Resilience is a property that profoundly affects how the world works. It refers to the ability to avoid permanent damage when the environment changes. How resilient is your body to novel germs? Or the financial system to people promising what they can’t hold? Or the Internet to censurship? Or food supply to a pandemic?
Those are questions whose answers say something deep about our risk exposure. Though resilience usually requires effort to achieve, the alternative is permanent damage. By understanding ways in which things become resilient, we can work on increasing it in ourselves and in what we care about.
This essay describes 7 resilience patterns – ways in which objects achieve resilience – that I hope will provide a useful mental model for thinking about resilience in the world around us.
An object – a human, a plant, a car, a lake – can be resilient against some particular change in its environment – temperature, moisture, predators. Objects can be damaged.
Objects exist in larger systems which themselves can be considered objects whose resilience we can reason about. That is, we can talk about the resilience of a screw, the door-handle it holds in place, the door, the house, and the city. Be clear about what the object is, the relevant environmental changes, and the types of damage they incur.
1. Avoidance and Deflection
Objects can actively avoid harmful environments. When environments that would be harmful approaches, the object might have some method of avoiding it. If the harmful environment simply never appears, the object is fortunate, not resilient.
Fleeing is the classic example of avoidance. Camouflage another. Fighting attempts to deflect attacks as well as avoiding further attacks by neutralising the attacker.
2. Protection and Isolation
Objects can be protected by barriers that transforms an object’s immediate environment to be less harmful than the environment outside the barrier. This strategy is ubiquitus: clothes, houses, gated communities, quarantains, tortoise shells, and sunglasses. The more complex the object’s interaction with the environment, the harder effective isolation is.
Isolation can be cheap, simple, and effective, but can also have poor failure characteristics: Clothes that get wet in cold weather, lost sun-glasses in a sunny snowscape, or a small breach in a large quarantained area.
Isolation is not an integral part of the functional system. The isolation can – and should – be considered an object with resilience characteristics of its own.
Objects can improve their toughness such that environmental changes damage it less. Toughness is a form of protection that is integral to the object: tougher skin, effective immune system, stronger spider webs.
Redundancy can allow parts of the object to fail without damaging the functionality of the overall object. Redundancy is often a simple strategy to adopt but can be costly or infeasible. Fish lay eggs expecting most to never be fertilised, insect species produce individuals expecting most to perish without reproducing, and software architects design services that work even if some number of servers fail. Backups is a weaker form of redundancy since it’s necessary to actively put them in place to reverse the damage and that process can itself be costly and error prone.
The ability to reverse damage is powerful, but it is a complex or specialised process and is therefore relatively rare. Healing is the canonical example of regeneration. A cast iron pan can regenerate its non-stick surface when used with oily food. Forests regenerate after a fire.
Flexibility is the ability to avoid damage for a large number of environments. It is often achieved at the price of efficiency compared with objects without flexibility. The value of the trade-off will depend on the cirumstances. Omnivorousness and toolbuilding are classic flexibility tactics.
Adaptation is the ability of the object to change itself. This could include the acquisition of other resilience strategies. Evolution is the adaptation strategy of life (it is not strictly a strategy of individual species since evolution changes the species). Learning is another example. Adaptation is powerful but rare aside from evolution (which is ubiquitous). Its success depends on it being fast enough compared with environmental changes.