The Necessity of Complexity

Cities — crucibles of innovation and economic development, befitting the well-being and prosperity of inhabitants — possess what is arguably humanity’s greatest invention: the manifold exchange of diverse assortments of ideas. Social, economic, or otherwise, this dynamic is catalysed by propinquity, the aspect of ‘nearness’ and connectedness engendering the recombinant mutation of information as it courses through cities. In economic terms, described as knowledge externalities or spillovers, these processes provide a mechanism describing how the diffusion and accretion of human capital can be both the cause and the consequence of human agglomeration (Rauch 1991; Florida 2003; Glaeser 2011). These mechanisms and their requisite connectivity and diversity are of necessity mirrored in historical cities’ structures, artefactual manifestations of the deeper workings of complex systems.

Jane Jacobs provides a prescient synthesis of these ideas. Her vociferous attacks on the urban planning establishment (Jacobs 1961) and unorthodox forays into urban economics (Jacobs 1969) argued, at heart, that it is specifically diversity and its requisite complexity that provides the energising force sustaining vibrant economies and healthy neighbourhoods. From an economic point of view, the hallmark of Jacobs’ hypothesis is that this dynamic flourishes due to spillovers between diverse entities within competitive environments. Now known as Jacobs Externalities, this idea inspires formal economic models describing the role of the external effects of human capital as an explanation for economic growth (Lucas 1988; Desrochers & Hospers 2007), a view which has gained acceptance in economic research (Glaeser et al. 1992; Nowlan 1997; Feldman & Audretsch 1999) showing that increases to economic diversity are “strongly associated with increased output, productivity, and growth” (Quigley 1998, p.136). A similar dynamic is observed for social heterogeneity and creative capital (Florida 2003). Importantly, these processes often cannot be observed at overly coarse or aggregate scales (Beaudry & Schiffauerova 2009). Ongoing developments in high-resolution geospatial analysis methods combined with the improved granularity of data make it increasingly feasible to zero in on the level at which this dynamic operates.

A common thread binds Jacobs’ ideas on economic development with her thoughts on planning and engenders the essence of her argument. Misplaced emphasis on efficiency — at the expense of complexity and diversity — manifests urban planning (and economic policy) that severs the necessarily elaborate webs of social and economic processes. She describes such approaches as ‘preformationist’, meaning that growth is erroneously assumed to result from the simple quantitative expansion of pre-existing and static arrangements, therefore leading to the mistaken impression that city processes are simplistic and should be optimised. The familiar mantras espoused by modernist architects: buildings are machines for living in; form follows function; less is more, even if legitimate and necessary criticisms of the state of architecture at the time, became debilitating once applied at the larger scale of neighbourhoods and cities (Lyon 1999). Planners “declared themselves enemies of diversity, fearing chaos and complexity because they saw it as disorganised, ugly, and hopelessly irrational” (Harvey 1989, p.74), master plans consequently imposed idealised abstractions of social and functional order reinterpreted in the name of efficiency. Heavy-handed slum clearances and large-scale infrastructure projects consequently dismembered the urban fabric, in some cases decimating entire neighbourhoods (Harvey 1989; Marshall 2009; Flint 2011). A more recent manifestation of the efficiency paradigm has emerged within Smart Cities and Digital Twins hype, positing that connected citizens and ubiquitous sensors could streamline all manner of city services ranging from garbage collection to utility provision to citizen e-services. However, dark undercurrents often accompany these notions: despite increasingly decentralised access to technology, systems are oft conceived and managed using centralised and top-down archetypes that are brittle and biased; private interests may supersede public interests; infrastructure networks may bypass lesser represented or underprivileged citizens; and large-scale idealised urban development schemes — sometimes with an eerie resemblance to modernist master plans — prove unable to support the complexities required by local economies or in support of vibrant streets (Graham & Marvin 2001; Greenfield 2013; Hill 2013; Townsend 2013; Sterling 2014).

Jacobs emphasises that she “does not mean that cities are economically valuable in spite of their inefficiency and impracticality but rather because they are inefficient and impractical” (Jacobs 1969, p.228), meaning that the very mechanisms underlying these perceived inefficiencies are a necessary dynamic for the development of cities and the reason for the agglomeration of people in the first place. She describes this as an ‘epigenetic’ view of growth, wherein processes of development arise as an accretive co-evolutionary process from overlapping “webs of interdependent co-developments” (Jacobs 2000, p.19). This proliferation of accidental and unstable combinatorial possibilities allows countless unexpected and innovative information entanglements to take root. It is these processes that foster longer-term discovery and resilience, and it is also these processes that are otherwise incapacitated by the brittleness introduced by the efficiency paradigm. Jacobs’ thinking bears a resemblance to Stuart Kauffman’s notion of supracriticality: The point at which a critical mass of inter-relationships may trigger explosions in the diversity of molecular species (Kauffman 1995, p.116) and bouts of co-evolutionary development on coupled fitness landscapes to an edge of chaos (Kauffman & Johnsen 1991). Kaufman, in turn, explicitly connects these concepts back to Jacobs’ economic theories wherein “the web structure of an economic system is itself an essential ingredient in how that economic system grows and transforms” and “diversity begets diversity, driving the growth of complexity” (Kauffman 1995, p.295–296). Thus, in complex systems terms, cities can be framed as The Visible Expression of Co-evolving Complexity (Allen 2012), or as dissipative structures harnessing flows of energy — in the form of ideas, relationships, and resources — constantly adapting in order to seek out and maximise the beneficial use of these flows (Prigogine 1996). More intuitively, inspired by Darwin’s tangled bank analogy (Darwin 1859, p.489), Jacobs likens these processes to high-biomass rainforests interleaving innumerably diverse assortments of species into complex cascades of interdependencies capable of extracting maximal benefit from the sun’s energy (Ellerman 2005). “Sunlight is captured in the conduit, it’s not only converted but repeatedly reconverted, combined and recombined, cycled and recycled…” (Jacobs 2000, p.46). Critically, Jacobs’ insight is that it is not simply the quantity of sunlight at an ecosystem’s disposal, but the complexity and richness with which the sun’s tendrils can be enfolded and interwoven to extract seemingly magical multiplicative gains, ergo the importance of complexity for the growth of economies and the adaptive resilience of neighbourhoods. These dynamics are necessarily complex, fluid, and unpredictable and resonate strongly with more recent complex systems interpretations of diversity and its rich history of ecological interpretations and methods (Marshall 2009; Page 2011).