Land-use change is associated with multi-century loss of elephant ecosystems in Asia

Understanding historic patterns of land use and land cover change across large temporal and spatial scales is critical for developing effective biodiversity conservation management and policy. We quantify the extent and fragmentation of suitable habitat across the continental range of Asian elephants (Elephas maximus) based on present-day occurrence data and land-use variables between 850 and 2015 A.D. We found that following centuries of relative stability, over 64% (3.36 million km2) of suitable elephant habitat across Asia was lost since the year 1700, coincident with colonial-era land-use practices in South Asia and subsequent agricultural intensification in Southeast Asia. Average patch size dropped 83% from approximately 99,000–16,000 km2 and the area occupied by the largest patch decreased 83% from ~ 4 million km2 (45% of area) to 54,000 km2 (~ 7.5% of area). Whereas 100% of the area within 100 km of the current elephant range could have been considered suitable habitat in the ye..., Elephant occurrence data
Elephant occurrence locations were initially compiled from the Global Biodiversity Information Facility (https://www.gbif.org/), Movebank (https://www.movebank.org/) and published literature as well as data contributed by the authors based on direct sightings, data logged via tracking devices, and camera traps (n>5000 locations). Records were first checked visually for irrelevant points (e.g., occurrences outside natural continental range, from GBIF) and then refined to include locations representing ecosystems where the species could conceivably flourish, including but not exclusively limited to protected areas. To minimize sampling bias that could result in model overfitting, we further subsampled data to cover the full distribution as widely as possible while eliminating redundant points located within any particular landscape. For instance, thousands of potential redundancies from collar-based tracking datasets were removed by using only one randomly sele..., Spreadsheet data: Microsoft Excel / Google sheets / Open Office
GIS data: ArcGIS / R / QGIS
Rdata or scripts: R / R Studio / Notepad ++

厘清大时空尺度下的土地利用与土地覆被变化历史格局，对于制定高效的生物多样性保护管理策略与政策具有关键意义。本研究基于公元850年至2015年的当代物种出现数据与土地利用变量，量化了亚洲象（Elephas maximus）整个大陆分布范围内适宜栖息地的范围与破碎化程度。研究结果显示，在经历数百年的相对稳定后，自1700年以来亚洲全境已有超过64%（336万平方千米）的适宜象类栖息地丧失，这一变化与南亚殖民地时期的土地利用活动，以及随后东南亚的农业集约化进程高度吻合。平均斑块面积从约9.9万平方千米降至1.6万平方千米，降幅达83%；最大斑块的面积也从约400万平方千米（占总面积的45%）下降至5.4万平方千米（占总面积的约7.5%），降幅同样为83%。而在[年份缺失]，当前象类分布范围100千米范围内的全部区域均可被视为适宜栖息地。

象类出现数据
象类出现点位最初整合自全球生物多样性信息设施（Global Biodiversity Information Facility, GBIF，网址：https://www.gbif.org/）、Movebank（网址：https://www.movebank.org/）、已发表文献，以及作者基于直接目击、追踪设备记录与红外相机所获得的数据（共n>5000个点位）。研究人员首先通过目视检查剔除无效点位（例如来自GBIF的、超出自然大陆分布范围的记录），随后对数据进行筛选，保留该物种可合理存续的生态系统内的点位，包括但不限于保护区。为尽可能降低可能导致模型过拟合的采样偏差，我们进一步对数据进行子采样，以尽可能覆盖完整分布范围，同时剔除特定景观内的重复点位。例如，通过仅保留项圈追踪数据集中随机选取的一个点位，以剔除数千条潜在重复记录。

电子表格数据：Microsoft Excel / Google 表格 / Open Office
地理信息系统（GIS）数据：ArcGIS / R / QGIS
R数据或脚本：R / R Studio / Notepad++