Cities

Chicago, urban trees provided a service for air cleansing that is equivalent to US$ 9.2 million dollars and their long-term benefits are estimated to be more than twice their costs (McPherson et al. 1994).

There is a broader set of public health issues around healthier lifestyles in cities. It is estimated that physical inactivity accounts for 3.3 per cent of all deaths globally and for 19 million disability-adjusted life-years (Bull et al. 2004). Green urban transport is a unique opportunity to link physical activity and emissions reduction by promoting walking and cycling. In Europe, more than 30 per cent of trips made by cars are for distances of less than 3 km and about half still below 5 km, in theory allowing for their replacement by cycle journeys (European Commission 1999).

It is no coincidence that cities with a long tradition of applying land-use planning, public transport strategies and a focus on public green space are among the healthiest cities in the world. Portland was rated number one of the 100 largest USA cities in meeting Healthy People 2000 goals (Geller 2003), Vancouver is first amongst the Canadian cities (Johnson 2009), Copenhagen and Munich rank amongst the top 10 healthiest and safest cities and Melbourne among the healthiest and safest in Australia (Sassen 2009).

Ecosystem services and risk reduction Urban greenery and vegetation represent a range of ecosystem services with significant wider welfare effects (TEEB 2010). A study of Toronto’s Green Belt estimated the value of its ecosystem services at CA$ 2.6 billion annually, an average of around CA$ 3,500 per hectare (Wilson 2008).

Ecosystem services further play a critical role in risk reduction measures. Tropical cities such as Jakarta have dramatically increased their risk exposure to flooding as a consequence of local deforestation. The city’s most recent floods in 2007 affected 60 per cent of the city region, killed 80 persons and forced more than 400,000 residents to leave their homes (Steinberg 2007). Similarly, the 2005 floods in Mumbai, which killed more than 1,000 people and paralysed the city for almost five days (Revi 2008) were linked to a lack of environmental protection of the city’s Mithi River (Stecko and Barber 2007).

Restoration of urban ecosystems is part of the city greening effort, which can reduce the impact of freak weather conditions. Coastal regions in particular can benefit both in terms of lives and money. Mangrove re- planting in Vietnam, for example, saves US$ 7.3 million annually on dike maintenance while it costs only US$ 1.1 million (International Federation of the Red Cross and Red Crescent Societies 2002). More generally, an increase in the amount of green cover in urban areas not only increases a city’s ability to reabsorb CO2

but also ameliorates the urban heat island effect (McPherson et al. 1994).

Safeguarding natural ecosystems in cities’ hinterlands is also important in reducing their exposure to risk. This is of particular relevance to fresh water supply and food security. As they have expanded, many cities have exhausted local fresh water sources and rely on importing water from their wider region. Such requirement to import water is already associated with enormous costs for cities such as Mexico City and São Paulo. In New York City, the protection of its fresh water supply has allowed the city to avoid paying US$ 5 to US$ 7 billion for an additional filtration plant (TEEB 2010).

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