Are fire mediated feedbacks burning out of control?

Abstract. Contributing to recent discussions regarding the evidence for and against forest and savanna representing alternative steady states (ASS) across much of the tropical lands, we here address several issues raised by Staal and Flores (2015) in a recent commentary published in this journal (Biogeosciences, 12, 5563–5566, 2015). Our analysis shows that – in what could alternatively be titled "A Tale of Five Fallacies" – substantial errors in reasoning exhibited by both Staal and Flores (2015) and the ASS community in general in terms of arguments invoked as providing support for ASS as a key factor determining tropical vegetation distributions. Specifically we: (1) demonstrate that bimodal distributions of canopy cover need not necessarily be associated with ASS ("fallacy of confirmation bias"); (2) show that models suggesting the mathematical feasibility of ASS can never be taken as any sort of proof as to their actual existence ("fallacy of misplaced concreteness"); (3) conclude that studies failing to make climate-independent associations between soil properties and forest/savanna distributions (and thereby concluding that ASS must be present) have inevitably failed to measure the right things. Or in many cases, not even made the required measurements ("fallacy of suppressed evidence"). Moreover, we also find: (4) assertions that ASS associated concepts such as detrimental effects of fire on soil chemical properties and positive effects of forest tree species on soil fertility are totally without foundation ("fallacy of wishful thinking") and (5) a strong tendency amongst ASS advocates to take results from temperate ecosystems and incorrectly assume that this provides support for the existence of ASS in the tropical forest and savanna lands ("fallacy of hasty generalisation"). We conclude all arguments presented to date in support of the widespread existence of ASS in the tropical regions to be flawed. As an alternative, we suggest that forest-savanna transitions may be better understood as reflecting the effects of soil physical and chemical properties on tropical vegetation structure and function with fire-effected feedbacks simply serving to reinforce these patterns through a "sharpening switch" mechanism.