Priority River Habitat - Rivers

"One of the two datasets that make up the Priority River Habitat Map. Consists of rivers and streams that exhibit a high degree of naturalness. The naturalness classification used to map priority river habitat is based on recent work to review the river SSSI series. It evaluates four main components of habitat integrity: hydrological, physical, physico-chemical (water quality) and biological. An additional classification of the naturalness of headwaters (defined as streams with a catchment area of <10km2 to coincide with WFD typology boundaries) uses land cover data as a surrogate for direct information on river habitat condition (information which is generally lacking on headwaters). Streams and rivers operating under natural processes, free from anthropogenic impact and with a characteristic and dynamic mosaic of small-scale habitats that supports characteristic species assemblages (including priority species), are the best and most sustainable expression of river ecosystems. Key elements are:
a natural flow regime; natural nutrient and sediment delivery regimes;
minimal physical modifications to the channel, banks and riparian zone; natural longitudinal and lateral hydrological and biological connectivity; an absence of non-native species; low intensity fishery activities.
These conditions provide the best defence against climate change, maximising the ability of riverine ecosystems to adapt to changing conditions. They also provide the most valuable and effective transitional links with other priority habitats, including lakes, mires and coastal habitats. In English rivers and streams, high levels of naturalness are rare.
" Attribution statement: © Natural England copyright. Contains Ordnance Survey data © Crown copyright and database right [year].

该数据集为构成优先河流栖息地图的两个数据集之一。包含展现高度自然性的河流和溪流。用于绘制优先河流栖息地的自然性分类，基于对河流SSSI系列的最新研究成果。该分类评估栖息地完整性的四个主要组成部分：水文、物理、物理化学（水质）和生物。对源头自然性的附加分类（定义为流域面积小于10平方公里，以符合WFD类型边界）利用土地覆盖数据作为直接信息（通常在源头缺乏此类信息）关于河流栖息地状况的替代。在自然过程中运作、不受人为影响，并具有支持典型物种群（包括优先物种）的特征性和动态的小尺度生境镶嵌的河流和溪流，是河流生态系统最理想且最具可持续性的表达形式。关键要素包括：
- 自然的水流模式；
- 自然的营养和沉积物输送模式；
- 对河道、河岸和河漫滩区的最小物理改造；
- 自然纵向和横向的水文和生物连通性；
- 非原生物种的缺失；
- 低强度的渔业活动。
这些条件为抵御气候变化提供了最佳防御，最大化了河流生态系统适应变化条件的能力。它们还提供了与其他优先栖息地（包括湖泊、泥炭地及沿海栖息地）之间最有价值和最有效的过渡联系。在英国的河流和溪流中，高自然性水平较为罕见。

致谢声明：© 自然英格兰版权所有。包含军事情报数据 © 英国政府版权和数据库权利 [年份]。