| Desertification is one of the important styles for land degradation and research hotspots in the research field of global land degradation and restoration,which has raised widespread concerns from international organizations such as the United Nations(UN),Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services(IPBES),and Intergovernmental Panel on Climate Change(IPCC)in recent years.Mongolian plateau is the typical representative of Arid and semi-arid areas,whose desertification change is vital for some major global issues,like climate change,global carbon cycle,and biodiversity.However,the desertification process,trend,driving mechanism,and its ecological effects in Mongolian Plateau are not clear.Our government attaches great importance to land degradation and restoration,irrational human behaviors,and positive human activities of ecological restoration and reconstruction co-exist.Plus,climate change is becoming more and more intense.Under this background,how does desertification change in the Mongolian plateau?What's the driving mechanism?What's the ecological effect of desertification change?The exploration of these scientific problems will rich theoretical research of desertification.It will also provide decision making support for“integrated protection and restoration of the mountain,forest,farmland,lake,grass,and sand”,the construction of“Beautiful China”,and is vital for the realization of many important goals,such as Land Degradation Neutrality(2030),Carbon Neutral,the UN fifteenth Sustainable Development Goals,and UN Ten Year Plan for Ecosystem Restoration2021-2030.This study selected Mongolian Plateau,a typical arid and semi-arid region,as the study area to explore the desertification process,trend,driving mechanism,and its ecological response.First,based on vegetation data,we applied the Google Earth Engine(GEE)and Markov model to detect the desertification process and trend.Then,using climate data and socio-economic data,combing correlation analysis,time lag cross-correlation,and generalized linear model(GLM),we tried to find the main factors and driving mechanism of the desertification trend.Finally,utilizing vegetation data,weather and climate data,digital elevation model(DEM)data,soil property data,we used synthetically In VEST Model,RUSLE Model,RWEQ Model,and method for ecosystem service value based on per unit area to probe the ecological effects of desertification change and its contributions to local,regional,and global population.The main results are as follows:(1)In recent 20 years,the desertification area of the Mongolian Plateau is decreasingReduction in the desertification area and decrease in desertification degree:the desertified area of the Mongolian Plateau as a whole decreased in recent 20 years,with a net fall in the desert area of 167,623 km~2,equivalent to almost 75%of the total area of the United Kingdom.58.56%and 41.44%of this reduction area have occurred in Inner Mongolia and Mongolia,respectively.The most significant changes in desertification on the Mongolian Plateau are transitions between adjacent grades from more severe desertification to the lower grades,although there are transitions at all grades.Compared with Mongolia,desertification in Inner Mongolia shows a more distinctive reverse trend,with the mean rate of descending one grade in Inner Mongolia of 37.5%exceeded that in Mongolia(28.75%)by almost 10%.At the other end of the scale,the conversion ratio from extremely severe to severe desertification in Mongolia is higher(39%)than in Inner Mongolia(32%),however,the downward transition rates of all the other desertification grades are lower in Mongolia that in Inner Mongolia.The spatial heterogeneity of desertification evolution is significant:in general,most of the reductions have occurred in the northern and eastern parts of the plateau.For example,in Inner Mongolia,Chifeng in the south-east has the biggest decline in total desertified land(23,460 km~2),while Wuhai in the west experiencing the lowest reduction,by an insignificant 42.84 km~2.In Mongolia,the net decrease is greatest in Dornod(north-east),while a very little decrease was recorded in Omnogovi in the south.However,when considering the desertification severity degree,the greatest reductions in the most severe desertification generally have occurred in western areas.(2)The driving mechanism of desertification evolution in the Mongolian Plateau is complexClimate factors appear to have been more significant in the decrease of desert areas more than human interventions.Climate drivers,particularly enhanced precipitation as represented in annual and May-September contributes 77.98%and 74.44%to desertification reduction in Inner Mongolia and Mongolia,respectively.With the increase of human activities,the role of climate change will be weakened.The effects of human activities on desertification evolution relatively lag behind and complex.The driving mechanism of desertification evolution is complex.Desertification evolution is driven by natural factors and human activities.Climate change is the basic mechanism,and human activities are the intervention mechanism.The interaction of the two has positive and negative effects on desertification through biophysical,socio-economic,vegetation climate hydrological feedback.The changes in precipitation,temperature,and wind speed have significant(positive and negative)driving effects on desertification evolution.However,with the aggravation of human activities,the role of climate change is gradually weakening.The changes in human activities,such as urbanization,agricultural production,grazing,mining,and so on,produce positive and negative feedback on desertification evolution through direct or indirect effects and become the external driving force of desertification evolution.(3)Desertification evolution in Mongolian Plateau leads to the enhancement of ecological effectFrom the change of time:due to the reduction of the desert area and vegetation restoration,all ecosystem service value has increased.The total ecosystem service value increased 119.094 billion yuan,with an increase of 6.39%.Among these,the value of soil retention increased most,its increased amount and rate is 35.875 billion yuan and74.35%,respectively.The increased value of environmental purification is the smallest,9.474 billion yuan,increasing 2.12%.From the perspective of regional differences:the increase of total ecosystem service value in Mongolia is much smaller than that in Inner Mongolia.In specific,the total value of ecosystem service in Inner Mongolia and Mongolia increased 8.95%and 4.33%,respectively.The proportion of different ecosystem service values is quite different:the proportion of biodiversity and carbon sequestration is the largest,which is 32.39%and32%,respectively.While the percentage of windbreak and sand-fixation is the smallest(1.98%).In recent 20 years except for the proportion of soil retention and windbreak and sand-fixation increased slightly,with an increase of 1.65%and 0.83%,respectively,the proportion of all the other ecosystem service values decreased.On the whole,the ecosystem service value of the Mongolian Plateau has the most contribution to the global,accounting for about 63%of the total value,followed by the contribution of ecosystem service value to the local,accounting for about 30%.The contribution ecosystem service value to the region is relatively small,accounting for about 7%. |
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