*5.2. Climatic Factors That Influence the Evolution of Agricultural Land*

The links between the land and the global climate have long been known [73]. Thus, the scientific literature provides positive examples of that problem. It points out that land degradation is a complex process involving the natural ecosystem and the socioeconomic system. Climate and land-use changes are the two predominant driving factors [74]. However, it is clear that climatic factors, including temperature or rainfall, can impact land-use. In this study, the pivotal factors that can influence agricultural land's transition focus on the rainfall.

Generally, the projected changes in climate include recurring climate extremes like droughts, flooding, and outbreaks of pests and diseases exposing the region to the vulnerabilities of the changing environment [75]. The agricultural sector is one of the first affected by this change [64] because rainfall is the main factor affecting agricultural production [76]. Therefore, the erratic spatio-temporal distribution of rainfall can often be the origin of an increase or a decrease in the cropland. Past studies emphasized two normal years with a dryness trend in 2012 and 2013 in West African, particularly Senegal [77]. This dryness can have a negative influence on the area planted. For instance, our study shows a decrease in cropland during the periods of 2012–2015 and 2015–2018. Indeed, the inter-annual evolution of rainfall during the period 1985–2014 in the region of Kaolack shows thirteen years out of thirty that are deficient compared to the average of the series which is 604.0 mm of rain. The most deficient year was 2014 with 423 mm [78]. The above background confirms the rainfall results analyzed for the whole study area. Indeed, the analysis made on the evolution of the rainfall shows that the rainfall varies from one year to another. Indeed, Figure 5 shows three periods. The results of the second period show that the rainfall is decreasing and 2014 is the most deficient year of the whole period. Similarly, after an increase in rain in 2015, the rainfall decreased over the third period. Accordingly, the decrease/fluctuation in rainfall during this period may explain the reduction or increase in cropland in the Groundnut Basin.

**Figure 5.** Annual evolution of rainfall: 2009 to 2018. Source CRHS 2021.

On the other hand, our analysis reflects the decline of urban and built-up in the regions of Kaolack and Kaffrine. Formerly inhabited areas are abandoned, leaving the place to fallow. These two regions are predominantly agricultural (Figure 2). Therefore, this situation has been proven in some studies in the past. Indeed, the decline of groundnut cultivation, coupled with the disappearance of certain industrial facilities for processing this raw material, has aggravated the situation, leading to a massive displacement of populations from the former urban centers of the Groundnut Basin to the metropolis of Dakar [65]. Therefore, many socio-economic and climatic factors can influence agricultural land, and some studies demonstrate about 74% of farmers perceived that erratic rainfall seasonality contributes significantly to the land-use change and agricultural land abandonment [79].
