017). The 2003 European heat wave, for example, killed more than 70,000 people (Robine et al. 2008). Thousands in India and hundreds in Pakistan died as temperatures surpassed 45°C in 2015 (Masood et al. 2015; Sarath Chandran et al. 2017). In 2021, a lingering heat wave shattered records in western North America, spiking heat-related illnesses and killing hundreds, an event the World Weather Attribution initiative described as “virtually impossible without human-caused climate change” (WWA 2021). Records suggest July 2021 was the hottest month on record (NOAA 2021).

Some urban residents are more susceptible to these risks than others. In general, lower-income and marginalized communities are disproportionately exposed to the deleterious effects of heat islands (UN DESA 2020). Children, people above the age of 50, and those with preexisting health conditions are particularly vulnerable to heat-related illnesses (Kovats and Hajat 2008). Densely settled and lower-income communities often lack access to places to cool down, such as shaded green spaces and open areas (Harlan et al. 2006; Luber and McGeehin 2008). In addition, many low-income households lack insulation, air conditioning, and access to resources necessary to cope with extreme temperatures (Harlan et al. 2006; Ko 2018).

What roles can trees and forests play?

Trees in urban areas can mitigate the urban heat island effect, especially locally, by the following actions (Figure 3):

  • Shading surfaces and people. Tree canopies intercept and reflect up to 90 percent of incoming solar radiation. Shade makes heat more tolerable and can protect people from excessive sun exposure during travel, work, or leisure (Nowak and Dwyer 2007). Trees that shade buildings can reduce surface temperatures in a wide variety of contexts (Wang et al. 2014); for example, surface temperatures were reduced by 11°C–25°C in Sacramento, California (Akbari et al. 1997); by 5°C–7°C in Akure, Nigeria (Morakinyo et al. 2013); and by 9°C in Melbourne, Australia (Berry et al. 2013). In Bangalore, India, streets with trees had local ambient air temperatures that were 5.6°C lower than streets without trees, and their surface temperatures were 27.5°C lower (Vailshery et al. 2013).
  • Cooling the air via evapotranspiration. During the day, trees may create lower air temperatures by releasing water into the air as they photosynthesize (Bowler et al. 2010a; Säumel et al. 2016). As water vapor is released, it takes with it some of the ambient heat. Large trees with ample access to water may evaporate more than 100 liters of water in a single day, which dissipates about 70 kilowatt-hours of solar energy that would otherwise remain stored in the urban environment (Fath 2018).

Effects of cooling are most pronounced locally. A 2010 global meta-analysis found that parks were, on average, 0.94°C cooler during the day than surrounding urban areas, with greater benefits in larger parks and in those containing trees (Bowler et al. 2010a). A more recent review suggests large urban parks and green spaces (more than 10 ha)—especially those with mature trees—can reduce air and surface temperatures by 1°C–2°C (Aram et al. 2019). Some evidence shows that areas adjacent to green spaces also are cooler (Mohajerani et al. 2017), from a few hundred meters (Tyrväinen et al. 2005; Aram et al. 2019) to perhaps as much as a kilometer (Bowler et al. 2010a).

The urban forest can both reduce the risk of heat-related illness or death and increase perceived comfort for residents (Taha 1997; Tyrväinen et al. 2005; Salmond et al. 2016; Gunawardena et al. 2017; Wolf et al. 2020):

  • Researchers estimate that in 97 U.S. cities alone, urban tree cover helps to avoid 245–346 premature deaths and 50,000 hospitalizations annually (McDonald et al. 2020).
  • In Toronto, residents in neighborhoods with the lowest tree canopy cover (less than 5 percent) made 5 times as many heat-related emergency calls as residents in neighborhoods with more than 5 percent canopy cover and nearly 15 times as many emergency calls as residents in neighborhoods with more than 70 percent canopy cover (Graham et al. 2016).

Figure 3 | Localized Cooling Benefits from Trees through Shading and Evapotranspiration

Notes: Pavement and concrete in cities absorb energy from the sun and then radiate that energy out, heating the air in cities more than in the surrounding countryside. Urban trees provide shade, preventing pavement and concrete from heating up, and also cool the air by transpiring water. Trees can cool neighborhoods by up to 4 degrees Fahrenheit (McDonald et al. 2016).

Source: Authors. Adapted from McDonald et al. (2016).

Caveats and considerations

Urban forests may complement or be incorporated into other interventions to reduce the urban heat island effect. These interventions include permeable pavements and green roofs (Mohajerani et al. 2017).

Cooling by urban trees will be greatest in local areas, and forests may not provide net benefits in some situations, such as these:

  • Trees and shrubs very close to buildings may prevent nighttime radiative cooling of buildings (Bowler et al. 2010a; Wang et al. 2014; Ko 2018).
  • Tall trees can reduce wind speeds (Mohajerani et al. 2017). This can be a benefit in cold climates but can be a disadvantage in warm or humid climates (Ko 2018). At night, tree canopies can also reduce airflow and thus retain heat (Bowler et al. 2010a; Salmond et al. 2016).
  • The microclimate-altering effects of urban trees and other vegetation are more pronounced in cities in warm and dry climates (Taha 1997).
  • Because evapotranspiration increases humidity (Salmond et al. 2016), high levels of evapotranspiration may reduce comfort for urban dwellers in hot, humid climates, even as evapotranspiration lowers near-ground temperatures. However, the increase in humidity may be small compared to the reductions in temperature (Vailshery et al. 2013).

Some species provide more cooling benefits than others. Leaf area index, evapotranspiration rate, crown diameter, and the albedo of different tree species affect the cooling benefits they provide (Jim and Chen 2009; Bowler et al. 2010a; Smithers et al. 2018). Fast-growing, long-lived, and drought-tolerant native species of trees with relatively reflective surfaces are most likely to deliver cooling benefits (Smithers et al. 2018).

Goal 2: Enhancing Urban Air Quality


Air pollution threatens the well-being of most urban dwellers. An estimated 9 out of 10 people breathe polluted air worldwide (WHO 2016). Responsible for approximately 4.2 million deaths globally in 2016 (WHO 2016), exposure to ambient air pollution is considered one of the greatest risk factors for global public health (Burnett et al. 2018). Exposure to air pollution disproportionately affects residents of low- and middle-income countries. It disproportionately affects lower-income and racial or ethnic minority residents, as documented in North America (Landrigan et al. 2018; Tessum et al. 2019; Nicolaou and Checkley 2021).

Air pollution needs to be addressed at the source (Baldauf and Nowak 2014; EPA 2019) because more pollutants are emitted than can reasonably be contained with mitigation measures. But eliminating air pollution is an intractable challenge to even the most well-resourced governments—especially pollution from nonpoint sources such as vehicles and woodsmoke/biomass burning from residences. Trees and other green infrastructure can help to remove these pollutants locally and/or be used to create barriers between pollutant sources and the people or organisms exposed (Baldauf and Nowak 2014; Hewitt et al. 2020; Wernecke and Pool 2022).

What roles can forests play?

Typically, urban forests reduce air pollution by around 1 percent at the city scale (Litschke and Kuttler 2008; Baldauf and Nowak 2014; Salmond et al. 2016; Sicard et al. 2018; Xing and Brimblecombe 2020). But even a modest reduction in pollution can be very valuable to cities. For example, in 2010, forests in the continental United States (both inside and outside of cities) removed an estimated 17.4 million tons of air pollutants such as particulate matter (PM), contributing to health benefits—including 850 avoided premature mortalities—worth an estimated $6.8 billion (Nowak et al. 2014). However, reducing pollutants further may require a large expansion in tree canopy cover (Litschke and Kuttler 2008; Nieuwenhuijsen et al. 2017). Models of the effects of urban trees on local air quality (i.e., site scale) suggest larger reductions are possible with proper planning and species selection (Pugh et al. 2012; Janhäll 2015; Abhijith et al. 2017; Barwise and Kumar 2020).

Forests and other vegetation can have positive or negative effects because they interact with urban air pollutants in several different ways. Urban trees alter pollutant concentrations by trapping pollutants or by redirecting airflow:

  • Removing particles from the air (deposition) by either taking in gaseous pollutants or having particles settle on their surfaces (Beckett et al. 1998). Trees remove pollutants at faster rates than other types of vegetation (Fowler et al. 2004). Dense but porous vegetation serves as an ideal surface for deposition, superior to the comparatively smooth surfaces of buildings and roads.
  • Dispersing pollutants (dilution) in the urban environment by altering airflow patterns and slowing wind (Abhijith et al. 2017). Dilution of highly polluted air with clean air from surrounding areas enhances urban air quality. Trees can help or hinder dilution: they may act as an obstacle, slowing wind speeds and reducing the exchange between clean and polluted air, suppressing pollutant dispersion (Säumel et al. 2016; Abhijith et al. 2017; Xing and Brimblecombe 2020) or as a source of turbulence that increases the exchange, based on characteristics of the built environment and on meteorological conditions.

But trees can also emit two types of particles that affect air quality:

  • Biogenic volatile organic compounds (bVOCs) can act as precursors to pollutants such as ozone and secondary organic aerosols and can worsen air quality (Laothawornkitkul et al. 2009; Leung et al. 2011; Calfapietra et al. 2013; Cariñanos et al. 2017). Even healthy plants produce bVOCs (Smith 1981), but exposure to drought, pollutants, heat, and excessive sunlight, as well as physical injury or attacks by pests, may all induce the release of additional bVOCs (Laothawornkitkul et al. 2009; Calfapietra et al. 2013). Increases in global temperature may increase bVOC emissions further (Laothawornkitkul et al. 2009; Wang et al. 2014).
  • Allergenic pollen can undermine health (Smith 1981; Beckett et al. 1998; Cariñanos and Casares-Porcel 2011; Säumel et al. 2016; Eisenman et al. 2019; Hewitt et al. 2020). Climate change and air pollution have led to the increased production of pollen in some tree species (Cariñanos and Casares-Porcel 2011). Allergies due to pollen can decrease the quality of life of urban dwellers, and allergen exposure has been linked to ill health conditions such as cardiovascular disease, pneumonia, and asthma (Curtis et al. 2006). Air pollutant exposure can even worsen the health impacts of pollen. When pollen grains (as airborne PM) interact with other air pollutants, they can be modified, enhancing their allergic potential as well as their penetration potential into the respiratory tract (Eisenman et al. 2019). Exposure to air pollutants can also exacerbate allergy symptoms (Jianan et al. 2007; Cariñanos and Casares-Porcel 2011).

How do trees interact with the built environment?

Trees in urban “street canyons” formed by tall buildings may trap polluted air near the ground level (Figure 4, top; Abhijith et al. 2017; Hewitt et al. 2020). In these street canyons, the movement of air is already restricted. Trees with canopies higher than 1–2 meters (m) may slow wind speeds and limit air pollutant dilution, increasing the concentration of various pollutants in urban canyons by as much as 20–96 percent (Abhijith et al. 2017). The aspect ratio (i.e., the height to width ratio of buildings to road) influences airflow in the canyon, as does vegetation density, tree spacing, and wind direction (Abhijith et al. 2017).

On the other hand, hedges and shrubs (around 1–2 m tall) in street canyons may provide an effective barrier between pedestrians and traffic emissions while permitting adequate dispersion of air (Figure 4; Janhäll 2015; Säumel et al. 2016; Abhijith et al. 2017). This is because low, permeable hedges create vortices that may carry air away from footpaths along roads and generally have positive effects on air quality at ground level (Abhijith et al. 2017).

Similarly, in open road conditions, trees and hedges can reduce the concentration of pollutants near highways by serving as barriers between pollution sources and human receptors (Figure 5; Abhijith et al. 2017; Xing and Brimblecombe 2020). Unlike vegetation in urban canyons, these barriers provide maximum benefits when the trees or hedges are tall (>0.5 m), thick (>10 m), and moderately porous (Baldauf 2017). Empirical studies have shown reductions in pollutant concentrations of 15–60 percent when trees and hedges are used as barriers along open roads (Abhijith et al. 2017).

Figure 4 | Air Pollution in Urban Street Canyons

Note: Urban trees can trap pollutants in urban street canyons (top) but can also serve as effective barriers between pollutants and people in some situations (bottom).

Source: Authors. Adapted from Trivedi et al. 2020.

Figure 5 | Trees as Effective Barriers between Pollutants and Pedestrians

Source: Authors. Adapted from Abhijith et al. (2017).

Strategic plantings of trees along roadsides could shield sensitive populations from exposure to PM and other pollutants, especially in areas with insufficient green space. Because deposition of pollutants on plant surfaces decreases with distance, trees should be planted as near as possible to the source of pollution (e.g., a road with automobile traffic) without blocking cleaner air from the atmosphere from entering the area (Litschke and Kuttler 2008; Leung et al. 2011; Janhäll 2015).

Caveats and considerations

As a result of the interactions, without adequate planning, the net effect of the inner forest on air quality in any given local area may be neutral or negative (Litschke and Kuttler 2008; Leung et al. 2011; Baldauf and Nowak 2014; Salmond et al. 2016; Sicard et al. 2018; Eisenman et al. 2019; Xing and Brimblecombe 2020).

When it comes to enhancing air quality, tree characteristics matter. Different trees remove different amounts of pollutant particles, depending on the following:

  • Leaf texture (e.g., waxy, hairy) and surface area (Janhäll 2015). For example, leaves with many tiny hairs may capture more pollutants.
  • Growth form. Shrubs (i.e., woody plants with many stems) remove more PM than trees, but both remove more PM than other types of plants, such as grasses (Cai et al. 2017). However, if the vegetation is too dense, it can become a barrier forcing air to move over instead of filtering through.
  • Growth strategy. Evergreen coniferous species (e.g., pine) typically remove more pollutants and dust than deciduous species (e.g., sycamore or maple) because the tiny needle-like leaves of many coniferous species create an effective filter (Janhäll 2015). Evergreen species also bear leaves throughout the entire year and can thus intercept pollutants year-round (Cavanagh and Clemons 2006; Litschke and Kuttler 2008).

Adapting strategies to site characteristics and local context are important for good outcomes (Hewitt et al. 2020). A slew of factors in the built and natural environment affects whether trees will have a positive, negative, or neutral effect on air quality, including airflow patterns, wind speed, building height and density, local humidity, temperature, and proximity to and type of pollutant source, among other factors (Cavanagh and Clemons 2006; Litschke and Kuttler 2008; Elmqvist et al. 2015; Salmond et al. 2016; Cai et al. 2017; Kumar et al. 2019; Xing and Brimblecombe 2020).

Using low-emitting species can support air quality goals in urban areas by reducing bVOCs and pollen (Cariñanos and Casares-Porcel 2011; Calfapietra et al. 2013). Municipalities frequently overlook species selection during large-scale tree-planting projects (Churkina et al. 2015). One study estimated that selecting the low-bVOC-emitting tree species over high-emitting species in a large-scale tree-planting initiative in Denver would be equivalent to avoiding emissions from nearly 500,000 cars from inner-city traffic (Curtis et al. 2014).

More research is needed on how best to use trees to reduce air pollution in cities (Janhäll 2015; Abhijith et al. 2017; Eisenman et al. 2019; Kumar et al. 2019; Hewitt et al. 2020). In particular, research that explores the effects on dilution, empirically validates models, and reports on effects at multiple spatial scales is needed (Beckett et al. 1998; Janhäll 2015; Salmond et al. 2016; Xing and Brimblecombe 2020). Urban vegetation cannot substitute for source emissions reductions but can improve local conditions and lead to better health outcomes for residents.

Goal 3: Promoting Physical and Mental Health in City Residents


Living in cities presents health risks (Bai et al. 2012; Kuddus et al. 2020). As a result of heightened exposure to air, light, and noise pollution and decreased exposure to sunlight and key microorganisms, urban dwellers may be more vulnerable to noncommunicable, immune, and respiratory diseases and infections (Flies et al. 2019). Urban lifestyles often permit fewer opportunities for physical activity, time in nature, and spaces for social connection with neighbors (Frumkin 2002).

Mental health can also be affected by the social, economic, and environmental conditions of the city landscape. Urban living can increase the risk of developing some mental illnesses and disorders (Peen et al. 2010; Lecic-Tosevski 2019; Ventriglio et al. 2019). Abundant sensory stimuli and high population densities in cities can create stress, with few opportunities for coping. Stress manifests in both the brain and the body (McEwen 2008) and is a factor in illnesses ranging from depression to cardiovascular disease (Cohen et al. 2007).

Many of the environmental hazards of cities—such as exposure to air pollution, unsafe drinking water, or extreme temperatures—disproportionately affect lower-income communities and marginalized residents (Frumkin 2002; Kondo et al. 2015). Creating healthier cities will require interventions to reduce disparities in access to health care, increase availability of safe housing, and further improve sanitation (Dye 2008). But the urban forest also serves as a dispersed and relatively low-cost element of public health infrastructure.

What roles can forests and green spaces play?

Natural environments can reduce stress (Case Study 1; Hartig et al. 2014; McCormick 2017; Nesbitt et al. 2017; Kondo et al. 2018; Summers and Vivian 2018; Bratman et al. 2019). Exposure to urban forests and other elements of nature may reduce risks related to chronic stress by the following actions:

  • Providing opportunities for restoration (i.e., recovery) of a person’s adaptive capacity to cope with stressful life events or exposure to environmental stressors (Hartig et al. 2014; Bowler et al. 2010b).
  • Dampening the effect of urban stressors. Noise, for instance, is both a nuisance and an environmental stressor that can interfere with communication, alter behavior, and impair work performance (Stansfeld and Matheson 2003). The foliage of urban forests can create a physical barrier that absorbs the energy of sound waves and reduces noise overall (Nowak and Dwyer 2007; Dzhambov and Dimitrova 2014; Wang et al. 2014; Säumel et al. 2016).

Case Study 1 | Shinrin-yoku, or Forest Bathing (Japan and East Asia)

Leisurely visits to forests for relaxation, known as “forest bathing,” “forest therapy,” or shinrin-yoku in Japanese, can offer a suite of health benefits.a Shinrin-yoku combines both physical activity and stress-reducing behavior, such as mindfulness and is a cultural practice employed by many in eastern Asia and elsewhere.b

Walks in forest settings may increase immune system activity compared with walks in urban settings, including the activity of anti-tumorigenic natural killer cells.c The benefits from forest bathing may arise from the inhalation of phytoncides, or antimicrobial biological volatile organic compounds emitted by plants, such as alpha-pinene or limonene.d Research has examined the effects of shinrin-yoku on the cardiovascular system, the respiratory system, and mental health conditions including depression, anxiety, and mood disorders.e One review of studies on forest therapy found significant improvements in depression in 21 out of 28 studies identified,f and forest bathing has been successfully incorporated into other evidence-based therapy programs.g

Forest bathing may significantly reduce stress, including lowering salivary cortisol levelsh and both diastolic and systolic blood pressure.i Some evidence also suggests it can reduce insomnia and psychological distress associated with chronic illness and pain.j A review of randomized controlled trials found a consistent positive trend in a variety of psychological and physiological health outcomes after forest bathing.k Research on forest bathing is nascent but rapidly growing, and thus far it supports the benefits of forest bathing and provides yet another reason to conserve and allow access to intact inner and nearby forests.

Sources: a. Li 2010; Song et al. 2016; b. Hartig et al. 2014; c. see Li et al. 2008; Kuo 2015; d. Li 2010; Kuo 2015; e. Hansen et al. 2017; Oh et al. 2017; f. Lee et al. 2017; g. Hansen et al. 2017; h. Antonelli et al. 2019; i. Ideno et al. 2017; j. Hansen et al. 2017; k. Oh et al. 2017.

Exposure to nature—including forests and urban green spaces—is associated with better mental health and psychological well-being, including

  • improved mood, perceived well-being, sleep, and ability to focus (Bratman et al. 2019); and
  • reduced risk of some psychological disorders (Bratman et al. 2019) and better mental health outcomes (Wolf et al. 2020). For example, the presence of urban green spaces or residential greenness have been linked to lower anxiety and depression (see Braubach et al. [2017] or Vanaken and Danckaerts [2018]).

Exposure to forests and nature may benefit children’s mental development. A growing body of research shows that regular access to nature helps children thrive and is important for their mental health. Access to forests and nature has been found to improve cognitive functioning (Hartig et al. 2014; Jennings et al. 2016; McCormick 2017; Kondo et al. 2018) and reduce behavioral difficulties (Summers and Vivian 2018; Vanaken and Danckaerts 2018). Increased exposure to natural settings and outdoor activities in green spaces also may reduce attention-deficit/hyperactivity disorder (Braubach et al. 2017; Nesbitt et al. 2017; Summers and Vivian 2018; Vanaken and Danckaerts 2018), improve attention capacity (Tzoulas et al. 2007), enhance creative development (Bratman et al. 2019), and improve academic performance (Jennings et al. 2016; Bratman et al. 2019). For example, a study of more than 3,500 school-age children in London found that exposure to woodland was associated with higher cognitive development scores and lower risks of behavioral and emotional problems, even after controlling for other variables (Maes et al. 2021).

Exposure to green space, tree canopies, and urban nature is associated with better physical health (Case Study 1). Examples include the following:

  • Reduced risk of noncommunicable diseases, including cardiovascular disease (Nieuwenhuijsen 2018; Wolf et al. 2020) and type II diabetes mellitus (den Braver et al. 2018; Twohig-Bennett and Jones 2018)
  • Reduced indicators for stress and disease, such as salivary stress hormones, heart rate, and blood pressure (Meyer and Bürger-Arnd 2014; Hansen et al. 2017; Twohig-Bennett and Jones 2018; Wolf et al. 2020); forest bathing, in particular, seems to have positive effects on physiological states and immune activity (Case Study 1)
  • Lower body mass index (Lachowycz and Jones 2011; Wolf et al. 2020), a predictor of other health outcomes
  • Improved pregnancy and birth outcomes (Dzhambov et al. 2014; Braubach et al. 2017; Nesbitt et al. 2017; Twohig-Bennett and Jones 2018; Kloog 2019)
  • Reduced risk of premature death; most evidence supports a significant inverse relationship between premature mortality and residential greenness (Gascon et al. 2016; Twohig-Bennett and Jones 2018; Rojas-Rueda et al. 2019)

Exposure to forests and nature can improve people’s immune systems (Kuo 2015; Shanahan et al. 2015; Braubach et al. 2017). Being exposed to a diverse array of microorganisms—to which humans were exposed for much of our evolutionary history—may stimulate the immune system and enhance its ability to distinguish between beneficial and harmful bacteria, which can improve health outcomes, including autoimmune disorders, allergies, depression, or cancer (Rook 2013; Kuo 2015; Sandifer et al. 2015; von Hertzen et al. 2015; Lai et al. 2019). These microorganisms are accessed in forests and nature.

Preventing deforestation and degradation of intact forest ecosystems outside of cities may help control the spread of infectious diseases. Deforestation and land-use changes have been linked to the emergence and spread of pathogens (Karjalainen et al. 2010; Alimi et al. 2021; Austin 2021). For example, forest fragmentation and deforestation in North America is implicated in the increasing incidence of Lyme disease, while climbing rates of deforestation in Asia, Africa, and Latin America have been linked to increases in malaria and malaria vector populations (Karjalainen et al. 2010). Protecting highly biodiverse tropical forests may also prevent spillover of new zoonotic diseases, such as coronaviruses, from animal hosts to humans (Afelt et al. 2018; Sokolow et al. 2019).

Caveats and considerations

Urban trees can also sometimes pose health risks to urban residents, including the following:

  • Injury. Branches and tree roots can pose a risk of injury, for example, when roots displace sidewalk paving or when tree limbs (or entire trees) fall on roads or property (Escobedo et al. 2011).
  • Zoonotic diseases. Wooded areas may house unwanted animals, such as feral dogs, and pests that carry disease, such as ticks (Lyytimäki et al. 2008; Coutts and Hahn 2015; Lõhmus and Balbus 2015; von Döhren and Haase 2015; Stone et al. 2017).

To reduce these risks, cities may need to pursue targeted interventions. Examples include periodic tree trimming or removing hazardous trees, public education, and population control of animal hosts and vectors (Lyytimäki et al. 2008; Lõhmus and Balbus 2015). City leaders should include funding for tree pruning and removal in city budgets.

Goal 4: Creating Walkable, Safe Streets


Cities around the world are striving to increase opportunities for public transport and active transit (i.e., by foot or by bicycle) as part of their decarbonization strategies. But greener cities are not the only benefit of such efforts. Physical inactivity is a leading global health concern (Kohl et al. 2012), with many harmful effects on the body (Tremblay et al. 2010). Creating more inviting spaces for active transport, physical exercise, and recreation could be a health-environment win-win.

What roles can forests and green spaces play?

Physical activity may explain part of the connection between health and nature exposure (Hartig et al. 2014). But evidence connecting green space directly to increased physical activity remains mixed (Lee and Maheswaran 2011; Nieuwenhuijsen 2018). Evidence suggests green spaces may either have a positive (e.g., Lachowycz and Jones 2011; Calogiuri and Chroni 2014) or neutral (e.g., Hartig et al. 2014; Hankey and Marshall 2017; Kondo et al. 2018) effect on physical activity. In one recent review, however, 18 out of 19 studies suggested a positive effect of urban trees on levels of physical activity (Wolf et al. 2020).

By providing shade, reducing exposure to air pollution, and enhancing aesthetic appeal, street trees might encourage active transport (Figure 6; Kumar et al. 2019; Wolf et al. 2020). Perceived safety, distance to destination, and presence of infrastructure (e.g., sidewalks, bike lanes) also drive decisions related to active transit (Hartig et al. 2014).

Urban green spaces and large, mature trees have been associated with reduced levels of crime, aggressive behavior, and other antisocial activities (Kondo et al. 2015; Wolf and Robbins 2015; Jennings et al. 2016; Wolf et al. 2020). Although evidence remains mixed, researchers have found lower crime rates related to characteristics such as street tree density, when controlling for other confounding variables. For example, increased canopy cover has been associated with reduced rates of homicide in Bogotá (Escobedo et al. 2018), and reduced rates of gunshot assaults in Philadelphia (Kondo et al. 2017). In Baltimore, a 10 percent increase in canopy was associated with a 12 percent decrease in crime (Troy et al. 2012).

Well-placed and well-maintained urban trees also hold the potential to enhance transportation safety. The presence of trees may reduce the number of vehicle collisions (Lyytimäki et al. 2008; Wolf 2010; Van Treese et al. 2017). Trees may also help to demarcate the edge of the road or create a barrier between vehicles and pedestrians (Mullaney et al. 2015).

In addition, urban and nearby forests create spaces for recreation and play (Tyrväinen et al. 2005; O'Brien et al. 2017). Forested areas in and around cities can host hikers, campers, trail runners, birdwatchers, and provide space for children to engage in free play. The cooling and shading provided by trees moderates microclimates, which can encourage use. If accessing areas of urban nature is challenging or expensive, these benefits will not be equitably distributed among populations.

Figure 6 | Trees can be incorporated into urban streets to create favorable microclimates for active transit and play for children

Source: WRI Mexico.

Caveats and considerations

Aspects of urban trees can threaten residents’ safety when commuting or exercising.

  • As mentioned above, tree roots can damage sidewalks and some pavements (Randrup et al. 2001; Escobedo et al. 2011; Roy et al. 2012). Careful species and site selection for and maintenance of trees can reduce these risks and ensures accessibility for all users of public infrastructure.
  • Poorly placed trees can also be a hazard along roads. Trees and other vegetation may block lines of sight for drivers, bikers, and other commuters (Wolf 2006; Lyytimäki et al. 2008). Species selection, placement, and proper maintenance can reduce this risk.

Urban forests may also affect residents’ perceived safety (Figure 7, top; Kondo et al. 2015; Mancus and Campbell 2018). This is also mediated by the following factors:

  • Personal identity. Obstructed views or shaded spaces may increase fear of crime or danger, particularly in women, ethnic minorities, and the elderly—and in those who have experienced crime directly or indirectly in the past (Jansson et al. 2013; Maruthaveeran and Konijnendijk van den Bosch 2014). This depends on the city context.
  • Local context and characteristics of the forested area. Poorly maintained, poorly lit, or littered green spaces may be perceived as places for illicit activity or antisocial behavior (Tzoulas et al. 2007; Jansson et al. 2013; Maruthaveeran and Konijnendijk van den Bosch 2014; Kondo et al. 2015; von Döhren and Haase 2015; Wolf 2017).

Figure 7 | Inner Forests and Perceived Safety

Note: Areas with urban trees could make some residents feel unsafe (left), but these spaces can also be intentionally designed or maintained to increase perception of safety and resident comfort for all users (right).

Source: Authors. Adapted from Trivedi et al. 2020.

The quality and accessibility of green spaces affects how people use them for recreation and physical activity (Lee and Maheswaran 2011; Calogiuri and Chroni 2014). As described above, fear of crime may prevent certain groups from being physically active or commuting near these spaces, especially in the dark (Lyytimäki and Sipilä 2009; Jansson et al. 2013). In some contexts, maintaining vegetation and installing infrastructure (lights, etc.) may be necessary to create safe and accessible areas for all residents (Green City Partnerships 2019). Moreover, safeguards may need to be put in place to ensure that green spaces are used in a safe way that allows use by all residents (for example, regulating mountain biking on single-track pedestrian trails).

Goal 5: Supporting Community Connections


Strong social networks in communities form the foundation for thriving cities. Robust social networks may increase community resilience against disturbances such as natural disasters (e.g., Islam and Walkerden 2014; Townshend et al. 2015). In individuals, social relationships and shared trust support health and well-being (Hartig et al. 2014; Braubach et al. 2017) and buffer against stress (Jennings et al. 2016). Such social cohesion can also reduce feelings of loneliness and isolation (Wolf 2017), which have been linked to higher rates of illness and mortality (Kondo et al. 2015; Braubach et al. 2017).

What roles can forests and green spaces play?

Urban forests and other green spaces can enhance social well-being by providing cultural ecosystem services, including benefits such as aesthetic appeal, recreation, and spiritual connection (Millennium Ecosystem Assessment 2005). For centuries, trees have been planted in and around cities to beautify public spaces, gardens, streets, and yards to provide aesthetic benefits as they improve scenic quality or visual appeal (Roy et al. 2012; Säumel et al. 2016) and even produce pleasant smells and sounds (Zhou and Parves Rana 2011).

Furthermore, inner and nearby forests can promote a “sense of place”—the idea of identity and emotional connection to the local environment (Wolf et al. 2014; Jennings et al. 2016; O’Brien et al. 2017). When green spaces increase residents’ connections to their communities, they may be more likely to engage in health-promoting social or physical activities (Jennings et al. 2016). Sense of place may even stimulate economic activity—for example, it can drive the preferences of tourists and their intention to revisit certain locations (Hausmann et al. 2016).

By reinforcing a sense of place and stimulating feelings of attachment and belonging, well-kept green infrastructure may also foster community identity (Jennings and Gaither 2015; Jennings and Bamkole 2019):

  • Forests, woodlands, parks, and urban green spaces may also be places for recreating, for gathering culturally relevant foods, or for expressing oneself through photography or art (O’Brien et al. 2017).
  • Green spaces, especially those with temperature regulation by trees, can be desirable locations for social interaction (Lee and Maheswaran 2011; Zhou and Parves Rana 2011; Shanahan et al. 2015; Braubach et al. 2017; Nesbitt et al. 2017; Bratman et al. 2019).
  • Direct participation in tree-planting programs or other green space stewardship activities may stimulate a sense of community identity and ownership (Higgs 2003; Nowak and Dwyer 2007; Jennings et al. 2016).

Around the world, forests serve as settings for spiritual practice, sacred symbols, and spaces for contemplation for both individuals and groups (Daniel et al. 2012; O’Brien et al. 2017). For some people, forest environments trigger feelings of “awe” or transcendence (Dwyer et al. 1991; Williams and Harvey 2001; Kuo 2015; Irvine and Herrett 2018). Spirituality may mediate the relationship between human well-being and nature (Kamitsis and Francis 2013; Hansen et al. 2017). In addition to specific institutional spaces such as churches, mosques, or other formal structures of worship, forests and green spaces provide space for spiritual practice (Okyerefo and Fiaveh 2017; Ngulani and Shackleton 2019). For example, in Accra, Ghana, the Achimota Forest is considered a sacred place of gathering, where urban dwellers seek serenity (Okyerefo and Fiaveh 2017). In Japan and India, sacred shrine or temple forests have been protected as the areas around them are urbanized—sometimes for centuries (Ishii et al. 2010; Daniel et al. 2012).

Caveats and considerations

As with most benefits, the ways forests can provide cultural benefits should be considered with local context and perspectives in mind:

  • The aesthetic preferences of some groups may conflict with others. For example, non-native species are preferred by some, whereas others prefer native natural areas (Lõhmus and Balbus 2015; von Döhren and Haase 2015).
  • Spiritual services are not easily generalized or valued in economic terms. Their value may vary widely across urban subpopulations (Daniel et al. 2012).

Goal 6: Reducing Urban Environmental Inequity


The livable and sustainable cities of the future are equitable cities. But technological innovation, urbanization, and migration exacerbate existing income inequality in many nations—and climate change threatens to erase progress in reducing income inequality among nations (UN DESA 2020). Within cities, lower-income and marginalized communities disproportionately inhabit “riskscapes,” which are geographic areas with limited access to resources and high risk of exposure to environmental stressors and hazards such as pollution and natural disasters (Jennings et al. 2012; Kondo et al. 2015).

Inequality in the distribution, funding, and maintenance of urban tree canopies is an environmental justice issue (Jennings and Gaither 2015; Schwarz et al. 2015). Lower levels of urban tree canopy cover have been associated with lower-income populations (Schwarz et al. 2015; Jennings et al. 2016; Gerrish and Watkins 2018) and with racial or ethnic minority populations (Watkins and Gerrish 2018; Locke et al. 2021) in some cities (Jennings et al. 2016). Developments in monitoring technology are making it easier to identify and correct these trends. In 2021, for example, American Forests released its Tree Equity Score tool—which reflects levels of tree canopy cover and demographic income such as race or age in around 150,000 neighborhoods in 486 municipalities in the United States—providing valuable data to residents and community leaders alike.17

What roles can forests and green spaces play?

Forests in and around cities, as well as other types of green infrastructure, may be managed, protected, or expanded in ways that can help reduce inequities between groups of people. Addressing inequities in tree distribution helps to distribute the important health benefits provided by forests across all residents. Evidence suggests that lower-income and marginalized groups may benefit from the expansions in urban canopy cover (or other urban greening efforts) more than other groups (Braubach et al. 2017). For instance, access to and engagement with urban green spaces by lower-income and marginalized groups may reduce disparities in rates of cardiovascular disease, obesity, heat stress, or psychological illness (Jennings and Gaither 2015). Urban forest planting, management, and stewardship also present opportunities for employment as well.

Caveats and considerations

Careful planning is required to ensure that inner forest expansion does not exacerbate existing disparities in health and well-being in cities (Kondo et al. 2015; Jennings et al. 2016). Expanding urban forests (or other green infrastructure) may inflate property and housing costs in a way that burdens or contributes to the displacement of low-income residents in these areas—a phenomenon coined as eco-gentrification (Wolch et al. 2014; Wolf 2017). A scoping review of 15 empirical studies found that longtime residents who are negatively impacted by green gentrification can experience a lower sense of community and belonging, which may result in lower green space use when compared with newcomers (Jelks et al. 2021). Additionally, residents inhabiting rental properties may either lack the authority or incentive to plant trees on the property (Heynen et al. 2006).

To avoid unintended negative outcomes for residents and to provide benefits to those most in need, city leaders should work with community leaders and local grassroots organizations at every stage of forest planning, management, and development. When communities are not adequately engaged and consulted, well-meaning initiatives may fail to meet their objectives; for example, in Detroit nearly 24 percent of residents approached by a nonprofit declined to have trees planted in their yards, citing insufficient engagement and concerns about a lack of tree maintenance by the city in the past (Carmichael and McDonough 2018). Although inclusive governance and authentic community engagement can require greater investment of time and resources, it can help to prevent unintended negative outcomes and ensure that residents’ needs are met. This will ensure that trees and other green infrastructure are installed where they are most needed and in ways that reflect community preferences.

Goal 7: Ensuring Provision of Food, Medicine, and Raw Materials


As urban populations climb, cities grapple with issues of food security and nutrition (Crush and Frayne 2011). Many city residents lack access to fresh, nutritious food, leading to inequities in health among residents (Dixon et al. 2007). Still others lack adequate access to health care, cooking fuel, or raw materials for trades or crafts.

What roles can forests and green spaces play?

Forests—including those within cities—play an important role in supplying cultivated and foraged foods and medicines as well as other raw materials. Although cities rely heavily on imported goods and materials, opportunities to meet residents’ needs using urban and peri-urban ecosystems may help to address disparities in access among low-income or marginalized groups while reducing pressure on natural rural ecosystems near cities. Examples include the following:

  • In urban areas, forests can provide foods, fuel, and medicine, particularly to low-income or marginalized groups, particularly in developing countries (Karjalainen et al. 2010; Pramova et al. 2012; Lwasa et al. 2015; Wolf and Robbins 2015; Lindley et al. 2018). Such products may serve as invaluable safety nets—especially for low-income communities most at risk (Pramova et al. 2012).
  • Trees on the urban fringe provide fuelwood, medicine, food, and even products that can be sold for income, particularly in developing countries. This is especially the case for low-income residents and those who live in informal settlements (Shackleton et al. 2015). For example, wood gathered from urban and peri-urban eucalyptus plantations makes up the livelihoods of marginalized groups—primarily women—in Addis Ababa, Ethiopia (Fetene and Worku 2013). Urban foraging for foods and medicines can connect individuals to their cultural heritage or increase food security (Poe et al. 2013).
  • Trees—especially nitrogen-fixing species—may also complement agriculture in and around cities (Pramova et al. 2012). Integrating trees into farmland to improve or diversify agriculture (agroforestry) can ameliorate microclimate for crops, improve soil fertility, and reduce water stress, depending on the crop type and region (Pramova et al. 2012).
  • Trees in and around cities can diversify incomes by supplementing crop production, supporting animal husbandry, or providing raw materials (Salbitano et al. 2016). In the Pacific Islands, agroforestry in home gardens has historically enhanced diet diversity and provided raw materials for construction and craft making (Thaman et al. 2006).
  • Forest plants, fungi, and microbes represent an enormous reserve of compounds with potential pharmaceutical or nutritional value (Karjalainen et al. 2010). Even the urban forest can provide medicines that may be of particular importance to certain ethnic or cultural groups or to marginalized individuals. The medicinal value of the urban forest has been recognized in North America (Poe et al. 2013), Latin America and the Caribbean (Dobbs et al. 2019), and other regions.
  • By providing wood for fuel or timber, urban forests may also help shield some natural forests from overexploitation (Salbitano et al. 2017).

Caveats and considerations

To maximize these benefits, urban decision-makers should consider the following:

  • Some municipal policies and regulations specifically prohibit foraging and gathering from urban trees or woodlands (Shackleton et al. 2017).
  • Urban foraging and gathering may shield intact rural forests from overexploitation, but plants and fungi of the urban forest are also vulnerable to overharvesting (Shackleton et al. 2017). Investing in management and harvesting strategies is essential to prevent overuse.
  • When urban food cultivation takes place near road corridors or rights-of-way, it may be necessary to create barriers between the roadside and urban agriculture to reduce the risk of pollutant uptake by crops (Säumel et al. 2016).

Goal 8: Enhancing Economic Well-Being


Healthy cities are also economically secure cities. To be resilient, communities need to provide economic opportunities to residents and bolster small businesses. They also need to harness the power of nature to reduce municipal costs and address multiple problems simultaneously.

What roles can forests and green spaces play?

In some contexts, installing or managing urban trees can pay for itself through benefits accrued by the municipality and property owners (Nowak and Dwyer 2007). Estimates of benefit-cost ratios of urban trees vary widely, depending on species and location, from around 5:1 to 24:1 in a global review of studies (Roy et al. 2012). And because larger, more mature trees can provide more benefits, such as shade or air filtration, healthy and properly maintained urban forests represent a municipal capital investment that may actually appreciate in value over time (Stagoll et al. 2012; Salbitano et al. 2016).

Urban forests provide multiple economic benefits to municipalities and their residents:

  • Iconic forests and urban vegetation can stimulate tourism (Nesbitt et al. 2017; Salbitano et al. 2017) and green infrastructure in general (Wolf and Robbins 2015; Nesbitt et al. 2017; O’Brien et al. 2017). Research from North America also suggests that consumers may prefer shopping districts with greater numbers of trees, a preference reflected in the duration of time and their willingness to pay for various products (Wolf et al. 2005).
  • The presence of trees can increase property values (Nowak and Dwyer 2007; Roy et al. 2012; Mullaney et al. 2015; Nesbitt et al. 2017) in residential, rental, and commercial contexts. Adjacency or proximity to woodlands, urban parks, and other green infrastructure may also increase property values (Wolf and Robbins 2015; Jennings et al. 2017; Nesbitt et al. 2017; O’Brien et al. 2017). But green spaces and urban trees do not influence property values in all global contexts, due in part to perceived issues of safety or security (Cilliers et al. 2013).
  • The presence of trees can increase municipal revenue related to increased property taxes (Nowak and Dwyer 2007) or fees associated with tree removal during development.
  • Managing urban forests and green infrastructure can provide “green jobs” in nurseries, tree-care services, forest management, and other related areas (Case Study 2; Kondo et al. 2015).
  • In some cases, urban tree maintenance costs can be recouped when urban wood waste is repurposed. In the United States alone, waste from urban trees, yard waste, and even demolition could be worth an estimated $89—$786 million when repurposed into wood chips, lumber, and fertilizer (Nowak et al. 2019).
  • Forests can reduce energy costs in both residential and commercial settings and can reduce costs related to water management (see Sections 3 and 4 for more details).
  • As described above, the presence of trees and other green infrastructure could reduce public health costs, including those related to exposure to extreme heat and air pollution or improved mental health status. For example, findings from a recent analysis of the heat-related benefits of existing urban forests in the United States suggest that urban trees can provide between $17 and $42 per capita (for the entire United States) per year in benefits related to avoided death, illness, and electricity use alone, compared to the typical $5 per capita in expenditures necessary for urban forest maintenance (McDonald et al. 2020).

Caveats and considerations

Although they provide numerous benefits to economic well-being, urban trees are often costly. Like other urban assets and infrastructure, urban forest maintenance and management requires capital related to pruning, planting, emergency tree removal, and damage to pipes or roads by roots. Potential disservices may include damage to infrastructure, such as sidewalks (Randrup et al. 2001) or private property (Escobedo et al. 2011; Cilliers et al. 2013). Recognizing these costs creates realistic expectations for municipalities and encourages proactive, informed planning and management.

It is also important to consider the distribution of these benefits. By increasing land value and rental prices, proactive management or expansion of the urban forest may generate direct revenue for local governments—a win for tight-strapped municipalities. At the same time, increases in property value and subsequent increases in property taxes may place a financial burden on some property owners (Nowak and Dwyer 2007) or even contribute to their displacement (Wolch et al. 2014). To ensure that urban forest expansion and urban greening do not burden low-income residents, these projects should be tailored to suit local contexts and should incorporate extensive community input.

Concluding Thoughts

Forests and nature are important to human health and well-being in cities. Well-planned, well-protected, and well-managed forests in and around cities can ensure that residents have access to a suite of ecosystem services, including ameliorated microclimate and air quality, recreation, mental restoration, and much more. Forests and other green infrastructure can help to reduce poverty, increase social cohesion, and bring communities together, but these outcomes are more likely when community perspectives and needs are incorporated at all stages of forest planning and management.

Integrating trees and forests into city plans to support health and well-being is not always easy. For example, although the value of urban forests for recreation, heritage, and aesthetic value has been recognized in low- and middle-income nations, such as in Latin America and Africa, local governments often do not act to implement forest-based solutions—in part because of the need to prioritize pressing issues, such as access to housing and sanitation (Cilliers et al. 2013; Dobbs et al. 2019). And it may take years or even decades to reap some of the benefits created by trees and other green infrastructure. Yet few interventions offer as many potential cobenefits as urban forests.

For urban health and well-being, forests can offer diverse and dispersed benefits that cities need now more than ever. Many city residents have limited access to interact with forests and nature, and in many places these environments are increasing in use and declining in quality (Bratman et al. 2019). Urban leaders envisioning the vibrant, habitable cities of the future should integrate forests as NBS and essential aspects of urban infrastructure.