The last decade has been a fairly trying time for those of us living in and around Christchurch. We have had to live through earthquakes, wildfires, pandemics, and even the occasional Crusader’s loss. We are always being told to prepare for catastrophic events. But how easy or reasonable is that?

Donald Rumsfeld, a former US Secretary of Defence, once said “there are known knowns; there are things that we know that we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know”. While he took a lot of flak for this rather inelegant phrase at the time, it does get to the heart of the difficulty of preparing for events.

How do we apply Rumsfeld to preparing for these recent Christchurch events? Wildfires seem like a known known. Fires have become annual events in the dry east coast of New Zealand. Despite having one of the driest and hottest summers on record, we have managed to get through this year (so far), without having a major fire in the Christchursh area. But we can prepare. Prevention is good. Fire bans are common. Vigilance is high. We are getting better at planting firebreaks and so on. We know that these can occur and what to do when they happen.

It doesn’t stop them being major traumatic events though. I will not forget driving through the falling ash to evacuate my mother-in-law from her home on the lower Port Hills, as the fires raged a couple of kilometres from her.

Earthquakes seem like a known unknown. We always knew that Christchurch had the potential for large earthquakes. We were told to prepare (keep water in containers, food in tins, torches and batteries around the house and so on). We also knew that a big earthquake would have lots of effects. When the big quakes of 2010 and 2011 hit (with their years of aftershocks), and in the decade since, we have seen that there were a lot of unknowns. Red zones in the city where we can no longer build. Population shifts into surrounding towns. Increasing butterfly populations in the city. Long-term effects on mental wellbeing and anxiety. And so on.

Are we more prepared now for the next big quake? I guess. Building codes have changed. Support networks are a little stronger. Schools have more focus on resilience. Having been through several episodes where you are convinced that the shaking is so severe that the building that you are in must be about to collapse does keep preparations for dealing with earthquakes at the front of the mind. Even now, when going to a mall, I will generally park on the ground floor on the outer edge of the carpark building (mostly so there is a chance of retrieving the car if the building was compromised!).

The global pandemic seems like an unknown unknown. Sure, we knew there could be pandemics one day but no-one really saw one closing down the entire world for such a long time, confining the vast majority of humanity to their homes. Although New Zealand has been one of the least affected places on the planet, we still had a couple of months of lockdown, closed borders, and impacts on many professions (including universities who lost income from International students and reduced their workforces accordingly).

Could we have prepared? I shared our house with eight adults during our lockdown. For various reasons we ended up with sons and partners, brother-in law and family (including cat) living (and working) together. No preparation would have predicted that. Through good luck, rather than good management, we had a fairly old and large two-storied house (made more comfortable from the earthquake repairs). Crucially, we had fibre installed not long before the pandemic so that we could all continue to work online.

We all got on! And the weather was so good that we could go for walks and find some space when needed. All of these things were outside my immediate control.

I guess global pandemics are now known unknowns going forward. We can prepare a little, although any future pandemic crisis will have its own quirks to be discovered.

That brings us to climate-change.

The effects of climate-change definitely fit the Rumsfeld view. There are known knowns. From models we know that the east coast of New Zealand will become drier and the west coast will become wetter, and roughly by how much.

There are known unknowns. Extinction risk of some species will increase due to the impact of climate-change on species interactions, food availability, predator distributions, disease spread and so on. How much impact? We know this will happen, it is unknown as to how much and to which exact species.

And there are unknown unknowns. What are these? Well I guess that is the point. Earth is such a complex system that there will be many flow on affects from climate-change that we do not predict at this point, as we simply have not made that connection yet.

Perhaps there is also an unknown knowns category? I would suggest that this is when we know something but deliberately choose to ignore the information. This produces its own set of unpredictable outcomes. There are plenty of examples of science denying out there, from covid to climate to flat Earth, that would fit into this category.

A group of New Zealand biologists, including Lincoln University’s Tim Curran, have attempted to look at possible impacts on climate-change, particularly on conservation. They have used New Zealand as a case study in a paper published in Frontiers in Ecology and the Environment.

Island ecosystems are isolated, with many species only being found on a particular island. Islands often have high rates of extinction and are susceptible to invasive species. Any perturbation of island ecosystems can have large (and usually negative) effects on the species native to these islands.

This team concluded, on the basis of many NZ studies, that most impacts of climate-change would be indirect. Take invasive species. Species that are successful at invading areas, like islands, are generally resilient to sudden changes in habitat. They are likely to respond better, or at least faster, to environmental changes giving them a competitive advantage over native species.

Or take food web changes. Hoiho (yellow-eyed penguins) are already known to be susceptible to years with warmer sea temperatures. During these years the food web alters and hoiho adults struggle to survive, let alone find enough nourishing food for their chicks to make it through. This is not a great outcome when it happens once a decade, it will be catastrophic if it happens more frequently.

Macinnis-Ng and colleagues provide an elegant introduction into the known unknowns and hints at what some of the unknown unknowns may be. This paper is a good entry point into estimating the likely impacts of climate-change on our shaky isles. This is also a good to do list for doing research that will move species and climate effects into the known knowns.

Despite the inelegance of Rumsfeld’s ideas, the vocabulary of known unknowns and so on is becoming much more commonplace and academically useful. For Rumsfeld that really would have been an unknown unknown outcome!