Wonder walls: vertical greenery seeds urban biodiversity

Vertical gardens on a mass scale could help bring temperatures down in cities and boost biodiversity. Until now, “living walls” were novelty features on landmark buildings, but an innovative Austro-German living wall could pave the way to delivering greener urbanisation worldwide.

Modular gardens for urban biodiversity

More and more of us are moving into towns and cities even though built-up and densely populated areas are becoming hotter in the summer due to climate change and the urban heat island effect of dense populations. A city like Vienna in Austria, for instance, could hit 47 degrees Celsius by 2050. This is an astonishing forecast for eastern Europe, and one of the drivers for landscape architect Doris Schnepf to cofound the startup Green4Cities almost a decade ago.

“All the experts know we need to cool down cities, but the market wasn’t ready for it,” recalls Schnepf, then working at Vienna’s University of Natural Resources and Life Sciences. “We set up the startup to bring the academic theory to the market.”

One of her team’s green solutions, a Living Wall, has reached the market with the help of a three-year Austro-German research and development project. The Living Wall is a modular vertical garden system that can be quickly erected and easily maintained on the sides of buildings to boost biodiversity, insulate buildings and bring down temperatures caused by large populations in urban heat islands.

A system to deliver vertical gardens beyond the extraordinary

“If we just focus on one product or house, we won’t be able to transform our cities by 2050.” – Schnepf

In recent years, vertical gardens, or living walls, have popped up on landmark buildings, but Green4Cities and project partners believe their new product has mass-market potential. Together they established the startup NatureBase to sell it.

“Having a vertical garden on a museum or at the headquarters of one large company is great, but we don’t just need lighthouse projects. Greening needs to be applied on a mass level, which is why we conceived Living Walls as a mass-market solution.” – Schnepf

Such lighthouse projects include innovative designs by the French ecological engineer Patrick Blanc at Paris’ Museum of Science and Industry, created in 1986, or at Madrid’s CaixaForum cultural centre, created in 2007. Thirty years after Blanc’s first green wall, urban districts are still not being covered with lush vegetation. NatureBase’s management believes this is chiefly because the previous vertical gardens were expensive and difficult to maintain.

“If you look at a lot of vertical gardens around the world, you’ll notice many of the plants in them are dead because this is a very special environment for plants” – Schnepf

Plug and play plant panels

The challenges are clear: gardeners sometimes have to climb up ladders or be hoisted up on cranes or by harnesses to tend to plants on the sides of skyscrapers. That’s why NatureBase’s Living Walls are light and modular; they weigh less than 50 kilograms per square metre, and allow panels of plants measuring 80 by 50 centimetres to be easily added and removed. “These Living Walls really can play a part in helping developers and other investors achieve their environmental requirements and goals,” says co-managing director at NatureBase Johannes Anschober.

Gardeners select plants for the specific location and amount of sun a building receives. They grow them at a nursery, so the Living Wall can look good from the outset. Anschober (who is also a landscape architect) and the other researchers devoted a large part of their efforts to developing a better irrigation system for the Living Walls, using sensors to detect when plants need to be watered.

The consortium set up a pilot wall to test the technology at Vienna’s Kempelenpark. Part of the innovation came from collaboration between what Schnepf describes as “different realities”: the University of Natural Resources and Life Sciences in Vienna, German universities Johannes Gutenberg Mainz and Rheinische-Friedrich-Wilhelms in Bonn and building specialists, including Germany’s Magu Bausysteme and Austria’s Slavonia Baubedarf and tatwort Nachhaltige Projekte. More environmental expertise came from the German green roofing company Optigrün International.

Tackling the health and biodiversity threats of urbanisation

NatureBase fitted a green façade to the boilerhouse building of the Austrian family business Peneder, which specialises in firedoors. By simulating temperature reductions using a software developed by Green4Cities called GreenPass, NatureBase concluded the vertical gardens can reduce thermal comfort (the temperature humans “feel”) inside a building by 7 degrees Celsius and by 20 degrees outside.

That is food for thought for planners, given an estimated 70% of the world’s population will be living in urban areas by 2050, making cities the frontline for carbon reduction.

“Greening our cities is the only resource-efficient and sustainable solution to ensure our future health and quality of life.” – Anschober

Heatwaves in 2022 resulted in temperatures in cities like London and Paris in the region of 40 degrees Celsius or more, and excess deaths of more than 20,000 people in western Europe. Vulnerable groups, like the elderly, pregnant women and babies and young children can be particularly vulnerable to heat, which can kill by inducing heatstroke, breathing problems or heart attacks. As such, the United Nation’s Sustainable Development Goals strive to make cities “inclusive, safe, resilient and sustainable”.

Schnepf’s pitch is a simple one: “We need to plant trees wherever possible. Where that’s not possible, install a NatureBase Living Wall.” Green4Cities envisages an urban world where planners think carefully about planting trees and adding greenery on walls and balconies, as well as water sprays and fountains. The company hopes funding for projects will be spread beyond property owners, since the benefits to public health and welfare are clear.

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Posted 15 March 23