Temporal And Spatial Changes Of Drought In Africa And Its Impact On Agriculture From 2003 To 2017

Over the past century,severe weather events have occurred over many parts of the African continent and resulted in severe drought-related hazards.Climate change,drought and land degradation are the leading factors threatening sustainable food and livestock production on the continent.This,in turn,will severely affect the wellbeing of the people,especially the rural farmers whose main livelihood depends on agriculture activities in rain-fed regions.Africa climate range from Sahara Desert in north part to tropical in south part with centred by savanna and forest rain zone,and endures land degradation and frequent droughts due to water shortages and high summer temperatures.The region has been affected by climate change and environmental degradation,which led to affect the crop production in continent.We found that the Sahelian countries of the Africa has been the most affected over the past decades and therefore our study focused on the Sahelian countries to understand the effect of drought on crop production as follows:First,we investigated the temporal and spatial variations of land surface temperature(LST)in Africa to determine the effects of temperature on agricultural production.Although thermal infrared remote sensing technology can quickly obtain surface temperature information,it is greatly affected by clouds and rainfall.To obtain a complete and continuous dataset on the spatiotemporal variations in LST in Africa,a reconstruction model based on the Moderate Resolution Imaging Spectroradiometer(MODIS)LST time series and ground station data was built to refactor the LST dataset(2003-2017).The spatiotemporal analysis of the LST indicates that the change in the annual average LST from 2003-2017 was weak and the warming trend in Africa was remarkably uneven.Geographically,"the warming is more pronounced in the north and the west than in the south and the east".The most significant warming occurred near the equatorial region in South Africa(slope > 0.05,R > 0.61,P <0.05)and the central(slope = 0.08,R = 0.89,P < 0.05)regions.Seasonally,significant warming was more pronounced in winter,mostly in the west,especially in Mauritania(slope> 0.09,R> 0.9,P <0.5*).Furthermore,the study gave a concise report on the response of different surface types to surface temperature was inconsistent at different times,which provides important information for understanding the effects of temperature changes on crop yields,which is critical for the planning of agricultural farming systems in Africa.Second,the study presents an overview of issues related to soil moister content which is a key step in studying the impacts of drought on food production in Africa.To obtain long-term soil moisture data sets in Africa,data products from three different sensors(Advanced Microwave Scanning Radiometer-EOS(AMSR-E),Soil Moisture and Ocean Salinity(SMOS),Advanced Microwave Scanning Radiometer 2(AMSR2))over Africa were used.To improve the resolution of the SM products,the spatial weight downscaling model(SWDM)was used to downscale the passive microwave SM data from 25 km to 1 km resolution.The reconstructed SM products were used to analyze the spatiotemporal patterns of the SM over Africa from 2003 to 2017.Over the past 15 years,the results showed that the spatiotemporal patterns of the overall annual average SM over the period showed a significant decreasing trend(slope <-0.06,R = 0.750,P = 0.05*)and cyclical fluctuations.The most significant decreases in SM occurred in the savanna zone(slope->0.08,significant level >0.001***)and South Africa(slope-> 0.08,R-> 0.89),and a significant decreasing trend occurred in Namibia.Additionally,the Sahel belt in the north and west arid region showed decreasing trends,while rapid significant decreasing trends occurred in Sudan and Nigeria.From summer to winter,rapid significant decreasing trends occurred in Nigeria,Burkina Faso,and Malawi(slope <-0.07,R<-0.78),and the most significant decreases in SM occurred in winter.Approximately 60.63% of the study area exhibited a highly significant correlation between SM and land surface temperature(LST),and 58% of the area exhibited a significant correlation between SM and precipitation.The results are useful for understanding the hydrological and atmospheric cycles,drought conditions,and irrigation management in Africa.Finally,Due to infrequent rainfall,high temperatures,and reduction in SM,the Sahel suffers frequent droughts.The Sahel region is considered as one of the world's driest and extreme environmental conditions.In order to assess Spatio-temporal vulnerability of potential drought impacts,we used remote sensing and ground station data to evaluate drought conditions in the Sahel region from 1985 to 2015.Standardized precipitation index(SPI),standardized precipitation evapotranspiration index(SPEI),Vegetation Condition Index(VCI)anomaly,along with socio-economic indicators were performed.In addition,Pearson correlation coefficient was computed between drought indices and three main crops(Sorghum,Millet,and Maize)in the region to estimate the effects.The analysis showed that temperature increased from 1985 to 2015 by 0.78°C,which had a significant impact on crop yield for sorghum,maize,and millet with a statistical significance value of P > 0.05.In the decade spanning 1994 to 2005 alone,the temperature increased by 0.57°C which resulted in extreme drought in Algeria,Sudan,Chad,Nigeria,and Mauritania.For the effect of drought on crop production,high significance was noted on the SPI and SPEI-3 timescale: sorghum with SPI-3(r = 0.71)and SPEI-3(r = 0.65),Millet with SPI-3(r = 0.61)and SPEI-3(r = 0.72)and maize with SPI-3(r = 0.81)and SPEI-3(r = 0.65)during the study period.In the growing season,VCI anomaly had strong correlation with Sorghum/ Maize area by 42% and 30%,respectively.A significant agreement was also noticed between the combined drought index(CDI)and vulnerability Index(VI)in Burkina Faso(r=-0.676;P < 0.00),Mali(r =-0.768;P < 0.00),Mauritania(r= 0.843;P < 0.001),Niger(r=-0.625;P < 0.001)and Nigeria(r= 0.75;P < 0.005).The results indicate that the effectiveness of the above indices for evaluating agricultural drought in the Sahel region,and these can be used to identify areas which are most vulnerable to drought.