Green Heron Predicted Habitat - CWHR B058 [ds2045]

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预测生境模型（CWHR Predicted Habitat Models）指代各物种种群分布范围内的潜在适宜生境区域。此类模型基于以下三类核心输入构建：1）全州范围内可获取的最优植被地图（FVEG）；2）表征物种种群分布范围的地理信息系统（GIS）数据；3）涵盖700余种陆生脊椎动物的CWHR生境适宜性值数据库。生境适宜性等级划分为低（非零值且小于0.34）、中（0.34至0.66）、高（大于0.66），划分依据为物种三大生存必需条件——繁殖、觅食与隐蔽——的最大适宜性分值。需注意，过往版本的预测生境模型曾采用三大生存必需条件的平均分值，以生成各生境类型与阶段类别的综合适宜性评分。本模型的生境适宜性分值基于面积大于40英亩的生境斑块开发，其最优解读场景为面积大于200英亩的生境斑块。FVEG土地覆盖数据集整合了多项全州土地覆盖与区域植被测绘成果，这些测绘工作于不同时段（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（CALFIRE）汇编而成。FVEG采用加州各区域当前可获取的最精准、一致性最强的数据，并制定了决策规则以明确重叠区域中各数据层的优先级。同时通过交叉映射（Crosswalks）依据CWHR生境类型分类系统为各数据源赋予属性。将FVEG与CWHR生境类型进行属性关联后，可提取物种分布范围内具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预测适宜生境地图。由于FVEG整合了全州范围内多种不同的土地覆盖评估成果，不同物种（乃至分布广泛的物种的不同区域种群）的适宜生境预测能力存在差异。尽管此类地图代表了加州鱼类与野生动物部（CDFW）对目标物种适宜生境存在情况的最优估算结果，但仍受多项因素限制：1）特定区域植被地图的精度与分辨率；2）景观的动态变化特性——火灾与其他干扰事件的发生频率高于测绘更新频率，导致生境条件快速改变；3）专家知识的时效性，尤其当物种适应不断变化的土地与气候条件，以及其他物种种群分布发生迁移时；4）针对物种全分布范围的代表性样区开展物种专项调查的频率不足；5）集合种群动态特性，即种群在环境中因各类交互作用与响应而发生的迁移变化。CWHR预测生境模型的GIS数据不可用于判定某一特定地点是否存在目标物种。CWHR预测生境模型以分配给各物种的4位字母数字组合CWHR ID命名（亚种或其他亚分类群的物种ID为5位）。此外，还提供“CWHR修订跟踪表”，其中包含各物种的CWHR ID、学名、通用名、分布范围及生境模型数据的修订历史记录。CWHR物种种群分布模型、预测生境模型、覆盖全州所有CWHR生境类型分布的GIS数据，以及CWHR修订跟踪表，均可从https://www.wildlife.ca.gov/Data/CWHR下载获取。