Vertical Greening: When cities and nature grow together

Umwelt

Völkerrecht

This summer, the forausblog has teamed up with students from the Master’s course “Law of Sustainable Development” taught by Charlotte Sieber-Gasser at the University of Lucerne. Students were asked to come up with their very own ideas for policy measures that would render the presence of humankind on this planet more intra- and inter-generationally just. The policy measures have to work towards achieving one particular UN Sustainable Development Goal and need to be in line with international law. The best original policy measures were selected by Charlotte Sieber-Gasser and published by the forausblog.

Urbanisation is on the rise and brings about new challenges and intensifies existing ones. Nevertheless, by 2050, two-thirds of the world population will have no other choice than living in a city. Urbanisation is also a pressing issue in Switzerland: More than three-quarters of the Swiss population are city dwellers. Besides the risk of mental and physical human health issues (and, thus, possibly increasing health costs and decreased life expectancy), urban growth reduces biodiversity and humans’ touch with nature. In order to combat these negative side effects, Swiss cities must take responsibility: We suggest they need to have the duty to ensure vertical greening in relation to their population – the bigger the city the more vertical greening is required, as the size of a city influences the complexity of its problems.

 

Institutionalising a trend

Urban gardening is in fashion: an increased part of the population is re-greening and re-naturalising grey urban areas voluntarily and by themselves. Public administration, too, is getting actively engaged in greening the cities, even seeking to gain certified gold standard in being green (see also Andernach – The Eatable City). Vertical greening promotes sustainable development according to art. 73 of the Swiss constitution, and is in alignment with SDG 11 of making cities sustainable.

Why not use this existing motivation and bring it up to the next level of vertical greening? This involves all forms of greening walls such as green facades, living wall systems, vertical forests, and even eatable facades.

According to art. 75 of the Swiss Constitution, it’s the cantons which have the major legislative powers in spatial planning – the federal state only sets overarching guidelines in the Swiss spatial planning act and takes a coordinating role. Nevertheless, a commitment for all Swiss cities to vertical greening would be most effective for sustainable development. This could be achieved through adding an additional littera to art. 8a para. 1 of the Swiss spatial planning act: the cantonal guidelines should either determine which vertical greening concept their cities should follow or if they want to delegate this choice to their cities. Ensuring the principle of federalism (art. 3, art. 5a and art. 43a para. 1 of the Swiss Constitution), it’s the cantons or the cities themselves who can choose from a variety of options: they can issue a duty to green all future buildings, existing public buildings of their choice (in compliance with building regulations) or promote vertical greening for private buildings through incentive schemes (for example through tax reduction or subsidies).

 

Sustainable in a three-dimensional way

Depending on the choice of plants, vertical greenery can promote and preserve the local flora and fauna and, thus, increase biodiversity. Such endeavours are not only ecologically, but will also be economically sustainable: The more long-living and the lower the maintenance costs, the more it pays off financially. This is further enhanced by the other benefits of vertical greening:

In addition to the fact that greening increases the property value of a building, green facades contribute to the cooling and insulation of an edifice since the dense plant foliage works as an additional layer that absorbs the heat in hot summers but simultaneously stores the warmth in winter. This not only reduces the need for air conditioning, but also saves heating costs, lessening likewise CO2-emissions.

Besides, plants improve the urban climate in general. Even though it is often assumed that green facades result in higher water consumption, they are actually essential for a better water balance thanks to evapotranspiration. As water cannot be absorbed by hard surfaces such as asphalt and concrete, about 75 percent of rainfall in cities is lost directly to run-offs (likewise causing floods) compared to around 5 percent in forests, where the water is re-entering the natural cycle. Aside from that, water absorption by vegetation is crucial for cooling down the scorching temperatures in cities which result from the heat island effect. Urban infrastructure radiates the heat, leading to a higher temperature up to seven degrees in cities in comparison to rural areas. Not only are plants alleviating this problem thanks to humidification, but consequently, people are less exposed to heat-related health issues.

Speaking of health, it has been measured that already the mere sight of vertical gardens solely via screen lowers stress levels and raises the level of relaxation. This suggests that being surrounded by vertical gardens improves the overall individual well-being and quality of life and, thus, in the long-term, might reduce health costs.

As outlined above, ensuring that cities provide vertical greenery is a feasible and relatively simple way to help tackle the challenges that will come along with increasing urbanisation. The biggest advantage of a vertical greening policy is that it already builds on the palpable desire of city dwellers to make their grey environment vivid, improving their quality of life while fostering biodiversity and merging urban spaces with nature.

 

Image: Susanne Fratzky