The possible role of the Sahel Greenbelt on the occurrence of climate extremes over the West African Sahel

Abstract

The “Great Green Wall” of trees (GGW) is an emblematic Pan‐African initiative of re‐greening the Sahel through afforestation and assisted natural regeneration of trees in order to tackle desertification, soil degradation and to mitigate greenhouse gases. This study investigates (i.e., The Sahel Greenbelt) the potential impacts of the GGW and other assisted natural regeneration of trees on the frequency and intensity of extreme climate events over the Sahel and West Africa using the regional climate model (RegCM version 4.3). Our investigation shows that the Sahel greenbelt would increase significantly the number of rainy days (+9%) and the intensity of heavy rain events over the Sahel while extreme dry spells decrease (−4%). Important shifts appear in the modes of variability of all precipitation indices. These probability distribution shapes reveal tremendous intra‐seasonal variability as the new land use land cover (LULC) changes affect the regional climate. Changes in atmospheric circulation including increase of the moisture convergence and evapotranspiration appeared to be the main drivers of heavy rainfall changes. For temperature extremes, the maximum temperature shows significant decrease around the GGW area during summer and an increase in other seasons while the diurnal temperature range increases significantly without an evident change in temperature trends. Intra‐seasonal distributions of temperature extremes show less obvious changes compared to precipitation extremes. This investigation highlights the role of the planned and implemented re‐greening policies (i.e., afforestation by the GGW project and policies of assisted natural regeneration of trees) in affecting the frequency and the amplitude of some climatic extreme events (e.g., heavy rain events, maximum temperatures, etc.). These planned LULC policies need to be accounted for in the diagnostics and future projections of climate extremes over the region.

Mapping Land Use Land Cover Transitions at Different Spatiotemporal Scales in West Africa

“…This served as an objective and novel approach for identifying the major hotspots of LULC transitions and drivers of environmental change in West Africa. Such information is vital for policy interventions related to the environment, such as the "REDD+ Policy" [36][37][38] and the "Great Green Wall Initiative" [39][40][41], which require targeting hotspots with severe deforestation rates or environmental change in Africa.…”

“…Some authors contend that the current shift from rain-fed to irrigated agriculture in some parts of Africa may lead to widespread agricultural drought. It is expected that the renewed attention to the "Great Green Wall" may help to avert the devastating impact of climate and anthropic activities on desertification, soil degradation, and greenhouse gas emission [41]. The "Great Green Wall" was initially advocated as a means of reducing desertification in the Sahel through the planting of a broad continuous band of trees from Senegal to Djibouti [40].…”

Late 21st Century Projected Changes in the Relationship between Precipitation, African Easterly Jet, and African Easterly Waves

“…More recently, there have been remarkable efforts to improve our understanding of the West African climate system using a regional climate modeling approach [28][29][30][31][32][33][34][35]. For instance, a number of projects have been developed to advance the understanding of the WAM system [31][32][33][34][35] and to comparatively assess the modeling of the WAM mean climatology and its projected changes [29,36,37].…”

The Productive Landscape in the Desert Margin for the Sustainable Development of Rural Settlements: An Innovative Greenbelt for Maranjab Desert in Iran

“…The reforestation/afforestation options, as the large-scale implementation activities of planting trees, are used to generate favorable atmospheric circulation patterns for enhanced precipitation and evapotranspiration favorable to the regional climate [13]. Many afforestation projects on the edge of the desert have failed [14].…”