Statewide Terrestrial Irreplaceability Summary - ACE [ds1334]

Statewide Terrestrial Irreplaceability Summary, Areas of Conservation Emphasis (ACE), version 3.0.

Terrestrial Irreplaceability is a measure of the uniqueness of habitat areas for rare endemic species in the landscape, and is one measurement used to describe the distribution of overall species biodiversity in California for the California Department of Fish and Wildlife (CDFW) Areas of Conservation Emphasis Project (ACE). Other measures of terrestrial species biodiversity included in the ACE terrestrial biodiversity summary are native species richness and rare species richness.

Here, terrestrial irreplaceability represents the relative importance of each hexagon based on the uniqueness of habitat areas present for California rare endemic and near-endemic species. Hexagons with a high irreplaceability weight contain species or habitat conditions that occur in few places in the landscape. These area may be of high conservation value due to their unique contribution to biodiversity. The data provides, 1) a count of the total number of endemic species per taxonomic group in each hexagon based on documented species occurrence information, and 2) the irreplaceability weight, based on the rarity-weighted index (RWI), which weights the species count by the extent of the distribution for each species, so hexagons providing habitat for narrowly distributed species are given a higher score. Areas with a high RWI support rare species with few documented occurrences; these areas would be expected to support unique habitats or suites of species that are limited in distribution. The data can be used to view the distribution of rare endemic species in California, and to identify areas of high irreplaceability. Users can view a list of species that contribute to the biodiversity summary for each hexagon.

The terrestrial irreplaceability summary depicts the areas of highest irreplaceability within each ecoregion across the state. To achieve this, the data was normalized by taxonomic group and by ecoregion (see Data Sources and Models Used, below). The terrestrial irreplaceability by taxonomic group layers give a statewide overview of irreplaceability for each individual taxonomic group, showing counts of rare endemic species per hexagon and irreplaceability weights (RWI values) for amphibians, birds, mammals, plants, and reptiles.

全州陆地不可替代性总结数据集：保护重点区域（Areas of Conservation Emphasis，ACE）3.0版。

陆地不可替代性是衡量景观中稀有特有物种栖息地独特性的指标，同时也是加利福尼亚州鱼类和野生动物部（California Department of Fish and Wildlife，CDFW）保护重点区域项目用于描述加利福尼亚州全域物种生物多样性分布的指标之一。该保护重点区域陆地生物多样性总结报告中纳入的其他陆地物种生物多样性衡量指标还包括本土物种丰富度与稀有物种丰富度。

本数据集中的陆地不可替代性，是基于加利福尼亚州稀有特有物种与近特有物种现存栖息地的独特性，衡量每个六边形格网单元相对重要性的指标。不可替代性权重较高的六边形格网单元，其所承载的物种或生境条件在景观中仅少量分布。这类区域因其对生物多样性的独特贡献，往往具备极高的保护价值。

本数据集包含两类核心信息：1）基于已记录的物种出现数据，统计每个六边形格网单元内各分类群的特有物种总数；2）基于稀有度加权指数（Rarity-weighted Index，RWI）计算的不可替代性权重——该指数依据各物种的分布范围对物种数量进行加权，因此为狭分布物种提供栖息地的六边形格网单元将获得更高评分。

稀有度加权指数评分较高的区域，能够承载记录较少的稀有物种；这类区域预计可维持分布受限的独特生境或物种组合。

该数据集可用于可视化加利福尼亚州稀有特有物种的分布情况，并识别陆地不可替代性较高的区域。用户还可查看每个六边形格网单元对应的生物多样性贡献物种列表。

本陆地不可替代性总结数据集展示了全州各生态区内不可替代性最高的区域。为实现这一展示效果，数据集已按分类群与生态区进行了标准化处理（详见下文“数据来源与所用模型”部分）。

按分类群划分的陆地不可替代性图层，可从全州视角展示各单一分类群的不可替代性情况，具体呈现了每个六边形格网单元的稀有特有物种数量，以及两栖类、鸟类、哺乳类、植物与爬行类的不可替代性权重（RWI值）。