LBA-ECO LC-04 SATELLITE/CENSUS-BASED 5-MINUTE LAND USE DATA, AMAZONIA: 1980 AND 1995

Amazonia has been under considerable development pressure as croplands and pasture are established in areas formerly occupied by tropical forest and cerrado. Although this region is an important part of several important planetary biogeochemical cycles, the location and impact of human land use are not well understood. In particular, there is no existing satellite-based map of agriculture across the Amazon or Tocantins river drainage basins. Recent efforts have classified land cover across this vast region, although they disagree on the location and amount of cropland and do not directly address pasture, a land use that has grown in importance in the last 2 decades. Here we present an analysis of land cover and land use practices over the Amazon and Tocantins basins of South America. In this study, we demonstrate how satellite imagery and agricultural censuses can be merged in order to provide a geographically explicit, fine- scale description of land cover and land use practices. The result depicts the fraction of each 5-min (9 x 9 km) grid cell that was devoted to agricultural activity during the mid-1990s. The resultant map retains many of the characteristics of the agricultural census data, but with a much finer spatial resolution. During the mid-1990s, cultivated area is estimated to have been 1.7 x 10(7) ha (2.5% of the basin), natural pasture is estimated at 3.3 x 10(7) ha (4.9% of the basin), and planted pasture is estimated to cover 3.3 x 10(7) ha (4.9% of the basin). Perhaps more important than the quantities, however, is that these data sets provide a new blend of ground- based and satellite-based spatially explicit data. This snapshot can be used as a basis to project either forward or backward in time, as a new check of finer scale land use classifications or as a driver of ecosystem models.

亚马孙流域（Amazonia）长期承受着显著的开发压力：原热带森林与塞拉多稀树草原（cerrado）分布区域被改造为农田与牧场。尽管该区域是多项关键行星生物地球化学循环的重要组成部分，但人类土地利用的空间分布与影响机制尚未得到充分阐明。尤为突出的是，目前尚无针对亚马孙河与托坎廷斯河（Tocantins）流域的卫星遥感农业制图（satellite-based map of agriculture）产品。此前已有研究对这片广袤区域开展土地覆盖（land cover）分类，但不同研究对农田的分布与面积估算存在分歧，且未直接覆盖牧场这一近二十年来重要性持续提升的土地利用（land use）类型。本研究针对南美洲亚马孙与托坎廷斯流域的土地覆盖及土地利用模式展开系统性分析，验证了融合卫星影像（satellite imagery）与农业普查数据（agricultural censuses）的可行性，可生成具备地理空间明确性的精细尺度土地覆盖与土地利用描述结果。本次成果呈现了1990年代中期，每5分弧（9×9公里）网格单元内农业活动用地的占比情况。最终生成的地图既保留了农业普查数据的核心特征，同时拥有远更高的空间分辨率。据估算，1990年代中期该流域耕地总面积达1.7×10⁷公顷（占流域总面积的2.5%），天然牧场面积为3.3×10⁷公顷（占比4.9%），人工种植牧场面积同样为3.3×10⁷公顷（占比4.9%）。不过相较上述量化结果，本数据集的核心价值在于实现了地面调查数据与卫星遥感空间明确数据的创新性融合。该时空快照既可作为时空推演的基准，用于向前或向后推演土地利用变化，也可作为高精度土地利用分类结果的校验依据，或是作为生态系统模型的驱动输入数据。