The Human Footprint in the West

Humans have dramatically altered wildlands in the western United States over the past 100 years by using these lands and the resources they provide. Anthropogenic changes to the landscape, such as urban expansion, construction of roads, power lines, and other networks and land uses necessary to maintain human populations influence the number and kinds of plants and wildlife that remain. We developed the map of the human footprint for the western United States from an analysis of 14 landscape structure and anthropogenic features: human habitation, interstate highways, federal and state highways, secondary roads, railroads, irrigation canals, power lines, linear feature densities, agricultural land, campgrounds, highway rest stops, land fills, oil and gas development, and human induced fires. We used these input layers to develop seven models to estimate the total influence of the human footprint. These models either explored how anthropogenic features influence wildlife populations via changes in habitat (road-induced dispersal of invasive plants, oil and gas developments, human induced fires, and anthropogenic habitat fragmentation) or predators densities (spatial distribution of domestic and synanthropic avian predators). The human footprint map is a composite of these seven models. The final map consists of a 180 meter resolution raster data set with 10 human footprint classes.过去一个世纪以来，人类通过开发利用美国西部荒野及其蕴藏的资源，对该区域的野生环境造成了剧烈改变。为维持人类聚居而开展的城市扩张、道路与输电线路等基础设施建设、其他配套网络搭建及土地开发等人为景观改造行为，会影响区域内现存动植物的种群数量与物种种类。本研究针对美国西部区域构建了人类足迹（human footprint）地图，分析涵盖14类景观结构与人为要素：人类聚居地、州际公路、联邦与州级公路、次级公路、铁路、灌溉渠、输电线路、线性要素密度、农用地、露营地、高速公路服务区、垃圾填埋场、油气开发以及人为火灾。研究团队基于上述输入图层构建了7种模型，用以量化人类足迹的总影响强度。这些模型分别从两个维度探究人为要素对野生生物种群的作用路径：一是通过改变栖息地（如道路引发的入侵植物扩散、油气开发、人为火灾以及人为生境破碎化），二是通过影响捕食者种群密度（如家养鸟类及依附人类生存的鸟类捕食者的空间分布）。该人类足迹地图为上述7种模型的综合产物。最终生成的地图为分辨率180米的栅格数据集，共包含10个人类足迹等级。