Less cars, more Trees: 10 Reasons why Cities should plant as many urban trees as possible, with help of technology.

ONDIVIELA, José A.??Industry Advisor Cities & Regions. Microsoft Western Europe. // Director WW Observatory for Attractive Cities (www.attractivecities.com) at Universidad Francisco de Vitoria (Madrid, Spain). Social: https://www.dhirubhai.net/in/jondiviela/

Academic ORCID: https://orcid.org/0000-0001-6732-8754

Abstract

Planting trees in our urban ecosystem is becoming much more than an aesthetic necessity. The naturalization of our streets brings numerous benefits to human life. Plant trees and incorporate the care of city green spaces as a key element in urban planning is considered one of the essential solutions for current urban threads (National Geographic (2023). The additional costs due to the necessary gardening seem ridiculous compared to the enormous advantages that it entails. In an urban context where we are recovering spaces for humans and reducing dependence on private vehicles, we could and should find spaces to plant trees and make our cities a much healthier environment. As always, technology will help us manage this live urban asset. Let’s explore below the 10 fundamental reasons why we must replace stone and asphalt with forest canopy, and how information technologies can help us with this objective. As conclusion, we should consider planting urban trees as an investment on our cities sustainability and start now.

Keywords

Trees; Canopy; Environmental sustainability; Inclusive; Healthy City; Silver City; Carbon Neutral

1.- Cutting deaths from summer heat.

Hot southern cities are more used to heat waves. Due to global warming, extreme weather events are increasing in frequency. In parallel, there is an increase in heat waves in northern countries where they have never suffered these phenomena before.

Study from Barcelona (ISGlobal, 2023) points to 40% reduction in summer heat deaths and 1/3rd of premature deaths if current European urban trees canopy doubles (from 15% to 30%). It seems obvious that trees provide:

·??????Shade, which can help reduce the temperature in urban areas. Shade can reduce the amount of solar radiation that reaches the ground and can also cool the air through the process of evapotranspiration.

·??????Trees also release water vapor through their leaves in a process called evapotranspiration, which helps cooling the surrounding air. This can be especially beneficial during hot and dry weather conditions.

·??????Trees clean air, as we’ll explain below.

·??????Psychological benefits: In addition to the physical benefits, trees can also provide psychological benefits, such as reducing stress and improving mental health.

Then, the combination of reduced temperatures, increased humidity, cleaned air and phycological impact are reducing deaths from summer heat waves. (Kondo, 2018a).

2.- Reducing temperatures.

Same 93 European Cities study points to an average temperature reduction of 1,3C if that planting 2x is implemented. Cities plan to combat the inevitable global warming impact by creating climate shelters. ?Study from (Schwaab, 2021) in 293 European Cities concludes that planting trees is reducing land surface average temperatures (LSTs) up to 12C (yes, twelve!) in hot summer. Regional variation in temperature differences during hot extremes between areas covered 100% by urban trees and areas covered 100% by continuous urban fabric could reach 25C or more, depending on the country (mainly latitude). If we combine this with new asphalt materials, then reduction could be even higher.

3.- Improving air quality

Trees are important for filtering and purifying the air in cities, reducing pollution and improving the quality of the air we breathe. Trees can also help improve air quality by removing pollutants and trapping dust and particulate matter from the air (they can remove up to 60% of particulate matter from the air) (Novak et al, 2014). This can help reduce the risk of respiratory illnesses and other health problems related to poor air quality.

A recent study by the (Nature Conservancy, 2019) found that increasing tree canopy in cities by just 10% can improve air quality by up to 8%. The study also found that planting trees strategically in areas with high levels of air pollution can have an even greater impact on air quality.

It reduces risk of cardiovascular disease and cancer: A study published in the journal Environmental Pollution in 2018 found that increasing tree canopy cover in urban areas was associated with lower levels of fine particulate matter (PM2.5), a type of air pollution that has been linked to cardiovascular disease and cancer. The study also found that increasing tree canopy cover was associated with a lower risk of premature mortality from all causes. (Novak, 2006). And trees’ canopy also reduce noise pollution.

4.- Increasing CO2 fixing, then contributing to Carbon neutral task

On average, it is estimated that a mature tree can sequester about 22 kg of carbon dioxide per year, then a single tree can sequester about one metric ton of carbon dioxide over its lifetime, which is typically around 50 years. In terms of total carbon sequestration, a study published in the journal Nature (Pugh at al, 2019) estimated that global tree cover stores around 400 billion metric tons of carbon, which is about 30% of the total carbon in the atmosphere. This carbon is stored in the tree biomass, as well as in the soil and organic matter associated with trees. (Nowak et al, 2018)

These figures are used at Carbon Neutrality calculations.

That way all cities that are in the process of becoming carbon neutral must first calculate their carbon footprint. Then they have to evaluate all the processes that cause emissions either directly or indirectly (direct emissions from their activity, indirect emissions associated with their energy consumption or their value chain (municipal supplies and activities)) and propose change processes to achieve the maximum reduction in an evolutionary way. Once this final result is reached, those remaining emissions must be compensated with the amount of CO2 that the city forest mass is capable of re-fixing on the ground. Emissions that are not compensated with the city vegetal mass have to be compensated from another side: mainly by acquiring carbon offsets or investments that will reduce CO2 emissions in other places on earth (industrial processes or planting new forests elsewhere).

New chemical processes exist and are being investigated to sequester CO2 from the atmosphere and fix it in the form of rock in the earth (carbonates, etc) or by burying it, but they are still in an initial phase and show low efficiency, thus increasing our city forest mass is of crucial importance for the objective of containing climate change and avoiding an increase in temperature of more than 2oC. (IPCC, 2018).

5.- Creating a liveable / social friendly district (15’ City, Superblock, …)

The "15-minute city" concept is a planning strategy that aims to create urban neighborhoods where all daily needs can be met within a 15-minute walk, bike ride, or public transit trip. This includes access to housing, employment, services, and green spaces, including trees and parks. (Mertens & Schwanen, 2020). (Pradhan, Spies & Loefflad, 2020)

The impact of 15-minute city plans on tree planting and urban green space is likely to be positive, as these plans prioritize the creation of walkable, livable neighborhoods with access to nature. In many cases, this will involve the planting of new trees and the creation of new green spaces, such as parks and public gardens. (Saha & Pati, 2021)

Some cities have already implemented 15-minute city plans that prioritize tree planting and green space. For example, Paris has committed to planting 170,000 new trees by 2024 as part of its 15-minute city plan, which aims to create a greener, more sustainable city with improved quality of life for residents. (Ville de Paris, 2021).

By prioritizing tree planting and green space creation in 15-minute city plans, cities can help to create more livable, sustainable, and healthy urban environments for their residents. It also improves landscape: Trees and other types of urban vegetation can enhance the appearance and aesthetics of a city, which can increase quality of life and a sense of community.

6.- Build the ideal Green living space with 3-30-300 rule.

Forestry professor Cecil Konijnendijk launched the 3-30-300 rule last 2021, with the goal of stimulating the development of greener and healthier cities everywhere. More than a scientific facts-based conclusion, it is more a rule of thumb (but based on solid arguments) to provide an easy to understand direction to policymakers. Main aim is to generate more and better distributed green assets which will improve our quality of life. (Konijnendijk, 2021). In his NBSI’s report "Nature-based solutions in urban areas: The 3-30-300 rule for building renovation and urban climate resilience," he provides an overview of the 3-30-300 rule and how it can be used to promote green areas in cities at urban planning. It suggests that every home should enjoy:

·??????3 trees from every home. (decent-sized trees)

·??????30 percent tree canopy cover in every neighborhood

·??????300 metres from the nearest public park or green space

Every citizen should be able to see at least three trees (of a decent size) from their window. (Rugel, 2019) demonstrates after remarkable research the importance of having green areas nearby and visible for mental health and well-being. The COVID-19 pandemic has further highlighted this issue, leading to a greater preference for homes in green spaces and raising awareness of the benefits of nature. Cities should strive for even more abundant canopy cover whenever possible.

(Astell-Burt & Xiaoqi, 2020) have repeatedly found 30% to be a highly relevant threshold: a minimum percentage of canopy cover that ensures residents reap the expected health and wellness benefits. It seems an ideal figure: less would indicate an excessive predominance of cement, more would lead us to an isolated house in the middle of a forest and with little social interaction. By creating greener neighborhoods, we also encourage people to spend more time outdoors and interact with their neighbors (which in turn promotes emotional and social health). Many of the world's most ambitious cities in terms of environmental sustainability, such as Atlanta, Barcelona, Bristol, Cambridge, Canberra, Los Angeles, Oslo, Sydney, Vancouver have already set themselves the goal of achieving 30% or more canopy cover. Where it is difficult for trees to grow and thrive, for example in arid climates, the goal should be 30% vegetation (shrubs, grass, green open spaces)

We want to represent the maximum meters to the nearest park or green space with 300. Many studies have underlined the importance of having green spaces nearby and accessible. Specifically, the European Regional Office of the World Health Organization recommends a maximum distance of 300 meters (or its equivalent: 5 minute walk or 10 minute stroll) (WHO, 2016) to the nearest park, trail or green space, and that it must have the size of at least 1 hectare (Van den Bosh, 2016). This has a positive impact on physical and mental health by encouraging the recreational use of green spaces. It will be necessary to work within the local context and adapt the rule to the different needs of lower density or more dense suburban areas. In any case, efforts will be made to facilitate access to quality and accessible urban green spaces. In this regard, it is important to note that the term green space does not necessarily refer to park-like spaces. Linear green walkways with abundant vegetation, seating, and areas for playing and exercising can and should also be considered.

7.- Social Collective Task. Citizen Engagement.

Many cities are aligning the objectives of increasing their forest mass with a social motive. In this way, some cities are associating the number of trees planted with the number of citizens or doubling it. Others hope that citizens participate in the care and development of these new trees, protecting them and also increasing their number within private properties. Some cities with little available public space are encouraging their citizens to plant greenery on walls and roofs (Barcelona). It is clear that making citizens aware of the need to increase the urban forest mass immediately achieves collaboration in improving their urban space. Seems like an obvious target. The sense of citizens involvement achieves that this motion becomes a collective task where the citizen has a direct participation in the improvement of their city. This fosters the feeling of belonging, of a common destiny, and of solidarity among citizens.

As examples, NYC (USA) has more than double the 2007 initiative to plant one million trees (MillionTreesNYC) across the city by 2017

Toronto (CAN) and Melbourne (AUS) aim to increase the tree canopy cover from 28% and 22% to 40% by 2050 and 2040, respectively. The strategies include planting new trees, protecting existing trees, and encouraging private landowners to plant trees.

Nairobi, (KEN) shows special interest on addressing deforestation, air pollution, and climate change with a program called "Greening Nairobi" with the goal of planting 1 million trees in the city by 2022.?

Glasgow evolved its initial "Every Person, Every Street, Every Community" initiative aiming to plant at least two trees for every resident in the city to a more ambitious plan to plant ten trees for every person in Glasgow City Region. Presented at COP26, this means an opportunity for communities, schools, businesses and landowners to get involved and to work collectively to improve their living environment whilst tackling climate change. (Glasgow, 2022)

EUROCITIES Award Finalist (Eurocities Awards 2022), the city of Zaragoza (Spain) initiative to plant a tree for each citizen is receiving extraordinary citizen collaboration (associations, schools, etc). Faced with the climate crisis, the “Zaragozanians Forest” allows citizens to unite to build a green legacy that remains for future generations, betting on improving health and reducing the city's carbon footprint through absorptions of CO2. In addition, this project will help Zaragoza achieve its Carbon Neutral by 2030 goal within the EU Mission: Climate-Neutral and Smart Cities 112 participant cities. (Zaragoza, 2023)

8.- Improved health and well-being.

Trees and other types of urban vegetation can improve people's health and well-being by providing a green space for recreation and relaxation. This happens not only because of the promotion of physical activity, but also because of the improvement in mental health, memory and attention associated with living close to forest masses and enjoying them. Thus, green urban masses improve:

Physical activity: A study published in the Journal of Physical Activity and Health in 2015 found that residents of neighborhoods with higher levels of green space, including trees and other vegetation, were more likely to engage in physical activity. The study suggested that the presence of green spaces may encourage physical activity by providing opportunities for walking, jogging, and other forms of exercise. (Kaczynski ?et al, 2015)

Mental health, and it increases life satisfaction: Green spaces beauty is a natural tranquillizer for troubled minds. A study published in the journal Landscape and Urban Planning in 2019 found that people who live in neighborhoods with more trees and green spaces report higher levels of life satisfaction and lower levels of psychological distress. The study also found that the presence of trees and green spaces was associated with higher levels of social cohesion and a greater sense of community. (Houlden et al, 2019).

Memory and attention: A study published in the journal Environmental Health Perspectives in 2015 found that exposure to green spaces, including trees, was associated with better cognitive function in children. The study suggested that the presence of green spaces may help to improve memory and attention by reducing stress and providing opportunities for physical activity. (Dadvand et al.2015).

Accordingly, many cities are building huge green rings that allow leisure, recreation and sports without having to leave these green spaces. In some cases, the goal is to be able to run a marathon without having to go through the same place several times. These large green spaces have been shown to improve air quality, reduce noise and create healthier spaces for citizens.

Here are some examples of cities with plans to build green rings (parks and forests), along with links to more information:

·??????Madrid (Spain). The Madrid Metropolitan Forest is a project that aims to create a green ring around the city, made up of forests and parks. The goal is to increase the surface area of green spaces and improve air quality. (source: https://www.iberdrola.com/environment/madrid-metropolitan-forest)

·??????Berlin (Germany). The city of Berlin has a green ring that surrounds the city, made up of green zones, parks, and natural spaces. This green ring is known as the "Green Belt" and covers more than 1,000 hectares. (source: https://www.visitberlin.de/en/green-berlin)

·??????Buenos Aires (Argentina). The city of Buenos Aires is working on a project to build a green ring around the city, made up of parks and green areas. The goal is to improve the quality of life for residents and reduce air pollution. (source: https://www.argentina.gob.ar/ambiente/buenos-aires-verde)

·??????Montreal (Canada). The city of Montreal is working on a project called the "Green Belt", which aims to create a green ring of natural areas and parks surrounding the city. The goal is to improve air quality, reduce noise, and create a healthier environment for residents. (source: https://montrealgazette.com/news/local-news/montreal-to-create-a-green-belt-to-improve-air-quality)

·??????London (UK). The city of London has several projects to create green spaces and parks that surround the city. One of these projects is the "Green Grid", which aims to create a green ring of spaces that connect different areas of the city and improve the quality of life for residents. (source: https://www.london.gov.uk/what-we-do/environment/parks-green-spaces-and-biodiversity/green-grid)

9.- Silver City

Our cities are spectators of the constant phenomenon of population aging. The current decline in birth rates, together with the increase in life expectancy, and health improvements and medical advances are generating a high percentage of the population that will soon reach retirement age. It is said that in Europe, 50% of the population will be over 50 by 2050. It is therefore necessary to adapt our cities to this new reality. It is not about building new ones. Cities that are attractive to retain and attract young talent are also attractive to older people. It is simply necessary to strengthen social and health services, and adapt the physical environment, making it accessible to these people with reduced mobility. Additionally, the creation of public green spaces that improve physical and mental health will contribute to better care for the elderly. ?We must highlight the importance of urban green space for public health and how parks and open spaces can provide essential services that are critical to both urban ecological functioning and integrity. Urban green space also provides a wide range of ecosystem services that could help combat many urban ills and improve life for city dwellers, especially those with high health risk (elderly) (Wolch, Byrne and Newell, 2014). If we also plan spaces specially designed to encourage social contact between them, we will have adapted our city to become a Silver City.

Physical health benefits: Urban trees can provide shade, which can help to reduce the risk of heat-related illnesses and other health problems that are common in older adults. Trees can also improve air quality, which can have a positive impact on respiratory health.

Mental health benefits: Research has shown that exposure to nature and green spaces can have a positive impact on mental health and well-being. For older adults, spending time in green spaces and enjoying the benefits of urban trees can help to reduce stress, improve mood, and promote a sense of calm and relaxation. (Kondo et al, 2018b).

Social benefits: Urban trees can provide a space for social interaction and community building, which can be particularly important for older adults who may be at risk of social isolation. Urban trees can provide a space for outdoor activities and events, as well as opportunities for older adults to connect with others in their community. (Enssle & Kabisch, 2020)

10.- Biodiversity Improvement

Urban green areas can also provide a habitat for a variety of animal and plant species, contributing to biological diversity and ecosystem sustainability. (Lister, 2005)

In addition to traditional 3 R’s in Circular Cities (Reduce, Reuse, Recycle), we are incorporating two more: Redesign of processes and business models so they help with matter cycle, and Regenerate environments, restoring the relationship between our city and the natural ecosystem it is placed into. Planting urban trees can help regenerate natural spaces, support wildlife, birds, and pollination, and promote the recovery of local species.

According to the European Environment Agency (EEA, 2010) cities play an important role in hosting rare and endangered species and habitat types of European interest. In Europe, some 179 species covered by the Habitats Directive are linked to urban ecosystems. The value of wildlife in cities is often underestimated. Nature in cities is not just a matter of managed biodiversity, such as urban parks and gardens, botanical gardens or individual balconies. There are also other spaces such as urban wetlands, old abandoned industrial environments, the shoulders of roads and paths, abandoned spaces, ruins, peripheral orchards, rooftops, urban rivers and waterfronts lined with trees, and even cemeteries are potential reserves of urban biodiversity.

What’s the role of information technology on this urban forestation?

Like in most human activities, technology plays a relevant role in making this improvement process more accurate, faster, cheaper, less resource-intensive and more sustainable. The main phases where information technology becomes an excellent ally are:

·??????Inventory of vegetal structure. Observe canopy, determine size, type, situation (amount of flammable material, dryness, diseased trees, pests,...). Recording of the physical space in very high precision to determine the elements using AI. Calculation of trees and forest mass to assess CO2 absorption and offset the carbon footprint (carbon neutral objective)

·??????Care of the vegetal layer. Smart gardening. Evaluate conditions in real time (temperature, humidity, including water stress and growth). Predict meteorological threats (for example, the “Filomena” storm destroyed 12% of the forest mass in Madrid in a few hours...) Fire prevention. Urgent response (fight wildfires,...). Prevention and combat of pests and diseases of plants (caterpillars, fungi, viruses, etc.). Automatic irrigation systems based on sensor information. (IoT platforms and weather forecasting).

·??????Planning. Prioritize the areas to plant. Resource forecast. Budget. GIS environments for visualization and planning. Digital Twin systems for resilience and risk assessment and development of contingency plans for natural disasters (floods, severe drought, wildfire, etc.)

·??????Plantation. Use of drones to replant trees at inaccessible areas. Optimization of sowing conditions according to IoT data (sun orientation, wind, humidity, others). Interrelation with other areas of the city such as available water, traffic visibility, surrounding elements.

Some available information technology solutions are:

Cyclomedia. Street Smart uses Cyclomedia's high-resolution imagery and advanced data processing to identify and locate trees, assess tree health and condition, and generate reports on tree inventory and maintenance needs. The platform is used by cities, municipalities, and other organizations around the world to improve their urban forestry management practices. https://www.cyclomedia.com/en/solutions/use-case/vegetation-management

Treepedia: Treepedia is a free platform that maps and measures tree canopy coverage in some cities around the world. It provides a visual representation of the distribution of trees in urban areas and can help city planners and residents identify areas where more trees are needed. https://senseable.mit.edu/treepedia/

i-Tree: i-Tree is a free suite of tools that can be used to inventory, assess, and manage urban forests. It includes a variety of software tools, including i-Tree Eco, which can be used to estimate the environmental and economic benefits of urban trees, and i-Tree Canopy, which can be used to map and quantify the distribution of tree canopy in urban areas. Free?i-Tree tools are available in several countries, including the US, Canada, Australia and many countries in Europe. https://www.itreetools.org/

Citygreen: developed by the Australian company Citygreen Systems, Citygreen is a digital twin platform that allows city planners and urban designers to create 3D models of urban environments and simulate the effects of different landscaping and tree planting scenarios. It can be used to identify areas of a city that would benefit most from new trees and to design green infrastructure projects that maximize the benefits of urban trees. https://citygreen.com/

TreePlotter: TreePlotter is a web-based platform that allows cities and other organizations to map, manage, and monitor urban trees. It includes a range of features, including inventory and data management tools, reporting and analysis capabilities, and interactive maps and dashboards. https://planitgeo.com/treeplotter/

Bentley Systems iTwin. Based on inventory data (like that provided by Cyclomedia and IoT info), Bentley Systems generates a digital twin to run simulations about any physical condition impacting the city, making it possible to create a resiliency model or developing any “what-if” scenario. ?https://www.bentley.com/software/infrastructure-digital-twins/

CONCLUSION

Investing in planting trees will result in more environmentally sustainable and inclusive cities, with healthier and happier people. We have reviewed the evidences that justify the tangible and real benefits provided by the urban forest mass. It seems clear that planting and protecting trees is always good and provides a (at least partial) solution to many of the challenges our cities face today. In addition, they provide significant benefits at very little cost. In the long term and thinking about the unavoidable challenges that climate change poses for us, these results can be decisive, and make a profound difference between a city that invested a few years ago in planting a large forest mass and a city that did not in time or in quantity. In particular, the ten reasons outlined in this article (reducing deaths from heat waves, reducing the temperature in the city, improving air quality, contributing to sequestrating CO2-Carbon neutral, creating liveable/social friendly cities, creating the ideal green environment 3-30-300, promote a collective social objective, improve health (physical and mental condition), contribute to adapting the city to elderly-Silver City, improve biodiversity) are of particular importance and contribute directly or indirectly to promoting 15 of the UN SDGs 17 goals. In addition, the planting and protection of the forest mass supports the New Urban Agenda (NUA) of the United Nations. (Turner-Skoff and Cavender, 2019)

For us to perceive these benefits, the urban forest must be in perfect condition, cared for and diverse. It should be accounted for as an investment in future sustainability. Planting is not enough, like any investment, if you don't take care of it, its value depreciates and it can become a burden, an additional problem. Therefore, you must invest now and organize the care resources needed. As the Chinese proverb says, "The best time to plant a tree is twenty years ago, the second-best time is now" or as we say in Spain: "If you want oranges, you must first plant and care for an orange tree". Now is the time to evaluate the best way and decide to plant as many trees as possible.

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