A Satellite Assessment Of The Impact Of Drought And War On Syrian Cultivated Cropland Dynamics

Syria has suffered from severe socioeconomic shocks due to the extreme hydrological droughts and violent conflicts in the recent two decades,during which Syria’s agriculture was also seriously impacted.Previous research showed the severe droughts have caused the shortage of water and land resource,and the following conflicts further intensified the damage to agriculture.However,quantifying the extent of agriculture affected by the droughts and violent conflicts is still a challenge.First,there is a lack of long-term,nationwide and medium-high resolution cultivated cropland maps in Syria;Second,given the complexity of the climate condition,political policy,and military activity,it was difficult to attribute the cropland dynamics.To investigate the impact of droughts and conflicts on Syrian cultivated cropland,the annual Syrian cultivated cropland extent was mapped from 1998 to 2019.This paper adopted multi-source remote sensing data(mainly Landsat),combined analysis of spectral information,vegetation phenological information to generate the annual composited growing and non-growing seasons images.Based on the composited images,time-series of NDVI,and high-resolution images a Random Forest classifier was trained to map the cultivated cropland extent from 1998 to 2019.Then,this paper divided the discussion of cropland dynamics attribution into two stages: 1998-2011 and2012-2019 according to the year when the Syrian war broke.Through regression analysis,the relationship between precipitation and cultivated cropland area during1998-2011 was performed to construct non-war counterfactual scenarios with the fixed effects model.According to the difference between counterfactual scenarios and observations,this paper disentangled the impact of the precipitation and nonprecipitation factors on cultivated cropland area during wartime,and mainly discussed the comprehensive impact of war.Accuracy assessment through stratified random sampling showed the average overall accuracy of the classification results was 96.3%,the average overall producer’s accuracy was 84.5%,and the average user’s accuracy was 81.7%.The experimental results indicated Syrian cultivated cropland had suffered from apparently varying changes in the past two decades.During droughts,the negative impact of drought on cultivated cropland was almost spread all over the country due to the shortage of water.Compared with the drought in 1998-2000,the drought in 2007-2009 had a more serious impact on the cultivated cropland area in Syria.After the Syrian Civil War broke out,the annual average cultivation area has increased by approximately 16%,however,the impact of the war on the cultivated area was more comprehensive,complex,and heterogeneous,compared with the unidirectional impact of droughts.During the war,both the increase and decrease of the cultivated area caused by non-precipitation factors(e.g.war impacts)were found.In general,the decrease of the cultivated area caused by the non-precipitation factors was mainly distributed around the main conflict areas in Syria(e.g.Aleppo,Idlib,Deir＿ez-Zor governorate),while extensive increase of the cultivated area caused by the non-precipitation factors was mainly located in the relatively stable regions(e.g.Al-Hasakah governorate).This paper not only provides insights into the mechanism of natural and human disasters that affected agricultural cultivation activity,but also could give the community a perspective to remotely assess food security,effectively guide food assistance and reasonably devise aid policies.