This new state is called peat soil’s hot metastable state, where “metastable” refers to prolonged burning. The hot state can last for a long period of time, up to 10 years, until the peat burns out.
Another important finding is that a sudden transition from the normal cold state to the hot metastable state can be triggered by only realistic weather patterns, such as a hot summer or a global warming scenario. Most interestingly, the atmospheric temperature must rise faster than some critical rate to trigger the transition. If the atmospheric temperature rises by the same amount, but at a slower rate, the bioactive peat soil will remain in the normal cold state and will not transition to the hot metastable state.
There is no evidence yet that this happens in the real world, nor has it been demonstrated in the laboratory. For now, this is a phenomenon seen only in our models. However, we do know that compost (which is very similar to peat) burns in the same way. For example, the massive fires that broke out outside London during the 2022 heatwave were likely caused by spontaneous combustion of compost piles.
All of this suggests that the main driver of zombie fires isn’t actually temperature. Rather, it’s the rate at which the atmosphere is warming that causes the long-term burning of underground peat. Simply put, it’s speed, not heat, that’s the problem.
How to fight zombies
As the climate warms, weather will become more extreme, and it’s exactly these conditions that could lead to an increase in zombie fires. This is concerning because it could set off a vicious cycle: Gigatons of carbon released into the atmosphere from ancient peat soils could further exacerbate climate change, which means more fires, which means more extreme weather.
Indeed, zombie fires are an example of a rate-driven tipping point, where a system fails to adapt to rapid changes in external conditions and moves from its normal state to a different, often undesirable, state. The contemporary climate may be approaching or already exceeding a rate of change that is dangerous for certain natural systems, such as biologically active peat soils, which could explain the recent increase in zombie fires.
The only solution to prevent further zombie fires appears to be to limit climate change. While policymakers focus on dangerous levels of air temperature (heat), climate change (rate of change) may be equally or more relevant to our resilience in the short term.
