While many dense cities and city neighbourhoods are among the world’s healthiest places, others are among the world’s worst. Life expectancies at birth are half those of the healthiest cities and it is still common for one in ten children to die before the age of five. Health outcomes are even worse among the lower-income populations of such cities, with anywhere from 30 to 60 per cent of the populations living in such informal settlements. How does density figure in this?
Dense cities developed because of the advantages high density provided for the growth of industry, trade and services – what are often called the returns to agglomeration for businesses. These advantages can underpin large and economically successful cities even at the same time as health for much of the population and workforce remains very poor. For instance, Mumbai is a very successful city but it is also one where half the population lives in dense informal settlements that take up a small proportion of the land area and which have very inadequate or no provision for water, sanitation, drainage and health care. The same is true in many other cities in Africa, Asia and Latin America. As Arif Hasan notes in ‘Designing Density in Karachi: Alternatives to Apartment Blocks’ (2011), 62 per cent of Karachi’s population live in informal settlements that take up only 8 per cent of the land area. Similarly, in Nairobi, more than half the population lives in informal settlements that take up only a few per cent of the city’s land area.
But high density also brings potential advantages for the public good. Returns to agglomeration apply not only to businesses but also to the health and quality of life of city dwellers. For instance, dense cities and city districts provide agglomeration economies for the provision for piped water, good sanitation, drainage, health care, schools, policing and emergency services – but city governments need the competence and capacity to act on these, and they often have neither. High density informal settlements usually benefit residents by lowering the time and cost of travel to work and to access services – including those services that make cities special places to live such as theatre, music, museums, libraries, the visual arts, dance, festivals, the enjoyment of historic buildings and districts, diverse choices for eating and the enjoyment of being in a diverse and vibrant place. Cities have also long been places of social, economic and political innovation that have often driven similar changes at higher levels of government.
The residents of high-density informal settlements in central locations value the easy access that such areas provide to income-earning opportunities. The lower or more unstable a person’s income, the more they value accommodation close to income-earning opportunities. Dharavi in Mumbai is a popular place to live among low-income groups not because of its health advantages but because of the economic advantages which result from the large concentration of income-earning opportunities there. The pavement dwellers in Mumbai live where they live not for the health advantages but for the quick, easy and cheap access to income-earning opportunities. In large cities, most low-income groups do not want to move to the city periphery where land may be cheaper and more space available because it brings such high costs in time and money getting to and from work. Cities that work well have diverse accommodation possibilities for lower-income groups so they have a choice in regard to the trade-offs between good location, space and housing quality.
Dense cities also provide more possibilities of combining a high quality of life with lower greenhouse gas emissions. For instance, energy use per building can be cut far more in terraces and apartments than in free-standing housing. Dense cities make high-quality public transport cheaper and, when well-managed, encourage more walking and cycling. Compact urban development can interweave densely settled sites well-connected by public transport with green spaces for sport and recreation and enable urban dwellers to tap into local ecosystem services. Many of the most desirable and expensive residential districts in European cities are also high-density areas, often with terraces with three to six storeys as, for instance, is the case in Chelsea, London. High-income groups choose to live in such areas because of the high quality of life they provide.
There is not much point in singing the virtues of dense cities if these virtues depend on a competence, capacity and accountability of city and municipal governments that is not there. And what can be done for the hundreds of millions of urban dwellers facing very poor health and living conditions in high-density informal settlements? What to do about the informal settlements that may have first developed on the city periphery but, with the growth of the city, now have central locations that are very valuable and are thus under threat?
There are examples that show how dense informal settlements can be transformed into high-quality healthy living environments without displacing their low-income populations. In Thailand, the national government’s Community Organizations Development Institute (CODI) channels government funds in the form of infrastructure subsidies and housing loans direct to community organisations formed by low-income residents of informal settlements. These community organisations then plan and carry out improvements to their housing or develop new housing, and work with local governments or utility companies to provide or improve infrastructure and services. From 2003 to 2010, CODI’s Baan Mankong (secure housing) programme approved 745 projects, covering a total of 80,201 households. A considerable expansion of the programme is also planned within the next few years. Most of the participating communities had high densities but managed to secure more space per person within each house by expanding up to two to three storey terraces as they rebuilt.
This initiative has particular significance in three aspects: its large scale, its substantial community involvement and the extent to which it seeks to institutionalise community-driven solutions within local governments so that they address needs in all informal settlements in each urban centre. It is also significant in that it draws almost entirely from domestic resources, through a combination of national government, local government and household or community contributions. Support is also provided to networks of community organisations formed by the urban poor, to allow them to work with municipal authorities and other local actors and with national agencies on urban centre-wide upgrading programmes.
It is common for informal settlements to have densities of 300 to 500 people per hectare. By upgrading to two- or three-storey terraced housing, the Baan Mankong communities were able to achieve much-improved housing conditions and public space provision. Similar densities are also evident in some high-quality residential areas in wealthy European cities, typically four- to six-storey terraces.
Informal settlements with much higher densities – for instance between 1,500 and 3,500 people per hectare – present more of a challenge. This is the case in some of the informal settlements in Nairobi, in Dharavi in Mumbai and in some residential areas in Karachi. In principle, it is possible to support low-income housing development to achieve high density, applying the lessons of successful urban upgrading, but transferring them to high-density low-rise developments. But it is difficult for residents and their organisations to retain control of upgrading when this involves the construction of multi-storey buildings, as was the case in Sri Lanka, leaving them open to displacement or ill-suited upgrades.
Arif Hasan and colleagues have shown that it is possible to achieve high densities while meeting the needs and priorities of low- and middle-income residents in Karachi. Rather than constructing multi-storey buildings, small residential plots can be developed incrementally by the residents themselves, as long as the initial construction is sufficiently solid to allow safe expansion. This approach allows the family to retain control of the land and its development. Densities of up to 2,800 people per hectare were possible based on this kind of household-led development.
However, in very high-density settings, the trade-off between indoor space, space for transport, public and private open spaces such as squares, parks and gardens and space for public amenities is complex.
Bringing trunk infrastructure and a functioning road network into a dense informal settlement usually requires some loss of housing, and therefore the displacement of residents. So too will any expansion of public space and public services, such as schools and health care services.
One solution to this trade-off in very high-density informal settlements is to acquire land next to the settlement being upgraded so as to allow some reduction in density. Such land is, however, rarely available. To avoid moving (or being moved), residents may choose to sacrifice space within their homes for the economic advantages of the location and to maintain their social networks. Overcrowding is usually more tolerable if there is good provision for piped water, electricity and functioning, safe toilets and waste water disposal in each home.
Initiatives are underway that seek to upgrade informal settlements with very high densities. One such upgrade is ongoing in Pune, India, managed by Mahila Milan, a federation of women’s savings groups formed by those living in informal settlements or on the pavements, the National Slum Dwellers Federation and the Society for the Promotion of Area Resource Centres (SPARC). At the core of the programme is a process that engages each household in developing and agreeing to the best trade-offs for the upgrade. Another example can be found in Dharavi where around 600,000 people live in two square kilometres (1 1/5 square miles). An alternative plan to its commercial development centres around developing upgrading plans section by section with residents.
The trade-offs between living space and public amenities for any high-density upgrade are complex. These initiatives share a commitment by city governments to work with all the residents and their community organisations to seek the best workable compromise. This is much easier for governments in cases where representative organisations have been formed by those living in informal settlements and want to work with them, as is the case with the national and city federations of slum or shack dwellers that are now active in over 20 nations.
High density can serve development when it is created by people’s choice, even if this means living in informal settlements. This is especially so when city governments work with those living in informal settlements to take advantage of their agglomeration economies and provide the infrastructure and services that can transform health and quality of life.