Complexity And Emergence In City Systems: Implications For Urban Planning

Cities can be regarded as the quintessential example of complexity.
Insofar as we can define a hidden hand determining their morphology,
this is based on the glue that stitches together the actions of individuals
and organizations who build and plan the city from the ground-up, soto-speak.
When general systems theory entered the lexicon of science in
the mid-20th century, cities were regarded as being excellent examples
of systems with interactions between basic elements that demonstrated
the slogan of the field: the ‘whole is greater than the sum of the parts’.
Since then, as complexity theory has evolved to embrace systems theory
and as temporal dynamics has come onto the agenda, cities once again
have been used to illustrate basic themes: global organization from local
action, emergent morphology from simple spatial decision, temporal order
at global levels from volatile, seemingly random change at the level of
individual decision-making, evolution and progress through co-evolution,
competition, and endless variety.
Here we will sketch these ideas with respect to cities illustrating
particularly three key ideas which involve the tension between continuously
changing systems, qualitative transformations, and radical change based
on emergent properties of the whole. Our analysis has many implications
for a new theory of urban planning which is built from the bottom up,
rather than from the top down which is the traditional way in which such
interventions are currently carried out in the name of making better cities.
Contemporary problems such as ethnic segregation, urban sprawl, traffic
congestion, urban decline, and regeneration are all informed by the
perspective on complexity theory that we bring to bear here.