Resilient Cities in a Changing World AMPS | City, University of London Page 30 or otherwise benefit from exposure to damage. The concept of antifragility has been examined in diverse contexts including business,19 computer science,20 international security,21 logistics,22 psychology,23 and sustainable development.24 The concept is also being applied to urban planning and design.25 A defining characteristic of antifragile systems is not only can their capabilities and capacities to manage disruption improve to manage experienced disruptions, but they can also develop abilities to manage those not previously encountered or, perhaps, even imagined. An example is person who exercises regularly is an example of an antifragile system: the body undergoes a temporary metabolic shift as it moves faster or for longer periods of time and as it employs different muscle groups to lift heavy objects. Through such training, the body becomes more fit and able to do some things that were not explicitly undertaken—including things that were not anticipated when the exercise plan was created. As such, antifragility is a distinguishable quality (or goal) from systems that are (or intended to be) sustainable or resilient. It has been debated if sustainability is a component of resilience or if resilience is a component of sustainability or if they are distinct concepts.26 For this paper, differences are understood in terms of the kinds of uncertainties each approach emphasizes. Sustainability focuses on the long- term conservation of resources needed to maintain a system. With regards to environmental design, it considers the 'triple bottom line' of balancing environment, equity, and economics in such a way that does not reduce resources for future generations. This balance involves moral or ethical uncertainties.27 Resilience concerns a focus on abilities to withstand, recover, and adapt from external shocks and becomes increasingly important as a system's internal organization becomes more complex and as its exchanges with the system's environment become uncertain or volatile.28 With resilience, epistemological questions related to knowledge production about vulnerabilities and threats for purposes of governance. The difference between antifragility and both sustainability and resilience can be exemplified by vaccination. The introduction of a harmful, but weakened or neutralized pathogen or mRNA (like some COVID-19 vaccines) into a body allows a person to develop resistance to stronger doses of the same pathogen in the future. So, a flu shot in the autumn helps prevent contracting flu in the winter. The same shot, however, does not protect against measles. With antifragility, attention shifts from resilience's epistemological uncertainty and questions of exposure rates and potencies to questions of ontological uncertainty related to unknows in the environment and possible interactions of unknowns with the composition, organization, and behavior of the system. Succinctly, becoming more antifragile is not adapting to handle the same sort of crisis better, but to better handle crises in general. Figure 2 illustrates these relationships. Urban system qualities that contribute to antifragility include being emergent rather than resultant, risk allowing rather than risk averse, enabling small-scale rather than system-wide experiments, even rather than uneven distribution of resources, redundancy rather than efficiency, loosely rather than tightly coupled components, and variety and variability rather than uniformity.29 Also, urban systems can exhibit nonlinear dynamics, reciprocal feedback loops, time lags, heterogeneity, and surprises. These qualities combine to create uncertainty and volatility that can allow for the emergence of both positive outcomes and negative outcomes.30 While these qualities can support conditions that allow antifragility to develop, it is also possible to diminish the possibility by actions that contribute to fragility. These can include top-down actions that inhibit flexibility through extensive standardization or that pursue optimization of narrowly defined societal ends. An example in urban planning is strict zoning regulations. James C. Scott has written about such actions at the nation-state level.31 Instead, actions or the interrelations of actions to support antifragility include loosely coupled sub-systems, redundancy, and a willingness to fail at small-scale experiments. Borrowing from studies in biodiversity and landscape ecology,32 antifragile urban environments can be understood as being advanced through variety and variability at multiple scales.
