A Multiscale Index of Landscape Intactness for the Western United States

Landscape intactness has been defined as a quantifiable estimate of naturalness measured on a gradient of anthropogenic influence. We developed a multiscale index of landscape intactness for the Bureau of Land Management’s (BLM) landscape approach, which requires multiple scales of information to quantify the cumulative effects of land use. The multiscale index of landscape intactness represents a gradient of anthropogenic influence as represented by development levels at two analysis scales. To create the index, we first mapped the surface disturbance footprint of development, for the western U.S., by compiling and combining spatial data for urban development, agriculture, energy and minerals, and transportation for 17 states. All linear features and points were buffered to create a surface disturbance footprint. Buffered footprints and polygonal data were rasterized at 15-meter (m), aggregated to 30-m, and then combined with the existing 30-meter inputs for urban development and cultivated croplands. The footprint area was represented as a proportion of the cell and was summed using a raster calculator. To reduce processing time, the 30-m disturbance footprint was aggregated to 90-m. The 90-m resolution surface disturbance footprint is retained as a separate raster data sets in this data release (Surface Disturbance Footprint from Development for the Western United States). We used a circular moving window to create a terrestrial development index for two scales of analysis, 2.5-kilometer (km) and 20-km, by calculating the percent of the surface disturbance footprint at each scale. The terrestrial development index at both the 2.5-km (Terrestrial Development Index for the Western United States: 2.5-km moving window) and 20-km (Terrestrial Development Index for the Western United States: 20-km moving window) were retained as separate raster data sets in this data release. The terrestrial development indexes at two analysis scales were ranked and combined to create the multiscale index of landscape intactness (retained as Landscape Intactness Index for the Western United States) in this data release. To identify intact areas, we focused on terrestrial development index scores less than or equal to 3 percent, which represented relatively low levels of development on multiple-use lands managed by the BLM and other land management agencies. The multiscale index of landscape intactness was designed to be flexible, transparent, defensible, and applicable across multiple spatial scales, ecological boundaries, and jurisdictions. To foster transparency and facilitate interpretation, the multiscale index of landscape intactness data release retains four component data sets to enable users to interpret the multiscale index of landscape intactness: the surface disturbance footprint, the terrestrial development index summarized at two scales (2.5-km and 20-km circular moving windows), and the overall landscape intactness index. The multiscale index is a proposed core indicator to quantify landscape integrity for the BLM Assessment, Inventory, and Monitoring program and is intended to be used in conjunction with additional regional- or local-level information not available at national levels (such as invasive species occurrence) necessary to evaluate ecological integrity for the BLM landscape approach.

景观完整性（Landscape Intactness）被定义为基于人为影响梯度量化得到的自然性评估指标。我们为美国土地管理局（Bureau of Land Management, BLM）的景观管理框架开发了一套多尺度景观完整性指数，该框架需要多尺度信息以量化土地利用的累积效应。该多尺度景观完整性指数以两类分析尺度下的开发强度为表征，体现人为影响的梯度变化。

为构建该指数，我们首先针对美国西部17个州，整合城市开发、农业、能源矿产与交通领域的空间数据，绘制了开发活动带来的地表扰动足迹。对所有线性地物与点状地物进行缓冲区分析以生成完整的地表扰动足迹；将生成的缓冲区足迹与面状数据重采样为15米（m）分辨率栅格，再聚合至30米分辨率，随后与已有的30米分辨率城市开发与耕地空间数据进行融合。将扰动足迹面积以栅格单元占比的形式表示，并通过栅格计算器进行求和运算。为缩短处理时长，我们将30米分辨率的扰动足迹聚合至90米分辨率；本数据集发布中单独保留了90米分辨率的地表扰动足迹数据集，其名称为《美国西部开发活动地表扰动足迹》(Surface Disturbance Footprint from Development for the Western United States)。

我们通过圆形移动窗口，分别以2.5千米（km）和20千米为分析尺度，计算各尺度下地表扰动足迹的占比，以此构建地表开发指数。本数据集发布中单独保留了两个尺度下的地表开发指数，分别为《美国西部地表开发指数：2.5千米移动窗口》(Terrestrial Development Index for the Western United States: 2.5-km moving window)与《美国西部地表开发指数：20千米移动窗口》(Terrestrial Development Index for the Western United States: 20-km moving window)。

本数据集发布中，我们通过对两类分析尺度下的地表开发指数进行排序与融合，最终生成多尺度景观完整性指数，该指数命名为《美国西部景观完整性指数》(Landscape Intactness Index for the Western United States)。为识别完整景观区域，我们将地表开发指数≤3%的区域作为筛选标准，该阈值对应美国土地管理局及其他土地管理机构所管理的多功能用地中开发水平相对较低的区域。

本多尺度景观完整性指数的设计兼顾灵活性、透明性、可论证性，且可适配多种空间尺度、生态边界与管辖范围。为提升数据透明性并便于结果解读，本多尺度景观完整性指数数据集发布包附带四类组分数据，以供用户解析该指数：分别为地表扰动足迹、两类尺度（2.5千米与20千米圆形移动窗口）下的地表开发指数，以及最终的整体景观完整性指数。

该多尺度指数是为美国土地管理局评估、清查与监测计划设计的景观完整性量化核心指标，需配合国家级尺度无法获取的区域或局地层面信息（如入侵物种发生情况）使用，以满足美国土地管理局景观框架下生态完整性评估的需求。