Niamey, the capital of Niger, is particularly prone to floods, since it is on the banks of the Niger River, which in its middle basin has two flood peaks: one in summer (the red flood) and one in winter (the black flood). In 2020, the Niger River in Niamey reached its all-time highest levels following an abundant rainy season. On the other hand, the floods in Niamey have been particularly frequent in the last decade, a symptom of a change in hydroclimatic behaviour already observed since the end of the great droughts of the 1970s and 1980s and which is identified with the name of Sahelian Paradox. This study, starting from the analysis of the 2020 flood and from the update of the rating curve of the Niamey hydrometric station, analyses the rainfall–runoff relationship on the Sahelian basins of the Medium Niger River Basin (MNRB) that are at the origin of the local flood. The comparative analysis of runoffs, annual maximum flows (AMAX) and runoff coefficients with various rainfall indices calculated on gridded datasets allowed to hydroclimatically characterise the last decade as a different period from the wet one before the drought, the dry one and the post-drought one. Compared to the last one, the current period is characterised by a sustained increase in hydrological indicators (AMAX +27%) consistent with the increase in both the accumulation of precipitation (+11%) and the number (+51%) and magnitude (+54%) of extreme events in the MNRB. Furthermore, a greater concentration of rainfall and extremes (+78%) in August contributes to reinforcing the red flood’s positive anomalies (+2.23 st.dev in 2020). The study indicates that under these conditions the frequency of extreme hydrological events in Niamey will tend to increase further also because of the concurrence of drivers such as river-bed silting and levee effects. Consequently, the study concludes with the need for a comprehensive flood-risk assessment on the Niamey city that considers both recent hydroclimatic trends and urbanisation dynamics in flood zones hence defining the most appropriate risk-reduction strategies.

Climate change is significantly affecting ecosystem services and leading to strong impacts on the extent and distribution of glaciers and vegetation. In this context, species distribution models represent a suitable instrument for studying ecosystem development and response to climate warming. This study applies the maximum entropy model, MaxEnt, to evaluate trends and effects of climate change for three environmental indicators in the area of the Alpi Marittime Natural Park under the Municipality of Entracque (Italy). Specifically, this study focuses on the magnitude of the retreat of six glaciers and on the distribution of two different plant communities, Alnus viridis scrub and Fagus sylvatica forest associated with Acer pseudoplatanus and tall herbs (megaforbie), in relation to predicted increases in mean temperatures. MaxEnt software was used to model and observe changes over a thirty-year period, developing three scenarios: a present (2019), a past (1980) and a future (2050) using 24 “environmental layers”. This study showed the delicate climate balances of these six small glaciers that, in the next 30 years, are likely to undergo an important retreat (≈−33%) despite the high altitude and important snowfall that still characterize the area. At the same time, it is predicted that the two plant communities will invade those higher altitude territories that, not so long ago, were inhospitable, expanding their habitat by 50%. The MaxEnt application to glaciers has shown to be an effective tool that offers a new perspective in the climate change field as well as in biodiversity conservation planning.

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