City |
Thirty pilot cities
in the country are trying to trap and hold more water to deal with
problems from flooding and drought to extreme heat and pollution.
The effort,
launched by Chinese President Xi Jinping, relies on a range of
innovations, from green roofs on buildings to more urban wetlands. It is
already being hailed as a bold step to solve some of the environmental
problems plaguing the world's most populous country.
"It's a timely
reminder that dealing with urban climate challenges requires a holistic
approach," said Sunandan Tiwari, a sustainable urban development expert
at ICLEI - Local Governments for Sustainability, a global network of
1,500 cities, towns and regions.
PEOPLE AND WATER
Like many large
urban areas, Chinese cities are grappling with both rapid urbanisation -
more than half of the country's population lives in urban areas - and
extreme weather, such as severe floods, water shortages and heatwaves.
Both problems can leave more people at risk - but the sponge city effort, launched in 2015, aims to reduce the threats.
The pilot cities
have been charged with finding ways to absorb, store, filter and purify
rainwater, retain it within their boundaries, and release it for reuse
when needed instead of channelling it away through sewers and tunnels.
The cities,
including the capital Beijing, Shenzhen and Shanghai, receive funds and
practical help to redesign their urban areas in a water-sensitive way,
with the aim of turning 80 percent of China's urban areas into sponges
by 2030.
Flood control and water conservation, among other issues, are at the heart of the ambitious push.
But sponge cities
have another benefit that looks set to become a major plus as urban
areas in China and around the world get hotter: They can reduce the
impact of heat waves, which are more pronounced in built-up areas, where
concrete and asphalt trap heat.
Trees and other
plants absorb water and then release it through evaporation. That
creates a cooling effect, in the same way that sweat evaporating from
skin cools people.
"Cooling is largely
seen as a co-benefit of sponge cities. But with record temperatures in
China and many parts of the world, it is becoming a key element in
planning for climate-resilient cities," said Boping Chen, China director
at the Hamburg-based World Future Council, a think tank. GETTING HOTTER
Shanghai, China's most populous city with 24 million people, baked
under a record high temperature of 40.9 degrees Celsius (105 degrees
Fahrenheit) last July even as southern China was hit by torrential rain
and floods.
Efforts to build sponge cities aim to deal with both problems - and improve life for city residents.
"It's not just
about limiting the damage of flooding, it's also about coping with
rising temperatures, improving urban bio-diversity, better public health
and quality of life," Tiwari, of ICLEI, told the Thomson Reuters
Foundation.
Measures taken in
sponge cities include covering buildings with green roofs and facades,
and creating urban wetlands and trenches to filter run-off water that
can be used to replenish aquifers, irrigate gardens and urban farms,
flush toilets and clean homes.
The government has
allocated each pilot city between 400 million yuan and 600 million yuan
($60 million to $90 million) each year for three consecutive years, and
cities are encouraged to raise matching funds through public-private
partnerships and other financial ventures, according to a 2017 study in
the journal Water.
Lingang, in
Shanghai's Pudong district, has invested 800 million yuan in a 79 square
km (30 square mile) area it hopes will become China's largest sponge
city - one that experts say could be a model for other cities lacking
modern water infrastructure.
Lingang aims to
cover rooftops with plants, create wetlands for rainwater storage, and
create permeable pavements that store runoff water, allowing it to
evaporate to moderate temperatures.
Shanghai also
announced last year the construction of 400,000 square metres of rooftop
gardens, alongside other measures to green the city.
"Many of the sponge
cities have done really well but it is a long-term task that needs to
be done in a systematic way," said the World Future Council's Chen.
FOREST CITIES
While China faces
formidable financial and logistical challenges to creating sponge
cities, Italian architect Stefano Boeri has plans to make "forest
cities" in the country.
Boeri, who made
headlines when he covered two residential tower blocks in Milan with 800
trees, 4,500 shrubs and 15,000 other plants, has won planning approval
to build a forest city in Liuzhou in southern China. Conceived as a
green metropolis, the city will house 30,000 people and all its
buildings will be covered entirely with plants and trees, said Boeri,
who declined to give a cost estimate for the project.
In total, Liuzhou's
forest city aims to host 40,000 trees and almost one million plants
from more than 100 species, planted over buildings to improve air
quality, decrease temperatures and contribute to biodiversity, Boeri
said.
The city is
expected to absorb almost 10,000 tons of carbon dioxide - the equivalent
emissions of 2,000 passenger cars driven for a year - and 57 tons of
pollutants per year. The greenery will also produce some 900 tons of
oxygen every year, Boeri said.
He is working with
botanists and engineers to create a high nutrient soil mixture able to
retain water while still keeping weight to a minimum.
"Bringing forests
into the city is one of the most radical and efficient ways to deal with
climate change," Boeri told the Thomson Reuters Foundation.
"We sometimes joke and say we're building houses for trees," he said.
To increase energy
self-sufficiency, solar panels on the roofs will collect renewable
energy to power the buildings, while geothermal energy - heat and
cooling drawn from constant temperatures underground - will power
air-conditioning, adding to the project's green appeal.
Boeri also aims to
build vertical forests, similar to the one in Milan, in Nanjing,
Shanghai and Shenzhen in China and in other parts of the world.
NATURE AT WORK
While China's
sponge city programme is the most ambitious of its kind, urban planners
have embraced nature-based solutions to heat and water worries in other
parts of the world too.
The sponge city
initiative takes inspiration from the North American concept of
low-impact development, sustainable urban drainage systems in Europe and
water sensitive urban design in Australia and New Zealand, all of which
mimic nature's water cycle.
The southern German
city of Stuttgart, prone to high summer temperatures and air pollution,
also has been a pioneer of using nature to adapt to climate change.
Officials there
published a climate adaptation plan in 2012, but planners have been
thinking about the valley city's micro-climate as far back as 1938,
according to Hans-Wolf Zirkwitz, head of Stuttgart's Office for
Environmental Protection.
"Even before we
knew about climate change, our planning has been optimised with regards
to the climate and improving air quality, because of our local climate
conditions," Zirkwitz told the Thomson Reuters Foundation in emailed
comments.
City officials, for
instance, have created green ventilation corridors to enable fresh air
to sweep down from the city's surrounding hills and building regulations
that aim to keep these corridors free from new construction.
Thanks to a
combination of mandatory building requirements and subsidies, the city
of about 600,000 people also is a European green roof pioneer, with more
than 60 percent of its area covered by greenery to absorb pollutants
and reduce heat. ($1 = 6.6189 Chinese yuan renminbi)
No comments:
Post a Comment