大象传媒

The view of Cairo from the air is one of concrete buildings and tangled overpasses stretching as far as the eye can see. comprise less than 4% of the total urban built area, and recent construction projects have of tens of acres of the city鈥檚 already-sparse green space.

In megacities such as Cairo and Dhaka, Bangladesh, the lack of green space contributes to a host of problems: increased air pollution, higher air temperatures, and greater exposure to ultraviolet radiation, all of which are making these cities increasingly dangerous places to live. According to the World Health Organization, outdoor air pollution , most in low- and middle-income countries. Outdoor air pollution is particularly deadly in dense urban environments in these nations. In Cairo, for example, researchers estimate that in people over the age of 30 can be attributed to long-term exposure to two common air pollutants: nitrogen dioxide and fine particulate matter (PM2.5). That鈥檚 an estimated 20,000 deaths each year in this city alone.   

Why do cities like these lack green space? The natural environment often plays a role: Cairo, for example, is in a desert; it鈥檚 not naturally lush. Rapid urbanization in recent decades has also led to the development of informal neighborhoods and other new construction projects, exacerbating the problem. But mostly, it comes down to planning. 

Gardening on a rooftop is more than just a clever use of limited space.

For postcolonial cities, formative urban development occurred under colonial domination and focused on exploitation. Urbanist Garth Andrew Myers, author of , that 鈥渃ities were predominantly oriented around the extraction of goods for the metropole.鈥� They were never designed to be sustainable. 

Even today, foreign powers shape the development of postcolonial cities in pernicious ways. China鈥檚 Belt and Road Initiative is聽聽of foreign development projects that have caused environmental destruction and left developing nations with untenable debts. From 2015 to 2017, Egypt聽聽to finance infrastructure projects. But much of this recent development聽, which is , drought conditions to worsen, and extreme weather events like flash flooding and sandstorms to become more common across the nation.

Informal settlements, home to the cities鈥� most impoverished and marginalized communities, are the most vulnerable to rising temperatures, ultraviolet radiation, and air pollution. These neighborhoods have multiplied in both Cairo and Dhaka since the turn of the 20th century, and they often lack proper infrastructure and access to green space. 鈥淪ome areas in informal settlements have zero square meters per inhabitant of green space,鈥� says Abdallah Tawfic, co-founder of Cairo-based organization . 

These patterns hold true for many of the Global South鈥檚 largest cities. But organizations like Urban Greens as well as in Cairo and in Dhaka are committed to greening their cities by weaving rooftop gardens into the crowded cityscapes. The inspiration behind their projects is simple: 鈥淲e don鈥檛 have the space to plant trees, but we have 500,000 rooftops capable of taking the load of a rooftop garden,鈥� says Ahsan Rony, founder of Green Savers. 

Gardening on a rooftop is more than just a clever use of limited space, though. Rooftop gardens have substantial positive effects on air pollution and city temperatures. 鈥淗aving a green cover is the best thing that could happen to this environment,鈥� says Khaled Tarabieh, professor of architecture at the American University in Cairo. 

Cooler, Cleaner Cities

When a rooftop has a green cover, comprised of plants in raised beds, tables, or trellises, it shades the apartments on the upper floor, preventing overheating, especially in buildings that lack proper insulation, as is often the case in informal settlements. Rooftop gardens also reduce the heat that concrete structures absorb throughout the day and then re-emit at night, keeping cities cooler overall.

In Jeddah, Saudi Arabia, one of the world鈥檚 hottest cities, a study showed that indoor air temperatures in buildings with rooftop gardens were than those without gardens, even during the warmest hours of the day. That saves on energy, too, which can have knock-on environmental effects. Research also shows that even relatively small rooftop gardens can by more than half a degree Fahrenheit. 

With cooler temperatures, less ground-level ozone forms, reducing outdoor air pollution. that plants can remove ozone, particulate matter, sulfur dioxide, nitrogen dioxide, and carbon monoxide from the air. 鈥淚f you are living in a place where you have a thick green cover, you鈥檙e enjoying a better and healthier quality of life,鈥� Tarabieh says.

Rooftop gardens are also more practical than green walls or roofs, which are mounted on buildings. Green walls , but Tarabieh says these spaces often require more water than a rooftop garden of the same size, are much more difficult to maintain, and can even compromise the structures on which they are mounted.

Green Savers has worked on more than 5,000 rooftop gardens in Bangladesh since its founding in 2010. Most of its projects have been in Dhaka, the nation鈥檚 capital and one of the most densely populated cities in the world. But it has also expanded to the cities of Cox鈥檚 Bazar and Sylhet. 

Urban Greens is a much younger enterprise, but it鈥檚 growing fast. Founded in 2018, the organization partners with sponsors to provide hydroponic gardening supplies to low-income families for free and sells these same supplies to other customers. Interest in home gardening skyrocketed during the pandemic so the sales side of the business took off, according to Yahia El-Masry, the organization鈥檚 co-founder and business development manager. 

Reinvesting those profits has allowed Urban Greens to expand faster than anticipated. It is now launching new projects in Upper Egypt and a website called the 鈥淯rban Greens鈥� Network,鈥� which it hopes will inspire more Egyptian city dwellers to begin gardening. 鈥淲e want to create a network of practitioners to share knowledge and information and at the same time, invite other people,鈥� El-Masry says. 

Tending Community Health

Beyond rooftop gardens鈥� environmental benefits, they can also provide food and income to the families who tend them. Those are the goals of Schaduf, another Cairo-based organization working in urban agriculture. 鈥淓nvironmental and social change are both in the vision for the company,鈥� says Malik Tag, the organization鈥檚 business development manager.

Schaduf, founded in 2011, establishes produce-bearing rooftop gardens for Egyptian and migrant families in informal neighborhoods. The families that receive training and equipment from Schaduf grow gourmet leafy greens and herbs, and Schaduf connects them with upscale supermarkets to sell their produce for the best possible price.

In response to Bangladesh鈥檚 , Green Savers has also embraced a social mission, hiring and training young people as 鈥減lant doctors鈥� to tend to rooftop gardens.

The greatest challenge for all three organizations has been convincing funders and local residents that the cost and effort of maintaining rooftop gardens are worthwhile. This is particularly true for those peddling hydroponic systems, which come with a higher startup cost. But the organizations have all had success increasing interest through community workshops and school programs. 鈥淲e found that kids are really interested,鈥� Rony says. Many students, after learning about rooftop gardens in school, have convinced their parents to research them further. 

As global temperatures continue to rise, megacities like Cairo and Dhaka will require more significant interventions than urban agriculture alone to prevent air pollution and temperatures from increasing to unlivable levels. But initiatives to green these cities are an excellent place to start. As Tarabieh puts it, green rooftops may not solve all the cities鈥� problems, but, 鈥淲ill it give us an advantage? Absolutely.鈥�

CORRECTION: This article was updated at 12:31p.m. on July 9, 2020, to more clearly explain how foreign powers shape the development of postcolonial cities.聽Read our corrections policy here.