We call this modern state the warm metastable state of peat soils. In this context, “metastable” means long burning – the warm state persists for a long but finite time, up to 10 years, until the peat burns out.
Our other key finding is that a sudden transition from an ordinary icy state to a warm metastable state can be triggered by realistic climate patterns themselves, including summer heatwaves and global warming scenarios. Most interestingly, the escalate in atmospheric temperature must be faster than a certain critical value to trigger the transition. If the atmospheric temperature increases by the same amount but at a slower rate, the bioactive peat soil remains in its normal icy state and never changes to the warm metastable state.
We still don’t have proof that this happens in the real world and it hasn’t been demonstrated in the lab – for now it’s only a phenomenon observed in our models. However, we know that compost (very similar to peat) can catch fire in the same way. For example, a immense fire on the outskirts of London during the 2022 heatwave is likely to have been caused by a compost pile spontaneous combustion.
All of this suggests that atmospheric temperature is not actually a key factor in causing zombie fires. Rather, it is the rate of atmospheric warming that causes underground peat to burn for a long time. To put it simply, it’s not about heat, it’s about pace.
How to fight zombies
As the climate warms, the weather is becoming more and more extreme, and these are the conditions that could lead to more and more zombie fires. This is worrying because it could start a vicious cycle: gigatons of carbon released from historic peat soils into the atmosphere will likely make climate change even worse, which will mean more wildfires, more extreme weather, and so on.
Indeed, zombie fires are an example of speed-induced fires turning pointwhen the system does not adapt to too rapid changes in external conditions and goes from a normal state to another, often undesirable state. It is possible that today’s climate is approaching – or has already exceeded – hazardous rates of change for some natural systems, such as bioactive peat soils, which may explain the recent escalate in zombie fires.
It appears that the only solution to preventing further zombie fires is to reduce climate variability. While policymakers focus on hazardous levels of atmospheric temperature (heat), climate variability (the rate of change) may be equally or even more vital to our resilience in the brief term.