Salvaging polluted cities

As Delhi grapples with yet another harrowing bout of air pollution, the city finds itself ensnared in a thick blanket of toxic smog, pushing its air quality index to alarming levels again. With readings skyrocketing to 100 times the World Health Organization’s recommended limit, the severity of the situation has prompted drastic measures, including school closures and restrictions on construction activities. In the face of this crisis, the urgent need for effective solutions to combat air pollution has never been more evident. Planners and designers are reimagining cityscapes with verdant green corridors and tree-lined boulevards, weaving greenery seamlessly into the urban fabric.

Phytoremediation, the use of plants to clean up contaminated soil and water, or phylloremediation to clean polluted air, are well-researched, sustainable, and cost-effective solutions to combat pollution. Planting certain species, like the Ixora spp and Tecoma stans, one can create a natural air-purifying barrier, absorbing harmful substances such as hydrocarbons and aromatic compounds. Recent studies have shown that plants rich in ascorbic acid, like the mighty pipal and mango trees, are particularly effective at combating the adverse effects of pollution. Plant roots also play a crucial role in breaking down toxins, transforming harmful pollutants into less detrimental forms.

An avenue trees corridor. | Photo Credit: Getty Images/iStockphoto

Imagine, one tree can provide enough oxygen for four people in a day, while also absorbing over 48 pounds of carbon dioxide annually. Given India’s staggering population of 1.4 billion, the simple act of planting just one tree in our lifetime can dramatically enhance our immediate environment.

How have cities around the world battled air pollution? The High Line in New York City is a testament to this vision, transforming an old rail line into a vibrant greenway that breathes life into Manhattan’s concrete jungle, while the underline in Miami is reactivating the space under the metro with lush greenery and nodes for activities.

Freiburg going green with asphalt roads. | Photo Credit: Getty Images/iStockphoto

Meanwhile, sustainable neighbourhoods like Freiburg’s Vauban District prioritise green infrastructure, blending tree-lined streets with pedestrian-friendly design principles rather than prioritising cars and additional asphalt roads. Iconic public spaces like Chicago’s Millennium Park showcase the beauty of urban forestry, with sprawling gardens and shaded groves inviting visitors to reconnect with nature in the heart of the city.

Cheonggyecheon, a modern public recreation space in downtown Seoul, South Korea. | Photo Credit: Getty Images/iStockphoto

Landscape infrastructure takes centrestage in initiatives such as Seoul’s Cheonggyecheon Restoration Project, where neglected urban streams are reborn as vibrant green corridors.

Signs indicating Ultra Low Emission Zone (ULEZ) on a street in London. | Photo Credit: Getty Images/iStockphoto

London’s policy effort

On December 5, 1952, London was engulfed in a thick smog that triggered respiratory illnesses, leading to the Great Smog, a deadly event lasting nearly a week and claiming between 4,000 and 10,000 lives. In response, strict measures were taken to address pollution. It included the implementation of green infrastructure to mitigate coarse pollution, stricter emission standards for construction vehicles to reduce idling, and the replacement of local power generators with electric alternatives. Practices such as water recycling on site, prohibiting material burning, and revegetation of exposed areas due to earthwork were adopted. Site operators were encouraged to install green walls and vegetation to minimise dust and pollution impact, enhancing the local environment. Compliance with emission standards for heavier vans and mini-buses was enforced within the London Low Emission Zone.

Policy transformations in New York

Yet another instance of a city reversing the tide on pollution was seen in New York. The city has seen a remarkable 40% decrease in fine particulate matter pollution over the past two decades. Back in the 1960s, smog was pervasive. In 1966, the haze led to an alarming number of deaths, approximately 24 per day.

Green Architecture in New York City. | Photo Credit: Getty Images/iStockphoto

The passage of the 1967 Air Quality Act and the landmark 1970 Clean Air Act established federal standards for mobile sources of air pollution and hazardous air pollutants. In parallel, initiatives like tree planting programmes were launched by the Environmental Protection Agency (EPA) in the 1960s to address environmental conservation.

Delhi has done it before!

In India, the prospect of achieving clear skies is possible as seen during the pandemic. The COVID-19 lockdown in 2020 significantly improved air quality. Delhi, along with other cities, witnessed a drastic reduction in air pollution during the lockdown period. Encouraged by this positive change, several cities around the globe initiated measures to address pollution at its source.

Bogota, Colombia. | Photo Credit: Getty Images/iStockphoto

For example, Bogota in Colombia is transitioning to electric buses and metro systems to reduce air pollution by 10% by 2024, while also promoting bicycle usage with one million daily trips recorded in 2020. Similarly, Seoul, South Korea, announced a ban on diesel cars from the public sector and mass transit by 2025. They also unveiled plans to plant trees along rivers and roads to create wind paths that would direct cleaner air into the city centre. Seoul also aims to increase green space by 30% by 2030.

Bangkok’s green cover. | Photo Credit: Getty Images/iStockphoto

The Green Bangkok 2030 project aims to enhance green space in the city, with plans to open 11 parks and a 15km greenway to reduce reliance on private transportation. Paris has taken bold steps by banning polluting vehicles and repurposing road space for trees, pedestrians, and bike lanes, contributing to efforts to combat pollution.

The writer is landscape architect and Principal, Studio Arth, Miami, Florida.