CPULs require land, but in return they will enrich cities by reducing their environmental impact and bringing in spatial qualities until then only associated with rural or natural conditions.
The implementation of CPULs will be a slow process varying with the city under consideration. Each city will have to determine the scale and ambition for CPUL infrastructures. A long-established large city, like London for example, provides less scope for integrating CPULs and/or tracts of productive urban landscape close to its historic centre than it does close to its fringes (see Chapter 24).
Above all, the new open urban space will need. . . space. Land will have to be allocated, reclaimed, recycled or imaginatively found. Open urban space is precious: it is rare, and it can be converted into something else. Usually, it is converted into housing or other building development and thereby into money. CPULs will have to compete with commercial land-use activities, as well as with all other contemporary ways of designing or redesigning open urban space (see Chapter 14).
Urban agriculture, the proposed productive element of CPULs, could take on any shape and occupy virtually any space in the city – big, small, horizontal, sloped, vertical, rectangular, triangular, irregular, on brownfield sites, on greenfield sites, in parks, on reclaimed roads, on spacious planes or squeezed in corners. . . CPULs will appear in ever varying site-specific shapes and dimensions and at any urban scale. They could happen anywhere within the urban context, leading to many cities boosting the multiple use of their build space and keeping valuable inner-city space clear of construction at the same time.
Starting to implement CPULs will be most advantageous in those areas of the contemporary city which, at the moment, are given over to activities restricting space to mono – or non-use: car parks, roads, parking bays, shopping malls, warehouses, multi-storey car parks (at least the flat roofs and
plane facades), railway embankments, industrial wasteland, brownfield sites, etc. These inner-urban spaces are available in abundance with occupants and users being mostly positive about qualitative spatial and environmental improvement. Moreover, these spaces’ diversity in size and shape, and their location anywhere in urban networks make them ideal components of the continuous landscape strategy.
The emphasis of CPULs on connection and movement, on uninterrupted routes between local urban centres, will influence their layout and positioning (see Chapter 25). Whilst they will hold areas sufficiently sized for many activities, there will be other parts which will mainly provide continuous and direct urban connections. Both of these CPUL types will draw from well-established, existing or newly reclaimed open urban space. An extensive network of CPULs could be imagined as a contemporary city with every other road given over to farming, leisure, and pedestrian and cycle routes (plus occasional and emergency vehicular traffic), thereby connecting larger existing and new open spaces of any size and designation. It could look like Venice with the canals transformed to become fields.
However, reclaiming and recycling those areas poses two problems: the proposed sites could be toxic and their current mono-use activities would have to be accommodated somewhere else, either by redesign or relocation. Successful attempts to do this have taken place in various countries, mainly in connection with the necessary repair of existing urban tissue.
As costly and time-intensive as such solutions might be, and as much focused urban and architectural planning or communal support they might need, they will always have the advantage of being environmentally sensible in addition to providing the urban and socio-cultural benefits described above (see Chapters 3 and 17).