Reference: Hedblom, M. and Ignatieva, M. 2018. An alternative urban green carpet. Science 362: 148-150. DOI: 10.1126/science.aau6974
From green to yellow
This year, my native Sweden experienced one of its hottest summers ever. Over three months, the tone in the population’s perpetual weather conversation changed from excited – would we finally experience that elusive “real summer” we’d been waiting for? – to an apocalyptic sense of “is this ever going to end!?” In addition to the sweltering temperatures, my hometown of Malmö didn’t see a drop of rain for weeks on end, which is virtually unheard of in our recent history of wet and frankly dismal summers. As the newspapers declared critical shortages on essentials such as groundwater and ice-cream – the headlines for the latter somehow conveying the largest sense of panic – there was one very visual consequence of the drought. Large parts of the city were changing color: from green, to yellow.
People seemed less inclined to make use of these yellowed, prickly, visually unappealing areas than they would have been if the grass were green and healthy. It was a dramatic reminder of the value of green spaces in cities, and of what we might be seeing more (or less!) of with the changing climate.
Sustainability in urban greening
One of the most popular ways of providing urban greening is by establishing lawns. In Sweden, lawns account for more than half of the country’s total urban green area. In the US, a country known for its love of strictly managed lawnscapes, two percent of the country’s entire terrestrial area is comprised of lawns. Considering how much space we give these patches of urban grassland, it seems like a good idea to make sure we get as much out of them as we can. But in their current forms, lawns often create large costs, both economically and environmentally. This has prompted a surge of research efforts into figuring out how we can make our urban green spaces more sustainable.
Some people champion the carbon-binding qualities of lawns, professing that these areas could capture carbon in the same way as forests do, and in that way help reduce CO2 levels in the atmosphere. Unfortunately, these touted positive effects in carbon uptake are negated by the negative effects of intensive lawn management. It makes sense: the carbon-binding qualities of lawns will be rendered moot if the maintenance of those lawns leans heavily on fossil fuels for mechanical mowing, irrigation, and fertilization.
Redefining the lawnscape
Another problem with lawns is their contribution to the ecological simplification of urban environments, in that they play a big part in making urban ecosystems around the world more and more homogeneous. In other words, cities around the world are creating green spaces that look more or less the same, irrespective of where you find yourself. A small number of grass species dominate lawns globally, despite the vast species richness that exists among grasses. This simplicity in lawn design can likely be traced back to the French 17th century ideology of “man over nature”, with the neatly trimmed grass of Versailles providing a prime example (Image 1).
The mission to make lawns not only more sustainable, but also more visually and ecologically interesting, has inspired research initiatives that aim to promote new ideas for the design of green spaces. The urban meadow was an early initiative; it has the combined advantage of increased biological diversity and reduced spending on management, since the meadows only need to be mowed a couple of times per growing season. Despite decades of efforts, the idea has failed to take hold in urban planning; most likely a consequence of the deeply ingrained public perception that a neatly kept lawn is the epitome of urban nature.
Embracing wildness over uniformity
Today, one of the largest displays of alternative lawnscapes can be found in Berlin, where spontaneous vegetation has been allowed, and publicly accepted, as a part of landscape design. Gleisdreieck Park (Image 2) and Südgelände Nature Park, two popular parks established on abandoned railways, include sections that have grown wild, with vegetation composed of plant species that have spontaneously colonized the area. In Sweden and the UK, grass-free lawns have gained momentum within lawn research. They are exactly what the name implies: lawns that are composed only of herbaceous plants, with the purpose of creating a dense and biologically diverse greenspace that requires very little maintenance.
These new avenues of lawn research can help urban communities embrace wildness over uniformity in their urban ecosystems, but such a shift in the perception of what the “green” in green space should signify requires targeted outreach efforts. Demonstration displays, education initiatives, and an acceptance of a new ecological aesthetic within urban planning can all help to increase the public understanding of sustainable ways of greening our cities. An important part of the outreach will be to communicate how species diversity in urban green spaces can increase the resilience of these spaces to climate change.
Summers like the one northern Europe saw in 2018 will doubtlessly become more commonplace in the near future. By ensuring that green spaces are “functionally prepared” for the changed weather regimes, we might still be able to keep our green spaces green, instead of yellow.