Brant Predicted Habitat - CWHR B074 [ds2053]

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.加州野生动物栖息地关系（CWHR，California Wildlife-Habitat Relationships）预测栖息地模型可表征各物种在其分布范围内的潜在适宜栖息地区域。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优植被图（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数值的CWHR数据库。 栖息地适宜性等级划分为低（非零数值小于0.34）、中（0.34~0.66）和高（大于0.66），该划分基于物种3类生存必需条件——繁殖、觅食与遮蔽——对应的适宜性数值的最大值。需注意，此前版本的此类预测栖息地模型曾采用3类生存必需条件的平均值，以获取各栖息地类型与阶段类别的整体适宜性评分。 栖息地适宜性评分基于面积大于40英亩的栖息地斑块开发，其解读最佳适配面积大于200英亩的栖息地斑块。 FVEG土地覆盖数据集由加州林业与消防局（CALFIRE，California Department of Forestry and Fire Protection）整合多项全州及区域植被测绘工作成果构建而成，这些测绘工作于不同时段（大致为1990年起至发布之时）开展，且分辨率各不相同。FVEG采用加州各区域可获取的最新且一致的数据集。研究制定了决策规则，用于管控重叠区域内各数据图层的优先级。分类转换对照表（Crosswalks）被用于依据CWHR栖息地类型分类系统，为各类数据源匹配属性信息。将FVEG数据匹配CWHR栖息地类型后，即可提取各物种分布范围内适宜性数值非零的区域，进而生成一系列针对单一物种的预测适宜栖息地地图。 由于FVEG数据集整合了全州范围内多项不同的土地覆盖评估工作成果，因此其在判定适宜栖息地方面的预测能力会因物种而异，对于分布范围广泛的物种，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局（CDFW，California Department of Fish and Wildlife）针对CWHR体系内任意物种的适宜栖息地存在情况所做出的最优评估，但该类地图仍受多项因素限制：1）特定区域内植被图的精度与分辨率；2）景观的动态特性：火灾及其他干扰事件改变栖息地条件的频率，高于测绘工作的跟踪更新频率；3）专家知识的时效性：尤其是在物种适应土地与气候条件变化、以及其他物种分布范围发生迁移的背景下；4）针对物种全分布范围代表性样区开展物种专项调查的频率；5）集合种群动态：该概念描述种群因各类相互作用与响应而在其栖息环境内发生的迁移变化。 CWHR预测适宜栖息地的GIS数据不得用于判定某一特定地点是否存在某一物种。CWHR预测栖息地模型的命名依据为分配给各物种的4位字母数字混合CWHR标识符（CWHR ID）；对于亚种或其他亚类群，标识符长度为5位。此外还设有“CWHR修订追踪表”，其中包含各物种的相关记录，包括其CWHR标识符、学名、俗名、分布范围及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、涵盖全州所有CWHR栖息地类型分布的GIS数据，以及CWHR修订追踪表，均可通过https://www.wildlife.ca.gov/Data/CWHR下载获取。