Why Trees Are Important For Urban Areas?

"You don't know what you've got till it's gone," Joni Mitchell sang in "Big Yellow Taxi". 

Human population continues to increase and urban areas are growing and expanding. By 2050, about 70% of the world's population will live in cities (FAO, 2016). These concentrated populations would have a wide variety of challenges, ranging from people without access to clean water to pollution-related health issues. According to UNICEF, children will face longer, hotter and more frequent heatwave by 2050. The health of 57% of children in Europe and Central Asia is at risk atleast 6 times year due to heatwaves.

In such challenging conditions trees would play a important role for people and the planet. The benefits that trees provide can help cities and countries meet 15 of the 17 internationally supported United Nations Sustainable Development Goals. 

Trees are beautiful part of the natural environment, and constantly working to make Earth a healthier planet. Trees hold the key to human survival; land animals, including humans, dependent on them for whole life. 

Trees provide a range of benefits to human health. The USDA (United States Department of Agriculture) scientists at the forest service Pacific SouthWest Research Station (PSW) have found that every $1 spent on planting and caring for community trees yields two to five times that investment. Trees are called the lungs of the Earth because they absorb pollutants through their leaves, sequestering, and filtering contaminants in the air. So, by destroying trees we destroy facilities and functions important for life. 

Here are some important health benefits of trees: 

1- Trees filter the particles out of the air we breathe, which decreases our risk of respiratory problems, including asthma. One study found that in 2010, trees removed 17.4 million tons of air pollution across the US, which prevented 850 human deaths and 670,000 cases of acute respiratory symptoms. 

Scientists working in smoggy Houston say planting a 1.5-square-mile forest would make the air more breathable and could remove as much as 310 tons of ozone from the atmosphere over the course of 30 years. In the year 2014, India’s ozone pollution damaged millions of tons of the country’s major crops, causing losses of more than a billion dollars and destroying enough food to feed tens of millions of people living below the poverty line. Plants start to exhibit damage when they are exposed to ozone levels that reach 40 parts per billion or above. 

Trees are natural and low-cost solutions of healthy air. Best air filtration by trees occurs within 100 feet of a tree. So, street trees are associated with a lower occurrence of early childhood asthma; children living in areas with more street trees have lower prevalence of asthma.  

Trees absorb odours and pollutant gases (nitrogen oxides, ammonia, sulphur dioxide and ozone) and filter particulates out of the air by trapping them on their leaves and bark. 

On average, we eat about 2,000 calories a day and release about 2 pounds of carbon dioxide a day. About 15 trees are needed to take up the carbon dioxide that a person releases based on the food they eat.  

In one year, an acre of mature trees absorbs the same amount of CO2 produced when you drive your car 26,000 miles. 

2- The presence of trees in urban settings can improve mental health by reducing stress; trees lower the level of the stress hormone Cortisol. Thus, trees and greener environments are strongly linked to reduced negative thoughts, reduced symptoms of depression, better reported moods, and increased life satisfaction. 

3- Trees are responsible for fertile soil and agriculture production. Deforestation has adverse effects on soil. The soil would be unprotected, and vulnerable to reduction in soil quality and top soil nutrients. Soil erosion would become more prevalent, and eventually all the soil will lose its arability and agriculture will fall and leave the people starving. 

4- Trees reduce symptoms of ADD and ADHD, and help those with information processing issues, behavioural problems, attention deficit, and hyperactivity disorder symptoms. 

5- Residents of tree-lined communities feel healthier and have fewer cardio-metabolic conditions than those that live in less green areas. It happens due to stress-relieving properties of trees. 

6- The presence of trees can help people with neurodegenerative diseases. Thus trees help the patients to regain a sense of self. 

7- Forest food, including fruits and nuts, wild leaves, palms, wild roots and tubers, mushrooms and insects are a source of  nutritious food that helps to combat malnutrition. 

8- Trees can help reduce our exposure to water-borne pollutants because trees filter stormwater, and improve the water quality of runoff. 

9- Trees can help reduce our exposure to water-borne pollutants because trees filter stormwater, and improve the water quality of runoff. 

10- Trees release beneficial chemicals, phytoncides (chemicals released by trees and plants), which have beneficial effects on immune systems and increase the natural killer cells (cells of the innate immune system). 

11- Trees can prevent Cancer. Forest-bathing boosts our immune system by increasing Natural Killer cells which can kill tumour cells.

12- Forests help us stay happy, relaxed, and well. When we are exposed to nature, even for a short time, the parasympathetic nervous system gets active, lowering the blood pressure, pulse rate, inflammation, cortisol levels, and elevates the moods. As a result, we can feel increased vigour and decreased depression, anxiety, fatigue, and mental fog. 

13- Forests provide a rich reserve of compounds that are key ingredients in 25% of all medicines. Trees contain a wide variety of bioactive compounds which help in fight with diseases. 

14- Skin cancer is the most common form of cancer in the United States. Trees reduce UV-B exposure by about 50 percent, thus providing protection to children on school campuses and playgrounds - where children spend hours outdoors.  

15- Bioactive compounds of several medicinal plants have excellent ability to work against coronaviruses because these compounds are known to act on viral protein targets.

But, our trees are facing anthropogenic stress for survival. About 55% of the forests that covered the Earth are gone. Each year, 16 million hectares disappear. According to the World Resources Institute, only about 22% of the world's old growth forest cover remains "intact". Seven countries (Russia, Brazil, Canada, United States, China, Indonesia, and Democratic Republic of Congo) account for more than 60% of the total. 

Forest soils recover from disturbances slowly over many years, up to 80 years following a wildfire and as many as 30 years after clearfell logging (which removes all vegetation in an area using heavy machinery). During high-intensity forest fires, soil temperatures can top 500 degrees Celsius (932°F), which leads to the loss of soil. 

According to C40 Knowledge Hub, extreme heat events in cities can cause mortality spikes of up to 14%, as well as lower workforce productivity and damage to infrastructure such as roads and rail lines. Today, extreme heat impacts around 68 million people globally. This number is expected to increase 15-fold to around a billion if global heating reaches 2°C, while a 4°C rise would mean that nearly half the global population is affected. Unmitigated, urban heat could cost cities up to 11% of their Gross Domestic Product (GDP) by 2100.

Urban areas face significant challenges as the threat of extreme heat rises, owing to a built environment that concentrates and amplifies heat, creating urban heat islands temperature by 4 °C (7.2 °F) and nighttime temperatures by up to 2 °C (3.6 °F). The hot weather could also push prices up for food, making inflation even worse and results into heatflation.

One in four lives could be saved during extreme heat events in Los Angeles (USA), by increasing tree canopy. 

At a time when climate change is making heat waves more frequent and severe, trees are working as stationary superheroes to control climate crisis. Gardens, parks and street trees make up what is called an urban and community forest. These pockets of greenspace are vitally as important as important as rural forests. Green spaces such as parks act as are cooler than built-up areas and have “park cool island” effect. 

But, trees are not equitably distributed throughout our cities and towns, low income housing areas experiencing lower tree canopy than economically advanced housing areas. So, we should increase tree canopy to ensure tree-equity and health for all the people of the society.  

Globally, tens of millions of lives could be saved if cities invest an average of $4 per resident annually in planting urban trees.  

By 2050 the vast majority of humanity will live in cities, towns, and other urban areas. Among the most pressing of global urban environmental challenges is air that is either too dirty or too hot. 

Policymakers should maintain and plant more trees, develop more parks, and fund research about trees.

We, humans, should never forget the fact that it is only after 100+ years that forest become as they were before the cut. 

In future, trees would be one of the essential part of the solutions for a better and liveable planet. Save trees, forests, related Ecosystems for Nature and for future. 

Pic: Man-made Forest of Jalalpur village (Lucknow-Agra Expressway, on riverbank of Yamuna, Firozabad, Uttar Pradesh,India) 

Written by Prabhat Misra. 

YouTube Channel "Climate Change Conversation"