Intact Habitat Cores by Connectivity Importance

This layer was created as part of Esri’s Green Infrastructure Initiative and is one of five newly generated companion datasets that can be used for Green Infrastructure (GI) planning at national, regional, and more local scales. If used together, these layers should have corresponding date-based suffixes (YYYYMMDD). The corresponding layer names are: Intact Habitat Cores, Habitat Connectors, Habitat Fragments, Habitat Cost Surface, and Intact Habitat Cores by Betweeness. These Esri derived data, and additional data central to GI planning from other authoritative sources, are also available as Map Packages for each U.S. State and can be downloaded from the Green Infrastructure Data Gallery. This layer represents Intact Habitat Cores, symbolized based on their connectivity importance (Betweenness Centrality (BC). BC provides a metric depicting each core’s importance in a connectivity network, thus illuminating each core’s relative contribution to facilitating landscape connectivity and potential species movement. BC represents the number of paths that flow through a given habitat core. It is normalized by the total number of shortest paths between all pairs of nodes, except those paths connecting immediate neighbors. High BC values reflect greater use of that core in traversing the network, thus elevating the core’s importance in facilitating connectivity when compared to cores of lower value. Every time you change your viewing extent, the layer dynamically recalculates to depict the most important cores, based on its betweenness centrality value. The Habitat Cost Surface layer was used to generate a comprehensive network of Least Cost Paths (LCPs) amongst the Intact Habitat Cores layer. This was accomplished using the Cost Connectivity tool which was introduced in ArcGIS 10.4 and ArcGISPro in 1.3. The resulting Habitat Connectors layer was then utilized as the network upon which BC was calculated. The Betweenness_Centrality function in the NetworkX Python library was used to first calculate the number of cost based optimal paths passing through each core and then dividing this number by the range of values in the LCP Routes field. This work was based on the NetworkX Parallel Betweenness example. Data Coordinate System: NAD_1983_Albers本图层是Esri绿色基础设施倡议（Green Infrastructure Initiative）的组成部分，属于五套全新生成的配套数据集之一，可用于国家、区域乃至更精细的地方尺度的绿色基础设施（Green Infrastructure，GI）规划工作。若将这些图层组合使用，需为其添加对应的基于日期的后缀（YYYYMMDD）。对应的配套图层名称分别为：完整生境核心区（Intact Habitat Cores）、生境连接廊道（Habitat Connectors）、生境破碎斑块（Habitat Fragments）、生境成本表面（Habitat Cost Surface）以及基于介数的完整生境核心区（Intact Habitat Cores by Betweeness）。 这些由Esri衍生的数据，以及其他权威来源中对绿色基础设施规划至关重要的补充数据，均已按美国各州打包为地图包（Map Packages），可从绿色基础设施数据图库（Green Infrastructure Data Gallery）下载获取。 本图层代表完整生境核心区，其符号化表达基于各核心区的连接重要性——介数中心性（Betweenness Centrality，BC）。介数中心性是一种衡量指标，用于刻画每个生境核心区在连接网络中的重要程度，从而揭示其在促进景观连通性与物种潜在迁移方面的相对贡献。介数中心性指的是流经某一给定生境核心区的路径数量，其归一化处理基于所有节点对之间的最短路径总数（直接相邻节点间的路径除外）。介数中心性数值越高，代表该生境核心区在网络遍历中被使用的频率越高，相较于低数值核心区，其在促进连通性方面的重要性也更为突出。每当用户调整视图范围时，本图层会基于介数中心性数值动态重新计算，以展示当前范围内最重要的生境核心区。 生境成本表面图层被用于在完整生境核心区图层中生成一套完整的最小成本路径（Least Cost Paths，LCPs）网络。该操作通过成本连接工具（Cost Connectivity tool）完成，该工具于ArcGIS 10.4及ArcGIS Pro 1.3版本中首次推出。生成的生境连接廊道图层随后被用作计算介数中心性的网络基础。 研究使用了NetworkX Python库中的介数中心性（Betweenness_Centrality）函数，首先计算流经每个生境核心区的基于成本的最优路径数量，随后将该数值除以LCP路径（LCP Routes）字段中的数值区间。本数据集的生成参考了NetworkX并行介数计算示例。 数据坐标系：NAD_1983_Albers