全球红树林时空变化及演变趋势

Spatio⁃temporal changes and trends of global mangroves

红树林是全球重要的生态系统,了解红树林的时空变化特征及演变趋势对开展红树林的保护、恢复及可持续管理具有重要意义。基于谷歌地球工程(Google Earth Engine,GEE)云平台,利用全球红树林分布数据和陆地卫星(Landsat)系列光学影像特征指数数据,结合Theil-Sen中值趋势分析、Mann-Kendall检验、Hurst指数等方法,分析了全球红树林的时空分布特征、时空演变趋势及其可持续特征。结果表明:1990—2020年全球红树林面积呈先下降后上升趋势,总面积减少52174.18km^(2),年平均流失率达1.2%,红树林面积减少最多的地区为东南亚,其次为澳大利亚和新西兰、南美洲和东南非洲;红树林呈退化趋势变化的面积(81.44%)明显多于改善区域的面积(17.43%),其中澳大利亚和新西兰的退化趋势最为明显;2015—2020年全球红树林变化趋势有所改善,有73.85%的区域在未来是可持续的,持续改善区域面积(38.58%)大于持续退化区域面积(33.06%),且改善区域的可持续性明显高于不可持续性,表明2020年之后全球红树林整体上呈改善趋势变化。全球红树林时空变化特征和演变模式,可为生物多样性保护、沿海经济发展、生态环境的可持续改善提供重要支撑,对评估联合国2030可持续发展目标实现的状况具有重要影响。

Mangrove forests are intertidal herbaceous and woody wetland communities that grow on tropical and subtropical coastal mudflats and riverbanks,and are one of the most productive and biologically significant ecosystems,providing important support for the development of coastal ecology,economy and society in all aspects.However,mangrove forests are one of the most vulnerable and threatened ecosystems in the world due to their special growing locations.Aquaculture,urban development,environmental pollution,deforestation,and sea⁃level rise are constant threats to mangrove growth.This loss of mangrove forests greatly threatens the survival and development of human beings.In recent years,the management and conservation of mangrove forests have received worldwide attention,including methods for the scientific and effective monitoring of mangrove forests.Understanding of the spatial and temporal changes and trends of mangrove forests is very important for the conservation,restoration and sustainable management of mangrove forests.Based on the Google Earth Engine(GEE)cloud computing platform,this study used global mangrove distribution data and Landsat series optical image feature index data,combined with Theil⁃Sen median trend analysis,Mann⁃Kendall test,and Hurst index to analyze the spatio⁃temporal distribution characteristics of global mangrove forests,their spatio⁃temporal evolution trends and their sustainability characteristics.Firstly,the global mangrove area declined and then increased from 1990 to 2020,with a net decrease of 52174.18km^(2) in total area,and overall disappeared at an average rate of 1.2%per year.The most serious region of mangrove loss was in Southeast Asia over the world,followed by Australia and New Zealand,South America,and East and Southern Africa.The area of mangrove forests showing changes in degradation trends(82.8%)was significantly larger than the area of improved areas(17.43%),with the most pronounced degradation trends in Australia and New Zealand.Then,the global trend of mangrove forest change in 2015—2020 improved,73.85%of the global mangrove forests are sustainable in the future,with the area of persistently improving areas(38.58%)being larger than the area of persistently degrading areas(33.06%),and the sustainability of the improving areas being significantly higher than that of the unsustainable ones,indicating an overall improving trend change in global mangrove forests after 2020.The spatio⁃temporal changes and trends of global mangrove forests can provide important supports for biodiversity conservation,coastal economic development,and sustainable improvement of ecological environment,and will have a significant impact on the assessment of the realization of the United Nations 2030 Sustainable Development Goals(SDGs).