Gadwall Predicted Habitat - CWHR B085 [ds2062]

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预测栖息地模型代表各物种种群分布范围内的预测适宜栖息地区域。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地图（FVEG）；2) 代表物种种群分布范围的地理信息系统（Geographic Information System, GIS）数据；3) 收录700余种陆生脊椎动物栖息地适宜性分值的CWHR数据库。栖息地适宜性等级分为低（非零分值小于0.34）、中（0.34至0.66）与高（大于0.66），其划分依据为物种三大生存必需条件——繁殖、觅食与遮蔽——对应的适宜性分值中的最大值。需注意，此前版本的预测栖息地模型采用三大生存必需条件的平均分值，以生成各栖息地类型与阶段等级的综合适宜性评分。本数据集的栖息地适宜性评分基于面积大于40英亩的栖息地斑块生成，其解读效果在面积大于200英亩的栖息地斑块中最佳。 FVEG土地覆盖数据集是多份全州土地覆盖与区域植被测绘成果的整合产物，这些测绘工作于不同时期（大致为1990年至发布时）以不同分辨率开展，由加州林业与消防局（California Department of Forestry and Fire Protection, CALFIRE）汇总完成。FVEG采用加州各区域当前可获取的最新且一致的数据，研究人员制定了决策规则以明确重叠区域内各数据图层的优先级，并通过分类转换对照表（Crosswalks）依据CWHR栖息地类型分类体系为各类数据源赋予对应属性。将FVEG数据集关联CWHR栖息地类型后，即可提取各物种种群分布范围内具有非零适宜性分值的区域，进而生成一系列物种专属的预测适宜栖息地地图。 由于FVEG是全州范围内多份异质土地覆盖评估成果的整合集合，其判定适宜栖息地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。尽管上述地图代表了加州鱼类与野生动物部（California Department of Fish and Wildlife, CDFW）针对CWHR体系内各物种适宜栖息地分布的最优估算结果，但此类地图仍受多项因素限制：1) 特定区域内植被地图的精度与分辨率；2) 景观的动态特性：火灾与其他干扰事件改变栖息地条件的频率高于测绘工作的更新频率；3) 专家知识的时效性：尤其当物种适应土地与气候条件变化、以及其他物种种群分布发生迁移时；4) 物种专属调查的开展频率：调查样本需覆盖物种种群完整分布范围的代表性区域；5) 集合种群动态：该概念描述了种群因各类相互作用与响应而在其栖息环境中发生的分布变化。 带有预测适宜栖息地信息的CWHR 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各物种分配的4位字母数字混合CWHR编码（亚种或其他亚类群物种的编码为5位）。此外还设有"CWHR修订跟踪表"，其中收录了各物种的CWHR编码、学名、通用名、种群分布范围以及栖息地模型数据的修订历史记录。 CWHR物种种群分布模型、预测栖息地模型、涵盖所有CWHR栖息地类型的全州分布GIS数据，以及CWHR修订跟踪表，均可通过https://www.wildlife.ca.gov/Data/CWHR下载获取。