We call this new state the hot metastable state of peat soils. In this context, “metastable” means prolonged burning: the hot state lasts a long but finite time, up to 10 years, until the peat burns.
Our other key finding is that a sudden transition from the regular cold state to the hot metastable state can only be triggered by realistic weather patterns, including summer heat waves and global warming scenarios. The most interesting thing is that the increase in atmospheric temperature has to be faster than some critical rate to trigger the transition. If the atmospheric temperature increases by the same amount but at a slower rate, the bioactive peat soil remains in the normal cold state and never transitions to the hot metastable state.
We do not yet have evidence that this happens in the real world and it has not been demonstrated in a laboratory; for now, this is a phenomenon observed only in our models. But we do know that compost (very similar to peat) can catch fire in the same way. For example, a large fire outside London during a heatwave in 2022 was likely caused by a compost pile. in spontaneous combustion.
All of this suggests that atmospheric temperature is not actually the key critical factor for zombie fires. Rather, it is the rate of atmospheric warming that causes long burns of underground peat. Simply put, it’s not the heat, it’s the rhythm.
How to fight zombies
As the climate warms, the weather becomes more extreme, and these are precisely the conditions that can lead to more and more zombie fires. This is worrying as it could start a vicious cycle: the gigatonnes of carbon released into the atmosphere by ancient peat soils will likely make climate changes even worse, meaning more fires, therefore more extreme weather conditions, etc. .
In fact, zombie fires are an example of a speed-induced phenomenon. inflection point, where a system fails to adapt to too rapid changes in external conditions and goes from its regular state to a different, often unwanted state. It is possible that the contemporary climate is approaching (or has already surpassed) rates of change dangerous for certain natural systems, such as bioactive peat soils, which could explain the recent increase in zombie fires.
It seems that the only solution to avoid new zombie fires is to limit climate variability. While policymakers focus on dangerous levels of atmospheric temperature (the heat), climate variability (the rate of change) could be equally or even more relevant to our resilience in the short term.