Global fire regimes, their non-fire characteristics, and changes in time.

Fires as a disturbance regime are an important component of ecosystems, and are involved in many feedback loops within these systems such as climate-carbon feedbacks. The changing climate can influence fire regimes in multiple ways, both directly and indirectly. For example, changing weather patterns can directly alter the occurrence and timing of fire weather days. Weather patterns also influence vegetation growth and ecosystem composition, leading to changes in fuel availability and flammability. Meanwhile, humans also partially shape fire regimes via accidental and managed ignitions as well as various suppression measures.

In this study, we use 35 years of remote sensing data to establish global pyromes; regions of similar fire regimes, via their fire characteristics. This length of data period allows for the allocation of pyromes across multiple time segments, and for changes in their prevalence and spatial distribution to be observed. We have found that the majority of pyrome transitions occurring are shifts towards smaller or less frequent fires, and these transitions are widespread across the globe. However, some regions such as the Northern high latitudes, the Western United States, and Northern Australia are shown to experience larger or more frequent fires in the final observation segment of the study.

Following on from this, we use statistical methods to investigate relationships between pyromes and a wide variety of non-fire properties, including climate, vegetation, and human influence. This allows for inference of the most relevant drivers of pyrome change, both climatic and non-climatic. Initial results suggest for example, that population density is a more important predictor for pyromes with small and medium sized fires. However, there are significant challenges to disentangling the effects of such complex drivers within a relatively short observational period. Nevertheless, it is possible to build a picture of plausible fire regime evolution in regions with shifting environmental components.