What Asia’s trees tell us about heat inequality

For those of us living in cities, a hot, sunny day can feel brutal. Concrete buildings and tar roads trap heat from the sun and release it at night. Vehicle and air conditioning exhaust add to the urban heat island effect, in which cities stay warmer than surrounding areas. Needless to say, climate change and rising temperatures around the world don’t help matters. 

It’s a fact that cities aren’t built to be cool—at least compared to wild, vegetated spaces. Trees cool by providing shade and releasing moisture through their leaves. The cooling effect of a single healthy tree is equivalent to that of 10 air-conditioning units, which explains why a city’s coolest parts are often sparsely built or heavily vegetated.

These areas can be three to seven degrees cooler than built-up neighbourhoods. In Singapore for instance, the Orchard Road shopping district is four degrees warmer at night than forested Lim Chu Kang. 

We don’t fully know, to be honest. Data on urban tree cover and green open space is lacking in Asia, particularly in lower income countries. Green spaces, including urban forests and tree canopy, are rarely mapped, and in many cities no comprehensive inventories exist. What defines the urban forest has also evolved, making it hard for people to keep track of what counts as a green space. Are public parks and private gardens included? How about forests at the city’s edge?

What little we know, however, reveals that smaller, poorer cities in the region offer much less green open space per person than the World Health Organisation’s minimum standard (9m²). Even major cities in Asia average at 39m² per person—much lower than cities in Africa (74m²) and Latin America (255m²). 

This is worrying, and not just because greenery keeps us cool on a hot day. Trees and plants filter toxic air pollutants—and Asia’s concrete jungles are amongst the world’s most polluted.

Much of Asia’s forests has been swallowed by growing commodity-driven agriculture and urban growth. In many cities, forests and green open space are just patches on a map. And while governments are now seeing the importance of trees, they are still often the first to go when lands are converted or re-developed. 

But even where trees exist in the city, not everyone enjoys their benefits. 

In several places, you are more likely to live close to a public park or on a street with more trees if you are rich. This affects how protected you are from warmer air and surface temperatures. Studies based in the United States show that racist housing policies have led to unequal outcomes in health and well-being. In low-income districts populated by ethnic minorities and the elderly, more Americans have died or suffered health problems from the lack of trees and other green amenities. 

Is this a problem in Asia, too? 

Wealthier cities such as Tokyo and Singapore, have rolled out grand plans to green their cities. They have innovative green instructure, mass tree-planting schemes, and winding green belts that connect nature to urban spaces. But even here, richer neighbourhoods still enjoy more access to trees and green spaces.

Consider Singapore—the darling of successful public housing. Many residents live in mixed-income public housing designed around neighbourhood parks and other green spaces. Visitors to the Garden City always notice how greenery weaves through the cityscape, leaving few to doubt whether trees are evenly distributed across the city-state.

However, mapping income against tree density in Singapore reveals that even here, higher-income areas, such as Bukit Timah and Queenstown, have many more trees per capita than lower-income neighbourhoods like Choa Chu Kang, Tampines, and Geylang.  

Spatial inequality is starker in Hong Kong, where the poorest work three years and eight months just to make what the richest do in a month. Most of the city’s poor live in subdivided flats—or cage homes—that offer little breathing room, much less green space. 

In Hong Kong’s busy Mong Kok shopping district, families pay close to SG$600 for a tiny 30m² flat carved out from a larger apartment. Here, poorer residents squeeze all they own into a measly 0.6m². Those who secure public housing from the national Housing Authority get a little more: 2m² and open courtyards. 

If greenhouse gas emissions go unchecked, 215 million poor people in 500 cities in the global South will face extreme heat. Record temperatures in recent years have already claimed thousands of lives in Asia. In Hong Kong, Karachi, and Tokyo, hospitals and morgues overflow in the summer, as people fall to heat-related deaths and illnesses.

Air conditioning offers some relief to those who can afford it, but it’s a vicious cycle. It drives up carbon emissions and worsens the urban heat island effect. As people struggle to stay cool, they make their cities and the planet even hotter—leaving the world’s poorest to pay the price.

A green oasis in an underserved neighbourhood does much more than just keep its residents cool. Living close to a good-quality park or healthy forest improves overall health, and being around trees can reduce depression and anxiety. Green spaces even help prevent disease by improving air quality and encouraging physical activity. Nature’s effect on people’s mental health is most pronounced in low-income neighborhoods that have few trees or neglected or unsafe green spaces.

Trees also make for safer, more livable streets that serve as leisure and community areas. Communities in Asia’s cities find in green spaces a safe, free place to socialise and strengthen bonds. 

In urban slums across Bangalore, trees create gathering spots and collective spaces for domestic and daily activities, such as washing clothes and repairing tyres. These “tree canopy-created community centres” are places where traditional ecological knowledge is shared and medicinal or sacred plants are grown. 

Despite all the ways green spaces benefit poorer neighborhoods, vegetation in slum areas remains low. In New Delhi—which does fairly well with 22m² of green space per capita—residents in its eastern parts only access around 3m², while its urban slum residents have even less. Congestion, neglect, and residents’ financial constraints mean there is little space to grow and develop green spaces. 

Many local governments have yet to prioritise greening underprivileged neighbourhoods in development or community planning. But they are growing aware of greenery’s role in improving health, livelihoods, and social capital for the communities that need it most.

In Indonesia, Surabaya’s One Soul One Tree campaign aims to enhance the city’s forests and create alternative means of livelihood for poverty-stricken areas. Residents living along the beach are now responsible for protecting thousands of mangrove trees and harvesting syrup to create commercial batik fabric. 

Elsewhere in Indonesia, a West Javan community has taken it upon themselves to turn an area of their slum into a bonsai garden. The collection of miniature trees transformed a once run-down and dangerous space into a place of leisure and community. 

Adding green infrastructure, such as urban gardens and green roofs, to underused or abandoned spaces is one way to inject greenery into Asia’s dense cities. But greening the city should not come at the cost of social equity. In Mumbai, high-end development in mangrove areas has forced out the surrounding community. As green amenities expand across cities, they tend to drive up housing prices and push out low income or informal residents without land and legal rights. 

Local leaders and urban planners need to consult and involve communities in making green spaces accessible and fair. This also allows their communities to feel more ownership and pride in maintaining such spaces, while helping bridge the gap between the city’s haves and have-nots.

As global warming threatens lives around the world—especially in Asia—we’re running out of time to curb emissions. Asia’s need for trees and greenery has never been stronger.

The Intergovernmental Panel on Climate Change (IPCC) predicts that the world is set to blow past the 1.5 degree Celsius warming threshold by 2040. More erratic and extreme weather will soon rage across the globe, with devastating effects on the most vulnerable. 

Nearly a third of the world already suffers deadly heat episodes of 20 days or longer each year. More will unless cuts to greenhouse gas emissions are made. By 2050, between 500 to 700 million people in South Asia will likely face a 20 percent higher incidence of lethal heat waves. 

Trees and foliage cannot solve everything, but they have become the infrastructure of life and death in the fight against climate change. Equitable green spaces are critical in the fight against rising temperatures, air pollution levels, and mental health crises. Cooped up indoors as the COVID-19 pandemic continues, Asia’s city dwellers need trees more than ever—but they must grow and protect them together.