The relationship between pyrodiversity and biodiversity

• It has been postulated that biodiversity increases with pyrodiversity. • Yet inconsistent relationships are observed in empirical studies. • We build a simple model of how biodiversity relates to pyrodiversity. • The model predicts diverse relationships – increasing, decreasing and non-monotonic. • While ecological complexity exists, it is not needed to explain this diversity. The paradigm that "pyrodiversity begets biodiversity" postulates that biodiversity increases as the diversity of the fire regime, often measured by times since fire, in a region increases. The pyrodiversity paradigm was derived from a “thought experiment” rather than from explicit theory based on fire ecology and species’ responses to fire regimes. Empirical studies report a diverse range of responses, with researchers suggesting that this diversity can be explained by extra details such as the nuances of individual studies or the complexity of fire regimes and species’ responses. We explore the relationship between pyrodiversity and biodiversity by developing a simple model in which species respond only to time since fire, and calculate biodiversity metrics in landscapes exposed to different distributions of fire intervals. Biodiversity and pyrodiversity are defined in this theoretical framework, with a wide range of relationships between pyrodiversity and biodiversity predicted, even for this simple model in which time since fire is the only driving variable. Biodiversity can increase or decrease with pyrodiversity in different circumstances. An even wider range of relationships between biodiversity and pyrodiversity would be expected in real fire ecology situations that are more complex. Our theoretical analysis shows that inconsistent empirical support for the paradigm “pyrodiversity begets biodiversity” is unsurprising, and that a diversity of relationships between pyrodiversity and biodiversity is expected.