Green walls - good or bad for the environment?
Controversy’s been brewing across the Tasman about the use of green or living walls. Richard Kirk, the national president of the Australian Institute of Architects, recently questioned the “responsibility” of their use from a sustainability standpoint.
Green walls have become a common marketing feature here and around the world, including Australia. An example there is One Central Park in Sydney, which has created some of the tallest living walls in the world. It uses them on the sides of its floor-to-ceiling glass towers. Jean Nouvel included the walls to create “continuity so the façades extend the park into the sky.” They are home to 250 species of Australian flowers and plants, and irrigation water from the living walls is used as part of the complex’s recycled water network.
However, Kirk pointed out that the maintenance cost of living walls was substantial. Horticulturalist Patrick Honan estimated that those at One Central Park would cost around $700,000 a year to maintain.
While Kirk claimed he could only see the benefits in living walls used internally in buildings, Jock Gammon, the founder of the company responsible for maintaining One Central Park's green walls, cited several key benefits for their external use. Plants act as carbon sinks, minimise water runoff, improve air quality, and even increase retail spend in areas they are used. He says they add green to cities when there is no space for additional parks, and create a cooling effect in urban areas. Gammon believes living walls increase biodiversity too - One Central Park's walls are home to bees, wasps, frogs, and a family of peregrine falcons. Overall, the green wall has made the development an icon.
Linda Corkery, the national president of the Australian Institute of Landscape Architects, hit back by saying she agreed with Richard Kirk that “cities must continue to improve existing urban green space and parklands, and look for every opportunity to create more open space for city residents and visitors.”
However, Corkery also pointed out “there aren’t many developers who are likely to do this unless their development approval conditions require it. Wherever we have an opportunity to bring more green, more landscape into the city, we should be ensuring that happens. With increased development density, we must look for ways to continually renew urban ecological systems, and create more beautiful and liveable spaces.”
In the 10 years between 2007 and 2017, Singapore, for example, has increased its green wall and roof coverage by 805%. Dr Sara Wilkinson, from the University of Technology, Sydney, says “many global cities are realising the need to remain attractive, liveable, and desirable and that this can be achieved partly through making urban settlements as green and natural as possible.”