- As the public pays more attention to climate change and global warming, urban areas worldwide are looking for ways to build up green spaces
- From Gardens by the Bay in Singapore to a vertical forest in China, how useful are these projects for the planet - and people?
From lettuce farmed on New York’s skyline to a vertical forest in the Italian city of Milan, green initiatives are running wild in cities around the world.
Replanting initiatives have been sprouting up since the start of the 21st century as urban development goals have shifted and alarm about global warming has grown.
And they’ve had an impact.
In some cities around the world, thanks to planting schemes on walls and roofs, the temperature during the warmest month in so-called street canyons - flanked by high-rise buildings on either side - can be reduced by 3.6 to 11.3 degrees Celsius at the hottest time of day, according to a report by the French Agency for Ecological Transition.
Green spaces have also been shown to improve health and wellbeing, including by reducing stress, anxiety and depression, improving attention and focus, better physical health and managing post-traumatic stress disorder, said Stephanie Merchant of Bath University’s department for health in Britain.
“However, it’s about where they are created in relation to the needs of the local communities,” she added.
Green spaces are good for the environment and for mental health.
So, are all urban replanting projects worthwhile?
For a scheme to be seen as “virtuous”, it must fulfil as many functions as possible, said economist and urban planner Jean Haentjens, who co-authored the book Eco-urbanisme (Eco-Urbanism).
In addition to lowering the temperature, he said it should also preserve biodiversity, improve wellbeing, raise awareness, be appealing to residents and be suitable for its social context.
So, do these projects fit the bill?
Singapore’s otherworldly garden
The imposing “forest” of giant manmade trees constructed from reinforced concrete and steel, covered in real flora and fauna, is a Singapore landmark.
Towering 25 to 50 metres over the city-state’s business district, the 18 solar-powered supertrees light up the night sky, their canopies looking like flying saucers.
Vast glass greenhouses also showcase exotic plants from five continents, as well as plant life from tropical highlands up to 2,000 metres above sea level, complete with an artificial mountain and indoor waterfall.
The Cloud Forest at Gardens by the Bay in Singapore. Photo: AFP
The Gardens by the Bay project, awarded the World Building of the Year in 2012, says the idea was to create “a city in a garden”.
But pointing to the construction and maintenance costs, Philippe Simay, a philosopher on cities and architecture, called it a “disneyisation” of nature. “Why make trees from concrete when you can have real ones?” he asked.
However, it is a great public relations effort, says Claire Doussard, a teacher in planning and development and a research fellow at the French National Centre for Scientific Research, highlighting its “technical know-how” and awareness-raising among the public about the threat of climate change.
Farming on a New York rooftop
With buildings all around, the Statue of Liberty in the distance and heavy traffic below, the Brooklyn Grange rooftop farm grows more than 45 tonnes of organic produce a year.
It was launched about a decade ago by friends living in New York who wanted “a small sustainable farm that operated as a business”, co-founder Gwen Schantz said.
In a built-up city, Simay noted, it had been found that such initiatives were “fighting effectively against heat islands” where heat-conducting concrete and asphalt make cities warmer than their surroundings.
People visit the Brooklyn Grange rooftop farming company and sustainability centre during an open day, in the New York City neighbourhood of Brooklyn. Photo: AFP
Now covering three rooftops and totalling more than 22,000 square metres, the farm cultivates a wide variety of vegetables.
But it has to limit the soil depth to about 30 centimetres and “irrigate the soil a little more frequently, because it dries out very quickly”, Schantz said.
Doussard said that the logistics of rooftop farming, where water and soil must be hauled up and produce brought down, means: “These farms must be profitable because there are a lot of constraints.”
Milan’s vertical forest
By covering two high-rise apartment buildings from top to bottom in more than 20,000 trees and plants, Italian architect Stefano Boeri said he’d wanted to make trees “an essential component of architecture” and create something that could “contribute to reducing pollution”.
The Bosco Verticale (Vertical Forest) in the heart of Milan sees cherry, apple and olive trees spilling over balconies alongside beeches and larches, selected and positioned according to their resistance to wind and preference for sunlight or humidity.
The Vertical Forest high-rise complex (Bosco Verticale) in the modern district of Puerta Nuova in Milan. Photo: AFP
The award-winning project opened in 2014 and, said Simay, is “an indisputable technical feat with an ecosystem function, a large diversity of trees, plants, insects”.
But, he added, concrete and steel were required to support it all, while setting it up was costly and energy-consuming.
And the price that the luxury apartments go for is also often a talking point.
Riyadh’s mass tree planting
Today, any greenery in Riyadh, Saudi Arabia, is almost lost in between the multi-lane highways and gigantic interchanges, but within nine years the city plans to have added 7.5 million trees.
The reforestation is part of an expensive green initiative that also includes creating 3,000 parks in the Saudi capital.
It will require one million cubic metres of water daily, which will be recycled water from an irrigation network, the Riyadh Green website says.
People walk on a tree-lined street in the Saudi capital of Riyadh. Photo: AFP
But it will contribute towards reducing normal temperatures by one or two degrees Celsius and improve the quality of life with less air pollution and dust, according to project head Abdelaziz al Moqbel.
“Reintroducing trees in the desert is very virtuous, you gain in terms of cooling,” architect and urban planner Cedissia About said.
She said the big question would be whether products used to keep the plants healthy, which also scare off birds and insects, will be used when the aim is to boost biodiversity.
Chengdu’s apartment blocks turned jungle
It promised inhabitants of a Chinese megacity life in a vertical forest, with luxuriant plants and greenery on their balcony.
“The air is good when you wake up in the morning, and the green trees are good for us elderly people,” said Lin Dengying, who lives in one of the eight towers making up Qiyi City Forest Garden in Chengdu, which opened in 2018.
A woman rests on a balcony covered with plants in Qiyi City Forest Garden in Chengdu, China. Photo: AFP
Some parts look like a treehouse perched within a tropical forest, while other places look overrun by their own vegetation, like a jungle is invading and bursting off the terraces.
Recently, Global Times newspaper reported that only about 10 families had moved into the more than 800 apartments, due to what some residents said was an infestation of mosquitoes.
It shows, said Doussard, the need not only to consider a project’s environmental impact, but also its “liveability”.