City wants private individuals to take responsibility

They are green, large and have leaves. They are good for the climate and against the summer heat. And sometimes they have to make way for an underground car park.

Trees – like the ones that once stood here on a street in the Höngg residential district, before they had to give way to the dreams of many families: modern apartments with large rooms, high windows and – of course – a new underground car park.

It’s quiet this morning in Höngg, only a construction worker says loudly over the phone: “Boss, I need a new heat meter!” Next to old houses with a lot of greenery are new buildings made of concrete, some recently completed. There is space for more families – but fewer trees.

Aerial photos of this housing estate from 2013 and 2020 show on a very small scale what is happening in the city of Zurich on a large scale: It is becoming less green – very slowly and hardly noticeably. And that especially on private property, around residential or office buildings.

Because despite the new parks and green spaces, despite the 160 new trees planted every year by the city: Zurich’s tree cover is shrinking.

This shows a new analysis of the city, which was presented on Thursday. According to this, the area covered by treetops decreases by 1.25 percent every year. The analysis refers to data from 2014 and 2018. These were determined with laser beams that scanned the city from an airplane in search of tree canopies. The city assumes that the tree loss will continue to this day – exacerbated by the severe storms and snowfalls of 2021.

The popcorn effect makes trees disappear

It’s the first time that tree cover has been measured not just in public space, but across the city. So also on private properties like those in Höngg, which lost a fifth of their tree area between 2014 and 2018.

In the Höngger estate – highlighted as an example in the municipal report – some of what is currently happening throughout the city happened: the buildings tend to be larger, they are closer together, and there are more underground car parks. The space for the trees and their roots is becoming scarce. A city expert calls it the “popcorn effect” when new buildings are suddenly bigger – and the trees are gone.

The city is worried about this development. Action must be taken urgently, said City Councilor Richard Wolff (al.) at the media conference. “Trees filter the air, produce oxygen and store CO₂ and reduce the heat in summer.» Instead of less, the city needs more greenery in view of global warming.

The city’s goal: a quarter of its area should be covered by treetops by 2050. The last measurement in 2018 was 17%. And yes: the trend is falling. So how does the city intend to achieve its goal?

Motivation – and maybe a bit of compulsion

She wants to plant more trees herself, especially in less green areas like Aussersihl, Oerlikon or Altstetten. New avenues are to be created and parks are to be planted even more. The costs for this are not yet known. The city decided last autumn to plant 1,200 new trees by next year – for CHF 1.8 million.

But that won’t be enough. That’s why the city wants to encourage others to give the trees more space. “We need the private on board,” said City Councilor André Odermatt (sp.) At the media conference. “We have to show them the importance of trees. But new regulations will also be needed to achieve our goal.”

What Odermatt means by this: In the short term, private landowners should be encouraged through information and advice not to do without trees despite densification. In the medium term, however, they should also be able to be forced to do so.

Resistance to tree protection

Specifically, the city wants to expand its protected areas for trees. Trees can only be felled in these areas with a permit. In addition, she would like to include specifications for tree density in the municipal structure plan – and possibly also in the building and zoning regulations, which would make them binding for private individuals. In addition, the construction of underground car parks should be limited.

There is already resistance to these plans. Albert Leiser, director of the Zurich homeowners’ association, says: “I don’t want any more tree protection, no prevention of underground parking, no state coercion and no paternalism.” Where there is construction, there is change. But it is important that a good solution is sought with all parties involved.

When asked about the compulsion, City Councilor Wolff reacted soothingly. “It needs the right mix of funding and rules,” he said. Many builders and architects are very open anyway when it comes to the question of trees. “So there is hope.”

Optimistic – despite everything

There is also a very practical reason why the city is focusing more on motivation than on regulations for the time being. Some of their plans collide with cantonal law. For example, this currently stipulates that any larger tree must not be closer than eight meters to the neighbor’s fence. This makes it difficult to plant new trees, especially in residential areas. And it limits the city’s room for manoeuvre: Where no tree is allowed to be planted, the city cannot ask a homeowner to do so either.

The regulation is currently being revised as part of the entire cantonal planning and building law. Outcome: uncertain – and years away. All too soon, the city will hardly be able to give the private sector specifications on a large scale.

But despite the narrow legal scope, despite political resistance, despite fewer trees and the additional loss of 2,000 trees in the storms last year: the city is optimistic. If everything goes as planned, their goal could be achieved: a quarter of the city’s area covered with trees by 2050.

More trees and more apartments – is that possible?

Those responsible also see no contradiction to another goal of urban policy – ​​the creation of more living space. The homeowner representative Leiser is completely different: “On the one hand, more living space is required, on the other hand more trees. It is practically impossible to do both at the same time and in the same place.”

Densification – not only in the living space, but also in the trees. City councilor Odermatt, on the other hand, thinks that both are possible, for example by building higher or cleverly placing underground car parks. It just has to be planned well.

And if one thing became clear at Thursday’s media conference, it was that the city has planned a lot in recent years when it comes to trees. Now they just need to be planted.