Level III Ecoregions of EPA Region 4

Ecoregions by EPA region were extracted from the seamless national shapefile. Ecoregions denote areas of general similarity in ecosystems and in the type, quality,...按美国环境保护署（EPA）划定分区的生态区数据，均从无缝全国形状文件（shapefile）中提取得到。生态区（Ecoregions）指在生态系统及其类型、质量等方面具有总体相似性的区域……