Department of Earth & Environment, Boston University, Boston, MA, USA.
Instituto do Homem e Meio Ambiente da Amazônia - Imazon, Belém, Brazil.
Glob Chang Biol. 2020 May;26(5):2956-2969. doi: 10.1111/gcb.15029. Epub 2020 Mar 6.
Anthropogenic and natural forest disturbance cause ecological damage and carbon emissions. Forest disturbance in the Amazon occurs in the form of deforestation (conversion of forest to non-forest land covers), degradation from the extraction of forest resources, and destruction from natural events. The crucial role of the Amazon rainforest in the hydrologic cycle has even led to the speculation of a disturbance "tipping point" leading to a collapse of the tropical ecosystem. Here we use time series analysis of Landsat data to map deforestation, degradation, and natural disturbance in the Amazon Ecoregion from 1995 to 2017. The map was used to stratify the study area for selection of sample units that were assigned reference labels based on their land cover and disturbance history. An unbiased statistical estimator was applied to the sample of reference observations to obtain estimates of area and uncertainty at biennial time intervals. We show that degradation and natural disturbance, largely during periods of severe drought, have affected as much of the forest area in the Amazon Ecoregion as deforestation from 1995 to 2017. Consequently, an estimated 17% (1,036,800 ± 24,800 km , 95% confidence interval) of the original forest area has been disturbed as of 2017. Our results suggest that the area of disturbed forest in the Amazon is 44%-60% more than previously realized, indicating an unaccounted for source of carbon emissions and pervasive damage to forest ecosystems.
人为和自然的森林干扰会造成生态破坏和碳排放。亚马逊地区的森林干扰以森林砍伐（森林转化为非林地）的形式发生，森林资源的开采会导致森林退化，而自然事件会导致森林破坏。亚马逊雨林在水文循环中的关键作用甚至导致了一种干扰“临界点”的推测，这种推测可能导致热带生态系统的崩溃。在这里，我们使用 Landsat 数据的时间序列分析来绘制 1995 年至 2017 年亚马逊生态区的森林砍伐、退化和自然干扰图。该地图用于对研究区域进行分层，选择基于其土地覆盖和干扰历史的样本单元。应用无偏统计估计器对参考观测样本进行分析，以获得每两年一次的时间间隔的面积和不确定性估计值。我们表明，退化和自然干扰，主要发生在严重干旱时期，对亚马逊生态区的森林面积产生的影响与 1995 年至 2017 年的森林砍伐一样大。因此，截至 2017 年，估计有 17%（1,036,800±24,800km²，95%置信区间）的原始森林面积受到干扰。我们的研究结果表明，亚马逊地区受干扰森林的面积比以前认识到的要多 44%-60%，这表明存在未被计入的碳排放源和对森林生态系统的普遍破坏。
