Western Toad Predicted Habitat - CWHR A032 [ds1998]

CWHR Predicted Habitat Models represent areas of predicted suitable habitat for each species within its range. These models are built from the following principal inputs: 1) a statewide, best-available vegetation map (FVEG); 2) GIS data representing a species’ range; 3) the CWHR database of habitat suitability values for over 700 terrestrial vertebrate species. Habitat suitability ranks of Low (non-zero values less than 0.34), Medium (0.34-0.66), and High (greater than 0.66) are based on the maximum suitability value across the 3 species life requisites: reproduction, feeding, and cover. Note that previous versions of these Predicted Habitat Models used an average across the 3 life requisites in order to obtain an overall suitability score for each habitat type and stage class. Habitat suitability scores were developed based on habitat patch sizes greater than 40 acres in size and are best interpreted for habitat patches greater than 200 acres in size. The FVEG landcover dataset is an aggregation of multiple statewide landcover and regional vegetation mapping efforts, conducted at different points in time (approximately 1990 up to time of publishing) and at various resolutions, compiled by the California Department of Forestry and Fire Protection (CALFIRE). FVEG uses the most current and consistent data available for each region of the state. Decision rules were developed that controlled which layers were given priority in areas of overlap. Crosswalks were used to attribute the various data sources according to the CWHR habitat-type classification system. Attributing FVEG with CWHR habitat types allows for the extraction of areas with non-zero suitability values for each species within the bounds of its range, creating a series of maps of predicted suitable habitat which are species-specific. Because FVEG is an amalgam of disparate landcover assessment efforts across the state, the predictive power for determining suitable habitat will vary between species, and possibly even regionally for species which are widely distributed. While these maps represent CDFW’s best estimate of the presence of suitable habitat for any given species in the CWHR system, these maps are also limited by several factors: 1) the accuracy and resolution of vegetation maps in a given region; 2) the dynamic nature of the landscape in which fire and other disturbance events alter conditions at a greater frequency than mapping efforts can track; 3) the currency of expert knowledge, particularly as species adapt to changing land and climate conditions and the shifting of other species’ ranges; 4) the frequency of species-specific surveys across a representative sample of a species’ entire range; 5) metapopulation dynamics, which describes the shifting of populations within their environment as result of numerous types of interactions and responses. CWHR GIS data representing predicted suitable habitat should not be used to indicate the presence or absence of a particular species at any specific site. CWHR predicted habitat models are named according to the 4-character alpha-numeric CWHR ID assigned to each species (5 characters in the case of subspecies or other sub-taxa). There is also a “CWHR Revision Tracking Table” containing a record for each species, its CWHR ID, scientific name, common name, and range and habitat model data revision history. CWHR species range models, predicted habitat models, and GIS data of the statewide distribution of all CWHR habitat types, along with the CWHR revision tracking table, are available for download at https://www.wildlife.ca.gov/Data/CWHR.CWHR预测栖息地模型（CWHR Predicted Habitat Models）代表了各物种在其分布范围内的适宜栖息地预测区域。此类模型基于以下核心输入构建：1）全州范围内可获取的最佳植被图（FVEG）；2）表征物种分布范围的地理信息系统（GIS, Geographic Information System）数据；3）涵盖700余种陆生脊椎动物栖息地适宜性分值的CWHR数据库。 栖息地适宜性等级划分为低（非零分值小于0.34）、中（0.34~0.66）与高（大于0.66），该分级依据物种繁殖、觅食、隐蔽3类生命需求的最大适宜性分值确定。需注意，此前版本的预测栖息地模型采用3类生命需求的平均值，以获取每种栖息地类型及阶段类别的整体适宜性分值。 栖息地适宜性分值基于面积大于40英亩的栖息地斑块制定，最适用于解读面积大于200英亩的栖息地斑块。 FVEG土地覆盖数据集是对多项全州土地覆盖及区域植被制图工作的整合成果，这些工作于不同时段（大致为1990年至发布时）开展，分辨率各不相同，由加州森林与消防局（CALFIRE, California Department of Forestry and Fire Protection）编制。FVEG采用该州各区域可获取的最新且一致的数据集。针对重叠区域，制定了决策规则以明确各图层的优先级。通过跨源对照表，依据CWHR栖息地类型分类系统为各类数据源赋予属性标识。 将FVEG与CWHR栖息地类型完成属性关联后，可提取各物种在其分布范围内拥有非零适宜性分值的区域，进而生成一系列针对特定物种的适宜栖息地预测地图。 由于FVEG是全州范围内多项不同土地覆盖评估工作的整合产物，其在判定适宜栖息地方面的预测能力会因物种而异，对于分布广泛的物种，甚至可能因区域不同而存在差异。 尽管此类地图代表了加州鱼类与野生动物部（CDFW, California Department of Fish and Wildlife）对CWHR系统中任一物种适宜栖息地存在情况的最佳估算，但仍受若干因素限制：1）特定区域内植被图的精度与分辨率；2）景观的动态性——火灾及其他干扰事件改变栖息地条件的频率高于制图工作的更新速率；3）专家知识的时效性，尤其是在物种适应不断变化的土地与气候条件、其他物种分布范围发生转移的背景下；4）针对物种整个分布范围的代表性样本开展物种特异性调查的频率；5）集合种群动态——即种群在环境中因多种类型的相互作用与响应而发生的迁移变化。 CWHR表征预测适宜栖息地的地理信息系统数据不得用于指示任一特定点位是否存在某一特定物种。 CWHR预测栖息地模型按照为每个物种分配的4位字母数字式CWHR ID命名，亚种或其他亚分类群的物种ID为5位。此外还设有“CWHR修订跟踪表”，其中包含每个物种的相关记录，包括其CWHR ID、学名、通用名，以及分布范围与栖息地模型数据的修订历史。 CWHR物种分布范围模型、预测栖息地模型、涵盖所有CWHR栖息地类型全州分布的地理信息系统数据，以及CWHR修订跟踪表，均可从https://www.wildlife.ca.gov/Data/CWHR 下载获取。