In a recent paper in this journal, Bradshaw and colleagues analyse country statistics on flood characteristics, land cover and land cover change, and conclude that deforestation amplifies flood risk and severity in the developing world. The study addresses an important and long-standing question, but we identify important flaws. Principal among these are difficulties in interpreting country statistics and the correlation between population and floods. We review current knowledge, which suggests that the removal of trees does not affect large flood events, although associated landscape changes can under 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.

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The hydrological effects of the conversion of forested land to other land uses (and vice versa) are to a large degree unknown. The present study investigate the effect of natural regrowth of forest on the regional hydrological cycle, and in particular the effects on streamflow. The Dragonja catchment (covering SW Slovenia and NW Croatia) was chosen because the land use changed significantly in this region over the last 50 years. Satellite data and field observations were used to study the hydrological effect of land use change. Historical remote sensing data from Landsat and ASTER revealed a significant change from agriculture to forest within the catchment. From 1973 to 2002 26% changed from agricultural field to forest. In the same period both the baseflow and the storm and flood frequency dropped significantly. A large part of the streamflow changes may probably be linked to precipitation changes in this region, making the hydrological study on reforestation a difficult task. Until now no significant link between reforestation and changes in the hydrological cycle was found and more research is needed to fully understand the hydrological system in this region.

Emerging Issues in Tropical Ecohydrology; Cuenca, Ecuador, 5–9 June 2016