中国荒漠化潜在发生区域150年变迁:过去、现在和未来

150-year shift of potential geographical distribution of desertification in China:Past,present and future

土地荒漠化是影响人类生存和发展的全球性重大生态问题,我国也是世界上荒漠化最严重的国家之一.当前中国荒漠化潜在发生区域是否发生变化及近百年来变化规律尚不清楚,很多研究对未来干旱的预测忽略了CO_(2)对潜在蒸散的影响,高估了未来荒漠化扩张的趋势.本研究基于《联合国防治荒漠化公约》对荒漠化发生区域的定义,考虑未来CO_(2)浓度增加对潜在蒸散的影响,利用高分辨率格点气象数据(CRU TS4.06)以及第六次国际耦合模式比较计划(CMIP6)的10个全球气候模式数据,分析了当前中国荒漠化潜在发生区域空间分布、过去120年的演变规律和未来30年变化趋势.研究表明:(1)以1991~2020年为基准期,中国荒漠化潜在发生区域约为480万km^(2),约占全国陆域面积的50%.(2)过去120年(1901~2020年)中国荒漠化潜在发生区域总面积呈先减小后增加的趋势,变化转折点发生在1978年;气候整体转向更湿润,潜在发生面积减少3.5万km^(2).(3)未来从低到高3种排放强度下,到2050年中国荒漠化潜在发生区域面积相比现状分别下降5.51%、4.70%和3.73%,随排放强度增加荒漠化潜在发生区域面积变大;未来整体气候转向更湿润,不考虑CO_(2)浓度增加的影响,会高估荒漠化潜在发生区域的面积.综上所述,预计未来中国荒漠化潜在发生区域的面积将减少,但我国仍有接近一半的国土面临潜在的荒漠化风险,维持较低的排放强度有助于降低荒漠化潜在发生区域的面积.

Land desertification is a major ecological challenge facing the world,profoundly affecting human life and sustainable development.As one of the countries with the most severe desertification issues across the world,China has a population of580 million living on 6.6 million square kilometers of dry land.The climate in northern China has changed significantly over the past 20 years.Precipitation,aridity index,and comprehensive humidity index have all shown significant nonlinear increasing trends in the northwest region.However,whether the current potential geographical distribution of desertification(PGDD)in China has changed and the changing pattern in the past century is still unclear.Recent research found that it underestimated the impact of increasing CO_(2)on future potential evapotranspiration.This resulted in an overestimation of changes in potential evapotranspiration when predicting future aridity,thereby exaggerating the prediction of future desertification expansion.Here we investigated the current spatial distribution of PGDD in China and its historical evolution over the past 120 years(1901-2020),and predicted the spatial pattern trend of PGDD in 2050.This analysis considered the impact of increasing CO_(2)concentrations on future potential evapotranspiration based on the modified Penman-Monteith(PM)equation by using high-resolution gridded meteorological data(CRU TS4.06)and datasets from ten global climate models within the Coupled Model Intercomparison Project Phase 6(CMIP6).The results show that the PGDD area in China is approximately 4.8 million square kilometers,accounting for nearly 50%of the country's land area in the baseline period of 1991-2020.In the past 120 years(1901-2020),the total area of PGDD in China has shown a trend of first decreasing and then increasing,with 1978 as the turning point.The study founded that the smallest area of PGDD in China occurred in the 1970s.During this period of 1901-2020,the changes in aridity of PGDD in China generally showed a trend of“dry in the east and wet in the west”.From 1901 to 2020,the area that became wetter in the PGDD was four times the area that became drier.The overall climate became wetter,resulting in a decrease in PGDD area of approximately 35000 square kilometers in 2020.It is projected that by 2050,China's PGDD is expected to decrease by 5.51%,4.70%,and 3.73%respectively compared with the current situation from low emissions to high emissions under three shared socioeconomic pathway scenarios.The lower the emission intensity,the smaller China's PGDD.Compared to the modified PM equation that takes into account changes in CO_(2)concentration,the traditional PM equation overestimates the area of PGDD in China.To sum up,the total area of PGDD in China has shown a downward trend over the past120 years.However,nearly half of China's land area remains vulnerable to desertification risks.Keeping the emission intensity low helps reduce the area of PGDD.The climate of PGDD in China will become humid in the future.Current research mainly analyzes changes in PGDD based on natural climate conditions,without quantitatively considering the impact of human activities on desertification.In future studies,more comprehensive approaches are needed to integrate the impact of human activities and natural conditions on PGDD and conduct in-depth analysis and assessment to gain a deeper understanding of the dynamic changes in these regions.Finally,the understanding of current and future situations of PGDD in China will be conducive to its formulation of national key ecological project planning and desertification prevention and control strategy.