Humankind's future will largely be decided in cities. Half the world's population already lives in them, and by 2050 this will have risen to 70 per cent. Cities are where global challenges and problems are concentrated: they consume three quarters of the world's resources and generate three quarters of all emissions.
But cities are also places where innovation occurs and solutions emerge. Implementing good solutions in them can have a big impact and bring direct benefits to many people and businesses. Cities are dynamic and hold the potential, know-how and experience that can make a difference to future global development. It is therefore appropriate and highly commendable that one of the United Nations’ 17 Sustainable Development Goals is to “make cities and human settlements inclusive, safe, resilient and sustainable”.
The commitment of cities and the effectiveness of the measures they can take can be seen in the efforts to combat air pollution in Zurich. By the 1980s, Swiss cities including Zurich had reached very high air pollution levels. Thresholds for nitrogen oxides, particulate matter, ozone and sulphur dioxide were continually exceeded by considerable amounts. The Swiss government's response was a nationwide air pollution control ordinance, which came into force in 1986 and has been steadily revised and tightened ever since. This provided the Zurich city government with the basis for taking action in areas such as industry, transport and heating systems.
Thanks to its rigorous enforcement of the national ordinance, the city achieved good reductions in the major pollutants throughout the 1990s and 2000s. Nitrogen oxide emissions fell by around 50 per cent between 1990 and 2000. The downward trend flattened thereafter, but in 2016 emissions were down to around just 30 per cent of the 1990 level. Stricter exhaust emission regulations for vehicles, refurbishing heating systems and retrofitting municipal waste incinerators all contributed to this decrease.
Pollution by particulate matter showed a parallel reduction: improvements achieved by 2000 were rapid and significant, though the pollution burden has decreased at a slower rate since. The overall pollution level has been reduced by about half, and Zurich only occasionally exceeds the long-term threshold.
These efforts have resulted in Zurich performing very well by international standards. In a 2015 study on air quality in 23 European cities, the European Environmental Bureau concluded that Zurich had the cleanest air. This is all the more gratifying since air quality in most other European cities has also improved.
These results must not tempt us to cease or reduce our commitment to clean air. Even though our air is now cleaner than at any time in the last 30 years, pollution is still too high and action needs to be taken. Air pollutants cause health problems, and pose a particular threat to sensitive ecosystems. We estimate that air pollution in Zurich leads to additional health costs of around 200 million Swiss francs ($203 million) and around 70 million Swiss francs' worth of damage to buildings each year.
The city government has therefore set its sights on protecting the population from excessive particulate matter and nitrogen dioxide pollution by 2025. The thresholds are to be maintained at all times, even near busy roads. Attaining this ambitious goal will entail another major reduction in emissions.
Road traffic is a central starting point. It remains a principal source of pollutants - responsible, in particular, for 47 per cent of nitrogen dioxide and 37 per cent of particulate matter. The city's "Urban Transport 2025" strategy has introduced measures to encourage yet more travel by public transport, bicycle or on foot. Voters gave the city government a mandate to increase the proportion of public transport, pedestrian and bicycle traffic locally by at least ten percentage points between 2012 and 2022.
This target is already halfway to achievement: public transport, pedestrian and bicycle traffic now account for 75 per cent of Zurich's total. Almost half the households in the city no longer have their own car, and we continue to invest in expanding an already excellent public transport system and infrastructure for pedestrians and cyclists. The city administration is setting a good example: official vehicles are only replaced if staff bicycles or car sharing are not viable alternatives.
The city's government cannot simply decide and decree the solution and result. It needs the support of everyone, especially the public and the business community. So consistent and transparent information is important. The city offers environmental advice tailored to businesses, for example. It produces expert reports on the status of work to combat air pollution, and exploits new digital opportunities. A smartphone app displays current air quality in the city and throughout Switzerland, while a free-of-charge SMS service sends notifications when ozone and particulate matter exceed thresholds.
Despite the achievements to date – and an outlook suggesting that further improvements can be expected – clean air in the city remains a challenging goal. We must continue working on it, step by step and with unrelenting commitment.
For me, however, the reduction of air pollutants in Zurich demonstrates something more fundamental: change and improvement are realistic even in the face of major challenges. Of course, as a prospering and comparatively affluent city, we had a good foundation to begin with and the resources necessary for tackling air pollution. And clearly, we face other major challenges in the form of climate change and persistent overconsumption of resources. Yet the success achieved so far by politics, business and society acting together makes me optimistic.
Advancing urbanization will be one of the most influential trends of the 21st century and the potential of cities is yet to be fully exploited. If cities are integrated and included, they will become indispensable, constructive and strong partners in helping find solutions for the future.