Forest--flood relation still tenuous--comment on ‘Global evidence that deforestation amplifies flood risk and severity in the developing world’by CJA Bradshaw, NS Sodi, KS-H. Peh and BW Brook

In a recent paper in this journal, Bradshaw and colleagues analyse country statistics onflood characteristics, land cover and land cover change, and conclude that deforestationamplifies flood risk and severity in the developing world. The study addresses animportant and long-standing question, but we identify important flaws. Principal amongthese are difficulties in interpreting country statistics and the correlation betweenpopulation and floods. We review current knowledge, which suggests that the removalof trees does not affect large flood events, although associated landscape changes canunder some circumstances. Reanalysis of the data analysed by Bradshaw and colleagues shows that population density alone already explains up to 83% of the variation in reported flood occurrences, considerably more than forest cover or deforestation (o10%). Feasible explanations for this statistical finding – whether spurious or causative – are not difficult to conceive. We, therefore, consider the conclusion of Bradshaw and colleagues to be unsupported. However, their study is a valuable first step to show how these or similar flood data might be used to further explore the relationship between land cover and flooding.