Indigenous burning shapes the structure of visible and invisible fire mosaics

Context: In many regions of the world, Indigenous people continue to shape landscape patterns using fire. Some studies show that Indigenous fire regimes create a diverse “visible mosaic” of time-since-fire ages. Less is known about the underlying, cumulative spatiotemporal patterns of fires that are hidden beneath visible fire scars—termed the “invisible fire mosaic”—despite its role in shaping biota in fire-prone landscapes. Objectives: We investigated how distance from Indigenous communities affects landscape patterns, focusing on aspects of the visible (i.e., time-since-fire diversity and maximum landscape area burnt) and invisible (i.e., number of years burnt, diversity of fire frequency patches, and number of unique fire histories) fire mosaic. Methods: We quantified fire histories for 450 landscapes across Western Australia. We calculated the distance of each landscape to the nearest Indigenous community (a proxy for the intensity of human landscape use) and used regression models to investigate how distance influenced the properties of the visible and invisible fire mosaic. Results: Landscapes near Indigenous communities experienced more frequent fire, had higher time-since-fire diversity, higher diversity of fire frequency patches, and a greater number of unique combinations of fire histories (seasons, interval lengths, and time-since-fire ages). Pyrodiversity was negatively related to the maximum area burnt, supporting the notion that Indigenous burning limits fire size. Conclusions: Indigenous burning creates distinctive visible and invisible fire mosaics which dwarf the pyrodiversity of more distant areas, thereby potentially crafting ecosystem states that profoundly differ from those without human presence.