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The benefits of trees for livable and sustainable communities



We live in an era influenced by humans to the point that the Earth's systems are now altered. In addition, a majority of the world's population live in cities. To meet the needs of people in a changing world, The United Nations General Assembly created the United Nations Sustainable Development Goals (UN SDG) to improve the quality of life for people. These broad goals outline the greatest challenges of our time. An effective strategy to assist in meeting these goals is to plant and protect trees, especially in cities where the majority of people live. This paper serves as a critical review of the benefits of trees. Trees promote health and social well‐being by removing air pollution, reducing stress, encouraging physical activity, and promoting social ties and community. Children with views of trees are more likely to succeed in school. Trees promote a strong economy and can provide numerous resources to the people that need them. While cities are getting hotter, trees can reduce urban temperatures. They provide habitat and food for animals. Finally, trees are valuable green infrastructure to manage stormwater. Money spent on urban forestry has a high return on investment. As we navigate this human‐dominated era, we need skilled people who understand the nuances of the built environment and trees as we strategically plan the cities of the future. The overwhelming evidence from the scientific literature suggests that investing in trees is an investment in meeting the UN SDG, and ultimately an investment for a better world.
Plants, People, Planet. 2019;00:1–13.    
DOI: 10.1002/ppp3.39
The benefits of trees for livable and sustainable communities
Jessica B. Turner‐Skoff | Nicole Cavender
This is an op en access article under the terms of the C reat ive Commo ns Attri bution License, which permits use, dis tribut ion and reproduction in any medium,
provide d the original work is properly cited.
© 2019 The Authors, Plants, People, Planet © New Phy tologis t Trust
The Mor ton Arboretum, Lisle, Illinois, USA
Jessica B. Turner‐Skoff, The Morton
Arboretum, 4100 Illinois Route 53, Lisle,
Illinois 60532, USA.
Societal Impact Statement
Trees play a critical role for people and the planet. Numerous studies have dem‐
onstrated that the presence of trees and urban nature can improve people’s men‐
tal and physical health, children's attention and test scores, the property values in
a neighborhood, and beyond. Trees cool our urban centers. Trees are essential for
healthy communities and people. The benefits that trees provide can help cities and
countries meet 15 of the 17 internationally supported United Nations Sustainable
Development Goals. This critical review provides a comprehensive argument that
trees should be considered an important part of the equation by project managers
and civic leaders as we collectively work toward reaching these sustainability goals.
We live in an era influenced by humans to the point that the Earth's systems are now
altered. In addition, a majority of the world's population live in cities. To meet the needs
of people in a changing world, The United Nations General Assembly created the United
Nations Sustainable Development Goals (UN SDG) to improve the quality of life for peo
ple. These broad goals outline the greatest challenges of our time. An effective strategy
to assist in meeting these goals is to plant and protect trees, especially in cities where
the majority of people live. This paper serves as a critical review of the benefits of trees.
Trees promote health and social well‐being by removing air pollution, reducing stress,
encouraging physical activity, and promoting social ties and community. Children with
views of trees are more likely to succeed in school. Trees promote a strong economy and
can provide numerous resources to the people that need them. While cities are getting
hotter, trees can reduce urban temperatures. They provide habitat and food for animals.
Finally, trees are valuable green infrastructure to manage stormwater. Money spent on
urban forestry has a high return on investment. As we navigate this human‐dominated
era, we need skilled people who understand the nuances of the built environment and
trees as we strategically plan the cities of the future. The overwhelming evidence from
the scientific literature suggests that investing in trees is an investment in meeting the
UN SDG, and ultimately an investment for a better world.
benefits of trees, cities, climate change, ecosystem services, human health, sustainability,
United Nations Sustainable Development Goals, urban forest
This current era, the Anthropocene, is driven by human influence
and it has ushered in a growing number of direct and indirect chal‐
lenges that can greatly impact the health and prosperity of people
and the planet (Ellis, 2015). Climate change is driving an unprece‐
dented number of extreme climatic events and causing ocean levels
to rise (Goudie, 2019). The human population continues to increase
(UN, 2015a) and metropolitan regions are growing and expanding.
By 2050, most of the world's population (70%) will live in cities (FAO,
2016). These concentrated populations have a wide variety of chal‐
lenges, ranging from people not having access to clean water to pol‐
lution‐related health issues (UN, 2015b).
People and cities need efficient and effective solutions to address
the challenges of this current era. In 2015, the United Nations (UN)
outlined 17 goals for sustainable development. The UN Sustainable
Development Goals (UN SDG), while ambitious, have the promise to im
prove the quality of life for the billions of people on this planet and serve
as a strong example of what the global society prioritizes (UN, 2015b).
Environmental and nature‐based solutions can help address a
majority of these outlined goals. Previous work has aligned envi‐
ronmental topics, such as plant conservation (Sharrock & Jackson,
2017), soil and soil science (Keesstra et al., 2016), and the prevention
of land degradation (Vlek, Khamzina, & Lulseged, 2017) as solutions
to meet the UN SDG. One additional way to address the challenges
that the urban population faces is to provide people with green
spaces and to plant, maintain, and protect trees (FAO, 2016; Endreny
et al., 2017; Endreny, 2018; World Resources Institute, 2018). The
direct and indirect benefits of trees and nature are vast (Blackmore,
2009; Brack, 2002; Hirons & Thomas, 2018; Kuo, 2015; Tyrväinen,
Pauleit, Seeland, & De Vries, 20 05), and much research has focused
on the benefits of trees to urban residents (Jennings & Johnson
Gaither, 2015).
This paper provides a critical and succinct review on how the
benefits of trees can increase the well‐being of a majorit y of the
world's population. The authors classify the benefits of trees into
five categories: (a) health and social well‐being; (b) cognitive de
velopment and education; (c) economy and resources; (d) climate
change mitigation and habitat; and (e) green infrastructure (Table 1).
In addition to the benefits in these categories, the presence of trees
and green space can help a city to meet Goal 11, sustainable cities
and communities, of the UN SDG through providing universal access
to green and public spaces. This paper expands on the work of the
FAO (2016) and highlights additional goals of the UN SDG that can
be met through a healthy urban forest.
2.1 | Health and social well‐being
One of the most important benefits for human health that urban
forests can provide is the interception and reduction of air pol‐
lution (McDonald et al., 2007, 2016; Nowak, Crane, & Stevens,
2006; Nowak, Hirabayashi, Bodine, & Greenfield, 2014; Nowak,
Hirabayashi, Doyle, McGovern, & Pasher, 2018). Air pollution (e.g.
particulate matter (PM), ozone, carbon monoxide, polycyclic aro‐
matic hydrocarbons, nitrogen dioxide, sulfur dioxide, etc.) is linked
to bronchitic symptoms, intraocular pressure (leads to glaucoma),
myocardial infarction (i.e. heart attacks), changes in autonomic and
micro‐vascular function, autism, blood pressure, cognitive develop
ment problems in children (slower processing speeds, behavioral
problems, attention deficit/hyperactivity disorder symptoms), blood
mitochondrial abundance, heart failure, and mortality in humans
(Berhaneetal.,2016;Dietal.,2017;Hoeket al.,2013;Mustafićet
al., 2012; Nwanaji‐Enwerem et al., 2019; Peterson et al., 2015; Shah
et al., 2013; Volk, Lurmann, Penfold, Hertz‐Picciot to, & McConnell,
2013; Weichenthal, Hatzopoulou, & Goldberg, 2014; Zhong et al.,
2016). Trees remove a tremendous amount of air pollution. It is esti‐
mated that from the contiguous United States, urban trees remove
711,000 metric tons of air pollution each year (Nowak et al., 2006).
Previous research demonstrated that out of 35 woody species stud‐
ied, all accumulated PM (Mo et al., 2015). Further, Chen, Liu, Zhang,
Zou, and Zhang (2017) suggested that PM2.5 accumulation capacity
increases as a tree matures, and a diverse planting of species aug‐
ments the trapping of PM2.5.
There is a link between trees, green spaces and mortality, and it
is documented in the literature (James, Hart, Banay, & Laden, 2016;
Nowak et al., 2018; Villeneuve et al., 2012). In one particular study,
the authors associated the increase in cardiovascular and respiratory
deaths with the infestation and death of ash trees (genus Fraxinus)
in counties within the United States (Donovan et al., 2013). Having
more trees, especially the right mature species planted in the right
locations, can reduce particulate matter and other forms of air pol‐
lution, which could reduce mortality and morbidity in our urban
Beyond pollution removal, the presence of trees provides
additional direct and indirect benefits to human health and well
ness (Donovan, 2017). Regardless of why trees provide so many
benefits (see Biophilia hypothesis [Wilson, 1984; Keller t & Wilson,
1995] and Attention Restoration Theory [(Kaplan & Kaplan, 1989;
Kaplan, 1995]), the presence of trees and green space promotes
well‐being. Trees and greener environments are strongly linked
to reduced negative thoughts, reduced symptoms of depression,
better reported moods, and increased life satisfaction (Berman
et al., 2012; Bratman, Hamilton, Hahn, Daily, & Gross, 2015; Li,
Deal, Zhou, Slavenas, & Sullivan, 2018; Lohr & Pearson‐Mims,
2006; Mayer, Frantz, Bruehlman‐Senecal, & Dolliver, 2009; Taylor,
Wheeler, White, Economou, & Osborne, 2015; White, Alcock,
Wheeler, & Depledge, 2013). A view of trees can help patients re
cover in a hospital (Ulrich, 1984) and reduce diastolic blood pres
sure and stress in research participants (Hartig, Evans, Jamner,
Davis, & Gärling, 2003; Jiang, Larsen, Deal, & Sullivan, 2015).
Residents of tree‐lined communities feel healthier and have fewer
cardio‐metabolic conditions than their counterparts (Kardan et al.,
2015). The presence of trees can even improve the condition of
people with a neurodegenerative disease (Mooney & Nicell, 1992).
In addition, as people value trees and natural environments, they
like being around them and viewing them (Dwyer, Schroeder, &
Gobster, 1991; Kaplan, Kaplan, & Wendt, 1972; Lohr, Pearson‐
Mims, Tarnai, & Dillman, 2004). The presence of trees and green
spaces may encourage physical activity (Bell, Wilson, & Liu, 20 08;
Ellaway, MacIntyre, & Bonnefoy, 2005), which is related to physi
cal and mental health. Given the multi‐faceted health benefits of
the ecosystem service ecotherapy (Summers & Vivian, 2018), the
very act of planting and caring for trees may promote mental and
physical health. Trees not only make people happier and healthier,
but they make communities more livable.
Well‐maintained trees are associated with improving the social
capital and ecology of a community (Coley, Sullivan, & Kuo, 1997;
Elmendorf, 2008; Holtan, Dieterlen, & Sullivan, 2015; Kuo, 2003;
TABLE 1 A high‐level overview of the benefits that urban trees provide, and how the direct and indirect benefits relate to the
corresponding United Nations Sustainable Development Goals. Further, the presence of trees and green space can help a city meet Goal 11,
or sustainable cities and communities, through providing universal access to green and public spaces
Benefit of urban trees categor y
Corresponding United Nations Sustainable
Development Goals
Scientific benefits of tree s
Health and social well‐being
Trees promote physical and mental health for urban
resident s. They support community ties and reduced
crime rates.
Goal 3: Good health and well‐being Reduce pollution
Goal 11: Sustainable cities and communities Improve physical and mental health
Goal 16: Peace, justice, and strong
Strengthen community ties
Increase physical activity
Decrease aggression and violence
Reduce crime
Cognitive development and education
Trees increase a student's ability to succeed in school. Goal 4: Quality education Improve student performance
Reduce stress
Increase in concentration
Reduce symptoms of ADD/ADHD
Increase in attention
Increase in self‐discipline
Economy and resources
Trees are good for the economy and they reduce energy
bills. They provide many resource s, such as food, to a
Goal 1: No poverty High return‐on‐investment
Goal 2: Zero hunger Support tourism
Goal 7: Affordable and clean energy Increase home prices and rental
Goal 8: Decent work and economic growth Reduce energy use and bills
Goal 10: Reduced inequalities Promote food sustainability
Goal 12: Responsible consumption and
Provide resources and firewood
Climate change mitigation and habitat
Trees mitigate the Urban Heat Island Effect and store and
sequester carbon. They are important for habitat.
Goal 3: Good health and well‐being Reduce Urban Heat Island Effect
Goal 13: Climate action Store and sequester carbon
Goal 15: Life on land Provide critical habitat
Green infrastructure
Trees are important forms of infrastructure, especially for
storm water management
Goal 3: Good health and well‐being Manage storm water
Goal 6: Clean water and sanitation Reduce pollution
Goal 9: Industry, innovation and
Protect life below water and on land
Goal 11: Sustainable cities and communities
Goal 12: Responsible consumption and
Goal 14: Life below water
Goal 15: Life on land
Kuo, Sullivan, Coley, & Brunson, 1998), reducing violence and ag‐
gression in households (Kuo & Sullivan, 2001a), and limiting crimi
nal activity in neighborhoods (Donovan & Prestemon, 2012; Kuo &
Sullivan, 2001b; Troy, Morgan Grove, & O'Neil‐Dunne, 2012; Troy,
Nunery, & Grove, 2016). In one study, Kondo, Han, Donovan, and
MacDonald (2017) demonstrated that the loss of ash trees due to
the emerald ash borer in Cincinnati, Ohio, USA, was positively asso‐
ciated with increases in crime. This could be an example of “cues to
care,” which is the idea that a well‐tended landscape is valued and
viewed (Troy et al., 2016). While there is a perception that the pres‐
ence of trees can increase crime, it is likely related to unmanaged and
smaller trees that provide greater protection to a criminal (Donovan
& Prestemon, 2012). Regardless of this perception, evidence indi‐
cates that trees make residents feel safer (Kuo, Bacaicoa, & Sullivan,
Based on literature cited, trees can help meet our societal goals
as outlined in the UN SDG, especially Goal 3: Ensure healthy lives
and promote well‐being for all at all ages; Goal 11: Make cities and
human settlements inclusive, safe, resilient and sustainable; and
Goal 16: Promote peaceful and inclusive societies for sustainable
development, provide access to justice for all and build effective,
accountable, and inclusive institutions at all levels. These benefits
from trees, if distributed throughout communities, can help make
cities more sustainable and livable (Table 1).
2.2 | Cognitive development and education
To increase liter acy and numer acy, children nee d to have access to na‐
ture, and at the very least, green and natural views of trees (Berman,
Jonides, & Kaplan, 2008; Faber Taylor, Kuo, & Sullivan, 20 02; Lin,
Tsai, Sullivan, Chang, & Chang, 2014; Tennessen & Cimprich, 1995).
As reviewed in Kuo, Browning, Sachdeva, Lee, and Westphal (2018),
stress levels, concentration, and intrinsic motivation are likely strong
factors in a child's success as a student. Students who are focused,
attentive, and engaged are more likely to succeed in school and
receive a quality education. At tention Deficit Disorder (ADD) and
Attention Deficit Hyperactivity Disorder (ADHD) can impact a stu
dent's success in school (Rief, 2012). Green environments, such as
open spaces with big trees, are related to reduced symptoms of ADD
and ADHD (Faber Taylor & Kuo, 2009; Faber Taylor, Kuo, & Sullivan,
Tree cover is strongly linked to student academic performance
(Kuo, Browning, Sachdeva, et al., 2018; Kweon, Ellis, Lee, & Jacobs,
2017; Matsuoka, 2010). In one study, views of trees and shrubs at
schools, as opposed to grass, were strongly related to future edu‐
cation plans and graduation rates (Matsuoka, 2010). Li and Sullivan
(2016) found that students who had views of trees and green en‐
vironment from their classrooms, as compared to being in a room
without windows or a room with a view of a brick wall, scored sub‐
stantially higher on tests measuring attention, and they had a faster
recovery from a stressful event. Students who learn in the presence
of trees and nature have improved classroom engagement (Kuo,
Browning, & Penner, 2018). Trees can promote a qualit y education,
which has innumerable advantages for society. Access to trees sup‐
ports a quality education and can help countries meet the UN SDG,
especially Goal 4: Ensure inclusive and equitable quality education
and promote lifelong learning opportunities for all (Table 1).
2.3 | Economy and resources
Trees provide many ecosystem services that can benefit a cit y envi‐
ronment, ranging from reducing energy use and removing pollution
(Nowak & Greenfield, 2018) to increasing property values, devel‐
oping the local economy, and supporting tourism (Nesbitt, Hotte,
Barron, Cowan, & Sheppard, 2017). In the United States alone, it is
estimated that trees provide $18.3 billion in annual value due to air
pollution removal, reduced building energy use, carbon sequestra
tion, and avoided pollutant emissions (Nowak & Greenfield, 2018).
Allocating resources in tree planting and maintenance can be a fis‐
cally sound decision based on the benefits and ecosystem services
that tree s provide (McPherson, Simpson, Peper, Maco, & Xia o, 2005).
This high return on investment can be multiples of invested capital
over time (McPherson, van Doorn, & de Goede, 2016). Many ben‐
efits are not fully captured in this return on investment. In addition,
the presence of shade trees can re duce the rate of ageing of road and
pavement surfaces (McPherson & Muchnick, 2005), influence shop
pers to visit a shopping area (Wolf, 2005), and increase the selling
price of a home (Anderson & Cordell, 1988; Donovan & Butry, 2010;
Sander, Polasky, & Haight, 2010). As long as trees do not block the
view of an office building, quality landscaping with properly main
tained trees can increase rental rates (L averne & Winson‐Geideman,
2003). A properly planted tree can also reduce energy use (Akbari,
2002; Donovan & Butr y, 2009; Pandit & Laband, 2010; Simpson,
1998), which can reduce the cost of energy bills.
While urban trees can provide economic benefits, they can also
provide resources, such as food, to a community. The idea that trees
can provide food security and promote well‐being is not new. In fact,
agroforestry was previously recognized as a way to meet the United
Nations Millennium Development Goals (Garrity, 2004). Hundreds
of tree species are used for agroforestry to promote food sustain‐
ability and nutritional security (Dawson et al., 2013; Or wa, Mutua,
Kindt, Jamnadass, & Simons, 20 09). Urban orchards, or urban food
forestry, can be an efficient way to consistently provide free or
low‐cost nutrient‐dense food to the people that need it (Clark &
Nicholas, 2013). Urban street trees can provide many resources
to the inhabitants of cities. In New York City, 88% of tree species
present are forgeable for medicine, food, etc., including nine out of
ten of the most common tree species (Hurley & Emer y, 2018). The
“Incredible Edible” movement is an example of how underutilized
plots in urban environments can be used to grow food, as a means to
reduce food deserts and build communit y (Morley, Farrier, & Dooris,
2017). Planting urban orchards in available spaces could prove an im‐
portant tool to reduce hunger and increase social ties. Urban forag‐
ing may not be practiced in areas of higher oppor tunity (Larondelle &
Strohbach, 2016), and so it may not receive the attention it deserves
as a solution for food security.
Forests also provide the habitat for non‐timber forest products
(NTFP) that can provide valuable resources to a local community
(Turner, 2015). Some examples of NTFP include American ginseng
(Panax quinquefolius L.), maple syrup (derived from Acer spp.) and
nuts (from trees like the European Chestnut, Castanea sativa Mill.;
Poe, McLain, Emery, & Hurley, 2013; Turner, 2015). Traditionally
NTFP are associated with a rural environment, yet urban NTFP can
provide additional financial, food, and medicinal security to people
living in cities (Kaoma & Shackleton, 2015; McLain, Hurley, Emer y, &
Poe, 2013; McLain, Poe, Hurley, Lecompte‐Mastenbrook, & Emery,
2012; Poe et al., 2013).
Finally, wood is an important source of material and energy for
much of the world. Trees that are cut down in cities or communities
can be used for timber (Sherrill, 2003). This could be used for fuel
or for producing goods. Innovative programs can promote sustain
ability and creative usage of urban wood. An example of this is the
“Working for Water” program which trains people in South Africa
to remove woody invasive species, and then the cleared wood can
be used for a variety of secondary industries (Binns, Illgner, & Nel,
2001). While this program works with invasive species, it serves
as an example of creative solutions involving the community with
urban issues involving trees. Urban forests can also help supply
affordable energ y to people that need it (FAO, 2016). It is import
ant to note, however, that burning wood is a large contributor to
air pollution in urban environments (Favez, Cachier, Sciare, Sarda‐
Estève, & Martinon, 2009). Therefore, if wood is used for fuel, it
should be burned in such a way that the benefits outweigh the
harm to human health. Trees are a valuable resource, even after
they are cut down.
Trees can help countries meet the UN SDG by providing food,
resources and economic advantages to countries. These goals in‐
clude: Goal 1: End poverty in all its forms ever ywhere; Goal 2: End
hunger, achieve food security and improved nutrition, and promote
sustainable agriculture; Goal 7: Ensure access to affordable, reliable,
sustainable, and modern energy for all; Goal 8: Promote sustained,
inclusive and sustainable economic growth, full and productive em‐
ployment and decent work for all; Goal 10: Reduce inequality within
and among countries; and Goal 12: Ensure sustainable consumption
and production patterns.
2.4 | Climate change mitigation and habitat
Climate change directly impacts where people live. One of the
most pressing risks for human health associated with a changing
climate are the increases in heat‐related deaths, diseases, and infec
tious diseases (Patz, Campbell‐Lendrum, Holloway, & Foley, 2005).
The increase in heat and heat‐related health problems is especially
prevalent in cities, where the Urban Heat Island Effect increases the
impact of heat waves (Ward, Lauf, Kleinschmit, & Endlicher, 2016).
Properly placed trees can mitigate temperatures in built environ‐
ments. Not only do trees provide shade through intercepting and
absorbing light, but through evapotranspiration trees actively cool
the air of cities (EPA, 2008; Hirons & Thomas, 2018; Schwab, 2009).
An analysis of 94 urban areas around the world indicates that trees
have a significant impact on the temperature, and are responsible
for, on average, 1.9°C (SD 2.3) of cooling in a city (Figure 1a). Trees
incorporated into the built environment can reduce a city's tempera‐
ture by 9°C (Figure 1b). This reduction of temperature in major cities
(Akbari, Pomerantz, & Taha, 2001; Loughner et al., 2012; McDonald
et al., 2016) can ultimately help ameliorate the impact of climate
change on human health.
One of the key ways to limit the impacts of climate change is to
reduce the amount of carbon released into the atmosphere. Trees
are beneficial to storing carbon, which is a major contributor to cli
mate change (Nowak, 1993). Nowak and Crane (20 02) determined
that not only do urban trees in the coterminous United States se
quester 22.8 million tons of carbon each year, but the urban forest
in this area stores 700 million tons of carbon. The more mature a
tree is, the more carbon it stores in its woody biomass (Schwab,
2009). Although trees are not the single answer, healthy and ma
ture trees have the potential to make significant carbon mitigation
Finally, trees, specifically mature ones, perform a keystone role
in terrestrial ecosystems (Manning, Fischer, & Lindenmayer, 2006).
Trees are critically important, especially in urban areas, as they pro‐
vide food and habitat for birds, invertebrates, mammals, and plants
(Fahey, Darling, & Anderson, 2015; Schwab, 2009; Tyrväinen et al.,
2005). Improving and maintaining biodiversity is necessary for a sus
tainable city.
Therefore, planting and protecting trees can help a country meet
the following UN SDG: Goal 3: Ensure healthy lives and promote
well‐being for all at all ages; Goal 13: Take urgent action to com‐
bat climate change and its impacts; and Goal 15: Protect, restore,
and promote sustainable use of terrestrial ecosystems, sustainably
manage forests, combat deser tification, and halt and reverse land
degradation and halt biodiversity loss.
2.5 | Green infrastructure
Trees are considered “decentralized green infrastructure” and can be
important tools for managing water, especially in an urban ecosys‐
tem (Berland et al., 2017). Water runoff is a serious issue in the city
environment, as runoff can increase the exposure to pollution and
cause property damage (Braden & Johnston, 2004). Trees can help
reduce and intercept stormwater and improve the quality of run‐
off water (Berland et al., 2017; Bolund & Hunhammar, 1999; Brack,
2002; Livesley, McPherson, & Calfapietra, 2016; Scharenbroch,
Morgenroth, & Maule, 2016). With less contact on impervious sur‐
faces, stormwater is cooler and has fewer pollutants when it enters
local waterways and water‐related ecosystems (Schwab, 2009).
Trees can also be valuable in phytoremediation, where they can re‐
move heavy metals and other contaminants from the environment
(French, Dickinson, & Putwain, 2006). While gray infrastructure de
preciates over time, trees appreciate in value as they mature (Hauer
& Johnson, 2003). Therefore, an investment in trees can make eco‐
nomic sense and align with the UN SDG.
Green infrastructure protects life below water and life on land,
while promoting sustainability. The abilit y of trees to reduce the pol‐
lution in the waterways is beneficial to human health and well‐being.
Therefore, by promoting trees as green infrastructure, the following
UN SDG can be met Goal 3: Ensure healthy lives and promote well‐
being for all at all ages; Goal 6: Ensure availability and sustainable
management of water and sanitation for all; Goal 9: Build resilient
infrastructure, promote inclusive and sustainable industrialization
and foster innovation; Goal 11: Make cities and human settlements
inclusive, safe, resilient and sustainable; Goal 12: Ensure sustainable
consumption and production patterns; Goal 14: Conserve and sus
tainably use the oceans, seas and marine resources for sustainable
development; and Goal 15: Protect , restore and promote sustainable
use of terrestrial ecosystems, sustainably manage forests, combat
desertification and halt and reverse land degradation and halt biodi‐
versity loss (Table 1).
FIGURE 1 (a) Trees greatly contribute to urban cooling. Cities included in this evaluation have an estimated population in the
metropolitan area greater than 2 million in the year 200 0, a metropolitan area greater than 1,000 km2, and an urban heat island effect
greater than 1°C (Center for International Earth Science Information Network ‐ CIESIN ‐ Columbia University, 2016). The effec t of trees on
urban cooling was calculated by subtracting the temperature in areas without trees from the obser ved temperatures; (b) while the standard
deviation is large, it is not normally distributed. The impact of trees on cooling the urban environment is ecologically and statistically
significant. Figures are created by Dr Christy Rollinson, Forest Ecologist at The Morton Arboretum
While the above outlines how the benefits of trees can help build
sustainable cities in the future and reach the collective agenda of
the UN SDG , there are important considerations associated with this
review. First, while there is strong evidence that nature benefits hu‐
mans, much of the research conducted has been correlative. Future
studies should address methodological limitations and minimize po
tential errors or bias in research (such as self‐repor ting moods, sam‐
pling bias, lack of control group, and short‐time frames of research;
Keniger, Gaston, Irvine, & Fuller, 2013). Despite these concerns, the
vast number of studies illustrating the breadth of benefits related to
trees is compelling.
Many of these papers describe the importance of urban green
space. Green space can be defined as herbaceous or woody vege‐
tated areas such as parks, forests, or gardens (Jennings & Johnson
Gaither, 2015). It is unlikely that the papers that asked questions
about green space focused on grassy fields that lacked trees. In
addition, research shows that green spaces without trees or dense
vegetation can have negligible or negative impacts on people (Kuo,
Browning, Sachdeva, et al., 2018; Kweon et al., 2017; Matsuoka,
2010; Reid, Clougherty, Shmool, & Kubzansky, 2017).
While this review stresses the importance of trees, this is not
to say that other forms of nature will not provide similar benefits.
However, in the space‐limited cit y, trees are practical. They provide
a strong return on investment given their vertical orientation and
Trees do not only provide positive benefits, however, as there
can be negative associations surrounding trees. These disservices to
people can range from financial strains associated with tree mainte‐
nance and care, to property damage, to safety issues associated with
limited visibility and securit y, and the inconvenience of messiness
(Escobedo, Kroeger, & Wagner, 2011; Lohr et al., 2004; Lyytimäki &
Sipilä, 20 09; Roy, Byrne, & Pickerin g, 2012; Staudhammer, Escobedo,
Luley, & Bond, 20 09; Wyman, Escobedo, Stein, Or fanedes, &
Northrop, 2012).
One of the most commonly cited disservices associated with
trees is the production of biogenic Volatile Organic Compounds
(bVOCs) which react with nitrogen oxides, to increase air pollution
in the form of ozone (Hirons & Thomas, 2018; Salmond et al., 2016).
This negative impact on air quality can be exasperated during heat
waves (Churkina et al., 2017) or in street canyons (Salmond et al.,
2016). As it is situational, measuring the impact of bVOCs is com‐
plicated. Species, number of trees, and location planted makes
a difference in the type and amount of air pollution produced or
accumulated by trees (Calfapietra et al., 2013; Donovan, Stewart,
Owen, MacKenzie, & Hewitt, 2005; Janhäll, 2015). Complicating the
issue of disservices/benefit s, the amount of ozone that a tree inter‐
cepts and uptakes may be greater than any ozone produced through
bVOCs (Calfapietra et al., 2013; Salmond et al., 2016). Further, trees
are more effective at absorbing and accumulating gas and particu
late pollutants than other city surfaces (as reviewed in Salmond et
al., 2016).
Since trees can produce disservices, trees should be valued for
what they holistically contribute to a community, rather than being
valued for singular benefits. For example, while trees in a street can‐
yon may result in more localized pollution, they may provide second‐
ary benefits such as reducing the movement of pollutants to other
locations or masking noise pollution (Salmond et al., 2016). In fact,
the benefits of trees are often so valued that any disser vices that can
be associated with them are outweighed (Lohr et al., 2004; Wyman
et al., 2012). When planting trees, people can reduce possible disser‐
vices through careful species selection, and selecting species with
low potential for invasion. Resources exist, like the Northern Illinois
Tree Selector (2019), which can help people select the appropriate
tree for the appropriate site, all the while considering disservices,
services, and if a tree species has invasive traits.
The benefits of trees are relative to seasonal and temperate zone
differences. Another important consideration is that not all trees are
equal. Some benefits may be more pronounced in specific species
(Chen et al., 2017; Grote et al., 2016; Xiao & McPherson, 2016).
Benefits differ within a species as well. A small street tree does not
provide the same benefits as a large, 100‐year‐old tree. Mature and
old trees are increasingly rare, and yet they can provide the great‐
est benefits (Lindenmayer, 2017; Lindenmayer & Laurance, 2017;
Lindenmayer, Laurance, & Franklin, 2012). Given that they are single
organisms, large old trees provide a disproportionate impact on bio
diversit y and ecological processes, from providing habitat for other
animals and plants to facilitating important ecological cycles (Le
Roux, Ikin, Lindenmayer, Manning, & Gibbons, 2015; Lindenmayer,
2017; Lutz et al., 2018; Stagoll, Lindenmayer, Knight, Fischer, &
Manning, 2012). A larger tree can provide substantially greater ben‐
efits than a smaller tree can (Stephenson et al., 2014). There is also
cultural value associated with large and mature trees (Blicharska
&Mikusiński,2014).Citiesand urban centers should managetheir
forests to conserve large‐diameter trees to maximize the ecosystem
services the trees can provide (see Cavender & Donnelly, 2019).
Few trees reach maturity in an urban environment (Watson &
Himelick, 2013). While many cities participate in tree plantings,
the lack of follow‐up care can impact survival rates, thus result in a
waste of resources (Widney, Fischer, & Vogt, 2016). However great
the number of benefits a mature tree can provide, it takes time for
the benefits of trees to exceed the costs associated with the planting
and maintenance (Vogt , Hauer, & Fischer, 2015). One way to increase
survival rates of planted trees—and thus, ensure a wise investment—
is to garner community support with tree plantings. This can reduce
vandalism and create a sense of ownership (Black, 1978). For exam‐
ple, Sklar and Ames (1985) found that trees planted with community
participation had significantly higher survival rates (~60%–70%) as
compared to trees that were planted without community participa
tion (<1%). Involving the local community in tree planting may also
increase neighborhood ties ( Watkins et al., 2018). This may lead to a
positive social effect.
A major issue that extends beyond the scope of this paper is that
often low‐income countries have the greatest need for improved
urban conditions, and therefore, they may have the greatest need for
trees. However, many of these countries may not have the climate to
support trees; they may be xeric or in areas that are susceptible to
droughts (McDonald et al., 2016). The variance in climates empha‐
sizes the importance of proper selection of trees, identifying trees
that are adapted to local climates or have high plasticity and can
survive in unfavorable conditions. Green infrastructure that collects
and integrates stormwater drainage where trees are planted may
offer a solution to tree survival in xeric environments. Regardless,
water availability must be considered before planting (McDonald et
al., 2016).
Moving for ward, emphasis should be placed on reducing the in‐
equality of tree distribution in the urban forest within and among
cities. Trees and green spaces are often unequally distributed among
communities with var ying demographics such as income and race
(Jennings, Johnson Gaither, & Gragg, 2012; Landry & Chakraborty,
2009; Pincetl, 2010). Schwarz et al. (2015) found that when analyz‐
ing seven major cities, the authors found a strong relationship be‐
tween urban tree cover and income: the lower the income, the fewer
the trees. Decision‐makers may underestimate the importance of
trees and plants in humanitarian work due to bias of plant blindness
(Balding & Williams, 2016), but this paper illustrates the benefits.
Future research is needed to understand all of the benefits and
disservices that trees provide to people. First, moving beyond cor‐
relation, more experimental studies should be conducted that eval‐
uate the benefit of trees to people. Jennings and Johnson Gaither
(2015) outlined how future research should focus efforts on un‐
derstanding how health and green space are related in low‐income
populations and rural minorities. Historically, research has been
geographically biased with many of the studies occurring in North
America and Europe (Keniger et al., 2013). There are many opportu‐
nities to expand this research to the southern hemisphere. Given the
short‐time frame of most social and psychological studies (Keniger
et al., 2013), longitudinal studies will help determine longer‐term im‐
pacts of trees and nature on people. As discussed in Salmond et al.
(2016), researchers should work to understand the scale of benefits
or disser vices. This includes a more localized approach to research,
such as understanding the local impacts of street trees in regulating
air qualit y, rather than at regional scale. In addition, rather than fo‐
cusing on individual pollutants, research is needed that investigates
the interaction of air pollution, pollen, and temperature at a local
scale (Salmond et al., 2016). Understanding the benefits of nature,
beyond trees, is important for strategic urban planning in xeric en‐
vironments. Finally, while there are trade‐offs between disservices
and services, future‐focused urban planning and research is needed
so the right species are planted in the right environment to minimize
the negative impacts of any disservices and maximize the benefits.
Investing in trees will result in sustainable cities with happier and
healthier people. We reviewed the substantial evidence to better
understand the tangible and real benefits that trees provide. While
there are considerations, planting and protecting trees is a real so‐
lution to many of society's challenges, offering high potential with
relatively small input and energ y. The results can be profound in the
long term. In particular, the five categories of benefits outlined in
this article (health and social well‐being, cognitive development and
education, economy and resources, climate change mitigation and
habitat, and green infrastructure) are of particular importance, es
pecially as there is a great global migration into cities. While previ‐
ous work illustrated that trees can help meet several of the UNSDG,
this review demonstrates that planting and protecting of trees can
directly and indirectly contribute to 15 of the 17 goals. This is more
than previously described. Beyond the UN SDG, the planting and
protecting of trees support s the United Nation's New Urban Agenda
(NUA). The NUA, which was created to promote the development
of sustainable cities, stresses the importance of green and quality
public spaces, as well as green infrastructure (United Nations, 2017).
For people to receive their benefits, the urban forest needs to be
healthy and diverse to create the most sustainable and livable com‐
munities possible.
We have entered a new era in which humans are the dominant
species and the main influencer of the planet. The built environ‐
ment as it currently exists is not conducive to most trees (Watson
& Himelick, 2013). In order to receive the benefits that trees pro‐
vide, we need people who have the skills required to care for trees.
Horticulture experts and plant scientists are of vital importance to
the world, and they need to be future‐focused in their work, ac‐
tively seeking positive outcomes for society's challenges (Blackmore
& Paterson, 2006; Raven, 2019; Smith, 2019). This new era of the
Anthropocene requires a new era of horticulture. Experts need to
understand how to address society's needs and the realities of the
urban environment, while taking trees and adapting them to where
people live. This requires skills in arboriculture, sourcing, cultivation,
production, and care in a way that is calculated and encompasses
urban planning. We also need broad engagement across all sectors
(Cavender & Donnelly, 2019) to strategically plan and manage the
urban forest to gain the most benefits (Miller, Hauer, & Werner,
If we want to have the benefits of urban trees in the future, we
must think of our urban forests as an investment. Like any invest‐
ment, if trees are not cared for, they depreciate in value and can
become a liability. Through planting and care, however, urban for‐
ests can have compounding benefits, trickling through ever y layer
of society, leading to a better world. A s the proverb says, “The best
time to plant a tree is twenty years ago, the second best time is now.”
We must act now for a better world.
The authors thank Dr Christy Rollinson for her analysis and creation
of the figure. Thanks to Claudia Wood, Rita Hassert, and Maureen
Sullivan for their assistance and input, and to Dr Steve Tichy for his
medical expertise. In addition, we thank the two anonymous review‐
ers who provided excellent feedback. We thank tree champions
everywhere and The Morton Arboretum supporters and colleagues
who work to understand, plant and protect trees for a healthier and
more beautiful world.
Jessica B. Turner‐Skoff‐00021032‐0986
Nicole Cavender‐0001‐5804‐061X
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How to cite this article: Turner‐Skoff JB, Cavender N. The
benefits of trees for livable and sustainable communities.
Plants, People, Planet. 2019;00:1–13. https ://
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... Além de remover a poluição do ar, reduzir as temperaturas urbanas e gerenciar as águas pluviais (TURNER et al., 2019), as florestas atuam como força estabilizadora do clima e se apresentam como uma das soluções para mitigar os efeitos das mudanças climáticas. ...
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A biotecnologia como instrumento de sequestro de carbono: bactérias, microalgas e árvores geneticamente modificadas A preocupação das populações de vários países e da comunidade científica global tem sido crescente nos últimos anos com relação às mudanças climáticas. O Aquecimento Global atinge níveis alarmantes e gera apreensão na comunidade internacional que teme danos irreversíveis ao planeta. A intensificação do Efeito Estufa em virtude da emissão excessiva de gases como o dióxido de carbono tem agravado esse cenário. Frente a esse problema, muitos pesquisadores têm dedicado seus esforços para criar tecnologias que visam neutralizar ou compensar os danos gerados pelos gases poluentes. Entre as alternativas disponíveis, o biossequestro de carbono ganhou espaço nos últimos anos, seu objetivo é utilizar organismos vivos para aprisionar o carbono atmosférico de forma a minimizar os impactos do aumento da temperatura do planeta. Esse artigo apresenta uma revisão da utilização de Escherichia coli, Microalgas e Árvores Geneticamente Modificadas, como biossequestradores potenciais de carbono atmosférico.
... De fundamental importância para o planeta, as árvores contribuem para que os países atinjam 15 dos 17 Objetivos do Desenvolvimento Sustentável das Nações Unidas (TURNER et al., 2019). Elas atuam como sumidouro de dióxido de carbono e seu manejo diminui as emissões de gases do efeito estufa (DOMKE et al., 2020). ...
... Além de remover a poluição do ar, reduzir as temperaturas urbanas e gerenciar as águas pluviais (TURNER et al., 2019), as florestas atuam como força estabilizadora do clima e se apresentam como uma das soluções para mitigar os efeitos das mudanças climáticas. ...
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A biotecnologia como instrumento de sequestro de carbono: bactérias, microalgas e árvores geneticamente modificadas A preocupação das populações de vários países e da comunidade científica global tem sido crescente nos últimos anos com relação às mudanças climáticas. O Aquecimento Global atinge níveis alarmantes e gera apreensão na comunidade internacional que teme danos irreversíveis ao planeta. A intensificação do Efeito Estufa em virtude da emissão excessiva de gases como o dióxido de carbono tem agravado esse cenário. Frente a esse problema, muitos pesquisadores têm dedicado seus esforços para criar tecnologias que visam neutralizar ou compensar os danos gerados pelos gases poluentes. Entre as alternativas disponíveis, o biossequestro de carbono ganhou espaço nos últimos anos, seu objetivo é utilizar organismos vivos para aprisionar o carbono atmosférico de forma a minimizar os impactos do aumento da temperatura do planeta. Esse artigo apresenta uma revisão da utilização de Escherichia coli, Microalgas e Árvores Geneticamente Modificadas, como biossequestradores potenciais de carbono atmosférico.
... Nowadays, urban green areas' multifunctional value is taken into account as a factor of sustainable development (Su et al., 2010;Kabisch et al., 2015). Their values are recognized and are part of the United Nations Sustainable Development Goals (Turner-Skoff and Cavender, 2019). Along the same lines, the 2030 biodiversity strategy of the European Union encourages cities to develop 'urban greening plans' including urban forests, parks, gardens, and tree-lined streets (European Commission, 2020). ...
Urban trees are a fundamental and key component of urban green areas, however, they are subject to several stresses which can compromise their mechanical integrity through the development of defects such as wood decay. In this study, we evaluated the structural health state of trees in four urban parks in the city of Mytilene, Greece, using structural traits of the trees, their trunk surface temperature distribution as recorded using infrared thermography, and spatial statistics both at single tree and at park level. We developed thermal indices by analyzing data from 334 trees belonging to three main species (Robinia pseudoacacia, Morus alba and Melia azedarach). We estimated temperature spatial dependence across each tree trunk using Moran's I index, while statistically significant spatial clusters were assessed using local spatial autocorrelation statistics. Relationships between tree traits, thermal, and spatial indices were established using linear and logistic regression models. Finally, we used the Getis-Ord Gi* statistic for the identification of risky tree hotspots and we applied the kriging geostatistical procedure for mapping of such hotspots. Our results have shown that the thermal and spatial indices can sufficiently predict different types of structural defect, and to identify hotspots of risky trees and their spatial extent. This approach can successfully contribute to tree risk assessment for a more effective urban park management.
... But the social, economic, and environmental benefits of trees are well-established, even across climatic zones (ibid). These include energy savings, air quality improvements, stormwater management, heat island mitigation, carbon storage, increased property values, and improved physical and mental health, among others (McPherson et al. 2005;Roy et al. 2012;Turner-Skoff 2019). However, despite the importance of suburban tree cover, it is declining in many communities due in part to shifts toward larger or denser developments and the expansion of building footprints (Daniel et al. 2016;Lee et al. 2017). ...
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Tree cover is an important aspect of environmental quality and quality of life, but is declining in many metropolitan regions. This study examines tree cover and its relationship with scale in a type of suburban green space that is common in the United States, residential open space. A variety of urban and residential tree cover studies exist, but none examine the factors that explain the tree cover in these small open spaces, which have the potential to support significant conservation value in developed and developing areas. This study uses remote sensing, GIS analysis, and spatial statistics to examine the characteristics and configuration of 1,900 parcels of residential open space in Montgomery County, Pennsylvania, a suburban county in the northeastern United States. As no appropriate scale has yet been established, it examines two, the subdivision-scale and census tract-scale, in this initial exploration. Results indicate that tree cover is strongly positively associated with regional residential tree cover and the presence of waterways and negatively correlated with attached dwelling units and farmland. But while these variables have the most explanatory power, open space connectivity and local government ownership, both positively associated with tree cover, are also significant and have clearer implications for open space planners and decision-makers. Findings also highlight the benefits of examining multiple scales of effect in complex suburban landscapes.
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Contemporary cities face socio-environmental challenges that, if not addressed, undermine their sustainability and the well-being of their populations. Nature-based solutions are internationally recognized as one of the most efficient long-term strategies. Among these solutions, the Urban Green Spaces (UGS), as bridges of connection between nature and the urban, assume themselves as places of socialization, physical, cultural, and recreational activity, in addition to being able to play a role in mitigating atmospheric pollution and the effects of climate change. Although there is a considerable amount of literature dedicated to these spaces, there is still a gap in how the potential of ecosystem services, preferences, motivations, and emerging relationships of their users are mediated, considering the surrounding socioeconomic and territorial profile. Taking as a case study the city of Porto, located in the northern region of the Portuguese coast, integrated into the second largest area of the country, which suffered a significant loss of urban green structure during the second half of the 20th century, this investigation aimed to understand how UGS are responding to contemporary socio-environmental challenges. Of the 95 UGS identified in the city, twenty-five were selected, to which a triangulation technique approach was applied, namely the construction and application of a grid to assess the potential of ecosystem services, the construction and application of a questionnaire survey to 131 UGS users and, finally, the mapping of the human behavior of 975 users in four of the 25 UGS. Through univariate and multivariate statistical analyses, and using SPSS, R, and ArcGIS programs, it was possible to respond to the objective of the present investigation. The results make clear a situation of environmental injustice in the provision of UGS in the city, considering that, in areas of greater socioeconomic deprivation, these spaces tend to have less potential for ecosystem services, in general understanding by users. To propose a typology of UGS, five groups were identified: environmentally capable and socially expectant spaces, socio-environmentally active spaces, environmentally capable but socially dynamic spaces, socio-environmentally neglected spaces, and socio-environmentally unexplored spaces. With this proposal, it becomes possible to identify the dimensions that most need intervention, in addition to observing that the last two groups, with less potential for ecosystem services, are those that aggregate UGS that are in areas of the city of greater socio-economic deprivation. UGS are used to relax, socialize, and contact with nature amongst the dense urban fabric, in addition to promoting greater ecological awareness as the degree of attendance increases. The mapping of human behavior also revealed patterns and regularities between behaviors and the design of the UGS, as well as natural elements and urban furniture, contributing to a greater correspondence between human needs and space. In addition, the UGS with greater dynamism and frequency of users are in less deprived areas of the city. The answer to the objective initially proposed is that the UGS are responding to socio-environmental challenges at two paces: if, on the one hand, their socio-ecological potential is used by their users, on the other, not everyone benefits from them in an equitable way. The greatest expectation is that the results of this work can be a contribution to the definition of local strategies that enhance the ecosystem services of the city's UGS, providing equitable access for all to these spaces and satisfying the needs of their users toward green cities, fair and inclusive.
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Pekarangan is a typical Indonesian home garden. This article aimed to look at biophysical conditions of pekarangan between Sundanese migrants and non-migrants. A total of 40 pekarangans in Selajambe and Ciomas Rahayu villages, West Java, were chosen as representative locations for the Sundanese non-migrant population (native Sundanese), and 40 pekarangans in Tegal Yoso and Tanjung Kesuma villages, Lampung, were chosen as representatives of the Sundanese migrant population. Research has been carried out in the period 2019–2021. To measure the biophysical conditions of pekarangans , we analyzed the pekarangan area, pekarangan size, number of species and individual of pekarangan plants, vertical diversity and horizontal diversity of plants, and the relationship between the pekarangan area and number of species and individual plants. The results showed that the difference in conditions of the pekarangan was indicated by the difference in the area and size but not by the diversity of the plants. Both types of pekarangans have the same level of diversity, as indicated by the number of individual plants that are almost the same in number per 100 m ² . In addition, a strong and positive correlation (0.69–0.88) between the area of pekarangan and the number of individual plants indicated that the small to medium size or large pekarangan sizes had almost the same diversity of plants. The difference lied in the type of plant that is cultivated. Migrant pekarangans are dominant in cultivating food crops, while non-migrant pekarangans are dominant in cultivating ornamental plants. The selection of plants that have important and valuable functions can be a solution in maintaining the area of the pekarangan . Choosing plants with a variety of functions can be an option for a small to medium pekarangan size. To improve the biophysical conditions of the pekarangan was also inseparable from the involvement of economic, social, and cultural aspects in the pekarangan .
Inexplicably, the review literature on biological invasions has often omitted those by plant pathogens. Here, we provide a review on the consequences of invasions by forest pathogens, whether non-native and introduced or native and invasive due to ecosystem-level alterations such as those caused by climate change, practices associated with forestry, and the planting of exotic hosts. Together, these two classes of invasive pathogens can be defined as emergent and can lead to the rise of novel plant diseases causing detrimental effects on affected ecosystems. This chapter will present examples of such detrimental effects with a focus that goes beyond the mortality of the main host plants, by including ecosystem-level, evolutionary, economic, and societal impacts associated with disease outbreaks caused by emergent tree pathogens.
Plant biodiversity in the dry ecosystem of the savanna is constantly under threat of extinction, thereby contributing to the ongoing climatic crisis. The systematic compilation of plant species growing in any region is an important tasks of ecological research centered on conservation. In the present study, a comprehensive and systematic inventory of the diversity and population structure of trees and shrubs growing on the Ungwar Jeji campus of Federal University Birnin Kebbi Northwestern Nigeria was provided. The data was collected using a standard 50 × 50 quadrat with 156 total sample plots stratified into plantation area (PA), undisturbed area (UA), building area (BA), and drive/walkways area (DA). Diversity indices were computed using PAST 3.17 software. The campus is richly endowed and diverse in species as revealed by the Margalef's species richness value of 4.753 and the Diversity Index Value (Shannon_ H′) of 2.51, respectively. The inventory recorded 39 species belonging to 17 families of trees (66.67%) and shrubs (30.77%). Fabaceae has the most species (30.77%), while the least families recorded 1 species (2.5%) each. Azadirachta indica and Acacia podalyriifolia recorded an IVI of 55.4 and 99.62 making them the most important tree and shrub species respectively. Ficus platyphylla (2.82%) is the least. Most of the species encountered are of least concern (89.19%) except for Vitellaria paradoxa, which is Vulnerable (2.70%) according to the IUCN Red List version 2021–2. This preliminary inventory is useful for the planning and implementation of a sustainable conservation strategy on the campus. DNA conservation of the species is recommended.
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As urban forestry continues to evolve as a profession, foresters and arborists can expect many challenges as well as opportunities. The continuing development of cities has become linked to a much greater emphasis on urban vegetation, the growing demand for recreation amenities within the urban environment, and the careful and successful management of vegetation in an urban ecosystem. New ways to incorporate the highly versatile urban forest resource into the urban fabric will undoubtedly benefit the lives of its residents.
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Research suggests that the formation of neighborhood social ties (NSTs) may substantially depend on the informal social contact which occurs in neighborhood common spaces, and that in inner‐city neighborhoods where common spaces are often barren no‐man's lands, the presence of trees and grass supports common space use and informal social contact among neighbors. We found that for 145 urban public housing residents randomly assigned to 18 architecturally identical buildings, levels of vegetation in common spaces predict both use of common spaces and NSTs; further, use of common spaces mediated the relationship between vegetation and NSTS. In addition, vegetation and NSTs were significantly related to residents' senses of safety and adjustment. These findings suggest that the use and characteristics of common spaces may play a vital role in the natural growth of community, and that improving common spaces may be an especially productive focus for community organizing efforts in inner‐city neighborhoods.
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The need for urban greening increases with global urbanization. Trees are major assets to livable urban areas, providing valuable environmental services to combat challenges such as pollution, urban heat, and flooding, as well as to improve social cohesion, human health, and well‐being. Investments in tree planting and arboriculture yield valuable returns, but trees face many challenges in the unnatural and stressful urban environment and in a rapidly changing climate. Botanical gardens have expertise in growing plants in designed landscapes. We urge their increased involvement with urban forestry to improve sustainability of cities and human lives. Summary Improving urban forests is one of the solutions to achieving several of the United Nations Sustainable Development Goals and making cities healthier and more livable for people. Priority should be given to protecting mature trees and promoting long‐lived trees in the future. Achievement of this goal requires recognition of the myriad stresses trees face in built landscapes as well as the challenges related to climate change. Because all people living in communities are affected by the urban forest, developing solutions and forestry action plans should be a social endeavor and include diverse partnerships. Botanical gardens and arboreta can provide key resources in support of these efforts. They have a significant public reach, maintain a strong professional network, and can make important contributions to address key priorities including (a) protecting existing trees; (b) improving tree selection, diversity, and age structure; and (c) improving planning, standards, training, and management. A focus on below‐ground aspects, such as root development and soil composition, is a critical component for success. Horticultural and scientific knowledge combined with extensive public reach make botanical gardens and arboreta important potential partners in achieving urban forest objectives, but a greater call to action is needed. The need for urban greening increases with global urbanization. Trees are major assets to livable urban areas, providing valuable environmental services to combat challenges such as pollution, urban heat, and flooding, as well as to improve social cohesion, human health, and well‐being. Investments in tree planting and arboriculture yield valuable returns, but trees face many challenges in the unnatural and stressful urban environment and in a rapidly changing climate. Professional botanical gardens have expertise in growing plants in designed landscapes. We, the authors, urge their increased involvement with urban forestry to improve sustainability of cities and human lives.
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Humans, as a species, are very new on Earth, but we have had a profound effect on the Planet. The global ecosystem is necessary for every aspect of our lives; yet, we are not safeguarding it nor protecting the biodiversity of the other organisms we share the planet with. As a species, we depend on plants and agriculture for our very existence and they need to receive greater attention and focus. Plant scientists can work together to achieve a robust and sustainable future for all. The future of the Earth and its inhabitants has never been more uncertain, but there is still time for us to prevent further catastrophe. Plant scientists have a crucial role to play in the preservation of plant biodiversity and crop genetic diversity, both vital goals that will have a major impact on the success or failure of humanity’s attempts to prevent ecological disaster. At the 2017 International Botanical Congress in Shenzhen, China, a series of suggestions for the many important ways in which plant scientists could contribute to a sustainable future were proposed, and were accepted by the Delegates of the meeting. These included: conducting research in the context of the changing world, promoting plant science and international collaboration, building platforms for big data, generating a full inventory of plant species, protecting indigenous knowledge, and engaging the power of the public. Here, I describe this Shenzhen Declaration, the threats it aims to mitigate, and the key roles that plant scientists must play for the future benefit of mankind.
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Plants are fundamental to solving many of humanity's most important challenges: food insecurity, water scarcity, energy, health, and climate change. With more than 20% of the world's plant species currently threatened with extinction, the loss of plant diversity will result in reduced options for human innovation, adaptation, and resilience. The world's botanic gardens already conserve and manage around a third of all known plant species in their living collections as well as seed banks as an insurance policy against extinction and as a resource to support scientific research. This work needs to be expanded rapidly if we are to avoid further plant species extinctions. Historically, botanic garden science has been dominated by the disciplines of economic botany and taxonomy. Today, with around 20% of plant species threatened with extinction, the author argues that unless botanic gardens shift their efforts toward the conservation, management and use of plants, the loss of plant diversity will stifle human innovation, adaptation, and resilience. The enormous body of taxonomic knowledge, skills, data, and collections built up over the past two centuries is fundamental to managing plant diversity. These resources need to be used to address challenges such as food insecurity, water scarcity, renewable energy, human health, biodiversity conservation, and climate change. At a time when botanic gardens are increasingly seen as visitor attractions, rather than scientific institutions, refocusing their efforts is in the best interests of botanic gardens as well as those of broader society. The author gives examples of how botanic gardens are already supplying crop wild relatives to plant breeders; using their living collections to assess resilience to climate change and vulnerability to pests and diseases; and conserving rare and threatened plant species for future use. However, in spite of these efforts, only a small fraction of the estimated 60,000 plant scientists and specialist horticulturists in the world's botanic gardens are engaged in scientific research that has demonstrable impact on how we conserve or manage plant diversity. The author argues that it is time for botanic gardens to develop a new contract with society—a contract that delivers outcomes for society that only botanic gardens, as custodians of the world's plant diversity, can deliver.
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In the United States, schools serving urban, low-income students are among the lowest-performing academically. Previous research in relatively well-off populations has linked vegetation in schoolyards and surrounding neighborhoods to better school performance even after controlling for important confounding factors, raising the tantalizing possibility that greening might boost academic achievement. This study extended previous cross-sectional research on the “greenness”-academic achievement link to a public school district in which nine out of ten children were eligible for free lunch. In generalized linear mixed models, Light Detection and Ranging (LiDAR)-based measurements of green cover for 318 Chicago public schools predicted statistically significantly better school performance on standardized tests of math, with marginally statistically significant results for reading—even after controlling for disadvantage, an index combining poverty and minority status. Pupil/teacher ratio %bilingual, school size, and %female could not account for the greenness-performance link. Interactions between greenness and Disadvantage suggest that the greenness-academic achievement link is different for student bodies with different levels of disadvantage. To determine what forms of green cover were most strongly tied to academic achievement, tree cover was examined separately from grass and shrub cover; only tree cover predicted school performance. Further analyses examined the unique contributions of “school tree cover” (tree cover for the schoolyard and a 25 m buffer) and “neighborhood tree cover” (tree cover for the remainder of a school’s attendance catchment area). School greenness predicted math achievement when neighborhood greenness was controlled for, but neighborhood greenness did not significantly predict either reading or math achievement when school greenness was taken into account. Future research should assess whether greening schoolyards boost school performance.
Importance Elevated intraocular pressure is a major risk factor for glaucoma, a leading cause of irreversible blindness worldwide. Environmental air pollution has been suggested as a potential contributor to elevated intraocular pressure; however, no studies have demonstrated such an association to date. Objective To investigate the association of long-term ambient black carbon exposure with intraocular pressure in community-dwelling older adults. Design, Setting, and Participants This population-based analysis, conducted from October 18, 2017, through March 22, 2018, used data from the all-male, New England–based Normative Aging Study of the US Department of Veterans Affairs. The analysis included 419 older men with a total of 911 follow-up study visits between January 1, 2000, and December 30, 2011. Intraocular pressure was measured by Goldmann applanation tonometry during the study visits. Validated spatiotemporal models were used to generate 1-year black carbon exposure levels at the addresses of the participants. Main Outcomes and Measures An independently developed genetic score approach was used to calculate allelic risk scores for 3 pathways associated with black carbon toxicity: endothelial function, oxidative stress, and metal processing. The associations among black carbon exposure, allelic risk scores, and intraocular pressure were explored using linear mixed-effects models. Results All 419 participants were men with a mean (SD) age of 75.3 (6.9) years. The mean (SD) 1-year black carbon exposure was 0.51 (0.18) μg/m³, and the mean (SD) intraocular pressure for the left eye was 14.1 (2.8) mm Hg and for the right eye was 14.1 (3.0) mm Hg. Of the 911 visits, 520 (57.1%) had a high endothelial function allelic risk score, 644 (70.7%) had a high metal-processing allelic risk score, and 623 (68.4%) had a high oxidative stress allelic risk score. In fully adjusted linear mixed-effects models, the association of black carbon with intraocular pressure was greater in individuals with a high oxidative stress allelic score (β = 0.36; 95% CI, 0.003-0.73) compared with individuals with a low score (β = −0.35; 95% CI, −0.86 to 0.15). Conclusions and Relevance Ambient black carbon exposure may be a risk factor for increased intraocular pressure in individuals susceptible to other biological oxidative stressors. If additional studies confirm these results, monitoring ambient black carbon exposure and physiological oxidative stress may prevent the development and progression of intraocular pressure–related disease.
Many arborists learn tree work practices without fully understanding the biological and physiological principles behind them. However, outcomes for the health and longevity of trees are greatly improved when an arborist understands the science behind the care of tree root systems and crowns. In Applied Tree Biology, Drs. Hirons and Thomas draw upon their decades of experience in the laboratory, classroom, and the field - as well as the expertise of distinguished contributors to this volume - to provide those responsible for tree care with the scientific information that informs best practices for planting, pruning, soil decompaction, irrigation, and much more. Takes a multidisciplinary approach, integrating knowledge from plant biology, physiology, arboriculture, ecology, and more Provides a systematic presentation of fundamental tree biology and the scientific principles informing high quality tree care Presents accessible scientific information and best practices that help promote the health and longevity of trees Reflects the authors' decades of experience as tree biology researchers and educators, as well as their years of professional experience across the globe Applied Tree Biology is an indispensable source of practical, succinct information on tree biology, physiology, and ecology for professionals and interested amateurs involved with the care of trees. Arborists, foresters, and horticulturists at all stages of their careers will find this text particularly useful.